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1

Structural and Electronic Investigations of Complex Intermetallic Compounds  

SciTech Connect

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

Hyunjin Ko

2008-08-18

2

Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

3

Research on Intermetallic Compounds.  

National Technical Information Service (NTIS)

Laboratory effort was directed toward producing pure, nonporous samples of selected intermetallic compounds in the molybdenum-aluminum, molybdenum-germanium, molybdenum-selenium, and molybdenum-tellurium systems. Although samples of the desired phases wer...

M. Semchyshen J. Dahl C. Hallada J. Mair

1967-01-01

4

Twinning Mechanisms in Complex High Tm Intermetallic Compounds.  

National Technical Information Service (NTIS)

This program was divided into two sections involving two separate kinds of experiments: The first involved an investigation into the possibility of twinning in complex structures by inhomogeneous shears (without shuffles) possibly involving synchroshear, ...

D. P. Pope D. E. Luzzi

1999-01-01

5

Exploring the Structural Complexity of Intermetallic Compounds by an Adaptive Genetic Algorithm  

NASA Astrophysics Data System (ADS)

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.

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.

2014-01-01

6

New method for computer analysis of complex intermetallic compounds and nanocluster model of the samson phase Cd3Cu4  

NASA Astrophysics Data System (ADS)

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 Cu3Cd4 structure (Samson phase). Cu3Cd4 structure models were used to establish a structural relationship between nanoclusters in this intermetallic compound and nanoclusters in other complex crystal structures: ZrZn22, Ru7Mg44, NaCd2, and Mg2Al3.

Blatov, V. A.; Ilyushin, G. D.

2010-12-01

7

Gravity segregation of complex intermetallic compounds in liquid aluminum-silicon alloys  

SciTech Connect

Primary crystals of intermetallics that are rich in iron, manganese, and chromium form at temperatures above the liquidus, and because their density is higher than that of liquid aluminum, they cause gravity segregation in the melt. Segregation may occur either in the mold at slow cooling rates or in the bulk liquid in furnaces or ladles. The kinetics of settling of these intermetallic compounds in a melt of Al-12.5 pct Si having 1.2 pct Fe, 0.3 pct Mn, and 0.1 pct Cr has been studied. Sedimentation was investigated at 630 C for settling times of 30, 90, and 180 minutes in an electric resistance furnace. The effect of settling time and height of melt on the volume percent, number, and size of intermetallic compounds was studied by image analysis. The volume percent of intermetallics increases with distance from the melt surface. Both the number of particles and the average size increase during sedimentation. The rate of settling varies with position in the melt due to depletion of intermetallics near the surface and an increase near the bottom. The settling velocities obtained experimentally were compared with terminal velocities calculated by Stokes` law. Good agreement was generally found. The settling speed of intermetallics reaches the terminal velocity at very short times and very close to the liquid surface. Stokes` law is therefore applicable to virtually all locations within the melt.

Shabestari, S.G.; Gruzleski, J.E. [McGill Univ., Montreal, Quebec (Canada). Dept. of Mining and Metallurgical Engineering

1995-04-01

8

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

PubMed

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

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

2008-11-19

9

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

10

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

11

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

12

Nuclear magnetic resonance in intermetallic compounds  

Microsoft Academic Search

The nuclear magnetic resonance absorption of aluminium and cobalt has been studied in the intermetallic compounds NiAl, CoAl, FeAl, Al2NiCo, Al2FeCo, Al2FeNi and CoTi. The intensity measurements indicate a high degree of order in all the compounds studied, particularly NiAl and CoAl. The relatively large values of intensity at compositions appreciably different from the equiatomic value for these two series

G. W. West

1964-01-01

13

Intermetallic compounds in heterogeneous catalysis—a quickly developing field  

NASA Astrophysics Data System (ADS)

The application of intermetallic compounds for understanding in heterogeneous catalysis developed in an excellent way during the last decade. This review provides an overview of concepts and developments revealing the potential of intermetallic compounds in fundamental as well as applied catalysis research. Intermetallic compounds may be considered as platform materials to address current and future catalytic challenges, e.g. in respect to the energy transition.

Armbrüster, Marc; Schlögl, Robert; Grin, Yuri

2014-06-01

14

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

15

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

16

Driving Magnetostructural Transitions in Layered Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

17

Ruthenium tantalum intermetallic compounds containing iron or cobalt  

SciTech Connect

This patent describes an intermetallic compound of ruthenium and tantalum comprising: about 44 to 54 atomic percent tantalum, an element from the group consisting of about 2 to 30 atomic percent iron and about 5 to 35 atomic percent cobalt, and the balance substantially ruthenium, the intermetallic compound having good high-temperature hardness, and good room-temperature toughness.

Fleischer, R.L.

1992-10-13

18

Surface structures of complex intermetallic compounds: An abinitio DFT study for the (100) surface of o-Al13Co4  

NASA Astrophysics Data System (ADS)

The formation and the structural and electronic properties of the (100) surface of the complex intermetallic compound Al13Co4 have been investigated using ab initio density functional methods. While the layered crystal structure of the compound suggests that the (100) surface is formed by cleaving the crystal between adjacent flat (F) and puckered (P) layers, a simulated cleavage experiment shows that the P layer splits into two complementary parts to preserve the integrity of very stable clusters forming pentagonal bipyramids (PB’s). The stable surface is terminated by an incomplete P layer consisting of the tips of the PB clusters and exposing in the interstices that part of the underlying F layer forming the connection between the PB’s. The stability of this strongly corrugated surface is further confirmed by the calculation of the surface energies and of the formation energies of surface vacancies, as well as by a simulated high-temperature annealing. The analysis of the electronic structure shows that the stability of the PB clusters arises primarily from strong, partially covalent vertical Co-Al-Co bonds between the tips of the clusters. Simulated scanning tunneling microscopy (STM) images are provided to permit a comparison with the STM experiments of Addou [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.80.014203 80, 014203 (2009)]. Measured and simulated STM images are in good agreement, possible reasons for the remaining differences in the Al/Co contrast are discussed in detail.

Kraj?í, M.; Hafner, J.

2011-09-01

19

Do constitutional vacancies in intermetallic compounds exist?  

SciTech Connect

Here the authors present clear evidence strongly suggesting that there exists no fundamental difference between different types of intermetallics, and the constitutional vacancies do not exist in any B2 intermetallics. They show that all observed behaviors, including the abnormal behavior, can be simply understood in terms of the most common thermodynamic principle by considering the competition between two possible entropy-production processes (anti-site atom formation and vacancy formation) in intermetallics. This general view leads to a unified explanation to all observed defect structures in intermetallics. The result of the present study may alter many previous explanations about various properties of intermetallics, which rely on constitutional vacancies.

Ren, Xiaobing; Otsuka, Kazuhiro; Kogachi, Mineo

1999-10-08

20

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; Brück, E; Dou, S X

2013-05-24

21

Investigations on Ce- and Yb-Based Intermetallic Compounds.  

National Technical Information Service (NTIS)

The author describes investigations on a number of cerium- and ytterbium-based intermetallic compounds and alloys, yielding a lot of experimental results which could not always be put in a quantitative picture. All experimental data are consistent with a ...

R. A. Elenbaas

1980-01-01

22

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 solid–liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds.

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

2005-01-01

23

Vapor pressure measurement of zn-fe intermetallic compounds  

Microsoft Academic Search

Most galvanized steel sheets are produced by a continuous galvanizing line. Some of the operations include a subsequent heat\\u000a treatment termed galvannealing to form intermetallic phases on the surface. These galvanizing reactions are essentially regarded\\u000a as “making intermetallic compounds” in the Fe-Zn-M system. This makes it important to know the thermodynamic properties of\\u000a the system for any detailed discussion on

Kazuaki Mita; Shu Yamaguchi; Masafumi Maeda

2004-01-01

24

First Principles Study of Al-Li Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

The structural properties, heats of formation, elastic properties, and electronic structures of four compositions of binary Al-Li intermetallics, Al3Li, AlLi, Al2Li3, and Al4Li9, are analyzed in detail by using density functional theory. The calculated formation heats indicate a strong chemical interaction between Al and Li for all the Al-Li intermetallics. In particular, in the Li-rich Al-Li compounds, the thermodynamic stability of intermetallics linearly decreases with increasing concentration of Li. According to the computational single crystal elastic constants, all the four Al-Li intermetallic compounds considered here are mechanically stable. The polycrystalline elastic modulus and Poisson's ratio have been deduced by using Voigt, Reuss, and Hill approximations, and the calculated ratios of bulk modulus to shear modulus indicate that the four compositions of binary Al-Li intermetallics are brittle materials. With the increase of Li concentration, the bulk modulus of Al-Li intermetallics decreases in a linear manner.

Yu, Hai-li; Duan, Xiao-hui; Ma, Yong-jun; Zeng, Min

2012-12-01

25

Intermetallic Compounds of the Type MNi5 as Methanation Catalysts.  

PubMed

Catalytic reactions of carbon monoxide with hydrogen have been studied in which intermetallic compounds of the formula MNi(5) (where M is thorium, uranium, or zirconium) have been used as the catalysts. The materials perform effectively as methanation catalysts; ThNi(5) has a specific activity exceeding that of a typical commercial oxide-supported methanation catalyst by a factor of about 5. This material also shows superior resistance to hydrogen sulfide poisoning. Nickel, formed as a decomposition product of the MNi(5) intermetallic compound, is probably the active species, but its properties are influenced by the nature of M in the precursor MNi(5) system. PMID:17778546

Elattar, A; Takeshita, T; Wallace, W E; Craig, R S

1977-06-01

26

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-Zélis, L. A.

2004-11-01

27

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

National Technical Information Service (NTIS)

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

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

2004-01-01

28

Fundamentals of mechanical behavior in intermetallic compounds  

SciTech Connect

The fundamental aspects of deformation and fracture behavior of ordered intermetallics were investigated on the basis of quantum mechanical total-energy calculations and anisotropic elasticity theory for dislocations and cracks. These first-principles calculations were based on the local-density functional (LDF) theory. The LDF equations are solved either by full-potential linearized augmented plane-wave (FLAPW) method or by mixed-basis pseudopotential method. Our approach represents a major advance in applying LDF to solids, in which the LDF equations are solved without any shape approximation to the potential or change density and a high degree of variational freedom (and precision) can be achieved. The calculated elastic constants, various shear fault energies, defect self-energies, and cleavage energies were used in conjunction with the continuum modeling of dislocations and cracks to predict the mechanical behavior and to understand the underlying electronic mechanism of observed mechanical properties. 14 refs., 6 figs., 3 tabs.

Fu, C.L.; Yoo, M.H.

1991-01-01

29

Electronic, elastic and thermal properties of lutetium intermetallic compounds  

NASA Astrophysics Data System (ADS)

The electronic, structural, elastic, thermal and mechanical properties of Lutetium intermetallic compounds LuX (X = Mg, Cu, Ag, Au, Zn, Cd and Hg) have been studied using ab-initio full potential linear augmented plane wave (FP-LAPW) with the generalized gradient approximation (GGA) in their non magnetic phase. The ground state properties such as lattice constant, bulk modulus, pressure derivatives of bulk modulus are reported in CsCl-(B2 phase) structure. We also report the band structure and density of states at equilibrium lattice constant. The calculated band structures indicate that these intermetallics are metallic in nature. The second order elastic constants of these compounds are also predicted for the first time. The ductility of these compounds is determined by calculating the bulk to shear ratio B/GH.

Pagare, Gitanjali; Chouhan, Sunil Singh; Soni, Pooja; Sanyal, S. P.; Rajagopalan, M.

2013-04-01

30

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

31

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

32

Intermetallic compounds of the type MNiâ as methanation catalysts  

Microsoft Academic Search

Catalytic reactions of carbon monoxide with hydrogen have been studied in which intermetallic compounds of the formula MNiâ(where M is thorium, uranium, or zirconium) have been used as the catalysts. The materials perform effectively as methanation catalysts; ThNiâ has a specific activity exceeding that of a typical commercial oxide-supported methanation catalyst by a factor of about 5. This material also

A. Elattar; T. Takeshita; W. E. Wallace; R. S. Craig

1977-01-01

33

Electronic structure of Y 2M 17 intermetallic compounds  

Microsoft Academic Search

Using Haydock's recursion method, the density of states was computed for Y2M17 (M ? Fe, Co or Ni) intermetallic compounds, for non-ideal structures. A partial disorder was simulated displacing the Y atoms from the 2b to 2c positions and the M atoms from 4f to 4e positions. The magnetic moments, electron occupation number, electronic specific heat coefficient and Curie temperature

V. Crisan; V. Popescu; A. Vernes; D. Andreica; I. Burda; Simona Cristea; Alina Olinici

1995-01-01

34

Synthesis and Metallurgical Properties of Intermetallic Compounds.  

National Technical Information Service (NTIS)

The connections between synthesis conditions, metallurgical properties and physical properties were investigated in the highest T sub C niobium based A-15 superconducting compounds. Thick chemically vapor deposited Nb3Ge deposits with T sub C up to 23.0 K...

G. W. Webb G. Arrhenius

1975-01-01

35

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

36

Intermetallic compounds at aluminum-to-copper electrical interfaces: effect of temperature and electric current  

Microsoft Academic Search

The effects of intermetallic compounds on the electrical and mechanical properties of bimetallic friction welded Al-Cu joints was studied. The formation and growth of intermetallic compounds was studied in the temperature ranges 200-525°C. In addition, the effect of electrical current on the morphology and kinetics of formation of intermetallic compounds of bimetallic friction welded aluminum-copper joints was studied in the

M. Braunovic; N. Alexandrov

1994-01-01

37

Hot corrosion mechanism of intermetallic compound Ni 3Al  

Microsoft Academic Search

The molten salt-induced oxidation\\/sulfidation (hot corrosion) on nickel aluminide intermetallic compound (Ni3Al, Ni–11.7wt.%Al–0.6wt.%Zr–0.01wt.%B) has been studied in the 1%SO2\\/air gas mixtures. X-ray analyses for the hot-corroded specimen tested at different period of time show only NiO formed at 605°C, and NiO and NiAl2O4 at 800 and 1000°C. EDAX analyses reveal that AlSx and\\/or NiSx are produced beneath the oxide scales

W. H Lee; R. Y Lin

2003-01-01

38

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

39

Effect of Reflow Profile on Intermetallic Compound Formation  

NASA Astrophysics Data System (ADS)

Reflow soldering in a nitrogen atmosphere is a common process consideration in surface mount technology assembly. This is because the use of nitrogen in reflow equipment may benefit the process as well as the quality of the end product, where it can increase the reliability of the solder joint. So far, many papers have reported effects of cooling speed, type of solder pastes and solder fluxes on the reliability of lead-free solder joints. While the effects of reflow conditions on intermetallic compound (IMC) formation at the solder joint such as the atmosphere during the reflow process are still unclear. The present study investigated thoroughly the effect of different reflow soldering atmosphere, which is air and nitrogen on IMC formation and growth. Several techniques of materials characterization including optical, image analysis, scanning electron microscopy and energy dispersive X-ray analysis will be used to characterise the intermetallics in terms of composition, thickness and morphology. In addition, the effects of cooling rate and isothermal aging were also studied for the solder alloy Sn-4Ag-0.5Cu on electroless nickel/immersion gold (ENIG) surface finish. From the study, it was found that reflowing under nitrogen atmosphere had better effect on IMC formation and growth compared to reflowing under air. Besides, the cooling rate of solder during reflow also appears to have a significant effect on the final structure of the solder joint, and controlling the growth behaviour of the IMC during subsequent isothermal aging.

Siti Rabiatull Aisha, I.; Ourdjini, A.; Azmah Hanim, M. A.; Saliza Azlina, O.

2013-06-01

40

Interrelations Between Phase Diagrams and Hydriding Properties for Alloys Based on the Intermetallic Compound FeTi+.  

National Technical Information Service (NTIS)

Hydriding alloys based on the intermetallic compound FeTi have potential for the safe and convenient storage of hydrogen, both for mobile and stationary applications. In spite of its simple formula, the hydriding behavior of FeTi is quite complex and a st...

G. D. Sandrock J. J. Reilly J. R. Johnson

1977-01-01

41

Magnetoelastic properties of Nd 6Fe 13Cu intermetallic compound  

NASA Astrophysics Data System (ADS)

Magnetoelastic properties of Nd 6Fe 13Cu intermetallic compound are reported. To study the magnetoelastic behaviour of this compound, the thermal expansion as well as the longitudinal ( ?l) and transverse ( ?t) magnetostriction were measured by using the strain gauge method in the selected temperature range of 80-500 K under applied magnetic fields up to 1.5 T. An anomaly and invar-type effects are observed in the linear thermal expansion and ?( T) curves at the Néel temperature. The linear spontaneous magnetostriction decreases sharply by approaching the Néel temperature and also shows the short-range magnetic ordering effects when antiferromagnetic-paramagnetic transition occurs. In the low field region, the absolute values of the anisotropic magnetostriction are small and then start to increase with applied magnetic field. Each isofield curve of the anisotropic magnetostriction passes through a minimum and then approaches to zero with increasing temperature. This magnetostriction compensation arises from the difference in the magnetoelastic coupling constants of the sublattices in this compound.

Iranmanesh, P.; Tajabor, N.; Rezaee Roknabadi, M.; Fruchart, D.; Pourarian, F.

2011-09-01

42

Electrodeposition of Bi(x)Fe(1-x) intermetallic compound nanowire arrays and their magnetic properties.  

PubMed

There have been few reports on Bi-Fe intermetallic compounds because Bi and Fe are immiscible in the equilibrium states and neither alloy nor intermetallic compound exists in the binary system. In this paper, we show that, by using the nanometer-scale templates based synthesis in conjunction with the electrochemical deposition, it is possible to mix in solid solution elements that are immiscible in traditional fabrication methods. The preparation of Bi-Fe intermetallic compound nanowire arrays was investigated via an electrodeposition route by using a polycarbonate (PC) membrane template. Cyclic voltammetry, potentiostatic transient, and potentiostatic stripping were used to study the formation of Bi(x)Fe(1-x) intermetallic compounds. The compositions of Bi(1-x)Fe(x) intermetallic compound nanowire arrays were sensitive to the bath compositions and the electrodeposition potentials, and the length could be easily adjusted by varying the electrodeposition time. The electrodeposited Bi(1-x)Fe(x) intermetallic compound nanowire arrays had a parallel-to-the-wire easy magnetization. Furthermore, the spin-glass such as behavior and an unusually large characteristic time, which was about 5.26 h, were found in Bi(1-x)Fe(x) intermetallic compound nanowire arrays at room temperature. PMID:16671702

Li, Gao-Ren; Tong, Ye-Xiang; Kay, Lin-Gang; Liu, Guan-Kun

2006-05-11

43

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

44

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

45

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

46

New Interest in Intermetallic Compound ZnSb  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

47

Atomistic Simulation of Radiation-Induced Amorphization of Intermetallic Compounds.  

NASA Astrophysics Data System (ADS)

Electron irradiation-induced amorphization of the intermetallic compounds NiZr, NiZr_2, FeTi and CuTi was examined using molecular dynamics simulations. Embedded-atom potentials, fitted to the properties of the pure metals and compounds, were used to model the interactions between the atoms. Electron irradiation was simulated by two different processes: randomly chosen atoms of different species were exchanged to create chemical disorder, and Frenkel pairs were introduced into the simulation cell at random. The resulting configurations corresponding to various damage doses were relaxed and the thermodynamic, structural, and mechanical properties were evaluated as functions of dose. The evolution of the system structure during the simulation was monitored using a new approach that combines molecular dynamics with the multislice method. Electron diffraction patterns were calculated from simulated configurations in an effort to maintain consistency with experiments, and improve the sensitivity to structural changes. The results of the simulation indicate that the mechanism of amorphization can vary from compound to compound. Chemical disorder was sufficient to cause amorphization in NiZr and NiZr_2, while Frenkel pairs were required in addition to chemical disorder in CuTi, and FeTi. During the process of amorphization, the energy and volume increased with dose and saturated at the corresponding levels of a quenched liquid. The variation of the volume with dose was remarkably similar to that of the energy. The pair-correlation functions, diffraction patterns, and projection of atom positions indicated the occurence of amorphization. In addition, the elastic constants C_{44 } and C^' became equal. Prior to the attainment of elastic isotropy, the average shear elastic constant decreased by about 50% of its value in the perfect crystal. In an effort to understand the elastic softening prior to amorphization and explore similarities between melting and amorphization, the total mean-square atomic displacement was determined for isothermal disorder and isobaric heating in NiZr, NiZr_2, and FeTi. The results from this study have led to the formulation of a unified thermoelastic description of amorphization and melting with the total mean-square displacement as the basic link between these two processes. The findings of this work are in good agreement with experimental observations.

Devanathan, Ramaswami

48

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

49

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

Microsoft Academic Search

Magnetic fields have a large impact on the magnetic and superconducting properties of solids. High magnetic fields are required to reach magnetic saturation along a hard magnetic direction in a variety of rare-earth intermetallics, to break the ferrimagnetic moment configuration in specific 3d-4f intermetallics, to quench the strongly correlated electron states in heavy-fermion compounds, to reach the upper critical fields

J. J. M. Franse; F. R. Deboer; P. H. Frings; A. Devisser

1994-01-01

50

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

Microsoft Academic Search

Magnetic fields have a large impact on the magnetic and superconducting properties of solids. High magnetic fields are required to reach magnetic saturation along a hard magnetic direction in a variety of rare-earth intermetallics, to break the ferrimagnetic moment configuration in specific 3d-4f intermetallics, to quench the strongly correlated electron states in heavy-fermion compounds, to reach the upper critical fields

J. J. M. Franse; F. R. De Boer; P. H. Frings; A. De Visser

1994-01-01

51

Selecting high-temperature structural intermetallic compounds; The materials science approach  

SciTech Connect

Some 300 intermetallic compounds with high melting temperatures are candidate materials for the high-temperature turbines and engines of the future. Before these applications can be realized, however, the limited ductility of intermetallic materials must be overcome. Using melting temperature and density as figures of merit, and considering the effects of composition and crystal structure, the most likely candidates for these high-performance applications are identified in this article.

Fleischer, R.L.; Taub, A.I. (General Electric Co., Schenectady, NY (USA). Corporate Research and Development Center)

1989-09-01

52

Scallop formation and dissolution of Cu-Sn intermetallic compound during solder reflow  

NASA Astrophysics Data System (ADS)

In an effort to elucidate the mechanism of scallop formation during reflow of solder/Cu joints in flip-chip and ball-grid array technologies, a planar intermetallic compound layer (mostly Cu6Sn5) was initially formed by solid-state annealing of SnPb/Cu joints at 150 °C for ten days. Upon subsequent reflow, dissolution of the intermetallics and formation of scallops were observed. Detailed investigation has indicated that a thermal grooving process due to dissolution of the intermetallic compound during the initial reflow cycles contributes to the formation of scalloped structures, the morphology of which is dictated by the force equilibrium condition. Upon subjecting the solder joints to several reflows, the average intermetallic layer thickness was found to first decrease and then increase, which is shown to be in good agreement with the prediction made by a model based on simultaneous dissolution and growth of the intermetallic compound during reflow. The kinetics of dissolution-growth process during reflow has also been shown to depend on the initial intermetallic thickness and the shape of the solder cap.

Ma, D.; Wang, W. D.; Lahiri, S. K.

2002-03-01

53

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

Microsoft Academic Search

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

Z. D. Zhang

54

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

National Technical Information Service (NTIS)

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). Thes...

B. A. Cook J. L. Harringa Z. S. Tan W. A. Jesser

1996-01-01

55

Electronic structure and magnetic properties of the cubic Laves-phase intermetallic compounds  

NASA Astrophysics Data System (ADS)

Electronic structures of d-electrons in intermetallic compounds NbCo 2 and TaCo 2 with the cubic Laves-Phase structure are calculated in the tight-binding approximation. By using the calculated density of states curve and taking into account the effect of spin fluctuations, the temperature dependence of spin susceptibility in these compounds is calculated.

Yamada, H.; Inoue, J.; Shimizu, M.

1986-02-01

56

Calorimetric Study of the Intermetallic Compounds Ual sub 2 and Pual sub 2 .  

National Technical Information Service (NTIS)

Results of low temperature specific heat measurements are presented on the strongly paramagnetic intermetallic compounds UAl sub 2 and PuAl sub 2 in the temperature intervals 0.9 to 20 exp 0 K, respectively. These compounds are characterized by very narro...

R. J. Trainor M. B. Brodsky G. S. Knapp

1975-01-01

57

Characterization of intermetallic compounds in Cu-Al ball bonds: Mechanical properties, delamination strength and thermal conductivity  

Microsoft Academic Search

In high power automotive electronics copper wire bonding is regarded as most promising alternative for gold wire bonding in 1st level interconnects and therefore subjected to severe functional requirements. In the Cu-Al ball bond interface the growth of intermetallic compounds may deteriorate the electrical, thermal and mechanical properties. The layer growth and properties of these intermetallic compounds are crucial in

M. H. M. Kouters; G. H. M. Gubbels; C. A. Yuan

2012-01-01

58

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

59

Formation and nitridation of vanadium-aluminum intermetallic compounds.  

PubMed

V(5)Al(8) and V(3)Al intermetallics have been formed by interdiffusion, by annealing of sputtered V/Al-multilayers at 700 degrees C in vacuo; sapphire (102) was used as substrate. The V/Al intermetallics were nitridated in NH(3) at 900 degrees C for 1 min by RTP (rapid thermal processing). The samples were investigated with XRD (X-ray diffraction), SNMS (secondary neutral mass spectrometry), and AFM (atomic force microscopy). A 5-10 nm thick AlN film (001 textured) was formed by nitridation of V(5)Al(8) (110 textured) and 2-3% nitrogen was incorporated in the V(5)Al(8) bulk. Nitridation of V(3)Al resulted in the formation of VN and AlN. Direct nitridation of V/Al-multilayers showed that near the surface nitridation is faster than intermixing of the V and Al layers. The capability of VN as diffusion barrier for Al could also be shown. PMID:12397502

Lewalter, H; Bock, W; Kolbesen, B O

2002-10-01

60

Direct determination of cobalt site preferences at infinite dilution in iron-based intermetallic compounds (invited)  

SciTech Connect

Extremely low doping levels ({similar to}1 ppm) and unambiguous interpretation combine to make the Moessbauer-source technique an ideal method for determining cobalt site preferences in intermetallic compounds. Data on Gd{sub 2}Fe{sub 17} and Nd{sub 2}Fe{sub 14}B are presented and compared with earlier work using Moessbauer spectroscopy, NMR, and neutron diffraction.

Ryan, D.H.; Altounian, Z.; Liao, L.X.; Stroem-Olsen, J.O.; Muir, W.B. (Department of Physics, McGill University, 3600 University Street, Montreal, Quebec H3A 2T8, Canada (CA))

1990-05-01

61

Evaluation of Gibbs free energies of formation of Ce-Cd intermetallic compounds using electrochemical techniques  

NASA Astrophysics Data System (ADS)

Gibbs free energies of formation of six Ce-Cd intermetallic compounds, CeCd, CeCd2, CeCd3, CeCd58/13, CeCd6 and CeCd11, were evaluated systematically using electrochemical techniques in the temperature range of 673-923 K in the LiCl-KCl-CeCl3-CdCl2 molten salt bath. The linear dependence of the Gibbs free energies of formation on temperature yields to the enthalpies and entropies of formation of these intermetallic compounds. By extrapolating the Gibbs free energy of Ce-Cd intermetallic compounds to the Cd distillation temperature, it was clear that the Gibbs free energy of Ce-Cd intermetallic compounds decreases gradually from CeCd6 to CeCd2 and attains minimum value at CeCd2. This suggests on the Cd distillation from the U-Pu-Ce-Cd alloy that the dissolution of U or Pu into CeCd2 should be mostly taken into consideration.

Shibata, Hiroki; Hayashi, Hirokazu; Akabori, Mitsuo; Arai, Yasuo; Kurata, Masaki

2014-08-01

62

Characterization of intermetallic compound (IMC) growth in Cu wire ball bonding on Al pad metallization  

Microsoft Academic Search

As one of the alternative materials in chip interconnection, copper wire has become popular because of its lower cost and higher electrical conductivity than gold wire. Moreover it is known that long term reliability performance at high temperature of copper wire is better than that of gold wire because of slower Cu\\/Al intermetallic compound (IMC) growth than that of Au\\/Al

SeokHo Na; TaeKyeong Hwang; JinYoung Kim; HeeYeoul Yoo; ChoonHeung Lee

2011-01-01

63

Crystal growth and high-temperature properties of intermetallic compound nickel aluminide  

Microsoft Academic Search

Investigations have been performed to the studying single crystal growth mechanism of intermetallic compound Ni3Al and to understand its mechanical behavior in single crystal and polycrystalline form at elevated temperatures under an oxidizing environment. Two crystal growth techniques, electron beam zone melting and Bridgman method, are combined together to grow single crystals in this work. The effects of the concentration

Zhigang Xiao

1999-01-01

64

Crystal growth of rare earth–iron intermetallic compounds by the flux-creep-up method  

Microsoft Academic Search

A new flux method for the crystal growth of rare earth–iron intermetallic compounds was developed. In this method, the rare-earth flux creeps up the inner surface of a BN-coated crucible during the cooling process, and free-standing crystals are left on the bottom of the crucible. This method was applied to the crystal growth of compounds in Sm–Fe and Nd–Fe systems,

H. Samata; K Sakamoto; S Yashiro; Y Nagata

2001-01-01

65

Structural building principles of complex face-centered cubic intermetallics.  

PubMed

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

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

2011-08-01

66

Magnetic and Electrical Properties of U-Ge Intermetallic Compounds  

Microsoft Academic Search

We have clarified the magnetic and electrical properties of U7Ge, U5Ge3, U3Ge4 and UGe2, measuring the electrical resistivity, thermoelectric power, Hall coefficient, magnetic susceptibility, magnetization and specific heat. U7Ge and U5Ge3, which are Pauli paramagnetic compounds, become superconductive below 1.40 K and 0.99 K, respectively. The latter compounds U3Ge4 and UGe2 indicate ferromagnetism. Anisotropic properties of UGe2 are well reflected

Yoshichika Onuki; Isamu Ukon; Sung Won Yun; Izuru Umehara; Kazuhiko Satoh; Tadashi Fukuhara; Hideyuki Sato; Shigeru Takayanagi; Mikio Shikama; Akira Ochiai

1992-01-01

67

Intermetallic compound layer growth kinetics in non-lead bearing solders  

SciTech Connect

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

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

1995-04-01

68

Phase transformations during electrochemical incorporation of lithium in intermetallic compounds of aluminum  

Microsoft Academic Search

Comparative study of the regularities of the reaction and specific features of phase formation during electrochemical incorporation\\u000a of lithium from propylene carbonate solutions in intermetallic aluminum-based compounds (CuAl2, Mg2Al3, and NiAl) and pure metals (Al, Cu, Mg, and Ni) was performed. The initial stage of the process was shown to be dissolution\\u000a of lithium in the solid phase limited by

V. V. Ozeryanskaya; V. E. Guterman; I. L. Shukaev; V. P. Grigor'ev

1998-01-01

69

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 450°C, with postannealing at 450°C 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

70

Effect of intermetallic compounds on the thermal fatigue of surface mount solder joints  

Microsoft Academic Search

The effect of Cu-Sn intermetallic compounds (IMC) on the fatigue failure of solder joints during thermal cycling has been studied. The samples consist of components [leadless ceramic chip carrier (LCCC)] soldered onto FR-4 printed circuit board (PCB), and are prepared by conventional reflow soldering using a 63Sn-37Pb solder paste. The specimens are subjected to thermal cycling between -35°C and 125°C

P. L. Tu; Yan C. Chan; J. K. L. Lai

1997-01-01

71

Percolation model for elastic softening in intermetallic compounds during solid-state amorphization  

NASA Astrophysics Data System (ADS)

By using isobaric-isothermal molecular dynamics and an n-body effective potential, we show that the amorphization of NiZr2, mediated by chemical disorder, is preceded by an elastic softening and begins at the percolation threshold of the strain distortion regions associated with the antisite defects. The percolation model provides a unified description of the elastic softening and loss of crystalline order in intermetallic compounds resulting from irradiation or hydrogenation.

Massobrio, C.; Pontikis, V.

1992-02-01

72

Fabrication of NiTi intermetallic compound by a reactive gas laser atomization process  

Microsoft Academic Search

We attempted to synthesize NiTi intermetallic compound from two types of stranded wires, pure Ti wire (with a diameter of 300 ?m) and pure Ni wire (with diameters of 300 and 250 ?m). The stranded wire was melted and reacted using a laser, and the melted metal was gas-atomized using high-pressure Ar gas or coated on an aluminum base material.

Hiroshi Tomochika; Hiroyuki Kikuchi; Takao Araki; Minoru Nishida

2003-01-01

73

Phase selection of ternary intermetallic compounds during solidification of high zinc magnesium alloy  

Microsoft Academic Search

The phase selection of ternary intermetallic compound ? phase (Mg32(Al, Zn)49) and ? phase (Al2Mg5Zn2) in high zinc magnesium alloys was studied by using scanning electron microscope, X-ray diffractometer and differential scanning calorimeter, etc. The results indicate that, when adding element Si in Mg-8Zn-4Al-0.3Mn (ZA84) alloy, ? phase is promoted, whereas ? phase is inhibited. The Chinese script-type Mg2Si and

Shao-kang GUAN; Chun-xiang ZHANG; Li-guo WANG; Li-hong WU; Pei-lei CHEN; Ya-li TANG

2008-01-01

74

Topological fingerprints for intermetallic compounds for the automated classification of atomistic simulation data  

NASA Astrophysics Data System (ADS)

We introduce a method to determine intermetallic crystal phases by creating topological fingerprints using coordination polyhedra. Many intermetallic crystal phases have complex structures that cannot be determined from the information of their nearest neighbour environment alone, but need information from a further reaching local environment. We obtain the coordination polyhedra of each atom in the structure and use this information in a topological fingerprint to determine the crystal phases in the structure as locally as possible. This allows us to analyse complex crystal phases like the topologically close-packed phases and multi-phase structures. With the information extracted from the coordination polyhedra and topological fingerprint, it is also possible to find and identify point and extended defects. Therefore, our method is able to track interface regions in multi-phase structures, and follow structural changes during phase transformations.

Schablitzki, T.; Rogal, J.; Drautz, R.

2013-10-01

75

New intermetallic compounds in the Ce–Pt system  

Microsoft Academic Search

The Ce-rich part of Ce–Pt phase diagram has been investigated by means of differential thermal analysis (DTA), X-ray diffraction\\u000a (XRD), optical and electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Two new intermediate phases, Ce5Pt3 and Ce5Pt4, have been discovered and found to crystallize with tetragonal Pu5Pd3-type structure and orthorhombic Ge4Sm5-type structure, respectively. All the Ce-rich compounds of the

A. Janghorban; M. Lomello-Tafin; J. M. Moreau; Ph. Galez

2011-01-01

76

Neutron Scattering Study of TbPtin Intermetallic Compound  

SciTech Connect

Neutron diffraction techniques have been used to study the magnetic properties of a TbPtIn single-crystal as a function of temperature and magnetic field. In the absence of an externally applied magnetic field, the compound orders, below approximately 47 K, in an antiferromagnetic structure with propagation vector k=(1/2,0,1/2); the magnetic moments were found to be parallel to the [1 {ovr 2} 0] direction. Measurements at 4.2 K, with a magnetic field applied along the [1 {ovr 2} 0] direction, revealed metamagnetic transitions at approximately 20 kG and 40 kG.

Garlea, Vasile O [ORNL; Morosan, E. [Ames Laboratory; Bud'ko, S. L. [Ames Laboratory; Zarestky, Jerel L [ORNL; Canfield, P. C. [Ames Laboratory; Stassis, C. [Ames Laboratory

2005-01-01

77

Dual nature of electron spin resonance in YbCo2Zn20 intermetallic compound  

NASA Astrophysics Data System (ADS)

In single crystals of YbCo2Zn20 intermetallic compound, two coexisting types of electron spin resonance signals related to the localized magnetic moments of cobalt and to itinerant electrons have been observed in the 4.2-300 K temperature range. It is shown that the relative contribution of itinerant electrons to the total magnetization does not exceed 9%. We argue that the electron dynamics in YbCo2Zn20 and YbCuAl heavy fermion systems is determined by the effects produced by the magnetic subsystem of the localized 3 d-electrons. We also discuss general aspects of the electron spin resonance spectroscopy in underdoped ytterbium-based intermetallics and the spectral manifestations of the interplay between the efficiency of the hybridization of f-electrons with the electrons filling outer atomic shells, crystal field effects, and the effects related to the proximity to the quantum critical point.

Ivanshin, V. A.; Litvinova, T. O.; Sukhanov, A. A.; Ivanshin, N. A.; Jia, S.; Bud'ko, S. L.; Canfield, P. C.

2014-04-01

78

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.; Arróyave, R.

2014-07-01

79

Research on Fabrication and Tribological Properties of Ti-Al Intermetallic Compound Lubricate Film  

Microsoft Academic Search

\\u000a Ti-Al intermetallic compound solid lubricate films were fabricated on substrates of stainless steel by double-target reactive\\u000a magnetron sputtering. Chemical composition of the films ranged from 43.20 to 67.89at%Al by changing the relative position\\u000a of substrates to the targets. According to Ti-Al equilibrium diagram, the influence of chemical composition of films on friction\\u000a coefficient was studied by EDS, SEM and friction

Zhang Ye; Li Changsheng; Tian Mingxia

80

Nd 3+:YAG laser interaction with intermetallic compounds Hf 2Rh and Hf 2Co  

NASA Astrophysics Data System (ADS)

The results of an investigation of Nd 3+:YAG laser interaction with the intermetallic compounds Hf 2Rh and Hf 2Co are presented. The analytical expression for the laser pulse power is determined. Reflection spectra over a wide infrared region are measured to obtain the principal mechanism of absorption. The samples and the laser damage are investigated by the Taylor-Hobson Talysurf with a diamond needle for roughness measurements, optical microscope, scanning electron microscope (SEM) and electron microprobe analyses, and the results obtained are presented and discussed. Attention is paid to the validity of some principal relations characterizing the evaluation of the interaction.

Ivanovi?, N.; Sre?kovi?, M.; Milosavljevi?, A.; Ceki?, B.; Manasijevi?, M.; Popovi?, N.; Backovi?, N.; Djuri?, M.; Kunosi?, A.; Nemeš, K.; C?oguri?, G.; Mio?, U.

1993-12-01

81

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

82

Effects of intermetallic compounds on properties of Sn–Ag–Cu lead-free soldered joints  

Microsoft Academic Search

The effects of alloy composition on microstructural, especially the formation of large intermetallic compounds, and mechanical properties of various Sn–Ag–Cu solder joints were investigated. The range of Ag–Cu content of Sn–Ag–Cu alloys was from 3.0 wt.%Ag–0.5 wt.%Cu to 3.9Ag–0.7 wt.%Cu. The high Ag content alloys exhibit the formation of large Ag3Sn platelets especially at the solder–reaction layer interfaces, regardless of

K. S. Kim; S. H. Huh; K. Suganuma

2003-01-01

83

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.; Arróyave, R.

2014-04-01

84

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

85

Volume Change due to Intermetallic Compound Formation at the Al-Au Bond in Semiconductor Devices  

NASA Astrophysics Data System (ADS)

The molar volume of an Al-Au intermetallic compound was calculated and compared with those of Al and Au individually. It is well known that, though the molar volume of an AlAu4 compound is smaller than the sum of those of Al and Au, it is larger than that of Al. It is shown that this fact can be explained by taking into consideration the differences between the densities of Al, Au and Al-Au alloys and the component ratio of the compound. Practically, it is pointed out that this volume effect can induce pores at an imperfect bond between Al films and Au wires in Si devices. This suggests that such partial openings should be distinguished from Kirkendall voids.

Kato, Hiroshi

1986-06-01

86

In search of the elusive amalgam SrHg8: a mercury-rich intermetallic compound with augmented pentagonal prisms.  

PubMed

In confirmation of its predicted existence in the Sr-Hg phase diagram, the mercury-rich intermetallic compound SrHg(8) has been prepared by reaction of the elements at 200 degrees C. Single-crystal X-ray diffraction analysis revealed that it adopts a new structure type (Pearson symbol oP72, space group Pnma, a = 13.328(1) A, b = 4.9128(5) A, c = 26.446(3) A). The Sr atoms are centred within two types of 18-vertex Hg polyhedra formed by augmenting pentagonal prisms with octagonal waists. The condensation of these Sr@Hg(18) clusters is associated with the formation of a complex anionic Hg-Hg bonding network, as supported by electronic structure calculations which reveal strong mixing of Hg 6s and 6p states in highly delocalized bands superimposed with a narrower 5d band below the Fermi level. PMID:20544111

Tkachuk, Andriy V; Mar, Arthur

2010-08-14

87

Thermodynamics of hydrogen trapping in intermetallic compounds: application to LaNi/sub 5//H  

SciTech Connect

It has been observed for several intermetallic compound/H systems that deviations from Sieverts' law of ideal solubility occur which are in the opposite direction from the deviations from ideality which occur in pure metal/H systems. The principal source of nonideality on both types of interstitial solutions arises from the changes of the relative partial molar enthalpy of H/sub 2/ solution, ..delta..H/sub H/, with H content. The variations of ..delta..H/sub H/ with H content are, however, in the opposite directions for intermetallic/H and pure metal/H interstitial solutions. Relative partial molar entropies for solution of H/sub 2/ in the ..cap alpha..-phase of the LaNi/sub 5//H system are given at 298.2/sup 0/K. These have been determined from calorimetric determinations of ..delta..H/sub H/ and measurements of ..delta..G/sub H/ (=RT ln P/sub H/sub 2///sup 1/2/). The partial entropies show unusual extrema as a function of H content. A model based on trapping of H atoms is proposed which explains the variations of ..delta..H/sub H/ and ..delta..S/sub H/. Since the deviations from ideality arising from an increase of ..delta..H/sub H/ with H content seem to be limited to solids with at least two different ordered metal components, e.g., intermetallic compounds, it seems reasonable to assign the trapping sites to interstices which result from an interchange of metal atoms. This interchange may create interstices rich in those nearest-neighbor metal atoms which have the greatest affinity for H.

Flanagan, T.B.; Wulff, C.A.; Bowerman, B.S.

1980-09-01

88

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

89

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

90

Lattice dynamics of the mixed-conducting intermetallic compound alpha-LiAl  

NASA Astrophysics Data System (ADS)

The intermetallic compound, (ALPHA)-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 compounds. In order to elucidate the nature of the bonding in LiAl, the lattice dynamics of (ALPHA)-LiAl by inelastic neutron scattering was studied. Results for the phonon dispersion curves were 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

91

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

92

Electronic properties of Sn/Pd intermetallic compounds on Pd(1 1 0)  

NASA Astrophysics Data System (ADS)

We have studied the Sn/Pd(1 1 0) adsorption system by synchrotron radiation photoelectron spectroscopy and low-energy electron diffraction (LEED). For room temperature evaporation, two surface reconstructions were observed: c(2 × 2) and (3 × 1), corresponding to about 0.5 ML and 0.75 ML of Sn adlayer coverage. The Pd 3d and Sn 4d core levels as well as valence band spectra indicate a strong chemical interaction between Sn and Pd, and the formation of an intermetallic interface. Structural models are proposed for both of these phases based on the photoemission and CO adsorption results. We show that at coverage higher than 0.7 ML, tin is alloyed with the Pd crystal forming a subsurface layer of Pd-Sn intermetallic compound of stoichiometry which varies with tin coverage. CO adsorption occurs only at low temperature (120 K) and depends on the Sn coverage and reconstruction of the Pd(1 1 0) surface. We estimate the CO adsorption energy for the c(2 × 2)- and (3 × 1)-Sn/Pd(1 1 0) surfaces to be reduced by 40% compared to the clean palladium (1 1 0) surface.

Tsud, N.; Skála, T.; Šutara, F.; Veltruská, K.; Dudr, V.; Fabík, S.; Sedlá?ek, L.; Cháb, V.; Prince, K. C.; Matolín, V.

2005-12-01

93

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

94

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

95

Intermetallic compounds for strong high-temperature materials; Status and potential  

SciTech Connect

Materials of high strength have long been sought, but various needs - particularly those for aerospace applications - have added new dimensions: First, for use in aircraft and spacecraft parts of the least weight to do a given job are desired, i.e. materials of high specific strength (strength per unit density) or high specific stiffness (elastic modulus per unit density). Second, for inherently hot parts such as propulsion systems and their housings, strength and weight at elevated temperature are critical. The efficiency and total thrust of a jet engine increase with the peak temperature of the working fluid, and current limits are set by thermal constraints on materials. This paper reports that there are three features of the high- temperature intermetallics that give promise for better materials. First, many unexplored materials are available - about 400 binary compounds that melt above 1400{degrees}C. Second, the strong unlike-neighbor bonding that is responsible for ordering gives rise to high elastic moduli, and high moduli also imply high strength. Finally, some intermetallics have increasing strength with temperature (d{sigma}/dT {gt} 0) over a significant range. This behavior was first seen in Ni{sub 3}Al, later in other compounds of the same Ll{sub 2} structure, in B2 and DO3 (cubic) compounds, and in tetragonal Be{sub 12}Nb(D2{sub b}), and TiAl (Ll{sub 0}). This property of d{sigma}/dT {gt} 0 is of obvious use in giving high strength at elevated temperature; it is equally important in not giving very high strength at low temperatures and thereby diminishing the chances of brittle failure at ambient temperatures.

Fleischer, R.L. (General Electric Research and Development Center, Schenectady, NY (US)); Dimiduk, D.M. (Wright-Patterson Air Force Base, OH (US)); Lipsitt, H.A. (Wright State Univ., Dayton, OH (US))

1989-01-01

96

Crystalline intermetallic compounds in the K-Te system: The Zintl-Klemm principle revisited  

NASA Astrophysics Data System (ADS)

We have investigated the crystal structure, chemical bonding, and electronic properties of all known intermetallic compounds in the K-Te system, employing a first-principles local-density-functional approach including generalized gradient corrections. The structural parameters, such as equilibrium volume, lattice constants, and internal parameters are in very good agreement with experiment. The evaluation of the total and angular-momentum decomposed densities of states (DOS) and the partial charge densities gives further insight into the bonding properties of these solids. Our results confirm the validity of the Zintl-Klemm principle for the saltlike compound K2Te and for the two equiatomic phases ?-K2Te2 and ?-K2Te2 consisting of isolated K ions and covalently bounded Te2 dimers. In the compound K5Te3 ionic regions consisting of K+ and Te2- ions with closed octet shells and polyanionic regions with an atomic arrangement dominated by Te2-2 dianions coexist in the crystal lattice. In the electron-deficient-compound K2Te3, larger polyanions-Te2-3 trimers-have to be formed to achieve saturated covalent bonds. Our results illustrate the validity and astonishing flexibility of the Zintl-Klemm principle, which allows us to interpret all crystal structures in the K-Te system, from the saltlike octet compound to the Te-rich phases with extended polyanionic superstructures, on a common footing.

Seifert-Lorenz, Karin; Hafner, Jürgen

2002-09-01

97

Study of the Kinetics of Segregation of Gaseous Impurities Along the Grain Boundaries of the Intermetallic Compounds.  

National Technical Information Service (NTIS)

Gas analyses were performed on the intermetallic compounds Cu4Si, Cu5Si, and Ni3Sn2 after they had been melted under various atmospheres. Specimens were either vacuum melted, air melted, or under an air atmosphere containing water vapor. Gas analyses were...

D. P. Shashkov

1980-01-01

98

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

99

Tsuyoi Denshi Sokan O Yusuru Kinzokukan Kagobutsu No Gosei to Bussei Ni Kansuru Kenkyu (Study on Synthesis and Characteristics of Intermetallic Compound with Strong Electron Correlation).  

National Technical Information Service (NTIS)

Research was made on electronic structures of intermetallic compounds containing Ce and U with strong electron correlation. At the same time, thin films were prepared from such compounds to investigate the characteristic changes and new phenomena deriving...

H. Aoki S. Uji M. Yata K. Nakamura

1993-01-01

100

Antiferromagnetic ordering on the frustrated fcc lattice in the intermetallic compound GdPtBi  

NASA Astrophysics Data System (ADS)

The type of antiferromagnetic magnetic order in the half-Heusler intermetallic compound GdPtBi, where the Gd atoms form a magnetically frustrated fcc lattice, has been investigated using exchange constants calculated from first principles within the framework of the Green's function based magnetic force theorem. It is found that the degeneracy of the magnetic states on the fcc lattice with antiferromagnetic nearest neighbor interaction is removed by strong fourth-nearest neighbor interaction along the cube diagonal. We show that an antiferromagnetic ordering of so-called “third kind” occurs at low temperatures. The Monte Carlo simulations using our derived exchange constants predict an experimental Néel temperature (TN) with good accuracy. The estimated temperature dependence of the correlation functions in the paramagnetic region exhibit a typical behavior for a frustrated system—a massive short-range order is retained for temperatures which are one order of magnitude higher than TN.

Khmelevskyi, Sergii

2012-09-01

101

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

102

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

103

Electronic structure and plasticity anomalies of the intermetallic compound Co3Ti  

NASA Astrophysics Data System (ADS)

In order to explain the physical causes of the mechanical anomalies of the intermetallic compound Co3Ti we theoretically determine the dependence of the stacking-fault energy on the composition. The problem of evaluating that energy for Co3Ti is reduced to a problem of examining the difference of the specific energies of close-packed disordered phases of Co-Ti alloys in the ground state. The energies are calculated within the framework of a model based on the locator method of the electron theory of alloys. The stacking-fault energy is found to become zero in the direct vicinity of the Co3Ti composition. The possibility that alloying may have an effective influence on that quantity is demonstrated. The density of d states and the enthalpy of formation of Co-Ti alloys are calculated.

Skorentsev, L. F.; Simakov, V. I.; Demidenko, V. S.

1996-06-01

104

High-Temperature Resistant Intermetallic Compound Joints for Si Chips and Cu Substrates  

NASA Astrophysics Data System (ADS)

A thin-film joining method utilizing evaporated films as the joining material was newly developed for power semiconductor die attachment. When the evaporated films are completely transformed into intermetallic compounds (IMCs) with high melting points, the joint can exhibit the required high-temperature strength. In this study, a joint consisting of Cu6Sn5, (Ag,Cu)3Sn, and Cu3Sn IMCs was achieved at 573 K after 30 s. Results of nanoindentation tests revealed the hardness and elastic moduli of each IMC. In accelerated tests, a high-temperature strength of at least 15 MPa was shown for 3.6 Ms at 423 K or 500 cycles between 223 K and 403 K. These results suggest that the IMC joint has great potential as a die-attach material.

Takahashi, Toshihide; Komatsu, Shuichi; Nishikawa, Hiroshi; Takemoto, Tadashi

2010-10-01

105

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

106

Effects of the synthesis of intermetallic compounds on the growth and consolidation of detonation diamond nanocrystals  

NASA Astrophysics Data System (ADS)

The synthesis of intermetallic compounds belonging to the nickel-aluminum system in the presence of detonation nanodiamond (DND) particles leads to a significant change in the structure of consolidated nanocrystals. The broadening of (111), (220), and (311) X-ray diffraction reflections usually decreases by an order of magnitude, which indicates that the size of nanocrystals increases in approximately the same proportion. This effect significantly depends on the state of the surface of diamond nanoparticles. The X-ray data suggest that aluminum present in the initial metal-diamond mixture actively interacts with oxygen adsorbed on the surface of particles, which leads to the formation of Al2O3 oxide. The interaction between particles via cleaned interfaces at high temperatures leads to the activation of recrystallization processes.

Plotnikov, V. A.; Dem'yanov, B. F.; Makarov, S. V.

2009-10-01

107

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 400°C. 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

108

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

109

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

110

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

111

Polyanionic and octet phases in the K-Sb system. I. Crystalline intermetallic compounds  

NASA Astrophysics Data System (ADS)

The crystal structure, chemical bonding, and electronic properties of intermetallic compounds in the K-Sb system have been investigated using first-principle-local-density-functional calculations including generalized gradient corrections. It is shown that the chemical bonding obeys a generalized Zintl principle, i.e., a formally complete electron transfer from K to Sb. The stable crystal structure is determined for the stoichiometric octet compound K3Sb by the formation of an ionic lattice and at the equiatomic composition by the formation of covalently bonded Sb-? helices in close analogy to the isoelectronic chalcogen elements. At intermediate compositions the Sb atoms cluster together to form chainlike polyanion radicals, the electrons provided by the excess alkali metal serving to partially saturate the dangling bonds at the chain ends. It is demonstrated that density-functional theory describes the crystal structure of all compounds with high accuracy. The overbinding characteristic of the local-density approximation is most pronounced in the alkali-rich limit, but merely causes a scaling of all interatomic distances without distorting the structure. Gradient corrections substantially improve the prediction at large K content, but tend to overshoot in the Sb-rich range.

Seifert-Lorenz, K.; Hafner, J.

1999-01-01

112

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

SciTech Connect

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

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

1999-12-16

113

Magnetocaloric effects in RNiIn (R = Gd-Er) intermetallic compounds  

NASA Astrophysics Data System (ADS)

Magnetic properties and magnetocaloric effects (MCEs) of the intermetallic RNiIn (R = Gd-Er) compounds have been investigated in detail. GdNiIn and ErNiIn compounds exhibit a ferromagnetic (FM) to paramagnetic (PM) transition around the respective Curie temperatures. However, it is found that RNiIn with R = Tb, Dy, and Ho undergo two successive magnetic phase transitions with increasing temperature. In addition, a field-induced metamagnetic transition from antiferromagnetic (AFM) to FM states is observed in RNiIn with R = Tb and Dy below their respective AFM-FM transition temperatures (Tt). The maximal values of magnetic entropy change (?SM) of HoNiIn are -9.5 J/kg K at Tt = 7 K and -21.7 J/kg K at TC = 20 K for a magnetic field change of 5 T, respectively. These two successive ?SM peaks overlap partly, giving rise to a high value of refrigerant capacity (RC = 341 J/kg at 5 T) over a wide temperature span. It is noted that the RC value of GdNiIn is as high as 326 J/kg due to the relatively broad distribution of ?SM peak. Consequently, this RNiIn system shows large reversible ?SM and considerable RC values in the temperature range of 10-100 K.

Zhang, H.; Xu, Z. Y.; Zheng, X. Q.; Shen, J.; Hu, F. X.; Sun, J. R.; Shen, B. G.

2011-06-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

115

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

116

Crystal growth of rare earth iron intermetallic compounds by the flux-creep-up method  

NASA Astrophysics Data System (ADS)

A new flux method for the crystal growth of rare earth-iron intermetallic compounds was developed. In this method, the rare-earth flux creeps up the inner surface of a BN-coated crucible during the cooling process, and free-standing crystals are left on the bottom of the crucible. This method was applied to the crystal growth of compounds in Sm-Fe and Nd-Fe systems, and crystals of SmFe 2, SmFe 3, Sm 6Fe 23, and Nd 6Fe 13- xAl 1+ x were grown for the first time. In particular, SmFe 7 is a new phase in the Sm-Fe system with high performance as a permanent magnet. Since the chemical composition of the mixture in the crucible changes in accordance with the creep-up of the flux, this method may be promising in the search for new phases as well as for the crystal growth of known materials.

Samata, H.; Sakamoto, K.; Yashiro, S.; Nagata, Y.

2001-07-01

117

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

118

Preparation of Ta 2Al intermetallic compound films and their application as diffusion barriers to Cu penetration  

Microsoft Academic Search

The thermal stability of the CuTa2AlTaSi contact system, in which the intermetallic compound film of Ta2Al is used as a diffusion barrier to copper penetration, has been studied using Auger electron spectroscopy analysis. Although the examined contact system degrades by the interfacial reaction of silicide formation at the TaSi interface due to annealing, the system tolerates annealing at 650 °C

Akira Ohta; Atsushi Noya; Mayumi Takeyama; Masahiro Taguchi; Touko Sase; Katsutaka Sasaki

1996-01-01

119

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

120

Neutron diffraction study of the magnetic structure of the intermetallic compound DyRh2Si2  

Microsoft Academic Search

A study of the magnetic structure of the intermetallic compound DyRh2Si2 (I4\\/mmm) was performed using neutron (2.459 A?) diffraction of a powder sample. Below 52 K the diffraction patterns reveal a type I antiferromagnetic structure on the Dy sublattice, with a magnetic moment of 9.9±1 ?B per ion along c. The appearance of a weak 001 reflection below 18 K

M. Melamud; H. Pinto; I. Felner; H. Shaked

1984-01-01

121

Effects of bulk Cu6Sn5 intermetallic compounds on the properties of Sn-Ag-Cu-Ce soldered joints  

Microsoft Academic Search

Purpose – The purpose of this paper is to explore the formation and growth mechanism of bulk Cu6Sn5 intermetallic compounds, selecting Sn-Ag-Cu-Ce solders as specimens. Design\\/methodology\\/approach – In order to further enhance the properties of SnAgCu solder, trace amount of rare earth Ce was selected as alloying addition into the alloy; in previous investigations, the enhancements include better wettability, physical

Liang Zhang; Song-bai Xue; Li-li Gao; Zhong Sheng; Wei Dai; Feng Ji; Huan Ye; Yan Chen; Sheng-lin Yu

2011-01-01

122

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

123

Synthesis of NiAl Intermetallic Compound Nanosized Powders by Pulsed Wire Discharge  

NASA Astrophysics Data System (ADS)

NiAl nanosized powders were synthesized by pulsed wire discharge (PWD) using twisted Ni and Al wires with various number of turns (Nt). The X-ray diffraction (XRD) patterns indicated that the optimum conditions for synthesized NiAl nanosized powders were usage of a twisted Ni and Al wire with 0.4 turn/mm discharged in N2 gas. For clarifying the dependence of Nt on the powder purity, waveforms of current, voltage and deposited energy during the discharges were measured. From the waveforms, deposited energy ratio until a voltage peak (Kp), which is an index to evaluate volume fraction of evaporated wire, was calculated. In low Kp conditions, nanoparticles with low composition ratio of Ni(CNi) and large particles with high CNi were frequently observed. This result indicated that the Ni wire had a high boiling point than that of Al so that unevaporated Ni remained as large liquid droplets in the discharge. Decrease of Kp was thought that the increase of Nt introduced lattice defects by plastic deformation to increase the resistance and to evaporate the wire partially. From the results above, a method to synthesize NiAl intermetallic compound nanosized powders by PWD was successfully developed using Ni and Al twisted wires. In addition, Kp turned out to be important in synthesizing single-phase nanosized powders.

Koishi, Tetsuya; Ishihara, Satoru; Suzuki, Tsuneo; Nakayama, Tadachika; Suematsu, Hisayuki; Niihara, Koichi

2012-06-01

124

Investigations of Zr-Ni intermetallic compounds by perturbed angular correlations  

NASA Astrophysics Data System (ADS)

The hyperfine interactions experienced by 181Ta in ZrNi5 and Zr2Ni7 intermetallic compounds have been investigated by the perturbed angular correlation (PAC) technique. In ZrNi5, a strong electric quadrupole interaction (˜40%) with ?Q=72.0(1) Mrad/s, ?=0.25(1), ?=0 at room temperature has been found due to the presence of Zr2Ni7 contaminating phase produced during sample preparation in the arc furnace. A weak quadrupole interaction of Zr2Ni7 (˜5%) with ?Q=65(1) Mrad/s, ?=0.24(6), ?=0 has also been observed. The cubic component of ZrNi5 also has been observed (˜40% at room temperature) in this sample along with associated defect (15%). It is found that at 873 K, the cubic fraction increases to ˜54% at the cost of its defect fraction. No magnetic interaction in ZrNi5 has been observed which supports the earlier PAC results but rules out the result of strong magnetic ordering found from magnetization measurement. In Zr2Ni7, two regular fractions corresponding to two different crystallographic sites of Zr have been clearly identified with the parameters ?Q(1)=70.9(1) Mrad/s, ?(1)=0.28(1), ?=1.3(3)% and ?Q(2)=64(1) Mrad/s, ?(2)=0.34(8), ?=0 while contradictory results were reported from previous measurements.

Dey, C. C.

2013-09-01

125

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

SciTech Connect

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

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

1997-12-31

126

Influence of External Strain on the Growth of Interfacial Intermetallic Compounds Between Sn and Cu Substrates  

NASA Astrophysics Data System (ADS)

This study used a four-point bending procedure to investigate the influence of compressive and tensile strain on the growth of an interfacial Cu-Sn intermetallic compound (IMC) layer. The test specimens were prepared by depositing 25 ?m layers of matte or bright tin atop a copper substrate using electroplating. Samples were then placed in a furnace at 200°C, and external bending strain was applied through a strained substrate. Comparisons were made between samples undergoing tensile strain or compressive strain, and those without strain. We observed the influence of strain levels and aging time on the formation of the IMC. Both tensile and compressive strain influenced the formation of the Cu/Sn IMC. In matte tin samples, the IMC thickness increased under compressive strain and decreased under tensile strain. In contrast, in bright tin samples, the IMC thickness increased under both compressive and tensile strained substrate conditions. The growth rate of IMC was faster in strained bright tin samples than in strained matte tin samples. Moreover, the formation of IMC microscopic structures under external strain differed considerably according to the source of tin.

Hu, Tien-Chen; Hsu, Feng-chih; Huang, An-Wen; Lin, Ming-Tzer

2012-12-01

127

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

128

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.

129

Influence of aluminum impurity on the electronic structure and optical properties of the TbNi5 intermetallic compound  

NASA Astrophysics Data System (ADS)

The electronic structure of the TbNi5 - x Al x intermetallic compounds ( x = 0, 1, 2) is calculated in the local electron density approximation with the correction to strong electron correlations in 4 f shell of terbium ions. Spectral properties of these compounds are measured by ellipsometry in a wavelength range of 0.22-16 ?m. Frequency dependences of optical conductivity in the region of interband optical absorption are interpreted based on the results of calculations of electron densities of states. The relaxation and plasma frequencies of conduction electrons are determined.

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

2013-02-01

130

Structural and magnetic characteristics of the intermetallic compounds Ho2Ni17 and Er2Ni17  

Microsoft Academic Search

The intermetallic compounds Ho2Ni17 and Er2Ni17 crystallize in the hexagonal structure of Th2Ni17 with lattice parameters a=8.32 AA, c=8.03 AA and a=8.28 AA, c=8.03 AA respectively. The compounds are ferrimagnetic and the effective magnetic moments per formula unit (fu) determined from the paramagnetic region are mu eff\\/fu=16.51 mu B for Ho2Ni17 and mu eff\\/fu=15.27 mu B for Er2Ni17, very close

I. Pop; M. Andrecut; I. Burda

1993-01-01

131

Atomic jump frequencies in intermetallic compounds studied using perturbed angular correlation of gamma rays  

NASA Astrophysics Data System (ADS)

Atomic jump frequencies were determined in a variety of intermetallic compounds through analysis of nuclear relaxation of spectra measured using the nuclear hyperfine technique, perturbed angular correlation (PAC) of gamma rays. Observed at higher temperatures, this relaxation is attributed to fluctuations in the orientation or magnitude of electric field gradients (EFG) at nuclei of 111In/Cd probe atoms as the atoms make diffusive jumps. Jump frequencies were obtained by fitting dynamically relaxed PAC spectra using either an empirical relaxation function or using ab initio relaxation models created using the program PolyPacFit. Jump frequency activation enthalpies were determined from measurements over a range of temperatures. Diffusion was studied in the following systems: 1) Pseudo-binary alloys having the L12 crystal structure such as In3(La1-xPrx). The goal was to see how jump frequencies were affected by random disorder. 2) The family of layered phases, LanCoIn3n+2 ( n=0,1,2,3…?). The goal was to see how jump frequencies varied with the spacing of Co layers, which were found to block diffusion. 3) Phases having the FeGa3 structure. The goal was to analyze dynamical relaxation for probe atoms having multiple inequivalent jump vectors. 4) Phases having the tetragonal Al4Ba structure. The goal was to search for effects in the PAC spectra caused by fluctuations in magnitudes of EFGs without fluctuations in orientations. Ab initio relaxation models were developed to simulate and fit dynamical relaxation for PAC spectra of FeGa3, and several phases with the Al4Ba structure in order to determine underlying microscopic jump frequencies. In the course of this work, site preferences also were observed for 111In/Cd probe atoms in several FeGa 3 and Al4Ba phases.

Newhouse, Randal Leslie

132

In-situ reactive synthesis of the Ni3Al intermetallic compound and subsequent diffusion bonding with different steels for surface coating  

Microsoft Academic Search

The Ni3Al intermetallic compound has been in situ reaction synthesized from elemental powders to form a surface coating material and then diffusion bonded with three representative steels, i.e. a carbon steel, a stainless steel and a tool steel, in order to improve the high-temperature corrosion and wear resistance of these conventional materials. The as-reaction-formed intermetallic has been found to have

J. Duszczyk; J. Zhou; L. Marvina; L. Z. Zhuang

1999-01-01

133

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 Au–Al 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

134

Characterization of radiation-induced lattice vacancies in intermetallic compounds by means of positron-lifetime studies  

NASA Astrophysics Data System (ADS)

In the present paper a characterization of atomic vacancies in intermetallic compounds is given by means of positron-lifetime measurements after electron irradiation and comparison with the states after preparation, after long-time annealing, or in high-temperature equilibrium. In TiAl, Ti3Al, and Ni3Al no structural vacancies (detection limit CV=10-6) are observed at ambient temperature. This confirms that in these compounds slight deviations from stoichiometry are compensated by antisite atoms. In the Al-poor B2 alloys FeAl and NiAl, on the other hand, remnant vacancies exist due to the high thermal equilibrium vacancy concentrations and their slow diffusivities. The kinetics of vacancy elimination in FeAl and NiAl is discussed. A substantial temperature dependence of the positron lifetime in vacancies is detected in close-packed intermetallics which is attributed to an increased atomic relaxation or partial positron detrapping at high temperatures. In contrast to that, the temperature dependence of the positron lifetime in vacancies is small in the open-structured B2 aluminides. The lifetimes ?f of free delocalized positrons in transition-metal aluminides and in NiZr and NiTi can be correlated to those of the pure components, taking into account the densities of valence electrons. For the positron lifetimes ?1 of vacancies in intermetallic compounds, values of ?1/?f=1.5-1.7 are observed similar as in the pure metals. Annealing studies of B2-FeAl after electron irradiation yield time constants for the disappearance of vacancies identical to those deduced recently for the equilibration of thermal vacancies. In electron-irradiated Ti aluminides annealing processes at 250 K and 450 K are observed where the latter process is tentatively attributed to long-range migration of vacancies.

Würschum, R.; Badura-Gergen, K.; Kümmerle, E. A.; Grupp, C.; Schaefer, H.-E.

1996-07-01

135

Formation of Intermetallic Compound (IMC) in the H13Magnesium Alloy System  

Microsoft Academic Search

This paper documents research undertaken into the soldering of magnesium alloy high pressure die casting (HPDC). It is believed that the formation of intermetallic phases is because of the strong affinity for aluminium which exists in all magnesium alloy to iron which is the major element of all tool steel. Manganese plays an important role in this reaction. However, the

Caixang Tang

136

High Temperature X-Ray Diffraction Investigation of the Tini Intermetallic Compound.  

National Technical Information Service (NTIS)

At an elevated temperature of 1000 degrees C the TiNi intermetallic exists as ordered cesium chloride-B2 type lattice. The ordered structure may be stable or metastable depending upon cooling rate to room temperature. The ordered and disordered structures...

E. J. Planz

1968-01-01

137

Solid state intermetallic compound growth between copper and high temperature, tin-rich solders—part I: Experimental analysis  

Microsoft Academic Search

An experimental study was performed which examined the solid state growth kinetics of the interfacial intermetallic compound\\u000a layers formed between copper and the high temperature, tin-rich solders 96.5Sn-3.5Ag (wt.%) and 95Sn-5Sb. These results were\\u000a compared with baseline data from the 100Sn\\/copper system. Both the 96.5Sn-3.5Ag and 95Sn-5Sb solders exhibited the individual\\u000a Cu3Sn and Cu6Sn5 layers at the interface; the thickness

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

1994-01-01

138

Characterization of High-Temperature Abrasive Wear of Cold-Sprayed FeAl Intermetallic Compound Coating  

Microsoft Academic Search

FeAl intermetallic compound coating was prepared by cold spraying using a mechanically alloyed Fe(Al) alloy powder followed\\u000a by post-spray annealing at 950 °C. The high-temperature abrasive wear test was carried out for the FeAl coating at a temperature\\u000a range from room temperature to 800 °C. The high-temperature abrasive wear of a heat-resistant stainless steel 2520 was performed\\u000a for comparison. It was observed

Chang-Jiu Li; Hong-Tao Wang; Guan-Jun Yang; Chong-Gao Bao

2011-01-01

139

On the Asymmetric Growth Behavior of Intermetallic Compound Layers During Extended Reflow of Sn-Rich Alloy on Cu  

NASA Astrophysics Data System (ADS)

When solder interconnects are fabricated, a Sn-based alloy is melted between two substrates with metallization layers, such as Cu or Ni. From the reaction between Sn and Cu, a Cu6Sn5 intermetallic compound (IMC) layer is formed at the solder/Cu interfaces. The morphology of the IMC layer greatly influences the mechanical behavior of the solder joint. Here, we report on the characterization of a novel, asymmetric growth behavior of IMC layers in Sn-3.9Ag-0.7Cu solder joints, based on gravity-induced spalling of the IMC.

Yazzie, Kyle E.; Topliff, Jonathan; Chawla, Nikhilesh

2012-10-01

140

Structural and magnetic characteristics of the intermetallic compounds Ho2Al17 and Er2Al17  

Microsoft Academic Search

The intermetallic compounds R2Al17 (R=Ho,Er) crystallize in the Th2Zn17-type structure (space group R3m) with the lattice parameters a=8.5064 AA, c=13.0642 AA and a=8.4571 AA, c=13.0027 AA respectively (hexagonal cell). The refinements are based on the space group R3m and converge at the conventional R values: 4.8% for Ho2Al17 and 5.4% for Er2Al17. The magnetic susceptibility measurements show a paramagnetic behaviour

M. Andrecut; I. Pop; I. Burda

1993-01-01

141

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

NASA Astrophysics Data System (ADS)

The intermetallic compounds Mg 2Si, MoSi 2, WSi 2, CrSi 2, NbSi 2, Ti 5Si 3, TiSi 2, ZrSi 2 and Al 3Nb were investigated in a pressure range up to 70 kbar and a temperature range up to 1500°C 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 Mg 2Si to a hexagonal phase was observed at 70 kbar and 450°C. 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) (Mg 2Si) to 3350 (190) (WSi 2) kbar.

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

1995-05-01

142

Dendritic growth kinetics and disorder trapping of the intermetallic compound Ni3Sn under a static magnetic field  

NASA Astrophysics Data System (ADS)

Melts of the intermetallic compound Ni3Sn were undercooled using the glass fluxing technique with and without imposition of a static magnetic field of 1 T. Dendritic growth velocities in the undercooled melts were measured by in-situ monitoring of the recalescence process with a high-speed camera. The measured growth velocities show an abrupt increase at a critical undercooling of 190 K independent of the magnetic field. This observation presents evidence for complete disorder trapping in the Ni3Sn compound. The imposition of the magnetic field lowers the growth velocities for undercoolings below 190 K, but it does not alter the growth velocities for higher undercoolings. This impeding effect of the magnetic field can be explained within the framework of the current theory on dendritic growth by considering damped thermal transport in the undercooled melts.

Yang, Chao; Gao, Jianrong

2014-05-01

143

Characterization of High-Temperature Abrasive Wear of Cold-Sprayed FeAl Intermetallic Compound Coating  

NASA Astrophysics Data System (ADS)

FeAl intermetallic compound coating was prepared by cold spraying using a mechanically alloyed Fe(Al) alloy powder followed by post-spray annealing at 950 °C. The high-temperature abrasive wear test was carried out for the FeAl coating at a temperature range from room temperature to 800 °C. The high-temperature abrasive wear of a heat-resistant stainless steel 2520 was performed for comparison. It was observed that the abrasive wear weight loss of FeAl coating was proportional to wear cycles in terms of sample revolutions at the tested temperatures. It was found that with the increase of the test temperature higher than 400 °C, the wear rate of cold-sprayed FeAl coating decreased with the increase of test temperature, while the wear rate of the heat-resistant steel increased significantly. The results indicate that the high-temperature abrasive wear resistance of the cold-sprayed FeAl intermetallic coating increased with the increase of the wear temperature in a temperature range from 400 to 800 °C. The wear resistance of cold-sprayed FeAl coating was higher than that of heat-resistant 2520 stainless steel under 800 °C by a factor of 3.

Li, Chang-Jiu; Wang, Hong-Tao; Yang, Guan-Jun; Bao, Chong-Gao

2011-01-01

144

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

145

Influence of interstitial solutions (H, N) on cerium electronic state in Ce-Fe intermetallic compounds: X-ray Absorption Spectroscopy (XAS) study.  

National Technical Information Service (NTIS)

It is presented an x-ray absorption spectroscopy (XAS) investigation performed at the L-edges of the rare-earth and at the K-edge of iron in the R-Fe intermetallic compounds (La, Ce)(sub 2)Fe(sub 14)BH(sub (chi)) and Ce(sub 2)Fe(sub 17)(H, N)(sub (chi)), ...

J. Chaboy A. Marcelli L. Bozukov

1995-01-01

146

Electrical Resistivity of the Ce (Fe sub(1-X) Al sub(X)) sub 2 Intermetallic Compounds (X < = 0,20).  

National Technical Information Service (NTIS)

Electric resistivity measurements in function of the temperature (1,5 < = T < = 300 K) are made in the Ce (Fe sub(1-x) Al sub(x)) sub 2 pseudo-binary intermetallic compound series in the (x < = 0,20) iron concentrated region. The curves obtained show an a...

A. Y. Takeushi

1982-01-01

147

Early Interfacial Reaction and Formation of Intermetallic Compounds in the Sn-3.5Ag/Cu Soldering System  

NASA Astrophysics Data System (ADS)

The early interfacial reaction in the Sn-3.5Ag/Cu soldering system and the system's premelting behavior were found and characterized by differential scanning calorimetry incorporated into the reflow process. The results show that the early interfacial reaction occurs by way of melting and wetting of the solder layer adjacent to the Cu substrate at a temperature nearly 4°C below the actual melting point of Sn-3.5Ag solder due to solid-state diffusion of Cu atoms into the Sn-3.5Ag binary solder. Consequently, the early interfacial reaction brings about formation of Cu-Sn intermetallic compounds (IMCs) at a temperature below the melting point of Sn-3.5Ag, and a prolonged early interfacial reaction can lead to change of the Cu-Sn IMC morphology from planar-like to scallop-like and promote excessive growth of IMCs at the interface.

Zhou, M. B.; Ma, X.; Zhang, X. P.

2011-02-01

148

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

149

Intermetallic compound formation and morphology evolution in the 95Pb5Sn flip-chip solder joint with Ti\\/Cu\\/Ni under bump metallization during reflow soldering  

Microsoft Academic Search

Intermetallic compound formation and morphology evolution in the 95Pb5Sn flip-chip solder joint with the Ti\\/Cu\\/Ni under bump\\u000a metallization (UBM) during 350°C reflow for durations ranging from 50 sec to 1440 min were investigated. A thin intermetallic\\u000a layer of only 0.4 µm thickness was formed at the 95Pb5Sn\\/UBM interface after reflow for 5 min. When the reflow was extended\\u000a to 20

Kai-Zheng Wang; Chih-Ming Chen

2005-01-01

150

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

151

Molecular dynamics simulations of radiation damage in D019 Ti3Al intermetallic compound  

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) has been applied to simulate the radiation damage created in displacement cascades in D019 Ti3Al structural intermetallics. Collision cascades formed by the recoil of either Al or Ti primary knock-on atoms (PKA) with energy E = 5, 10, 15 or 20 keV were considered in Ti3Al single crystals at T = 100, 300, 600 and 900 K. At least 24 different cascades for each (EPKA, T, PKA type) set were simulated. A comprehensive treatment of the modelling results has been carried out. We have evaluated the number of Frenkel pairs, fraction of Al and Ti vacancies, self-interstitial atoms and anti-sites as a function of (E,T, PKA type). Preferred formation of both Al vacancies and self-interstitial atoms in D019 Ti3Al exposed to irradiation has been detected.

Voskoboinikov, Roman E.

2013-07-01

152

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

153

Estimation of point defect formation energies in the L1{sub 2}-type intermetallic compound Ni{sub 3}Ga  

SciTech Connect

There has been considerable interest in recent years in the properties of intermetallic compounds with the cubic L1{sub 2}-structure. One prominent example is the compound Ni{sub 3}Al which has gained technological importance in the development of the so-called superalloys due to some of its unique properties like high temperature strength and excellent corrosion resistance. Much less is known about the properties of the isostructural compound Ni{sub 3}Ga which may have similar interesting properties even if its (peritectic) melting point is considerably lower. This lack of information is certainly caused by the much higher cost of metallic gallium, nevertheless, Ni{sub 3}Ga might still be of interest for specific applications. Unfortunately, the number of experimental data points to be used for the evaluation was extremely limited, and the possible existence of vacancies on the two sublattices was a priori completely neglected. Therefore, it was considered worthwhile to determine carefully the composition dependence of the gallium activity in the Ni{sub 3}Ga-phase and to apply a newly developed statistical-thermodynamic model; this would not only yield a more accurate disorder parameter (since it would be based on a higher number of experimental data points) but also values for the energies of formation of the various point defects.

Semenova, O.P.; Yuan, W.; Krachler, R.; Ipser, H.

2000-02-01

154

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

155

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

156

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

157

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

PubMed Central

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

Pauling, Linus

1989-01-01

158

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

NASA Astrophysics Data System (ADS)

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

Kumar, Aditya; Chen, Zhong

2011-02-01

159

The effect of interface velocity on the chemical potential of hydrogen in the two-phase coexistence region of intermetallic compound-hydrogen systems  

SciTech Connect

Although the experimental variable in this investigation is the size of the aliquots of hydrogen employed, the fundamental variable is proposed to be the interface velocity, v. Because the rates of hydride formation and decomposition in intermetallic compounds such as LaNi/sub 5/ are reproducible and rapid, the interface velocities will be directly proportional to the hydrogen aliquot sizes employed for a given sample and gas handling volume.

Park, C.N.; Flanagan, T.B.

1984-07-01

160

Some features of the formation and destruction of dislocation barriers in intermetallic compounds: III. Thermoactivated straightening of dislocations along a preferred direction in Ni 3 Al  

Microsoft Academic Search

Based on an analysis of the dislocation structure, the process of self-blocking, i.e., the transformation of glissile superdislocations\\u000a into dislocation barriers without the effect of an external stress, has been investigated in the intermetallic compounds with\\u000a an L12 superstructure. Using different regimes of heating without stress after preliminary deformation both below and above the\\u000a temperature T\\u000a max corresponding to the

A. M. Patselov; O. V. Antonova; B. A. Greenberg; M. A. Ivanov; A. V. Plotnikov; I. I. Vedernikova

2007-01-01

161

Effect of casting and homogenizing treatment conditions on the formation of Al–Fe–Si intermetallic compounds in 6063 Al–Mg–Si alloys  

Microsoft Academic Search

The effect of casting and homogenizing treatment conditions on the formation of several Al–Fe–Si intermetallic compounds in 6063 aluminum alloy was investigated using X-ray diffraction and transmission electron microscopy (TEM). The four kinds of alloys containing 0.1 to 0.5 mass% Fe were melted and then cooled at three different cooling rates ranging from 0.06 to 50 K\\/s, following the homogenization

H. Tanihata; T. Sugawara; K. Matsuda; S. Ikeno

1999-01-01

162

Phase stability of the X 2AlTi (X: Fe, Co, Ni and Cu) Heusler and B2-type intermetallic compounds  

Microsoft Academic Search

Ordering and phase separation between the B2 and L21 phases in the X2AlTi (X: Fe, Co, Ni, Cu) intermetallic compounds were investigated. The B2\\/L21 continuous ordering was determined using the diffusion couple technique in the temperature range of 1273–1573 K. It was found that the substitution of Co for Fe results in raising the B2\\/L21 ordering temperature and that of

K Ishikawa; R Kainuma; I Ohnuma; K Aoki; K Ishida

2002-01-01

163

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

Microsoft Academic Search

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

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

1997-01-01

164

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

165

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

166

Magnetic Properties of Intermetallic Compound La0.3Y0.7Mn2Ge2  

NASA Astrophysics Data System (ADS)

Intermetallic compound La0.3Y0.7Mn2Ge2 with the ThCr2Si2-type structure is antiferromagnetic (AF) below Tt{=}170 K and ferromagnetic (F) between Tt and TC{=}340 K. Field-induced AF-F transitions are observed at temperatures below 170 K. The transition field at 4.2 K is 65 kOe on increasing field. The measurements of pressure effect on magnetic transition temperatures show that TC decreases and Tt increases with pressure and the F phase disappears at pressures above 8 kbar: dTC/dP{=}-1.2 K/kbar, dTt/dP{=}19 K/kbar for P<8 kbar and dTN/dP{=}5.7 K/kbar for P>8 kbar. The thermal expansion measurements show that the lattice constants a and c increases and decreases discontinuously, respectively, at Tt on heating. Spontaneous magnetostriction below TC is positive for both a and c. The results show that the magnetic properties is sensitve to the nearest Mn-Mn distance in the c-plane.

Kaneko, Takejirou; Kanomata, Takeshi; Yasui, Hiroyuki; Shigeoka, Touru; Iwata, Mituru; Nakagawa, Yasuaki

1992-11-01

167

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

168

Substitutional solutes in the laves phase intermetalic compounds Cr[sub 2] Zr and Cu[sub 2] M[sub g]; Solution hardening and defect structures  

SciTech Connect

This paper reports that hardness and strength can be attained in pure metals by solid-solution hardening. Although the primary mechanisms of solid-solution hardening are though to be known in dilute metal alloys, the mechanisms in intermetallic compounds are not established for most structure types. The mere existence of solution hardening is not well demonstrated. There are, however, data for the B2 compounds AgMg and, recently, AlCo, the L1[sub 2] structure Ni[sub 3]Al, and preliminary results for the C15 cubic Laves phase Cu[sub 2]Mg. The plan here is to examine further the Cu[sub 2]Mg data and present new results for defects, moduli, density, and hardening in a high-temperature C15 compound, Cr[sub 2]Zr (melting temperature 1673[degrees]C). A special feature, and complication, of intermetallics is that off-stoichiometry leas to constitutional defects--substitutions or vacancies that are created by deviations from stoichiometry. Thus, in order to understand hardening, we need to identify the sites of constitutional solutes in off-stoichiometric intermetallics and to quantify the elastic interactions with dislocations of both these solutes and of ternary additions.

Fleischer, R.L. (General Electric Co., Schenectady, NY (United States). Corporate Research and Development Center)

1992-10-01

169

Solid-State diffusion reaction and formation of intermetallic compounds in the nickel-zirconium system  

NASA Astrophysics Data System (ADS)

Chemical diffusion studies in the nickel-zirconium system are investigated in the temperature range of 1046 to 1213 K employing diffusion couples of pure nickel and pure zirconium. Electron microprobe and X-ray diffraction studies have been employed to investigate the formation of different compounds and to study their layer growth kinetics in the diffusion zone. It is observed that growth of each phase is controlled by the process of volume diffusion as the layer growth obeys the parabolic law. The activation energies for interdiffusion in NiZr and NiZr2, which are the dominant phases in the diffusion zone, are 119.0 ±13.4 and 103.0 ±25.0 kJ/ mole, respectively. The formation and stability of compounds over the temperature range have been discussed on the basis of existing thermodynamic and kinetic data.

Bhanumurthy, K.; Kale, G. B.; Khera, S. K.; Asundi, M. K.

1990-11-01

170

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

Microsoft Academic Search

Growth kinetics of interfacial Cu–Sn 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 170°C. 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

171

Disorder-induced amorphization of intermetallic compounds: A molecular dynamics study  

NASA Astrophysics Data System (ADS)

The reaction of the crystalline compound NiZr 2 to imposed chemical disorder has been studied by molecular dynamics in the isobaric canonical ensemble. The cohesive energy used is inspired by the second moment approximation of the local density of states in the tight binding model. Imposed chemical disorder induces swelling (3% for full disorder, 1% for 10% disorder). Above 10% disorder, the crystalline structure athermally collapses to an amorphous state which retains much of the local chemical order.

Massobrio, C.; Pontikis, V.; Doan, N. V.; Martin, G.

1991-03-01

172

Intermetallic growth behaviour of gold ball bonds encapsulated with green moulding compounds  

Microsoft Academic Search

The move towards lead-free microelectronics packaging assembly and environmentally-friendly packaging materials has prompted the need to replace Pb-Sn solders with Sn-Ag based systems that require higher peak reflow temperatures, as well as the elimination of bromine flame retardants from transfer moulding compounds. Alternative chemistries have been developed to replace Br-based flame retardants. However, the use of higher reflow temperatures has

S. Sutiono; A. Seah; S. Chew; D. Calpito; Saraswati; D. Stephan; F. Wulff; C. D. Breach

2005-01-01

173

Microstructural modifications induced by swift ions in the NiTi intermetallic compound  

Microsoft Academic Search

The conditions for track formation by irradiation with swift ions, in the shape memory NiTi metallic compound are studied. We observe that tracks are only induced in the monoclinic structure but not in the cubic one and only when the linear rate of energy deposition by electronic excitation ([dE\\/dx]e) exceeds 46 keV\\/nm. We show that the tracks are amorphous in

A. Barbu; A. Dunlop; A. Hardouin Duparc; G. Jaskierowicz; N. Lorenzelli

1998-01-01

174

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

175

Fracture toughness of ordered intermetallic compounds exhibiting limited ductility and mechanical properties of ion-irradiated polycrystalline NiAl. Final report, July 1, 1986--June 30, 1997  

SciTech Connect

The focus of the research performed under the auspices of this grant changed several times during the lifetime of the project. The initial activity was an investigation of irradiation-induced amorphization of ordered intermetallic compounds, using energetic protons as the bombarding species. Two significant events stimulated a change of direction: (1) the proton accelerating facility that the authors had been using at the California State University at Los Angeles became unavailable late in 1988 because of a personnel matter involving the only individual capable of operating the machine; (2) they learned that disordering and amorphization of intermetallic compounds produced interesting effects on their mechanical properties. Loss of access t the local accelerator prompted a collaboration with Dr. Droa Pedraza of the Oak Ridge National Laboratory (ORNL), enabling access to the accelerator at ORNL. The influence of disordering and amorphization on mechanical properties ultimately stimulated the development of a miniaturized disk-bend testing (MDBT) facility, the intent of which was to provide semiquantitative and even quantitative measures of the mechanical behavior of ion-irradiated ordered intermetallic alloys. The second phase of the project involved the perfection and usage of the MDBT, and involved exploratory experiments on unirradiated materials like amorphous alloy ribbons and brittle grain boundaries in Ni{sub 3}Al. This report is a brief summary of the research highlights of the project, organized according to the activity that was emphasized at the time.

Ardell, A.J.

1997-09-01

176

Magnetic behaviour of Er1-xZrxFe2 intermetallic compounds  

NASA Astrophysics Data System (ADS)

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 5 K 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 1.19 J kg-1 K-1 was found for the sample with x = 0.1 for an applied field change of 0-4 T. Large RCP(?S) values were obtained for all of the samples, mainly due to the wide ?TFWHM values of the ?SM(T) curves.

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

2013-11-01

177

Unequal wave vectors in short- versus long-range ordering in intermetallic compounds  

NASA Astrophysics Data System (ADS)

The sign of the formation energy ?HF of a compound indicates if the low-temperature long-range order (LRO) corresponds to compound formation (when ?HF<0) or to phase-separation (when ?HF>0). However, ?HF by itself does not tell us what type (ordering or clustering) of high-temperature short-range order (SRO) can be expected. The reason is that ?HF contains two types of contributions: an ``elastic,'' volume-deformation energy G(x) that reflects the energy invested in deforming the constituents A and B to the volume V(x) of the A1-xBx alloy, and a ``chemical'' energy ? that reflects A-B interactions (charge transfer and atomic relaxations) at a fixed V(x). We show that the LRO and the SRO have the same behavior only when the signs of ?HF and ? are the same: ordering tendencies (``type I'') when both ?HF<0 and ?<0, or phase-separating/clustering tendencies (``type III'') when both ?HF>0 and ?>0. However, ``type II'' systems (?HF>0 ?<0) can exhibit a phase-separating LRO and an ordering-type SRO. Direct self-consistent local-density calculations of the total energy coupled with Monte-Carlo simulated annealing calculations of the ensuing Ising-like cluster expansion illustrate these type I, II, and III behaviors in Ni-V, Ni-Au, and Pd-Rh, respectively.

Lu, Z. W.; Zunger, Alex

1994-09-01

178

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 5 K 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 1.19 J kg(-1) K(-1) was found for the sample with x = 0.1 for an applied field change of 0-4 T. 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; Gînsc?, O; Tetean, R

2013-11-20

179

Dissolution and Interfacial Reactions of (Cu,Ni)6Sn5 Intermetallic Compound in Molten Sn-Cu-Ni Solders  

NASA Astrophysics Data System (ADS)

(Cu,Ni)6Sn5 is an important intermetallic compound (IMC) in lead-free Sn-Ag-Cu solder joints on Ni substrate. The formation, growth, and microstructural evolution of (Cu,Ni)6Sn5 are closely correlated with the concentrations of Cu and Ni in the solder. This study reports the interfacial behaviors of (Cu,Ni)6Sn5 IMC (Sn-31 at.%Cu-24 at.%Ni) with various Sn-Cu, Sn-Ni, and Sn-Cu-Ni solders at 250°C. The (Cu,Ni)6Sn5 substrate remained intact for Sn-0.7 wt.%Cu solder. When the Cu concentration was decreased to 0.3 wt.%, (Cu,Ni)6Sn5 significantly dissolved into the molten solder. Moreover, (Cu,Ni)6Sn5 dissolution and (Ni,Cu)3Sn4 formation occurred simultaneously for the Sn-0.1 wt.%Ni solder. In Sn-0.5 wt.%Cu-0.2 wt.%Ni solder, many tiny (Cu,Ni)6Sn5 particulates were formed and dispersed in the solder matrix, while in Sn-0.3 wt.%Cu-0.2 wt.%Ni a lot of (Ni,Cu)3Sn4 grains were produced. Based on the local equilibrium hypothesis, these results are further discussed based on the liquid-(Cu, Ni)6Sn5-(Ni,Cu)3Sn4 tie-triangle, and the liquid apex is suggested to be very close to Sn-0.4 wt.%Cu-0.2 wt.%Ni.

Wang, Chao-hong; Lai, Wei-han; Chen, Sinn-wen

2014-01-01

180

Hot hardness comparisons among isostructural Be[sub 12]X intermetallic compounds  

SciTech Connect

Hot hardness has been measured in seven isostructural Be[sub 12]X compounds: Be[sub 12]Cr, Be[sub 12]Mn, Be[sub 12]V, Be[sub 12]Mo, Be[sub 12]Ti, Be[sub 12]Ta and Be[sub 12]Nb. All vacuum-hot-pressed (VHP) materials exhibited similar hardness levels (800 to 1000 kg/mm[sup 2]) at low temperatures ([lt]600 [degree]C), but sharply diverged at higher temperatures. Most compounds showed a sharp decrease in hardness above about one-half their melting temperatures except for Be[sub 12]Nb and Be[sub 12]Ti which maintained strength until higher temperatures. Ductile-brittle transition temperatures (DBTT's) of 600, 625, 690, 700, 700 and 850 [degree]C were determined for Be[sub 12]Cr, Be[sub 12]Mn, Be[sub 12]V, Be[sub 12]Mo, Be[sub 12]Ti and Be[sub 12]Nb, respectively. Hot-isostatically pressed (HIP) and VHP Be[sub 12]Nb heats both showed comparable behavior, indicating that the temperature required for macroscopic plasticity is not dependent on processing conditions. Differences in slip characteristics were observed between beryllides with similar melting temperatures, but differing DBTT's. Dislocations were activated on multiple slip systems in Be[sub 12]V during compressive deformation at 800 [degree]C. Similar behavior was not observed in Be[sub 12]Nb until test temperatures above 1000 [degree]C. It is proposed that dislocation mobility may be related to the stability between Be[sub 12]X and Be[sub 17]X[sub 2] phases. Larger refractory metal atoms such as Nb may form faulted layers related to Be[sub 17]X[sub 2] structures and thereby impede deformation at intermediate temperatures. Smaller atoms such as Cr, Mn, V and Mo do not form a stable Be[sub 17]X[sub 2] phase and thereby allow enhanced dislocation mobility at these temperatures.

Bruemmer, S.M.; Arey, B.W.; Brimhall, J.L. (Pacific Northwest Laboratory, Richland, Washington 99352 (United States)); Hirth, J.P. (Washington State University, Pullman, Washington 99164 (United States))

1993-07-01

181

Anode behaviors of magnesium-antimony intermetallic compound for lithium secondary battery  

NASA Astrophysics Data System (ADS)

Mg 3Sb 2 with a structure of A-type rare earth oxide (hexagonal) was synthesized by mechanical alloying (MA) and evaluated as a negative electrode material for rechargeable lithium batteries. Electrochemical tests demonstrated that the initial charge and discharge capacities of Mg 3Sb 2 were ca. 850 and 600 mA h g -1, respectively. Ex situ XRD of the Mg 3Sb 2 electrodes showed that several lithium-containing compounds such as LiMgSb and Li 3Sb were successively formed during the insertion of lithium into Mg 3Sb 2. As to LiMgSb synthesized by MA-method, the electrode performance was also investigated; it showed an excellent reversibility at the first cycle and a rechargeable capacity of ca. 200 mA h g -1 after the fourth cycle. The cycle life performance of LiMgSb electrode was significantly enhanced in comparison with that of Mg 3Sb 2.

Honda, Hitohiko; Sakaguchi, Hiroki; Tanaka, Ichiro; Esaka, Takao

182

Microstructural modifications induced by swift ions in the NiTi intermetallic compound  

NASA Astrophysics Data System (ADS)

The conditions for track formation by irradiation with swift ions, in the shape memory NiTi metallic compound are studied. We observe that tracks are only induced in the monoclinic structure but not in the cubic one and only when the linear rate of energy deposition by electronic excitation ([d E/d x] e) exceeds 46 keV/nm. We show that the tracks are amorphous in their centre and that a decrease of the monoclinic towards cubic transformation temperature is observed at the periphery of the track region. For [d E/d x] e=32 keV/nm, no individual tracks can be observed at low fluences, only a monoclinic ? cubic structure transformation is observed at high fluences. If [d E/d x] ? 17 keV/nm, swift ions are unable to induce any visible structural modification by electronic excitations. The track formation in this alloy is discussed within the framework of the classical Coulomb explosion and thermal spike models.

Barbu, A.; Dunlop, A.; Hardouin Duparc, A.; Jaskierowicz, G.; Lorenzelli, N.

1998-11-01

183

GMR in intermetallics  

SciTech Connect

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

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

1996-04-01

184

Surfaces of intermetallic compounds: An ab initio DFT study for B20-type AlPd  

NASA Astrophysics Data System (ADS)

The low-index surfaces of the AlPd compound crystallizing in the B20 (FeSi-type) structure have been investigated using ab initio density functional methods. The space group of the B20 structure is P213, with four threefold rotational axes along the <111> directions and three twofold screw axes along the <100> directions, but no inversion symmetry. The B20 structure exists in two enantiomorphic forms related by inversion. The termination of the structure perpendicular to the twofold screw axes is uniquely defined: The corrugated {100} surfaces are formed by the characteristic zigzag Al-Pd chains separated by shallow troughs. Perpendicular to the <210> directions the structure consists of slightly puckered planes containing Al and Pd in equal numbers. The {210} surfaces shows pseudo-fivefold symmetry. Their structure is shown to be closely related to that of the {110} surfaces of the B2 structure. Both the {100} and {210} surfaces undergo some structural relaxation, but no reconstruction changing their (1×1) periodicity. While perpendicular to the <100> and <210> directions only one surface termination is possible, perpendicular to the threefold <111> directions there are several possible surface terminations differing in structure and chemical composition. Because of the lack of inversion symmetry the threefold {111} surfaces have polar character. The (111) and (1¯1¯1¯) surfaces are not equivalent; the (111) surfaces of one enantiomorph are identical to the (1¯1¯1¯) surfaces of the other form (and vice versa). In both the (111) and (1¯1¯1¯) directions several surface terminations are possible. The formation of threefold surfaces has been studied by simulated cleavage experiments and by calculations of the surface energies of all possible terminations. Perpendicular to the <111> direction the lowest energy has been found for a bilayer with three Al atoms per surface cell in the upper layer and one Al and one Pd in the lower part. The preferable termination perpendicular to the <1¯1¯1¯> direction is more symmetric; it consists again of a bilayer with three Al atoms in the upper and three Pd atoms in the lower part. The surface energy of this termination further decreases if the Pd triplet is covered by additional Al atom. The calculated surface energies permit us to perform a Wulff construction of the equilibrium shape of AlPd crystallites. {100} and {210} facets together occupy 77% of the surface area in about equal proportion. The high anisotropy of the energy of the {111} surfaces results in the substantial difference of the surface areas of the opposite threefold facets.

Kraj?í, M.; Hafner, J.

2013-01-01

185

Magnetic behaviour of the intermetallic compound YbCo2Si2  

NASA Astrophysics Data System (ADS)

We report on a comprehensive study of the magnetic properties of YbCo2Si2 investigated using a single crystal. All data confirm a stable trivalent Yb state carrying a well-localized 4f moment, as well as a non-magnetic Co state. We observed a sizeable anisotropy in the magnetic susceptibility ?(T), with the moment in the basal plane twice as large as that along the c-direction. Combining this result with published neutron-scattering data puts strong constraints on the values of the crystalline electrical field (CEF) parameters. Our calculation yields one possible solution with a ?7 CEF ground state. A peak in the easy-plane susceptibility at low temperatures demonstrates that the previously reported magnetic ordering at TN?1.65 K is of antiferromagnetic (AFM) nature. In addition, we observed sharp anomalies in all measured properties, evidencing a further phase transition at TL?0.9 K, found to be first order, which corresponds to a change in the AFM structure. Both transitions are suppressed by a magnetic field B=2 T. Below TL the specific heat, C4f, shows a well-defined T3 dependence, as expected for AFM spin-wave excitations. Surprisingly, the resistivity, ?(T), also shows a T3 power law in the same temperature range, instead of the expected T5. This discrepancy might be related to more complex magnetic interactions, as also evidenced by the multiple transitions. By extending the linear fit of C4f/T versus T2 to T=0, the Sommerfeld coefficient ?0=0.13 J K- 2 mol-1 is extracted. Although magnetism in YbCo2Si2 is dominated by the RKKY exchange interaction, the enhanced ?0 and a weak Kondo-like increase in ?(T) indicate the presence of some interactions between the conduction electrons and the 4f moments.

Klingner, C.; Krellner, C.; Brando, M.; Geibel, C.; Steglich, F.

2011-08-01

186

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

187

Calculation of the crystal field and paramagnetic susceptibility of intermetallic compounds (TbxY1-x)Cu2 and Tb(CuxNi1-x)2  

Microsoft Academic Search

The crystal field parameters B20 and B22 of antiferromagnetic single crystals of rare earth intermetallic compounds (TbxY1-x)Cu2 (x=1,0.8,0.6,0.4,0.2,0.1,0.05) and Tb(CuxNi1-x)2 (x=1,0.95,0.9,0.8,0.7) were calculated from the least-squares fit to the reciprocal paramagnetic susceptibility along principal axes. The results of the calculation are in good agreement with the experimental values estimated from the anisotropic paramagnetic Curie temperatures on the basis of the

M. Andrecut; I. Pop; I. Burda

1993-01-01

188

Electrocatalytic mechanism and kinetics of SOMs oxidation on ordered PtPb and PtBi intermetallic compounds: DEMS and FTIRS study.  

PubMed

The electrocatalytic activities and mechanisms of PtPb and PtBi ordered intermetallic phases towards formic acid, formaldehyde and methanol oxidation have been studied by DEMS and FTIRS, and the results compared to those for a pure polycrystalline platinum electrode. While PtPb exhibits an enhanced electrocatalytic activity for the oxidation of all three organic molecules when compared to a Pt electrode, PtBi exhibits an enhanced catalytic activity towards formic acid and formaldehyde oxidation, but not methanol. FTIRS data indicate that adsorbed CO does not form on PtPb or PtBi intermetallic compounds during the oxidation of formic acid, formaldehyde and methanol, and therefore their oxidation on both PtPb and PtBi intermetallic compounds proceeds via a non-CO(ads) pathway. Quantitative DEMS measurements indicate that only CO(2) was detected as a final product during formic acid oxidation on Pt, PtPb and PtBi electrodes. At a smooth polycrystalline platinum electrode, the oxidation of formaldehyde and methanol produces mainly intermediates (formaldehyde and formic acid), while CO(2) is a minor product. In contrast, CO(2) is the major product for formaldehyde and methanol oxidation at a PtPb electrode. The high current efficiency of CO(2) formation for methanol and formaldehyde oxidation at a PtPb electrode can be ascribed to the complete dehydrogenation of formaldehyde and formic acid due to electronic effects. The low onset potential, high current density and high CO(2) yield make PtPb one of the most promising electrocatalysts for fuel cell applications using small organic molecules as fuels. PMID:18563235

Wang, Hongsen; Alden, Laif; Disalvo, F J; Abruña, Héctor D

2008-07-01

189

NaK 29Hg 48: A Contradiction to or an Extension of Theoretical Concepts to Rationalize the Structures of Complex Intermetallics?  

NASA Astrophysics Data System (ADS)

NaK 29Hg 48 is a new silver metallic, air-sensitive ternary alkali metal amalgam with metallic properties. It crystallizes in space group Pmoverline3n (No. 223, Z=2, a=1685.3(2) pm) and shows a superconducting phase transition at 2.5 K. Its crystal structure is characterized by novel icosahedral Hg 12 clusters centered by Na atoms and hexagonal antiprismatic Hg 12 clusters ("drums") centered by K atoms. Both cluster types are embedded in a matrix of K atoms. With respect to the topology of the cluster centers the three-dimensional arrangement corresponds to the A15 structure type (Nb 3Sn). The crystal structure of NaK 29Hg 48 is closely related to that of the complex intermetallic phases A3Na 29In 48 ( A=K, Rb, Cs) and others. It is an unexpected electron deficient borderline case with respect to electron counting rules (Wade's rules and Zintl-Klemm concept), which were successfully applied to explain the occurence of icosahedral and hexagonal antiprismatic In 12/Tl 12 clusters in the latter two compounds.

Deiseroth, Hans-Jörg; Biehl, Erik

1999-10-01

190

Thermal behavior and microstructure of the intermetallic compounds formed at the Sn 3Ag 0.5Cu/Cu interface after soldering and isothermal aging  

NASA Astrophysics Data System (ADS)

The thermal behavior and microstructure of the intermetallic compounds formed at the Sn-3Ag-0.5Cu/Cu interface after soldering at 250 °C for 60 s and aging at 150 °C for various times have been investigated by using differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and pull-off testing. The DSC result shows that the solidus and liquidus temperatures of the Sn-3Ag-0.5Cu solder alloy are 217 and 221 °C, respectively. The melting range of the Sn-3Ag-0.5Cu is 4 °C smaller than 8.5 °C for the Sn-37Pb solder alloy. The major intermetallic compounds are monoclinic ?'-Cu 6Sn 5, hexagonal ?-Cu 6Sn 5 and Ag 3Sn when aged at 150 °C for 0-300 h. When aged for 100-300 h, the morphology of Cu 6Sn 5 transforms from scallop-shaped to planar. The thickness of Cu 6Sn 5 increases from 4.1±0.4 to 7.8±0.3 ?m when aging time increases from 0 to 300 h. The maximum and minimum adhesion strengths are 12.44±0.53 and 2.22±0.46 MPa, respectively, for as-soldered and aged (150 °C for 300 h) ones.

Liu, Chih-Yao; Lai, Chien-Hong; Wang, Moo-Chin; Hon, Min-Hsiung

2006-04-01

191

Magnetic structure and enhanced TN of the rare-earth intermetallic compound TbRhIn5 : Experiments and mean-field model  

NASA Astrophysics Data System (ADS)

In this work the physical properties of the intermetallic compound TbRhIn5 were investigated by means of temperature-dependent magnetic susceptibility, electrical resistivity, heat-capacity, and resonant x-ray magnetic diffraction experiments. TbRhIn5 is an intermetallic compound that orders antiferromagnetically at TN=45.5K , the highest ordering temperature among the existing RRhIn5 (1-1-5, R=rare earth) materials, which in contrast to what is expected from a de Gennes scaling along the RRhIn5 series. The x-ray resonant diffraction data have allowed us to solve the magnetic structure of TbRhIn5 . Below TN , we found a commensurate antiferromagnetic structure with a propagation vector (1/2,0,1/2) and the Tb moments oriented along the c axis. Strong (over two orders of magnitude) dipolar enhancements of the magnetic Bragg peaks were observed at both Tb absorption edges LII and LIII , indicating a fairly high polarization of the Tb 5d levels. Using a mean-field model including an isotropic first-neighbor exchange interaction (JR-R) and the tetragonal crystalline electrical field (CEF), we evaluate the influence of the CEF effects in the physical properties of TbRhIn5 . The results reported here seem to corroborate a general trend of CEF-driven effects on TN along the RRhIn5 series.

Lora-Serrano, R.; Giles, C.; Granado, E.; Garcia, D. J.; Miranda, E.; Agüero, O.; Mendonça Ferreira, L.; Duque, J. G. S.; Pagliuso, P. G.

2006-12-01

192

First principle study on generalized-stacking-fault energy surfaces of B2-AlRE intermetallic compounds  

Microsoft Academic Search

First-principles calculations are used to predict the generalized-stacking-fault energy (GSFE) surfaces of AlRE intermetallics. The calculations employ the projector augmented-wave (PAW) method within the generalized gradient approximation (GGA) using the density functional theory (DFT). GSFE curves along ?111? {110} direction, ?110? {110} direction and ?100? {110} direction have been calculated. The fitted GSFE surfaces have been obtained from the Fourier

Shaorong Li; Shaofeng Wang; Rui Wang

2011-01-01

193

Reorganizations of complex networks: Compounding and reducing  

NASA Astrophysics Data System (ADS)

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

Shao, Fengjing; Sui, Yi

2014-12-01

194

Structural, stability and electronic properties of C15-AB2 (A = Ti, Zr; B = Cr) intermetallic compounds and their hydrides: An ab initio study  

NASA Astrophysics Data System (ADS)

The structural, stability and electronic properties of C15-AB2 (A = Ti, Zr; B = Cr) isomeric intermetallic compounds were systematically investigated by using density functional theory (DFT) and plane-wave pseudo-potential (PW-PP) method. The macroscopic properties including the lattice constant, bulk modulus and stability for these compounds were studied before and after hydrogenation. For parent compounds, the enthalpy of formation was evaluated with regard to their bulk modules and electronic structures. After hydrogenation of compounds at different interstitial tetrahedral sites (A2B2, A1B3, B4), a volume expansion was found for hydrides. The stability properties of hydrides characterized the A2B2 sites as the site preference of hydrogen atoms for both compounds. The Miedema's "reverse stability" rule is also satisfied in these compounds as lower the enthalpy of formation for the host compound, the more stable the hydride. Analysis of microscopic properties (electronic structures) after hydrogenation at more stable interstitial site (A2B2) shows that the H atoms interact stronger with the weaker (or non) hydride forming element B (Cr) than the hydride forming element A (Ti/Zr). A correlation was also found between the stability of the hydrides and their electronic structure: the deeper the hydrogen band, the less stable the hydride.

Sarhaddi, Reza; Arabi, Hadi; Pourarian, Faiz

2014-05-01

195

Possible complex organic compounds on Mars.  

PubMed

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

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

1997-01-01

196

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

197

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 800°C 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.

198

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 800°C 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

199

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

SciTech Connect

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

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

2005-08-01

200

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

PubMed Central

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

Pauling, Linus

1989-01-01

201

Oxidation of {gamma}{prime}-Ni{sub 3}Al and {gamma}{prime}-Ni{sub 3}Al(Si) intermetallic compounds at low-oxygen pressures  

SciTech Connect

The oxidation behavior of {gamma}{prime}-Ni{sub 3}Al and {gamma}{prime}-Ni{sub 3}Al(Si) (Ni{sub 75}Al{sub 20}Si{sub 5}) intermetallic compounds was studied at 1073 K and oxygen partial pressures of 5 {approximately} 9 x 10{sup {minus}6} atm, 1.2 x 10{sup {minus}14} atm, and 1.2 x 10{sup {minus}19} atm by means of a manometric apparatus, and Rhines packs of NiO/Ni and FeO/Fe, respectively. Oxidation kinetics were determined either by recording weight gains or by measuring the internal-oxidation-zone depths. The structures and morphologies of oxides were also studied. Relatively low oxidation rates occurred for both compounds when oxidized in the manometric apparatus, while fast internal oxidation was observed for both compounds in the NiO/Ni pack. The fastest oxidation occurred in the {gamma}{prime}-Ni{sub 3}Al compound in the FeO/Fe pack. A healing Al{sub 2}O{sub 3} layer was formed on the surface of {gamma}{prime}-Ni{sub 3}Al(Si) compound in the FeO/Fe pack, indicating a synergistic effect between the solute elements in the compound at the oxygen pressures corresponding to the dissociation of FeO. The oxidation rate was found to depend on the volume expansion associated with solute-atom oxidation.

Yi, H.C. [Guigne International, Newfoundland (Canada); Smeltzer, W.W.; Petric, A. [McMaster Univ., Hamilton, Ontario (Canada)

1996-04-01

202

Electronic Properties of a PLATINUM-GALLIUM(2) Single Crystal and Photoemission Studies of the Electron Correlation Effects in the Nickel-Gallium and the Nickel - Intermetallic Compounds.  

NASA Astrophysics Data System (ADS)

The electrical resistivity (rho ), magnetic susceptibility (chi), thermoelectric power (S), and specific heat (C _{rm p}) of a PtGa _2 single crystal were measured as a function of temperature (T). The metallic behavior of this intermetallic compound is shown from the room temperature resistivity value (19muOmega-cm) and the linear dependence of the S vs. T curve at temperatures above the Debye temperature (theta_ {rm D} = 187K). The diamagnetic susceptibility is independent of T. The density of states (DOS) at the Fermi energy (E_{rm F}) obtained from chi and S data agree within 22% and 15%, respectively, of the value obtained from a semiempirical band structure calculation. The low temperature C_{rm p} data, however, yielded a much smaller DOS at E _{rm F}. The electronic structures and the electron correlation effects of nine Ni-Ga and Ni-In intermetallic compounds were studied by x-ray photoemission spectroscopy (XPS). Ultraviolet photoemission spectroscopy (UPS) was used to further investigate the many-body effects, especially the resonant behavior of the 6-eV satellite, in NiGa. The satellites on the high binding energy side of both valence-band (VB) and core-level XPS spectra of these compounds decrease in intensity on alloying, which is related to the d-band filling. However, a complete filling of the Ni 3d band by alloying with Ga or In cannot be inferred. The VB satellite is resonantly enhanced near the 3p threshold (hv = 67 eV), and its centroid position is photon energy dependent. Surprisingly, the resonantly enhanced VB satellite in NiGa has about the same intensity as that for elemental Ni, even though the number of empty d-states contributing to the resonant enhancement is expected to be smaller in NiGa.

Hsu, Lishing

203

Anti-mackay polyicosahedral clusters in La-Ni-Mg ternary compounds: synthesis and crystal structure of the La(43)Ni(17)Mg(5) new intermetallic phase.  

PubMed

The crystal structure of the complex La(43)Ni(17)Mg(5) ternary phase was solved and refined from X-ray single crystal diffraction data. It is characterized by a very large unit cell and represents a new structure type: La(43)Ni(17)Mg(5) - orthorhombic, Cmcm, oS260, a = 10.1895(3), b = 17.6044(14), c = 42.170(3) A, Z = 4, wR1 = 0.0598, wR2 = 0.0897, 4157 F(2) values, 176 variables. The crystal structures of the La-rich La-Ni-Mg intermetallic phases La(4)NiMg, La(23)Ni(7)Mg(4), and La(43)Ni(17)Mg(5) have been comparatively analyzed. The constitutive fragments of these structures are binary polyicosahedral core-shell clusters of Mg(4)La(22) and Mg(5)La(24) compositions together with binary polytetrahedral clusters of nickel and lanthanum atoms. The structures of the Mg-La clusters are described in detail as a unique feature of the analyzed intermetallic phases; the dodecahedral Voronoi polyhedra are proposed as a useful tool to characterize polyicosahedral clusters. The arrangements of the building units in the studied phases show some regularities; particularly the i(4)3, i(5)3 and L-i(4) units, made up of polyicosahedral clusters and analogous to the Kreiner i(3) and L units, are proposed as structural blocks. PMID:19916494

Solokha, Pavlo; De Negri, Serena; Pavlyuk, Volodymyr; Saccone, Adriana

2009-12-21

204

Abnormal accumulation of intermetallic compound at cathode in a SnAg3.0Cu0.5 lap joint during electromigration  

NASA Astrophysics Data System (ADS)

Interfacial reactions in a SnAg3.0Cu0.5/Cu lap joint for naked and encompassed specimens were investigated contrastively under electric current stressing. After applying a constant direct current at 6.5 A for 144 h, an abnormal accumulation of bulk Cu6Sn5 intermetallic compound was found at the cathode for the naked specimen. But normal polarization phenomenon arose for the encompassed specimen at the same current density for 504 h. The abnormal accumulation phenomenon was explained by the mechanism that thermomigration and stress migration induced by temperature gradient dominated the migration process. A three-dimensional joint simulation model was designed to demonstrate how current crowding and temperature gradient can enhance the local atomic flux.

Li, Mingyu; Chang, Hong; Pang, Xiaochao; Wang, Ling; Fu, Yonggao

2011-03-01

205

The corrosion behavior of intermetallic compounds Ni 3(Si,Ti) and Ni 3(Si,Ti) + 2Mo in acidic solutions  

NASA Astrophysics Data System (ADS)

The corrosion behavior of the intermetallic compounds homogenized, Ni 3(Si,Ti) (L1 2: single phase) and Ni 3(Si,Ti) + 2Mo (L1 2 and (L1 2 + Ni ss) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EPMA: electron probe microanalysis) in 0.5 kmol/m 3 H 2SO 4 and 0.5 kmol/m 3 HCl solutions at 303 K. In addition, the corrosion behavior of a solution annealed austenitic stainless steel type 304 was studied under the same experimental conditions as a reference. It was found that the intergranular attack was observed for Ni 3(Si,Ti) at an initial stage of the immersion test, but not Ni 3(Si,Ti) + 2Mo, while Ni 3(Si,Ti) + 2Mo had the preferential dissolution of L1 2 with a lower Mo concentration compared to (L1 2 + Ni ss) mixture region. From the immersion test and polarization curves, Ni 3(Si,Ti) + 2Mo showed the lowest corrosion resistance in both solutions and Ni 3(Si,Ti) had the highest corrosion resistance in the HCl solution, but not in the H 2SO 4 solution. For instance, it was found that unlike type 304 stainless steel, these intermetallic compounds were difficult to form a stable passive film in the H 2SO 4 solution. The results obtained were explained in terms of boron segregation at grain boundaries, Mo enrichment and film stability (or strength).

Priyotomo, Gadang; Okitsu, Kenji; Iwase, Akihiro; Kaneno, Yasuyuki; Nishimura, Rokuro; Takasugi, Takayuki

2011-07-01

206

Evolution of the magnetic properties along the RCuBi2 (R = Ce, Pr, Nd, Gd, Sm) series of intermetallic compounds  

NASA Astrophysics Data System (ADS)

In this paper, the evolution of the magnetic properties along the series of intermetallic compounds RCuBi2 (R = Ce, Pr, Nd, Gd, Sm) is discussed. These compounds crystallize in a tetragonal ZrCuSi2 (P4/nmm) structure, and our single crystals of RCuBi2 grown from Bi-flux show no evidence for Cu-deficiency [Ye et al., Acta Crystallogr. C 52, 1325 (1996)] as previously reported for R = Ce. For R = Ce, Pr, Gd, and Sm, we found an antiferromagnetic ordering at TN ˜ 16 K, 4.2 K, 13.6 K, and 4.9 K, respectively. For R = Nd, we saw no evidence for a magnetic phase transition down to T = 2 K. These values of TN clearly show a dramatic breakdown of the De Gennes factor in this series. We discuss our data taken into account the tetragonal crystalline electrical field and the anisotropic Ruderman-Kittel-Kasuya-Yoshida magnetic interaction between the R-ions in this family of compounds.

Jesus, C. B. R.; Piva, M. M.; Rosa, P. F. S.; Adriano, C.; Pagliuso, P. G.

2014-05-01

207

Complex magnetic states of the heavy fermion compound CeGe  

NASA Astrophysics Data System (ADS)

The intermetallic compound CeGe exhibits unusual magnetic behavior owing to the interplay between Kondo and antiferromagnetic coupling. This system is interesting because the Kondo temperature is close to the Néel temperature, so there is a close competition between the low-temperature interactions, which can be tuned by varying external parameters such as pressure and applied magnetic field. Interestingly, magnetization measurements up to 12 kbar reveal that the Néel temperature is not affected by pressure. Measurements of the electrical resistivity show, however, that the sharp upturn below TN is sensitive to pressures up to 15 kbar. This suggests that pressure may change the complex antiferromagnetic spin structure. The validity of an explanation based on the magnetic superzones seen in the rare earths is discussed here.

Haines, C. R. S.; Marcano, N.; Smith, R. P.; Aviani, I.; Espeso, J. I.; Gómez Sal, J. C.; Saxena, S. S.

2012-07-01

208

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

209

SrZn2Sn2 and Ca2Zn3Sn6 — two new Ae-Zn-Sn polar intermetallic compounds (Ae: alkaline earth metal)  

NASA Astrophysics Data System (ADS)

SrZn2Sn2 and Ca2Zn3Sn6, 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 SrZn2Sn2 comprises (anti-)PbO-like {ZnSn4/4} and {SnZn4/4} layers. Ca2Zn3Sn6 shows similar {ZnSn4/4} layers and {Sn4Zn} 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. SrZn2Sn2 adopts the SrPd2Bi2 structure type, and Ca2Zn3Sn6 is isotypic to the R2Zn3Ge6 compounds (R=La, Ce, Pr, Nd). Band structure calculations indicate that both SrZn2Sn2 and Ca2Zn3Sn6 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 {Sn4Zn} layers of Ca2Zn3Sn6.

Stegmaier, Saskia; Fässler, Thomas F.

2012-08-01

210

55Mn NMR Study in Magnetically Ordered State of RMn2 (R=Rate Earth) Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

NMR of 55Mn has been observed in magnetically ordered state of cubic Laves phase compounds GdMn2, TbMn2, DyMn2 and HoMn2 and in hexagonal Lave phases ErMn2 and TmMn2. Magnetization and neutron diffraction studies have shown non zero Mn moment in cubic compounds only. Accordingly, we find that hyperfine fields at Mn site are larger in cubic than in hexagonal compounds. The observed hyperfine field values are used to estimate Mn moments in these compounds.

Shimizu, Kenji; Dhar, S. K.; Vijayaraghavan, R.; Malik, S. K.

1981-04-01

211

Experimental and theoretical studies on the C15 intermetallic compounds MV2 (M = Zr, Hf and Ta): Elasticity and phase stability  

NASA Astrophysics Data System (ADS)

The phase stability of C15 HfV2 was studied by specific heat measurements. The elastic constants of C15 HfV2 were measured by the resonant ultrasound spectroscopy. Total energy and electronic structure of C15 intermetallic compounds MV2 (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 HfV2 and ZrV2. 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 HfV2 and ZrV2 and the stability of C15 TaV2. The relationship between the anomalous elasticity and structural instability of C15 HfV2 and ZrV2 were also studied.

Chu, F.; Mitchell, T. E.; Chen, S. P.; Sob, M.; Siegl, R.; Pope, D. P.

212

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 Mössbauer 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. Blügel, 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

213

Intermetallic compounds LaNi/sub 5/- /SUB x/ Cu /SUB x/ and their hydrides in the sorption of hydrogen and the hydrogenation of olefins  

SciTech Connect

This paper studies the sorptive and catalytic properties of the intermetallic compounds (IMC) LaNi /SUB 5-x/ Cu /SUB x/ and also of their hydrides in the hydrogenation of propylene. The existence of an inverse dependence between the bond strength in the IMC-H system and the rate of formation of the alpha-phase of the hydrides was established. It was shown that the observed extremal dependence of the specific catalytic activity of the hydrides on composition is determined by the optimum value of the bond energy of the hydrogen in the IMC matrix. It was found that the rate of hydrogenation of an olefin on IMC hydrides follows a rate equation zero-order in hydrogen and first-order in olefin. In the case of the same IMC, on the contrary, the rate is first-order in H/sub 2/ and zero-order in C/sub 3/H/sub 6/. It is proposed that the sorptive and catalytic properties of the catalysts show the effect of the structure on the surface active center - a cluster.

Konenko, I.R.; Fedorovskaya, E.A.; Slinkin, A.A.; Starodubtseva, E.V.; Stepanov, Y.P.

1985-09-01

214

First-principles study of the structural properties and magnetism of R2CoIn8 (R=Y, Pr, Nd, and Dy) intermetallic compounds  

NASA Astrophysics Data System (ADS)

The electronic structure of R2CoIn8 (R=Y, Pr, Nd, and Dy) intermetallic compounds is calculated from first principles based on the density functional theory (DFT). The Kohn-Sham single-particle equations of the DFT are solved using two independent computational methods, namely APW+lo and FPLO. First the structural properties of Y2CoIn8 are studied. Good agreement of calculated equilibrium volume and c/a ratio with the experimental data is found. Also we minimize the forces at equilibrium volume and calculate the symmetry-free structural parameters of the space group P4/mmm for Y2CoIn8. In Y2CoIn8, the Co 3d states are almost fully occupied and situated below the Fermi level. We applied the fixed-spin-moment method and a stable paramagnetic ground state for Y2CoIn8 was found. Finally, the crystal field (CF) parameters were calculated for R=Pr, Nd and Dy from first principles. The microscopic tetragonal CF Hamiltonian was diagonalized and the obtained eigenvalues and eigenfunctions were used to predict the anisotropy of the magnetic properties of R2CoIn8 single crystals.

Diviš, M.

2012-07-01

215

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

216

The magnetoelastic properties of Co-rich Ho(Fe,Co,Ti)12 intermetallic compounds near the spin reorientation transition  

NASA Astrophysics Data System (ADS)

The thermal expansion and magnetostriction of Co-rich HoFe11-xCoxTi compounds were investigated; using the strain gauge method in the temperature range 77-560 K, under applied magnetic fields up to 1.5 T. Both linear thermal expansion coefficient and volume magnetostriction of HoFe2Co9Ti exhibit a large anomaly near the spin reorientation transition. In HoCo11Ti sample, this anomaly is only present in the volume curve at the spin reorientation transition. The temperature dependence of anisotropic magnetostriction shows a similar behaviour in both samples. There is no saturation in the isotherm curves of anisotropic magnetostriction in HoCo11Ti compound. In contrast, saturation behaviour starts approximately from T=410 K in HoFe2Co9Ti. The magnetovolume effect in Fe-containing compound at around spin reorientation transition in the maximum available magnetic field is approximately two times larger than that in the other sample. The anisotropic and volume magnetostriction results are discussed in terms of the contribution of magnetostriction attributed to the magnetic sublattices R and T and the local magnetic moment model.

Sanavi Khoshnoud, D.; Motevalizadeh, L.; Tajabor, N.

2013-10-01

217

Selective Adsorption of Organosulfur Compounds from Transportation Fuels by ??Complexation  

Microsoft Academic Search

Ab initio molecular orbital (MO) calculations were performed on the adsorption bond energies between the main sulfur compounds and the Cu on CuCl and CuY zeolite, for desulfurization of transportation fuels by ??complexation sorbents. The relative adsorption bond energies of these compounds were measured by the elution order, based on the breakthrough curves of these compounds, from a column of

Frances H. Yang; Ralph T. Yang

2005-01-01

218

The easy magnetization directions in R{sub 6}Fe{sub 23} intermetallic compounds: A crystal field analysis  

SciTech Connect

X-ray diffraction patterns on magnetically aligned powder samples of R{sub 6}Fe{sub 23} (R=Dy, Er, Ho, and Tm) show that these compounds all magnetize along a [111] easy direction. At first sight it is difficult to reconcile the common easy magnetization direction of Er{sub 6}Fe{sub 23} and Tm{sub 6}Fe{sub 23} on one hand, with Dy{sub 6}Fe{sub 23} and Ho{sub 6}Fe{sub 23} on the other, since the respective B{sub 20} rare earth crystal field parameters of these pairs of compounds are opposite in sign. In this article we show that the crystal field stabilization energy of the [111] direction, relative to either [100] or [110], varies as the square of the crystal field term B{sub 20}, thereby providing an explanation for the common [111] direction of easy magnetization. {copyright} {ital 1997 American Institute of Physics.}

Bowden, G.J.; Cadogan, J.M.; de Leon, H. [School of Physics, The University of New South Wales, Sydney, NSW 2052 (Australia)] [School of Physics, The University of New South Wales, Sydney, NSW 2052 (Australia); Ryan, D.H. [Physics Department, McGill University, 3600 University St., Montreal, Quebec, H3A 2T8 (Canada)] [Physics Department, McGill University, 3600 University St., Montreal, Quebec, H3A 2T8 (Canada)

1997-04-01

219

Preparation and Mechanical Properties of Fe 3 Al Nanostructured Intermetallics  

Microsoft Academic Search

Nanostructured Fe3Al intermetallic compounds were produced by using hydrogen arc plasma method. The transmission electron microscopy experiments showed that the average particle size of the as-synthesized was about 40-nm. The change in hardness of Fe3Al nanostructured intermetallic compounds with annealing temperatures was observed and evaluated.

Hao Chuncheng; Cui Zuolin; Yin Yansheng; Zhang Zhikun

2002-01-01

220

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

221

Preparation of hydride-forming intermetallic films  

Microsoft Academic Search

Amorphous and polycrystalline films of hydride-forming intermetallic compounds (IMCs) have been prepared by vacuum deposition methods. Structure and composition have been investigated by XRD, XPS and by fluorescent X-ray spectroscopy. La-Ni, Pr-Ni and Ni-Zr films have been obtained on water-cooled Cu substrates by magnetron sputtering of intermetallic targets under an Ar atmosphere. Amorphous films with compositions corresponding to PrNi5 and

O. K Alexeeva; A Chistov; V Sumarokov

1995-01-01

222

Intermetallic compound formation in Sn–Co–Cu, Sn–Ag–Cu and eutectic Sn–Cu solder joints on electroless Ni(P) immersion Au surface finish after reflow soldering  

Microsoft Academic Search

The interfacial reactions between Sn–0.4Co–0.7Cu eutectic alloy and immersion Au\\/electroless Ni(P)\\/Cu substrate were investigated after reflow soldering at 260°C for 2min. Common Sn–4.0Ag–0.5Cu and eutectic Sn–0.7Cu solders were used as reference. Two types of intermetallic compounds (IMC) were found in the solder matrix of the Sn–0.4Co–0.7Cu alloy, namely coarser CoSn2 and finer Cu6Sn5 particles, while only one ternary (Cu, Ni)6Sn5

Peng Sun; Cristina Andersson; Xicheng Wei; Zhaonian Cheng; Dongkai Shangguan; Johan Liu

2006-01-01

223

Processing of complex compound semiconductors in space  

NASA Technical Reports Server (NTRS)

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

Bachmann, K.

1985-01-01

224

First-Principle Study on Structural, Elastic and Electronic Properties of Binary Rare Earth Intermetallic Compounds: GdCu and GdZn  

NASA Astrophysics Data System (ADS)

First principle study on structural, elastic and electronic properties of binary copper and zinc based rare earth intermetallics have been carried out using the full-potential augmented plane waves plus local orbital (APW+ lo) within density functional theory (DFT). Results on elastic properties are obtained using generalized gradient approximation (GGA) for exchange correlation potentials. The equilibrium lattice parameter, bulk modulus and its pressure derivative have been obtained using optimization method. Young's modulus, shear modulus, Poisson ratio, sound velocities for longitudinal and shear waves, Debye average velocity, Debye temperature and Grüneisen parameters have been calculated. From electronic calculations, it has been found that electronic conduction in copper and zinc based rare earth intermetallics is mainly attributed to 3d-orbital electrons of Cu and Zn.

Singh, R. P.; Singh, R. K.; Shalu; Rajagopalan, M.

2012-03-01

225

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

226

Humic acid complexation of basic and neutral polycyclic aromatic compounds  

Microsoft Academic Search

Complexation by humic acid (HA) of basic (quinoline) and neutral (naphthalene) polycyclic aromatic compounds (PACs) was compared using fluorescence spectroscopy and equilibrium dialysis (ED). These compounds sorb to HA via cation exchange and hydrophobic interactions, respectively. Ionization of quinoline strongly affects its sorption to HA; maximum sorption is observed at pH close to logKb (4.92), and competition with H+ and

K. G. Karthikeyan; Jon Chorover

2002-01-01

227

Emission of complex fragments in compound nucleus decay  

SciTech Connect

The compound nucleus mechanism for complex fragment emission is discussed theoretically and demonstrated experimentally. The role of the potential energy as a function of mass asymmetry is shown in experimental charge distributions. This process is followed from near the threshold up to bombarding energies of several tens of MeV A. 12 refs., 12 figs.

Moretto, L.G.

1986-04-01

228

Reaction synthesis of intermetallics.  

National Technical Information Service (NTIS)

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, redu...

S. C. Deevi V. K. Sikka

1994-01-01

229

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.

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

2013-01-01

230

Integrating giant microwave absorption with magnetic refrigeration in one multifunctional intermetallic compound of LaFe(11.6)Si(1.4)C(0.2)H(1.7).  

PubMed

Both microwave absorption and magnetocaloric effect (MCE) are two essential performances of magnetic materials. We observe that LaFe(11.6)Si(1.4)C(0.2)H(1.7) intermetallic compound exhibits the advantages of both giant microwave absorption exceeding -42 dB and magnetic entropy change of -20 Jkg(-1)K(-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

231

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

232

Complex conductivity of UTX compounds in high magnetic fields  

SciTech Connect

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

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

2008-01-01

233

Complex conductivity of UTX compounds in high magnetic fields  

SciTech Connect

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

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

2009-01-01

234

Magnesium silicide intermetallic alloys  

SciTech Connect

Methods of induction melting an ultra-low-density magnesium silicide (Mg[sub 2]Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg[sub 2]Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 [times] 10[sup 5] Pa), at a temperature close to but not exceeding 1,105 C [+-] 5 C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg[sub 2]Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg[sub 2]Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg[sub 2]Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg[sub 2]Si matrix were found in the Mg[sub 2]Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

Li, G.H.; Gill, H.S.; Varin, R.A. (Univ. of Waterloo, ON (Canada). Dept. of Mechanical Engineering)

1993-11-01

235

Magnesium silicide intermetallic alloys  

NASA Astrophysics Data System (ADS)

Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not exceeding 1105 °C ± 5 °C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg2Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg2Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg2Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg2Si matrix were found in the Mg2Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

Li, Gh.; Gill, H. S.; Varin, R. A.

1993-11-01

236

Magnetic structure of R2CoGa8 (R = Gd, Tb and Dy) and evolution of the magnetic structures along the series of intermetallic compounds with R = Gd - Tm  

NASA Astrophysics Data System (ADS)

In this work we have determined the magnetic structure of R2CoGa8 (R = Gd, Tb and Dy) intermetallic compounds using X-ray resonant magnetic scattering in order to study the evolution of the anisotropic magnetic properties along the series for R = Gd-Tm. The three compounds have a commensurate antiferromagnetic structure with a magnetic propagation vector (1/2 1/2 1/2) with Néel temperatures of 21.0, 27.5 and 15.2 K for R = Gd, Tb and Dy, respectively. The critical exponent ? obtained from the temperature dependence of the integrated intensity of the resonant magnetic peaks suggest a 3D magnetism for the three compounds. The energy line shapes at the L2 and L3 edges of the magnetic peaks for these compounds present a purely dipolar character as demonstrated by comparison to first principle calculations. Comparing the simulated and integrated intensities corrected for absorption, we conclude that the magnetic moment direction is in the ab-plane for Gd2CoGa8 compound and parallel to the c-axis for the Tb2CoGa8 and Dy2CoGa8 compounds. This information is used to discuss the evolution of the magnetic structure of R2CoGa8 series for R = Gd-Tm where both the direction of the ordered moment and the ordering temperature evolution along the series can be explained through the competition between the indirect Ruderman-Kittel- Kasuya-Yoshida exchange interaction and crystalline electric field effects.

Giles, Carlos; Madergan, Jose Renato; Adriano, Cris; Vescovi, Rafael; Pagliuso, Pascoal

2013-03-01

237

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

238

Lasing characteristics of vapors of complex organic compounds  

NASA Astrophysics Data System (ADS)

Lasing in vapors of complex organic compounds under pumping by laser single pulses is studied theoretically. Attention is given to the chief feature of the gas phase, namely the relationship between the lasing characteristics of the active molecules and the vibrational energy in the ground excited states. It is shown that the drastic growth of the average vibrational energy of active molecules during the pump pulse results in a considerable deterioration of vapor lasing as compared to lasing in solutions. Lasing in POPOP vapors is taken as an example.

Abakumov, G. A.; Vorobev, S. A.; Lademan, Iu.; Simonov, A. P.

1980-02-01

239

Activation of the TCR complex by small chemical compounds.  

PubMed

Small chemical compounds and certain metal ions can activate T cells, resulting in drug hypersensitivity reactions that are a main problem in pharmacology. Mostly, the drugs generate new antigenic epitopes on peptide-major histocompatibility complex (MHC) molecules that are recognized by the T-cell antigen receptor (TCR). In this review we discuss the molecular mechanisms of how the drugs alter self-peptide-MHC, so that neo-antigens are produced. This includes (1) haptens covalently bound to peptides presented by MHC, (2) metal ions and drugs that non-covalently bridge self-pMHC to the TCR, and (3) drugs that allow self-peptides to be presented by MHCs that otherwise are not presented. We also briefly discuss how a second signal-next to the TCR-that naïve T cells require to become activated is generated in the drug hypersensitivity reactions. PMID:24214616

Louis-Dit-Sully, Christine; Schamel, Wolfgang W A

2014-01-01

240

Lasing characteristics of vapors of complex organic compounds  

NASA Astrophysics Data System (ADS)

A theoretical investigation is made of laser action in vapors of complex organic compounds pumped by giant laser pulses. Allowance is made for the main feature of the gas phase, namely, a dependence of the spectroscopic and lasing characteristics of the active molecules on the vibrational energy stored in the ground and excited states. It is shown that a possible substantial increase in the average vibrational energy of the active molecules during the pump pulse causes an appreciable deterioration in the lasing characteristics of vapors compared with solutions, even in the most favorable case without induced absorption. An analysis is made using the parameters of a system similar to the experimental values for l,4-bis[2-(5-phenyloxazolyl)]benzene (POPOP) vapor and allowance is made for neutral gases.

Abakumov, G. A.; Vorob'ev, S. A.; Lademann, Jürgen; Simonov, A. P.

1980-02-01

241

Large magnetic entropy change and refrigerant capacity in rare-earth intermetallic RCuAl (R=Ho and Er) compounds  

NASA Astrophysics Data System (ADS)

The magnetic properties and the magnetocaloric effects of RCuAl (R=Ho and Er) compounds have been investigated. Both HoCuAl and ErCuAl just undergo a second-order ferromagnetic-paramagnetic phase transition at TC. Large reversible magnetic entropy changes (?SM) are observed around their respective Curie temperatures due to the ferromagnetic-paramagnetic phase transition. For a field change of 0-5 T, the peak values of -?SM of RCuAl (R=Ho and Er) compounds are 23.9 and 22.9 J kg-1 K-1 at TC, with the values of refrigerant capacity of 393 and 321 J kg-1, respectively. These properties suggest that RCuAl (R=Ho and Er) compounds could be considered as attractive magnetic refrigerants working in low temperature range.

Dong, Q. Y.; Chen, J.; Shen, J.; Sun, J. R.; Shen, B. G.

2012-08-01

242

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

243

Magnesium silicide intermetallic alloys  

Microsoft Academic Search

Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not

Gh. Li; H. S. Gill; R. A. Varin

1993-01-01

244

Magnesium silicide intermetallic alloys  

Microsoft Academic Search

Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots\\u000a of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under\\u000a overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not

G. H. Li; H. S. Gill; R. A. Varin

1993-01-01

245

Intermetallic compounds of the heaviest elements and their homologs: The electronic structure and bonding of MM', where M=Ge, Sn, Pb, and element 114, and M'=Ni, Pd, Pt, Cu, Ag, Au, Sn, Pb, and element 114  

NASA Astrophysics Data System (ADS)

Fully relativistic (four-component) density-functional theory calculations were performed for intermetallic dimers MM', where M=Ge, Sn, Pb, and element 114, and M'=group 10 elements (Ni, Pd, and Pt) and group 11 elements (Cu, Ag, and Au). PbM and 114M, where M are group 14 elements, were also considered. The results have shown that trends in spectroscopic properties-atomization energies De, vibrational frequencies ?e, and bond lengths Re, as a function of M', are similar for compounds of Ge, Sn, Pb, and element 114, except for De of PbNi and 114Ni. They were shown to be determined by trends in the energies and space distribution of the valence ns(M') atomic orbitals (AOs). According to the results, element 114 should form the weakest bonding with Ni and Ag, while the strongest with Pt due to the largest involvement of the 5d(Pt) AOs. In turn, trends in the spectroscopic properties of MM' as a function of M were shown to be determined by the behavior of the np1/2(M) AOs. Overall, De of the element 114 dimers are about 1 eV smaller and Re are about 0.2 a.u. larger than those of the corresponding Pb compounds. Such a decrease in bonding of the element 114 dimers is caused by the large SO splitting of the 7p orbitals and a decreasing contribution of the relativistically stabilized 7p1/2(114) AO. On the basis of the calculated De for the dimers, adsorption enthalpies of element 114 on the corresponding metal surfaces were estimated: They were shown to be about 100-150 kJ/mol smaller than those of Pb.

Pershina, V.; Anton, J.; Fricke, B.

2007-10-01

246

Magnetocaloric effect of RM2 (R = rare earth, M = Ni, Al) intermetallic compounds made by centrifugal atomization process for magnetic refrigerator  

NASA Astrophysics Data System (ADS)

RM2 (R = rare earth, M = Al, Ni and Co) compounds have large entropy change and magnetic transition temperatures can be controlled by change of R and/or M so that are suitable to a magnetic refrigerator for hydrogen liquefaction under development. In order to improve refrigerator performance, spherical powdered HoAl2, DyAl2, and GdNi2 compounds with submillimeter diameter were synthesized by centrifugal atomization process. By measuring the magnetization and heat capacity, we obtained entropy change by magnetic fields and entropy as functions of temperature and magnetic field, which are essential for analysing the magnetic refrigeration cycle. All samples showed sharp magnetic transitions and had good potentials for use in magnetic refrigeration.

Matsumoto, K.; Asamato, K.; Nishimura, Y.; Zhu, Y.; Abe, S.; Numazawa, T.

2012-12-01

247

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Structural Feature and Solute Trapping of Rapidly Grown Ni3Sn Intermetallic Compound  

NASA Astrophysics Data System (ADS)

The rapid dendritic growth of primary Ni3Sn phase in undercooled Ni-30.9%Sn-5%Ge alloy is investigated by using the glass fluxing technique. The dendritic growth velocity of Ni3Sn compound is measured as a function of undercooling, and a velocity of 2.47 m/s is achieved at the maximum undercooling of 251 K (0.17TL). The addition of the Ge element reduces its growth velocity as compared with the binary Ni75Sn25 alloy. During rapid solidification, the Ni3Sn compound behaves like a normal solid solution and it displays a morphological transition of “coarse dendrite-equiaxed grain-vermicular structure" with the increase of undercooling. Significant solute trapping of Ge atoms occurs in the whole undercooling range.

Qin, Hai-Yan; Wang, Wei-Li; Wei, Bing-Bo

2009-11-01

248

A study of the real structure of intermetallic compounds R 2Fe 17 (R=Ce, Lu) using neutron powder diffraction, NMR and NGR methods  

NASA Astrophysics Data System (ADS)

The real structure of the Lu 2Fe 17 compound was shown to be a disordered variant of the Th 2Ni 17-type structure for which the exchange of places between Y in 2b-sites and `dumbbells’ of Fe (4f sites) is specific as well as a partial occupation of 4e-position by Fe atoms. Besides, some quantity of Y implants in 2c sites, causing a distortion inside the plane and splitting of Fe 12j-position into two. The real crystal structure of the Ce 2Fe 17 compound is close to an ideal one of the Th 2Zn 17-type. The results of neutron diffraction investigation, which allow one to determine fine structure distortions of the lattices “in the mean” are in good agreement with the NMR and NGR data reflecting local (in terms of interatomic spacings) changes.

Voronin, V. I.; Serikov, V. V.; Kleinerman, N. M.; Kuchin, A. G.

2000-03-01

249

Complex Hydride Compounds with Enhanced Hydrogen Storage Capacity  

SciTech Connect

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

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

2008-02-18

250

Electrocatalytic effects of Mo–Pt intermetallics singly and with ionic activators. Hydrogen production via electrolysis  

Microsoft Academic Search

The intermetallic phases along the Pt–Mo phase diagram, singly or in combination with specific ionic activators, have been investigated as cathode materials for the production of hydrogen by electrolysis from water KOH solutions in an attempt to decrease energy consumption. The influence of ionic activators (activating compounds) on energy consumption was significant. The intermetallic phases, as cathode materials, were activated

Dragica Lj. Stoji?; Tomislav D. Grozdi?; Milica P. Mar?eta Kaninski; Vojislav ?. Stani?

2007-01-01

251

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.

252

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

253

Recent advances in ordered intermetallics  

SciTech Connect

Ordered intermetallic alloys based on aluminides and silicides offer many advantages for structural use at high temperatures in hostile environments. Attractive properties include excellent oxidation and corrosion resistance, light weight, and superior strength at high temperatures. The major concern for structural use of intermetallics was their low ductility and poor fracture resistance at ambient temperatures. For the past 10 years, considerable effort was devoted to R&D of ordered intermetallic alloys, and progress has been made on understanding intrinsic and extrinsic factors controlling brittle fracture in intermetallic alloys based on aluminides and silicides. Parallel effort on alloy design has led to the development of a number of ductile and strong intermetallic alloys based on Ni{sub 3}Al, NiAl, Fe{sub 3}Al, FeAl, Ti{sub 3}Al, and TiAl systems for structural applications.

Liu, C.T.

1994-12-31

254

Monodisperse pattern nanoalloying for synergistic intermetallic catalysis.  

PubMed

Nanoscale alloys attract enormous research attentions in catalysis, magnetics, plasmonics and so on. Along with multicomponent synergy, quantum confinement and extreme large surface area of nanoalloys offer novel material properties, precisely and broadly tunable with chemical composition and nanoscale dimension. Despite substantial progress of nanoalloy synthesis, the randomized positional arrangement and dimensional/compositional inhomogeneity of nanoalloys remain significant technological challenges for advanced applications. Here we present a generalized route to synthesize single-crystalline intermetallic nanoalloy arrays with dimensional and compositional uniformity via self-assembly. Specific electrostatic association of multiple ionic metal complexes within self-assembled nanodomains of block copolymers generated patterned monodisperse bimetallic/trimetallic nanoalloy arrays consisting of various elements, including Au, Co, Fe, Pd, and Pt. The precise controllability of size, composition, and intermetallic crystalline structure of nanoalloys facilitated tailored synergistic properties, such as accelerated catalytic growth of vertical carbon nanotubes from Fe-Co nanoalloy arrays. PMID:24083558

Mun, Jeong Ho; Chang, Yun Hee; Shin, Dong Ok; Yoon, Jong Moon; Choi, Dong Sung; Lee, Kyung-Min; Kim, Ju Young; Cha, Seung Keun; Lee, Jeong Yong; Jeong, Jong-Ryul; Kim, Yong-Hyun; Kim, Sang Ouk

2013-11-13

255

Undercooling Behavior and Intermetallic Compound Coalescence in Microscale Sn-3.0Ag-0.5Cu Solder Balls and Sn-3.0Ag-0.5Cu/Cu Joints  

NASA Astrophysics Data System (ADS)

The microstructure of microscale solder interconnects and soldering defects have long been known to have a significant influence on the reliability of electronic packaging, and both are directly related to the solidification behavior of the undercooled solder. In this study, the undercooling behavior and solidification microstructural evolution of Sn-3.0Ag-0.5Cu solder balls with different diameters (0.76 mm, 0.50 mm, and 0.30 mm) and the joints formed by soldering these balls on Cu open pads of two diameters (0.48 mm and 0.32 mm) on a printed circuit board (PCB) substrate were characterized by differential scanning calorimetry (DSC) incorporated into the reflow process. Results show that the decrease in diameter of the solder balls leads to an obvious increase in the undercooling of the balls, while the undercooling of the solder joints shows a dependence on both the diameter of the solder balls and the diameter ratio of solder ball to Cu pad (i.e., D s/ D p), and the diameter of the solder balls has a stronger influence on the undercooling of the joints than the dimension of the Cu pad. Coarse primary intermetallic compound (IMC) solidification phases were formed in the smaller solder balls and joints. The bulk Ag3Sn IMC is the primary solidification phase in the as-reflowed solder balls. Due to the interfacial reaction and dissolution of Cu atoms into the solder matrix, the primary Ag3Sn phase can be suppressed and the bulk Cu6Sn5 IMC is the only primary solidification phase in the as-reflowed solder joints.

Zhou, M. B.; Ma, X.; Zhang, X. P.

2012-11-01

256

Equiatomic intermetallic compounds YTX (T = Ni, Ir; X = Si, Ge, Sn, Pb): a systematic study by (89)Y solid state NMR and (119)Sn Mössbauer 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 Mössbauer 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

Höting, Christoph; Eckert, Hellmut; Haarmann, Frank; Winter, Florian; Pöttgen, Rainer

2014-06-01

257

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

258

Methanation by catalysts formed from intermetallic compounds  

Microsoft Academic Search

The reaction of carbon monoxide with hydrogen (Hâ\\/CO = 3) to form methane was conducted over the temperature range 150 to 600°C) over a number of untreated alloys and alloys which were oxidized at 350°C for 12 h (Ni\\/sub x\\/Si\\/sub y\\/, Ni\\/sub x\\/Al\\/sub y\\/, Co\\/sub x\\/Si\\/sub y, Co\\/sub x\\/Al\\/sub y\\/, Fe\\/sub x\\/Si\\/sub y\\/, and Fe\\/sub x\\/Al\\/sub y\\/). In both untreated

H. Imamura; W. E. Wallace

1979-01-01

259

Intermetallic insertion anodes for lithium batteries.  

SciTech Connect

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

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

1999-11-12

260

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

261

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

262

Synthetic chelating agents and compounds exhibiting complexing properties in the aquatic environment  

Microsoft Academic Search

Synthetic chelating agents are utilized in many industrial applications because of their capability of binding and masking metal ions. This review of 20 main compounds includes chelating agents and other compounds, such as the organophosphonates or polycarboxylates, which, by binding metal ions, also exhibit some complexing properties. It aimed to gather data about production, use, toxicity, entry into the aquatic

Thomas P Knepper

2003-01-01

263

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

PubMed

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

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

2013-01-01

264

Thermodynamics of the sorption of cerium complex compounds on anionite  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

265

Structural chemistry of complex carbides and related compounds  

NASA Astrophysics Data System (ADS)

Complex carbides formed in ternary systems of a transition element ( M), a B-group element ( M'), and carbon and having a formula M2M'C (H-phase) or M3M'C (perovskite carbide) occur frequently. This reflects the simple geometry of the atomic arrangement of the metals and the filling mode by an interstitial stabilizer such as carbon or nitrogen. The phase relationship of the ternary combinations {Ti, Zr, Hf, V, Nb, Ta, Cr, Mn, and Ni}-aluminum-carbon was investigated. New complex carbides were found with the corresponding zirconium, hafnium, and tantalum combinations. The crystal structures in the case of Zr- and Hf-containing complex carbides can be characterized by a twelve-metal-layer sequence and by a ten-metal-layer sequence with carbon atoms again filling octahedral voids. The transition of structure types from TiC, Ti 2AlC, Ti 3SiC 2, ZrAlC 2, Zr 2Al 3C 5, to Al 4C 3 is also discussed.

Nowotny, Hans; Rogl, Peter; Schuster, Julius C.

1982-08-01

266

Synthesis of complex and diverse compounds through ring distortion of abietic acid.  

PubMed

Many compound screening collections are populated by members that possess a low degree of structural complexity. In an effort to generate compounds that are both complex and diverse, we have developed a strategy that uses natural products as a starting point for complex molecule synthesis. Herein we apply this complexity-to-diversity approach to abietic acid, an abundant natural product used commercially in paints, varnishes, and lacquers. From abietic acid we synthesize a collection of complex (as assessed by fraction of sp(3) -hybridized carbons and number of stereogenic centers) and diverse (as assessed by Tanimoto analysis) small molecules. The 84 compounds constructed herein, and those created through similar efforts, should find utility in a variety of biological screens. PMID:24273016

Rafferty, Ryan J; Hicklin, Robert W; Maloof, Katherine A; Hergenrother, Paul J

2014-01-01

267

Moessbauer investigation of intermetallic hydrides. Final report, 1 November 1982-31 October 1985  

SciTech Connect

This research was a study of hydrogen absorption in intermetallic hydrides. Mossbauer and x-ray-diffraction measurements were used to aid in a determination of the hydrogen-absorbing mechanism occurring in hydriding. Information was sought that would provide insight into the nature of bonding and interaction between the absorbed hydrogen and the various sites in the intermetallics. There was also interest in observing what happened to Sn in intermetallic compounds when hydrided. Studies were made of the changes in isomer shift and linewidth upon hydriding.

Oliver, F.W.

1985-12-21

268

High Pressure XRD Structural Study of Intermetallic Hydrogen Storage Material ZrFe2  

NASA Astrophysics Data System (ADS)

Intermetallic compounds show high hydrogen sorption capacities when pressurized with hydrogen. Further, they are also used in hydride compressors [1]. The structure of intermetallic ZrFe2, which can contain about 1.7 wt/% hydrogen around 0.18 GPa, was studied using XRD at high pressures up to 47 GPa using a diamond anvil cell and synchrotron x-rays. The cubic Fd3m Laves phase is found to be stable and the bulk modulus was found to be 163.5 GPa which compares well with other intermetallics. The variation of unit structural parameters and the equation of state are discussed.

Antonio, Daniel; Kumar, Ravhi; Cornelius, Andrew

2011-03-01

269

Fundamentals of mechanical behavior in structural intermetallics: A synthesis of atomistic and continuum modeling  

SciTech Connect

After a brief account of the recent advances in computational research on mechanical behavior of structural intermetallics, currently unresolved problems and critical issues are addressed and the knowledge base for potential answers to these problems is discussed. As large-scale problems (e.g., dislocation core structures, grain boundaries, and crack tips) are treated by atomistic simulations, future development of relevant interatomic potentials should be made consistent with the results of first-principles calculations. The bulk and defect properties calculated for intermetallic compounds, both known and as yet untested, can furnish insights to alloy designers in search of new high-temperature structural intermetallics.

Yoo, M.H.; Fu, C.L.

1993-08-01

270

Stability and conformation of the complexes of riboflavin with aromatic hydroxy compounds in an aqueous medium  

NASA Astrophysics Data System (ADS)

Overall equilibrium constants K' for the formation of molecular complexes of riboflavin with the conjugate forms of different aromatic hydroxy compounds are greater in magnitude than those involving the protonated forms of the hydroxy compounds. There is good agreement between the KB values determined by using absorption and emission methods. Based on the magnitude of KB, it is possible to differentiate between the donor capacities of the hydroxy compounds in the charge transfer complexes with riboflavin. Molecular modeling studies indicate stacking interactions for all the systems in an aqueous medium.

Datta, Silpi; Mukhopadhyay, Chaitali; Bhattacharya, Subirnath; Bose, Swapan Kumar

2006-05-01

271

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

272

Effect of interstitial elements on phase stability of selected intermetallics  

SciTech Connect

The possibility of modifying the complex crystal structure of selected refractory metal aluminides and silicides by alloying additions was investigated. The intermetallic compounds, Nb{sub 3}Si, Nb{sub 3}Al, Mo{sub 3}Si, Mo{sub 3}Al, V{sub 3}Si and Cr{sub 3}Si were alloyed with carbon or oxygen. V{sub 3}Au was studied as a model for the A15 {yields} L1{sub 2} structure change. Oxygen and carbon stabilized the perovskite structure in V {sub 3}Au. About 17.5 at. % oxygen was added to transform V{sub 79}Au{sub 21} to single phase L{prime}1{sub 2}, however, about 22 at. % carbon was needed to reach the single phase L{prime}1{sub 2}. In the case of Nb{sub 3}Si, it was difficult to decide whether the oxygen-stabilized phase is the L1{sub 2}-Cu{sub 3}Au or perovskite structure. No single phase was reached even with 35 at. % Oxygen. The stabilized phases were L1{sub 2}-Cu{sub 3}Au or L{prime}1{sub 2}, Nb{sub 5}Si{sub 3} and Nb s.s. It was not possible to stabilize the L1{sub 2}-Cu{sub 3}Au structure with the addition of carbon. Adding 20 at. % carbon resulted in the stabilization of Nb{sub 3}Au with a hexagonal structure, NbC, and Nb{sub 3}Si tet. No L12-Cu{sub 3}Au or perovskite structure was stabilized with the addition of oxygen or carbon in the case of Mo{sub 3}Al, Nb{sub 3}Al, V{sub 3}Si and Cr{sub 3}Si. The Pettifor schematic structural map for AB{sub 3} compounds was used to predict the structural changes in the above mentioned compounds.

Kassem, M.A.

1990-01-01

273

Nonstoichiometry of Al-Zr intermetallic phases  

SciTech Connect

Nonstoichiometry of metastable cubic {beta}{prime} and equilibrium tetragonal {beta} Al-Zr intermetallic phases of the nominal composition Al{sub 3}Zr in Al-rich alloys has been extensively studied. It is proposed that the ``dark contrast`` of {beta}{prime} core in {beta}{prime}/{sigma}{prime} complex precipitates, in Al-Li-Zr based alloys, is caused by incorporation of Al and Li atoms into the {beta}{prime} phase on Zr sublattice sites, forming nonstoichiometric Al-Zr intermetallic phases, rather than by Li partitioning only. {beta}{prime} particles contain very small amounts of Zr, approximately 5 at.%, much less than the stoichiometric 25 at.% in the Al{sub 3}Zr metastable phase. These particles are, according to simulation of high resolution images, of the Al{sub 3}(Al{sub 0.4}Li{sub 0.4}Zr{sub 0.2}) type. Nonstoichiometric particles of average composition Al{sub 4}Zr and Al{sub 6}Zr are observed also in the binary Al-Zr alloy, even after annealing for several hours at 600{degree}C.

Radmilovic, V.; Thomas, G.

1994-06-01

274

Structural and mechanistic features of intermetallic materials for lithium batteries  

NASA Astrophysics Data System (ADS)

An anode system based on intermetallic phases with a zinc-blende-type structure (InSb, GaSb and AlSb) has been studied for lithium-ion batteries. The compound, InSb, in particular, cycles well between 1.2 and 0.5 V. After an initial "conditioning" cycle, a mechanism involving lithium insertion into an open framework structure followed by indium extrusion in the potential range 1.2-0.7 V, appears to dominate; between 0.7 and 0.5 V, a more complex mechanism occurs involving indium extrusion from a stable fcc Sb anion array and subsequent lithiation of the extruded indium. In situ X-ray diffraction and extended X-ray analysis fine structure (EXAFS) data were obtained over the voltage window 1.2-0.5 V, where a rechargeable capacity of 300 mAh/g is achievable. The results indicate that after the "conditioning" reaction a Li yIn 1- ySb zinc-blende framework, in which Li atoms partially substitute for In, is responsible for the good cycling behavior of the cells. Isostructural AlSb and GaSb electrodes provide inferior electrochemical capacities.

Vaughey, J. T.; Johnson, C. S.; Kropf, A. J.; Benedek, R.; Thackeray, M. M.; Tostmann, H.; Sarakonsri, T.; Hackney, S.; Fransson, L.; Edström, K.; Thomas, J. O.

275

Extrusion-activated thermal explosion applied to intermetallics processing  

Microsoft Academic Search

The present study deals with synthesizing the NiAl compound through the thermal-explosion route akin to self-propagating high-temperature synthesis under the novel circumstance of extrusion-induced mechanical activation. Either route has the potential for addressing the intermetallics processing cost problem and both reactions may alike be significantly enhanced by prior activation. Reactant powders were homogeneously mixed and precompacted by cold isostatic pressing

M. Andasmas; D. Vrel; N. Fagnon; Th. Chauveau; A. Hendaoui; P. Langlois

2009-01-01

276

Structural and mechanistic features of intermetallic materials for lithium batteries  

Microsoft Academic Search

An anode system based on intermetallic phases with a zinc-blende-type structure (InSb, GaSb and AlSb) has been studied for lithium-ion batteries. The compound, InSb, in particular, cycles well between 1.2 and 0.5V. After an initial “conditioning” cycle, a mechanism involving lithium insertion into an open framework structure followed by indium extrusion in the potential range 1.2–0.7V, appears to dominate; between

J. T. Vaughey; C. S. Johnson; A. J. Kropf; R. Benedek; M. M. Thackeray; H. Tostmann; T. Sarakonsri; S. Hackney; L. Fransson; K. Edström; J. O. Thomas

2001-01-01

277

Zone leveling and solution growth of complex compound semiconductors in space  

NASA Technical Reports Server (NTRS)

A research program on complex semiconducting compounds and alloys was completed that addressed the growth of single crystals of CdSe(y)Te(1-y), Zn(x)Cd(1-x)Te, Mn(x)Cd(1-x)Te, InP(y)As(1-y) and CuInSe2 and the measurement of fundamental physico-chemical properties characterizing the above materials. The purpose of this ground based research program was to lay the foundations for further research concerning the growth of complex ternary compound semiconductors in a microgravity environment.

Bachmann, K. J.

1986-01-01

278

Pressure tuning of competing magnetic interactions in intermetallic CeFe2  

NASA Astrophysics Data System (ADS)

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, P. C.; Rosenbaum, T. F.

2012-07-01

279

Catalysis of hydrogen peroxide decomposition by some complex cobalt (II) compounds in mixed solvents  

Microsoft Academic Search

The volumetric and speetrophotometr ie method were used to study the catalase-like activity of the complex cobalt(II) compounds with N-substituted amino acids and o-phenanthroline toward hydrogen peroxide decomposition, as well as the peroxidase-like activity of the cobalt complex with o-phenanthroline. Kinetic expressions were found for the rate of the catalase and peroxidase reactions as functions of various parameters. It was

A. Ya. Sychev; Bui Ngok Tkho; S. F. Nedopekina

1969-01-01

280

A Method for Efficient Calculation of Diffusion and Reactions of Lipophilic Compounds in Complex Cell Geometry  

PubMed Central

A general description of effects of toxic compounds in mammalian cells is facing several problems. Firstly, most toxic compounds are hydrophobic and partition phenomena strongly influence their behaviour. Secondly, cells display considerable heterogeneity regarding the presence, activity and distribution of enzymes participating in the metabolism of foreign compounds i.e. bioactivation/biotransformation. Thirdly, cellular architecture varies greatly. Taken together, complexity at several levels has to be addressed to arrive at efficient in silico modelling based on physicochemical properties, metabolic preferences and cell characteristics. In order to understand the cellular behaviour of toxic foreign compounds we have developed a mathematical model that addresses these issues. In order to make the system numerically treatable, methods motivated by homogenization techniques have been applied. These tools reduce the complexity of mathematical models of cell dynamics considerably thus allowing to solve efficiently the partial differential equations in the model numerically on a personal computer. Compared to a compartment model with well-stirred compartments, our model affords a more realistic representation. Numerical results concerning metabolism and chemical solvolysis of a polycyclic aromatic hydrocarbon carcinogen show good agreement with results from measurements in V79 cell culture. The model can easily be extended and refined to include more reactants, and/or more complex reaction chains, enzyme distribution etc, and is therefore suitable for modelling cellular metabolism involving membrane partitioning also at higher levels of complexity.

Dreij, Kristian; Chaudhry, Qasim Ali; Jernstrom, Bengt; Morgenstern, Ralf; Hanke, Michael

2011-01-01

281

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

Microsoft Academic Search

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

Eylem Cetin; Mustafa Odabasi; Remzi Seyfioglu

2003-01-01

282

ION COMPOSITION ELUCIDATION (ICE): A HIGH RESOLUTION MASS SPECTROMETRIC TECHNIQUE FOR IDENTIFYING COMPOUNDS IN COMPLEX MIXTURES  

EPA Science Inventory

When tentatively identifying compounds in complex mixtures using mass spectral libraries, multiple matches or no plausible matches due to a high level of chemical noise or interferences can occur. Worse yet, most analytes are not in the libraries. In each case, Ion Composition El...

283

STUDIES ON SOME THIAZOLYLAZO COMPOUNDS AND THEIR COBALT, NICKEL, AND COPPER COMPLEXES  

Microsoft Academic Search

The thiazolylazo compounds and their Co, Ni and Cu complexes of barbituric acid, uracil, thiouracil, citrazinic acid, chromotropic acid, gallic acid, pyrogallol and salicylic acid were prepared and characterized by H NMR, IR and the effect of pH on the electronic absorption spectra. The mode of ionization, the electronic transitions and the dissociation constants were discussed. The stoichiometries of the

M. S. Masoud; G. B. Mohamed; Y. H. Abdul-Razek; A. E. Ali; F. N. Khairy

2002-01-01

284

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

285

Intermetallic-Based High-Temperature Materials  

SciTech Connect

The intermetallic-based alloys for high-temperature applications are introduced. General characteristics of intermetallics are followed by identification of nickel and iron aluminides as the most practical alloys for commercial applications. An overview of the alloy compositions, melting processes, and mechanical properties for nickel and iron aluminizes are presented. The current applications and commercial producers of nickel and iron aluminizes are given. A brief description of the future prospects of intermetallic-based alloys is also given.

Sikka, V.K.

1999-04-25

286

Ruthenium(II) phosphine/diimine/picolinate complexes: inorganic compounds as agents against tuberculosis.  

PubMed

This paper describes the synthesis and characterization of four new ruthenium complexes containing 1,4 bis(diphenylphosphino)butane (dppb), 2-pyridinecarboxylic acid anion (pic) and the diimines [(2,2'-bipyridine (bipy), 4,4'-dimethyl-2,2'-bipyridine (Me-bipy), 4,4'-dichloro-2,2'-bipyridine (Cl-bipy) and 1,10-phenanthroline (phen) as ligands, with formulae [Ru(pic)(dppb)(bipy)]PF(6) (SCAR01), [Ru(pic)(dppb)(Me-bipy)]PF(6) (SCAR02), [Ru(pic)(dppb)(Cl-bipy)]PF(6) (SCAR03) and [Ru(pic)(dppb)(phen)]PF(6) (SCAR04). Additionally, the in vitro anti-Mycobacterium tuberculosis (MTB) activity, cytotoxicity and activity against in vitro infection of these complexes and two more complexes, cis-[Ru(pic)(dppe)(2)]PF(6) (SCAR05) and cis-[RuCl(2)(dppb)(bipy)] (SCAR06), and their free ligands are described and discussed. All compounds showed excellent MIC against MTB, low cytotoxicity and a selectivity index higher than 10. Also, all compounds showed significant intracellular inhibition and the compound SCAR05 showed a better activity than rifampin and SQ109. This is the first report of activity against in vitro infection of ruthenium compounds. PMID:21875763

Pavan, Fernando R; Poelhsitz, Gustavo V; Barbosa, Marilia I F; Leite, Sergio R A; Batista, Alzir A; Ellena, Javier; Sato, Leticia S; Franzblau, Scott G; Moreno, Virtudes; Gambino, Dinorah; Leite, Clarice Q F

2011-10-01

287

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

288

A Mössbauer Study of Tin-Based Intermetallics Formed During the Manufacture of Dispersion-Strengthened Composite Solders  

NASA Astrophysics Data System (ADS)

Mössbauer spectroscopy was used to characterize dispersion-strengthened composite solder powders that were formed through hot gas spray atomization. To perform quantitative measurements, we first measured the relative recoilless fractions of eutectic solder and three intermetallic compounds: Cu3Sn, Cu6Sn5, and Ni3Sn4. These results were then used to determine the concentrations of intermetallic species present in various composite solder samples. Mössbauer spectroscopy was shown to be an effective tool in the analysis of dispersion-strengthened composite solders and was preferentially sensitive to the presence of tin-based intermetallics and oxides.

Reno, Robert C.; Panunto, Michael J.; Piekarski, Brett H.

1997-12-01

289

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

290

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

PubMed

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 550-650nm by exciting at an appropriate wavelength. The intensity of the 616nm peak of Eu(III) was found to be sensitive to complexation. The ratio of the intensities of 616 and 592nm 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. PMID:19233719

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

2009-06-01

291

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

292

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

293

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

Microsoft Academic Search

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 550–650nm by exciting at an appropriate

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

2009-01-01

294

Intermetallic growth in gold ball bonds aged at 175°C: comparison between two 4N wires of different chemistry  

Microsoft Academic Search

Gold wires of different chemistry (denoted as Types A and B) are ballbonded on identical metallization and isothermally aged\\u000a at 175°C. In both wire types the same intermetallic compounds Au4Al and Au8Al3 grow with parabolic time dependence as long as there is a supply of Al from the bondpad. After Al is completely reacted,\\u000a composition of intermetallics in Type A

C. D. Breach; F. W. Wulff

2009-01-01

295

Regional assessment of ambient volatile organic compounds from biopharmaceutical R&D complex.  

PubMed

Biopharmaceutical R&D complexes are major emission sources of volatile organic compounds (VOCs), which may pose potential health risks for staff on site and residents nearby. In this paper health risk assessments were performed for the VOCs in the ambient air of a typical biopharmaceutical R&D complex in China. Results showed halogenated and alkyl compounds were dominant components among 24 major VOCs from 9 selected sampling sites, inside or around the complex. The principal component analysis (PCA) indicated VOCs were generated predominantly from the biopharmaceutical research activities (factor 1 (F1), 71.6%) and traffic vehicles (factor 2 (F2), 15.4%), which were confirmed by contour maps of five selected VOCs (benzene, toluene, chlorobenzene, methylene chloride and n-hexane) simulated by Golden Software Surfer. The cumulative cancer risks for the staff on site and residents nearby were investigated and results showed the risk value were 1.01E--5 and 2.03E--5, respectively, higher than the threshold value of 1.0E--6. These results indicated that elevated VOCs from biopharmaceutical R&D complex are potential risks to the public health. Furthermore, the human health risk assessment revealed that 1,2-dichloroethane, methylene chloride, carbon tetrachloride and benzene were the dominant risk contributors for staff on site, while methyl chloride, carbon tetrachloride, 1,2-dichloroethane and tetrahydrofuran for residents nearby. As a conclusion, this work suggests that proper control strategy should be taken for VOCs releasing to minimize the public health risks, especially for the halogenated compounds. PMID:21831409

Pan, Y; Liu, Q; Liu, F F; Qian, G R; Xu, Z P

2011-09-15

296

Electrolytic hydrogen storage in reluctant intermetallic systems  

NASA Astrophysics Data System (ADS)

Composite electrodes were prepared by mixing, in the ratio 60/40 by weight, the powder of an electrochemically inhibited intermetallic compound (IMC), e.g. TiFe 50/50, TiNi 70/30 or TiNi 40/60 (alloy precursor grade) with Fe powder and pressing the mixture on to a Ni foam support. The charge capacity achieved in these composites was then compared with the capacity of "blank" electrodes in which the IMC had been replaced by an inactive metal (Ti or Ni). The blanks attained capacities in the range 150-200 mA h g -1, although these values were largely exceeded by some IMC+Fe composites due, presumably, to storage on hydrogen. The electrocatalytic properties of Fe are probably not sufficient to explain the activation of hydrogen absorption in the inhibited IMC, since X-ray and energy-dispersive analysis (EDAX) of activated samples did reveal that deep modifications occurred in some composites, in which the formation of new phases may have been induced by charging-discharging cycles.

Casellato, U.; Comisso, N.; Davolio, G.; Mengoli, G.

297

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

298

A complex relationship among chemical concentration, detection threshold, and suprathreshold intensity of bitter compounds.  

PubMed

Detection thresholds and psychophysical curves were established for caffeine, quinine-HCl (QHCl), and propylthiouracil (PROP) in a sample of 33 subjects (28 female mean age 24 +/- 4). The mean detection threshold (+/-standard error) for caffeine, QHCl, and PROP was 1.2 +/- 0.12, 0.0083 +/- 0.001, and 0.088 +/- 0.07 mM, respectively. Pearson product-moment analysis revealed no significant correlations between detection thresholds of the compounds. Psychophysical curves were constructed for each bitter compound over 6 concentrations. There were significant correlations between incremental points of the individual psychophysical curves for QHCl and PROP. Regarding caffeine, there was a specific concentration (6 mM) below and above which the incremental steps in bitterness were correlated. Between compounds, analysis of psychophysical curves revealed no correlations with PROP, but there were significant correlations between the bitterness of caffeine and QHCl at higher concentrations on the psychophysical curve (P<0.05). Correlation analysis of detection threshold and suprathreshold intensity within a compound revealed a significant correlation between PROP threshold and suprathreshold intensity (r=0.46-0.4, P<0.05), a significant negative correlation for QHCl (r=-0.33 to -0.4, P<0.05), and no correlation for caffeine. The results suggest a complex relationship between chemical concentration, detection threshold, and suprathreshold intensity. PMID:17220518

Keast, Russell S J; Roper, Jessica

2007-03-01

299

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

300

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

301

Investigations of intermetallic alloy hydriding mechanisms. Annual progress report, May 1 1979-April 30, 1980  

SciTech Connect

Investigations are being conducted on mechanisms involved with the hydrogen-metal interactions which control the absorption and desorption processes in intermetallic compounds. The status of the following investigations is reported: modeling of hydride formation; microbalance investigations; microstructure investigations; flexure experiments; resistivity experiments; and nuclear backscattering measurements. These investigations concern fundamental hydrogen interaction mechanisms involved in storage alloys.

Livesay, B.R.; Larsen, J.W.

1980-05-01

302

Structure, Magnetism, and Thermodynamics of the Novel Rare Earth-Based Ln5T4 Intermetallics  

Microsoft Academic Search

After approximately 30 years of dormancy, the binary, ternary, and multicomponent intermetallic compounds of rare earth metals (R) with the group 14 elements (T) at the R 5 T 4 stoichiometry have become a goldmine for materials science, condensed matter physics, and solid-state chemistry. In addition to providing numerous opportunities to clarify elusive structure-property relationships, the R 5 T 4

V. K. Pecharsky; K. A. Jr. Gschneidner

2007-01-01

303

The Characterization of Intermetallic Growth in Copper and Gold Ball Bonded on Thicker Aluminum  

Microsoft Academic Search

Wire bonding has been the most popular interconnection method in semiconductor device packaging. Recently, due to the increasing demand for enhancing the reliability of the device, fine wire diameter and more function property, attention has been focused on failure solution of wire bonding. Au-Al intermetalic compound formation and associated Kirkendall voids have resulted in wire bond failures. 2N gold alloy

Liangyi Hung; Yuwei Lin; S. Chen; Yupo Wang; C. S. Hsiao

2006-01-01

304

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 175°C 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

305

Methanol synthesis catalysts from thorium-copper intermetallics. Preparation and evaluation  

Microsoft Academic Search

Bureau of Mines research into the use of intermetallic compounds as catalytic materials has shown catalysts prepared from binary alloys of copper and thorium to be active for the synthesis of methanol from carbon monoxide and hydrogen. Activation of the alloys resulted in oxidation of the thorium yielding high surface area catalysts containing copper interspersed on thoria. For example, catalysts

Elizabeth G. Baglin; Gary B. Atkinson; Larry J. Nicks

1981-01-01

306

Abrasive wear of intermetallic-based alloys and composites  

SciTech Connect

In this study, the abrasive wear behavior of Fe3Al, TiAl, Ti3Al, Al3Ti, NiAl, Ni3Al and MoSi2, and composites based on these compounds, were assessed and compared to the behavior of selected metals, alloys and ceramics. Under the wear conditions used for these tests, the softer intermetallic compounds (e.g. TiAl and Fe3Al) behaved in a manner similar to the metals and alloys, whereas, the harder intermetallic compound (i.e. MoSi2) behaved more like a ceramic. The influence of Al atomic fraction, superlattice structure and ternary alloying additions on the wear behavior of Fe3Al was investigated. Controlling the Al content and third element additions affected wear resistance more than superlattice structure. Composite strengthening was also explored as a method for improving wear resistance. The addition of hard second phase particles (i.e. TiB2 to NiAl and SiC to MoSi2) was also very effective improving wear resistance. Surprisingly, the addition of softer Nb particles did not significantly degrade the wear resistance of a MoSi2 matrix, even at Nb additions of 40%.

Hawk, Jeffrey A.; Alman, David E.

1997-12-01

307

Environmental Effects in Advanced Intermetallics  

SciTech Connect

This paper provides a comprehensive review of environmental embrittlement in iron and nickel aluminizes. The embrittlement involves the interaction of these intermetallics with moisture in air and generation of atomic hydrogen, resulting in hydrogen-induced embrittlement at ambient temperatures. Environmental embrittlement promotes brittle grain-boundary fracture in Ni{sub 3}Al alloys but brittle cleavage fracture in Fe{sub 3}Al-FeAl alloys. The embrittlement strongly depends on strain rate, with tensile-ductility increase with increasing strain rate. It has been demonstrated that environmental embrittlement can be alleviated by alloying additions, surface modifications, and control of grain size and shape. Boron tends to segregate strongly to grain boundaries and is most effective in suppressing environmental embrittlement in Ni{sub 3}Al alloys. The mechanistic understanding of alloy effects and environmental embrittlement has led to the development of nickel and iron aluminide alloys with improved properties for structural use at elevated temperatures in hostile environments.

Liu, C.T.

1998-11-24

308

Compound  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

309

Limb-body wall complex: a compound anomaly pattern in body-wall defects.  

PubMed

Our presentation of four cases demonstrates the essential features of limb-body wall complex (LBWC), representing a compound anomaly pattern in body-wall defects. The diagnosis of this entity is based on two of the three following characteristics: (1) exencephaly/encephalocele and facial clefts; (2) thoraco- and/or abdominoschisis; and (3) limb defects. A definite association with internal anomalies and severe kyphoscoliosis makes a more distinct concept of the pathogenesis reasonable. Limb-body wall malformations result from a malfunction of the ectodermal placodes involving the early embryonic folding process. The poor prognosis of LBWC calls for early antenatal diagnosis. PMID:11527200

Pumberger, W; Schaller, A; Bernaschek, G

2001-07-01

310

Synthesis ZnS:Sm thin films from volatile complex compounds  

NASA Astrophysics Data System (ADS)

Deposition and characterization of ZnS, Sm2S3 and ZnS:Sm films are described. The films have been prepared by chemical vapor deposition using new volatile complex compounds, dithiocarbamates of Zn and Sm, as precursors. Characterization includes X-ray diffraction, chemical analysis of the film composition, ellipsometry and spectrophotometry. It has been shown that at relatively low temperatures (about 380 °C) monophase crystalline Sm2S3 films can be fabricated. Doping of ZnS by Sm with dopant concentration up to 2 at. % has been achieved. Effects of Sm doping on structural and optical properties of the film are presented.

Ivanova, Elena N.; Kovalevskaya, Yu. A.; Bessreguenev, Valentin G.

2002-09-01

311

Synthesis and properties of ZnS-EuS films grown from volatile complex compounds  

SciTech Connect

Deposition and characterization of films of ZnS, EuS and ZnS:Eu are described. The films have been prepared by chemical vapor deposition using new volatile complex compounds, dithiocarbamates of Zn and Eu, as precursors. Characterization includes X-ray diffraction, chemical analysis of the film composition, Raman spectroscopy, ellipsometry, and spectrophotometry. The spatial chemical homogeneity of the films has been determined using a recently developed method of differential dissolution and found to be uniform. Doping of ZnS by Eu with dopant concentration up to 0.3 at.% has been achieved. Effects of Eu doping on structural and optical properties of the films are presented.

Bessergenev, V.G.; Ivanova, E.N.; Kovalevskaya, Y.A. [Siberian Branch of Russian Academy of Sciences, Novosibirsk (Russian Federation). Inst. of Inorganic Chemistry] [Siberian Branch of Russian Academy of Sciences, Novosibirsk (Russian Federation). Inst. of Inorganic Chemistry

1997-10-01

312

Intermetallic insertion anodes for lithium batteries.  

National Technical Information Service (NTIS)

Intermetallic alloys have been investigated for many years as anode materials for lithium batteries and, more recently, as alternative electrodes to carbon, because of several intrinsic advantages including high capacity and safety. Some of the most studi...

C. S. Johnson A. J. Kahaian K. D. Kepler M. Scott M. M. Thackerary

1999-01-01

313

Environmental embrittlement in ordered intermetallic alloys  

SciTech Connect

Ordered intermetallics based on aluminides and silicides possess many promising properties for elevated-temperature applications; however, poor fracture resistance and limited fabricability restrict their use as engineering material. Recent studies have shown that environmental embrittlement is a major cause of low ductility and brittle fracture in many ordered intermetallic alloys. There are two types of environmental embrittlement observed in intermetallic alloys. One is hydrogen-induced embrittlement occurring at ambient temperatures in air. The other is oxygen-induced embrittlement in oxidizing atmospheres at elevated temperatures. In most cases, the embrittlements are due to a dynamic effect involving generation and penetration of embrittling agents (i.e., hydrogen or oxygen ) during testing. Diffusion of embrittling agents plays a dominant role in fracture of these intermetallic alloys. This chapter summarizes recent progress in understanding and reducing environmental embrittlement in these alloys.

Liu, C.T. [Oak Ridge National Lab., TN (United States); Stoloff, N.S. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Materials Engineering

1992-12-31

314

Kinetics of intermetallic growth at the interfaces of soldered metallizations  

NASA Astrophysics Data System (ADS)

Electronic joints are vital parts of electronic devices. In addition to ensuring electrical connectivity between electronic components, solder joints provide for a mechanical attachment between components and printed circuit boards. The mechanical integrity of a joint depends strongly upon the bonding between the solder and the soldered metallization. A good bonding is generally achieved, if an intermetallic layer grows at the solder/metal interface. However, as electronic devices shrink in dimensions, fast-forming intermetallics might grow at the solder/metal interface in an uncontrollable manner, and make up a large fraction of the overall volume of the joint to alter its properties. Moreover, with the elimination of the hazardous Pb from the composition of solders (used to fabricate electronic joints), other metallic additives are incorporated in the solder alloys to tailor their properties to the requirements of certain applications. Unlike Pb, many of the new metallic additives (Cu, Au, Ag, Ni...etc) are reactive with Sn and with the elements present at the metallization. These elements also diffuse very fast in Sn-based solders even at room temperature. Their presence in miniaturized electronic joints can alter the behavior at the solder/metal interface to form ternary or quaternary intermetallics instead of binary Sn-metal intermetallics. In this study, we investigated the growth mechanisms of ternary intermetallics in Pb-Sn/Au/Ni/Cu and Sn-Ag-Cu/Au/Ni/Cu microelectronic joints at the interface between the solder and the metallization. The lateral growth rates of ternary Au-Ni-Sn and Cu-Ni-Sn compounds at the solder/metal interfaces (during isothermal annealing of the joints) were measured by means of electron micrographs. The growth of these alloys at the interfaces was correlated with changes in the morphology, the microstructure and the composition of the bulk of the joint. Characterization of the different alloys present in the joints before and after annealing was carried out by wavelength dispersive spectrometric techniques. The suggested growth mechanisms were examined with simple numerical simulations of atomic diffusion in the solder.

Zribi, Anis B.

2002-09-01

315

Compound  

NASA Astrophysics Data System (ADS)

Recently, Cu-based chalcogenides such as Cu3SbSe4, Cu2Se, and Cu2SnSe3 have attracted much attention because of their high thermoelectric performance and their common feature of very low thermal conductivity. However, for practical use, materials without toxic elements such as selenium are preferable. In this paper, we report Se-free Cu3SbS4 thermoelectric material and improvement of its figure of merit ( ZT) by chemical substitutions. Substitutions of 3 at.% Ag for Cu and 2 at.% Ge for Sb lead to significant reductions in the thermal conductivity by 37% and 22%, respectively. These substitutions do not sacrifice the power factor, thus resulting in enhancement of the ZT value. The sensitivity of the thermal conductivity to chemical substitutions in these compounds is discussed in terms of the calculated phonon dispersion and previously proposed models for Cu-based chalcogenides. To improve the power factor, we optimize the hole carrier concentration by substitution of Ge for Sb, achieving a power factor of 16 ?W/cm K2 at 573 K, which is better than the best reported for Se-based Cu3SbSe4 compounds.

Suzumura, Akitoshi; Watanabe, Masaki; Nagasako, Naoyuki; Asahi, Ryoji

2014-06-01

316

Enantioseparation of extended metal atom chain complexes: unique compounds of extraordinarily high specific rotation.  

PubMed

Extended metal atom chains (EMACs) contain a linear metal chain wrapped by various ligands. Most complexes are of the form M(3)(dpa)(4)X(2), where M = metal, dpa = 2,2'-dipyridylamide, and X = various anions. The ligands form helical coils about the metal chain, which results in chiral EMAC complexes. The EMACs containing the metals Co and Cu were partially separated in polar organic mode using a vancomycin-based chiral stationary phase. Under similar conditions, two EMACs with Ni metal and varying anions could be baseline separated. The polar organic mode was used because of the instability of the compounds in aqueous mobile phases. Also, these conditions are more conducive to preparative separations. Polarimetric measurements on the resolved enantiomers of Ni(3)(dpa)(4)Cl(2) indicate that they have extraordinarily high specific rotations (on the order of 5000 deg cc/g dm). PMID:17192837

Warnke, Molly M; Cotton, F Albert; Armstrong, Daniel W

2007-03-01

317

Influence of complex formation on the laser radiation of oxoaromatic compounds  

SciTech Connect

It has been shown that the use of dye complexes with polar additives (proton donors) permits considerable broadening of the wavelength tuning range, and can increase the efficiency of laser radiation. In the present work, the acid-base reaction of some oxoaromatic compounds - N-phenylacridone, 3-methoxybenzanthrone, and oxazine 17 - in the ground and excited states in aprotonic solvents is investigated, together with its influence on the generational characterisitcs. The composition and structure of the complexes and also the influence of the acid-base properties of the components and the polarity of the solvent on the reaction of proton phototransfer are considered. The efficiency of laser radiation is determined primarily by the quantum yield of fluorescence of the generating form.

Krashakov, S.A.; Akimov, A.I.; Rodchenkov, G.M.; Uzhinov, B.M.

1985-12-01

318

METAL MATRIX COMPOSITES REINFORCED WITH INTERMETALLIC RIBBONS  

Microsoft Academic Search

The design procedure for low melting point alloy composites reinforced with melt-spun intermetallic ribbons for elevated temperature applications is presented. Long-range ordered Ni3Al intermetallic is selected as a candidate reinforcement by virtue of its ease of being ductilized by boron and an increase in yield strength with increasing temperature. A certain composition of Ni3Al alloyed with cobalt, tantalum, hafnium and

R. A. Varin; Z. Wronski; M. P. Metelnick

1990-01-01

319

Gd(3+) complexes conjugated to Pittsburgh compound B: potential MRI markers of ?-amyloid plaques.  

PubMed

In an effort towards the visualization of ?-amyloid (A?) plaques by T1-weighted magnetic resonance imaging for detection of Alzheimer's disease, we report the synthesis and characterization of stable, noncharged Gd(3+) complexes of three different 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid monoamide derivatives conjugated to Pittsburgh compound B, a well-established marker of A? plaques. The ligands L1, L2, and L3 differ in the nature and size of the spacer linking the macrocyclic chelator and the Pittsburgh compound B targeting moiety, which affects their lipophilicity, the octanol-water partition coefficients of the complexes ranging from -0.15 to 0.32. Given their amphiphilic behavior, the complexes form micelles in aqueous solution (critical micellar concentration 1.00-1.49 mM). The parameters determining the relaxivity, including the water exchange rate and the rotational correlation times, were assessed for the monomeric and the micellar form by a combined (17)O NMR and (1)H nuclear magnetic relaxation dispersion (NMRD) study. They are largely influenced by the aggregation state and the hydrophobic character of the linkers. The analysis of the rotational dynamics for the aggregated state in terms of local and global motions using the Lipari-Szabo approach indicates highly flexible, large aggregates. On binding of the complexes to human serum albumin or to the amyloid peptide A?1-40 in solution, they undergo a fourfold and a twofold relaxivity increase, respectively (40 MHz). Proton relaxation enhancement studies confirmed moderate interaction of Gd(L1) and Gd(L3) with human serum albumin, with KA values ranging between 250 and 910 M(-1). PMID:24297602

Martins, André F; Morfin, Jean-François; Geraldes, Carlos F G C; Tóth, Eva

2014-02-01

320

Compatibility of Au base thick films with solder alloys: Solid state growth of intermetallics  

SciTech Connect

Long term reliability of solder joints in thick film Au hybrid microcircuits require either minimization of the solid state growth of intermetallics or verification that if present, they do not compromise component performance. Intermetallic compounds such as AuIn{sub 2} or AuSn{sub 4} arise from the solid state reaction between Au thick films and 50Pb--50In or 63Sn--37Pb solder alloys, respectively; they are undesirable due to their brittle mechanical behavior caused by lack of a sufficient number of independent slip systems for plastic deformation. In addition, they may alter the resistivity of a circuit and thereby alter electronic performance. This paper will present a brief overview of the Au thick film inks/solder alloy systems whose intermetallic growth kinetics have been characterized at SNL, Albuquerque for hybrid microcircuit electronic applications. 6 refs., 3 figs., 2 tabs.

Stephens, J.J.; Romig, A.D. Jr.

1990-01-01

321

First principles electronic and thermal properties of some AlRE intermetallics  

NASA Astrophysics Data System (ADS)

A study on structural and electronic properties of non-magnetic cubic B 2-type AlRE (RE=Sc, Y, La, Ce, Pr and Lu) intermetallics has been done theoretically. The self-consistent tight binding linear muffin tin orbital method is used to describe the electronic properties of these intermetallics at ambient and at high pressure. These compounds show metallic behavior under ambient conditions. The variation of density of states under compression indicates some possibility of structural phase transformation in AlLa, AlCe and AlPr. Thermal properties like Debye temperature and Grüneisen constant are calculated at T=0 K and at ambient pressure within the Debye-Grüneisen model and compared with the others’ theoretical results. Our results are in good agreement. We have also performed a pressure-induced variation of Debye temperature and have found a decrease in Debye temperature around 40 kbar in AlRE (RE=La, Ce, Pr) intermetallics.

Srivastava, Vipul; Sanyal, Sankar P.; Rajagopalan, M.

2008-10-01

322

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

323

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.

Mazurek, Monica A

2002-01-01

324

Contribution a l'etude des mecanismes d'amorphisation par sollicitation mecanique de composes intermetalliques. (Contribution to the study of the amorphization mechanisms of intermetallic compounds by mechanical grinding).  

National Technical Information Service (NTIS)

This work aims at identifying the mechanisms responsible for amorphization of NiZr and NiZr(sub 2) compounds under ball-milling. In the first part, the effect of a localized deformation is studied: the deformation is produced by indentation on bulk sample...

D. Galy

1995-01-01

325

Europium-M-phosphorus (M = manganese, tin, indium) intermetallics: Synthesis, crystallography, and physical properties  

Microsoft Academic Search

Chapter One is an introduction to the structural and physical property studies of several intermetallic phases. Chapter Two presents the synthesis, structural characterization, magnetism, and magnetoresistance of two new compounds, Eu14MnAs11 and Eu14MnP11. Both compounds crystallize in the Ca 14AlSb11 structure type, which has a unique structural feature, Pn37-, that is best described as Pn 3- + Pn24-. They show

Amy Catherine Payne

2001-01-01

326

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

327

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

328

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

329

Molecular structure and reactions of azobenzene complexes with iron-lithium compounds  

Microsoft Academic Search

Reactions of azobenzene have been studied with heteronuclear iron-lithium compounds formed in the reaction of FeCl3 with LiPh, one of the dinitrogen reducing systems of the Vol'pin type: Ph4FeLi4(OEt2)4 (1) and (H2)FePh4Li4(OEt2)4 (2). The structures of the azobenzene complexes formed, (N2Ph2)3FeLi3(OEt2)3 (3) and (N2Ph2)3FeLi2(THF)2 (4), as well as an ether-containing analog of the latter, (N2Ph2)3FeLi2(OEt2)2 (5), were determined by X-ray

T. A. Bazhenova; N. S. Emelyanova; A. F. Shestakov; A. E. Shilov; M. Yu. Antipin; K. A. Lyssenko

1998-01-01

330

Neurotoxic effects of controlled exposure to a complex mixture of volatile organic compounds. Final report  

SciTech Connect

Subjective reactions of discomfort, impaired air quality, irritation of mucosal membranes, and impaired memory have been reported in chemically sensitive subjects during exposure to volatile organic compounds (VOCs) found in new buildings. 66 normal healthy male subjects aged 18-39 were exposed for 2.75 hrs to a complex VOC mixture at O and 25 mg/cu m. Each subject completed control and exposure sessions at one week intervals in counterbalanced order. Measurements included comfort ratings of eye, nose and throat irritation, symptom questionnaire and computerized behavioral tests. Subjects found the odor of VOCs unpleasant and strong and reported that VOC exposure degraded air quality, increased headache and produced general discomfort. VOC exposure did not affect performance on any behavioral tests. Results indicate that subjective reactions to VOCs are not limited to chemically sensitive individuals since the study population is a subgroup that is probably least likely to be affected by chemical exposure.

Otto, D.A.; Molhave, L.; Hudnell, H.K.; Goldstein, G.; O'Neil, J.

1990-03-01

331

Neurobehavioral and sensory irritant effects of controlled exposure to a complex mixture of volatile organic compounds  

SciTech Connect

Subjective reactions of discomfort, impaired air quality, irritation of mucosal membranes, and impaired memory have been reported in chemically sensitive subjects during exposure to volatile organic compounds (VOCs) found in new buildings. Sixty-six normal healthy male subjects aged 18-39 were exposed for 2.75 hr to a complex VOC mixture at 0 and 25 mg/m3. Each subject completed control and exposure sessions at one-week intervals in counterbalanced order. Measurements included comfort ratings of eye, nose and throat irritation, symptom questionnaire and computerized behavioral tests. Subjects found the odor of VOCs unpleasantly strong and reported that VOC exposure degraded air quality, increased headache and produced general discomfort. VOC exposure did not affect performance on any behavioral tests.

Otto, D.; Molhave, L.; Rose, G.; Hudnell, H.K.; House, D. (Environmental Protection Agency, Research Triangle Park, NC (USA))

1990-11-01

332

Time-Resolved X-Ray Microtomography Observation of Intermetallic Formation Between Solid Fe and Liquid Al  

NASA Astrophysics Data System (ADS)

Time-resolved in situ X-ray tomography combined with scanning electron microscopy was performed on an Al-Fe diffusion system at 973 K (700 °C) to study the formation of the main intermetallic compounds occurring at the interface. After nucleation on the liquid side of the interface, growth occurs in both liquid and solid directions. In the direction of the solid, growth starts with a particular tongue-like feature which then progressively thickens. The thickening is linked to the deformation of the iron matrix during the formation of the intermetallic compound. Growth in the direction of the liquid is slowed down by erosion.

Pasche, Guillaume; Scheel, Mario; Schäublin, Robin; Hébert, Cécile; Rappaz, Michel; Hessler-Wyser, Aïcha

2013-09-01

333

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

334

Antioxidant combinations of molybdenum complexes and organic sulfur compounds for lubricating oils  

SciTech Connect

An antioxidant additive combination for lubricating oils is prepared by combining (a) a sulfur containing molybdenum compound prepared by reacting an ammonium tetrathiomolybdate, and a basic nitrogen compound, with (b) an organic sulfur compound.

deVries, L.; King, J.M.

1983-09-06

335

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

336

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

337

Concentration effects on crystal fields in diluted intermetallics  

NASA Astrophysics Data System (ADS)

The magnetic excitation spectrum of intermetallic systems with localized 4f-electrons is primarily determined by crystal field effects. The merits of inelastic neutron spectroscopy to measure to crystal field splitting is demonstrated, discussing investigations on diluted rare earth intermetallics of the formula RE cLa 1- xAl 2, with RE = Tb and Tm. In the very diluted region ( c ? 0.003) the spectra are dominated by single ion behavior but show already the onset of extra non-single-ion intensity. Increasing concentration (0.01 ? c ? 0.15) leads to a drastic change of the spectra. We have chosen these systems in order to compare systems with similar crystal field level scheme but strongly different magnetic ordering temperatures of the compounds REAL 2. We study the influence of concentration on the inelastic ? 1-? 4 crystal field transition and on the elastic scattering intensity at T = 1.5 K and discuss the different concentration behavior for both systems.

Frick, Bernhard; Loewenhaupt, Michael

1985-10-01

338

Complex Chemistry and Biology of Redox-Active Compounds, Commonly Known as SOD Mimics, Affect Their Therapeutic Effects.  

PubMed

Abstract This Editorial has the intention to stress the complex chemistry and biology of redox-active compounds, regarded as SOD mimics. It further aims to caution the researchers of the importance of being up-to-date with the present knowledge on such compounds and their cellular redox biology when coming up with their conclusions, based on the particular species involved in their studies. Antioxid. Redox Signal. 20, 2323-2325. PMID:24650329

Batinic-Haberle, Ines; Spasojevic, Ivan

2014-05-20

339

Structure-Induced Covalent Bonding in Al-Li Compounds  

NASA Astrophysics Data System (ADS)

Formation mechanism of a deep pseudogap in the electronic density of states of the Al-Li Bergman and Zintl compounds is discussed with an emphasis on the differences among isostructural Al-Mg compounds. Since Li scatters electrons very weakly in comparison with Al and Mg, the potential landscape for electrons in Al-Li compounds is not that of the entire close-packed structure but that of the Al sublattice, which is a rather porous network like the diamond lattice. The porous network structure realized by the chemical decoration of close-packed structures enhances the covalent nature of electronic structures, hence the deep pseudogap in the electronic density of states. A concept of structure-induced covalent bonding in a network realized by the chemical decoration of close-packed structures may provide a novel picture in the electronic structures of complex intermetallic compounds.

Nozawa, Kazuki; Ishii, Yasushi

2010-06-01

340

Structure-induced covalent bonding in Al-Li compounds.  

PubMed

Formation mechanism of a deep pseudogap in the electronic density of states of the Al-Li Bergman and Zintl compounds is discussed with an emphasis on the differences among isostructural Al-Mg compounds. Since Li scatters electrons very weakly in comparison with Al and Mg, the potential landscape for electrons in Al-Li compounds is not that of the entire close-packed structure but that of the Al sublattice, which is a rather porous network like the diamond lattice. The porous network structure realized by the chemical decoration of close-packed structures enhances the covalent nature of electronic structures, hence the deep pseudogap in the electronic density of states. A concept of structure-induced covalent bonding in a network realized by the chemical decoration of close-packed structures may provide a novel picture in the electronic structures of complex intermetallic compounds. PMID:20867189

Nozawa, Kazuki; Ishii, Yasushi

2010-06-01

341

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

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available: Additional characterization data. See DOI: 10.1039/c4nr00313f

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

2014-05-01

342

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

NASA Astrophysics Data System (ADS)

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

You, Tae-Soo; Bobev, Svilen

2010-12-01

343

Formation of charge-transfer complexes between monosubstituted benzenes C 6 H 5 X and electron-donor organic compounds  

Microsoft Academic Search

Labile charge-transfer complexes (CTC) are examined for C6H5X with electron-donor organic compounds D that contain heteroatoms with nonbonding pairs (O, N, and Cl). The n(V) isotherms (derived by refractometry, and sometimes supplemented by other methods) for over 400 liquid C6H5X-D systems are surveyed to show that C6H5X shows the greatest tendency to form complexes if X is a type II

M. G. Voronkov; A. Ya. Deich

1967-01-01

344

Nonstoichiometry of Al-Zr intermetallic phases.  

National Technical Information Service (NTIS)

Nonstoichiometry of metastable cubic (beta)(prime) and equilibrium tetragonal (beta) Al-Zr intermetallic phases of the nominal composition Al(sub 3)Zr in Al-rich alloys has been extensively studied. It is proposed that the ''dark contrast'' of (beta)(prim...

V. Radmilovic G. Thomas

1994-01-01

345

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

346

Intermetallic coatings produced by TIG surface melting  

Microsoft Academic Search

The titanium aluminide intermetallic alloys possess high specific strength, high hardness and high temperature capabilities up to 800°C such as corrosion and oxidation resistance. These alloys can be suitable replacements for the conventional ceramic coatings applied in many components of chemical plants and aircraft engines to protect against high temperature oxidation and corrosion. The initial feasibility study of the forming

S Mridha; H. S Ong; L. S Poh; P Cheang

2001-01-01

347

An on-line HPLC method for detection of radical scavenging compounds in complex mixtures.  

PubMed

A rapid on-line method for screening of complex mixtures for radical scavenging components was developed using a methanolic solution of 2,2'-diphenyl-1-picrylhydrazyl (DPPH) stable free radical. The HPLC-separated analytes react postcolumn with the DPPH solution, and the induced bleaching is detected as a negative peak by an absorbance detector at 517 nm. An optimized instrumental setup is presented. The method is suitable for both isocratic and gradient HPLC runs with mobile-phase compositions ranging from 10 to 90% organic solvent in water or buffer (pH 3-6). The method is simple, has a broad applicability, and uses common instruments, inexpensive and stable reagents, and a time-saving and nonlaborious experimental protocol. It can also be used for quantitative analysis. The method was applied to several pure natural antioxidants and plant extracts. The limits of detection were 0.33-94 microg/mL, depending on the compound tested. PMID:10845381

Koleva, I I; Niederländer, H A; van Been, T A

2000-05-15

348

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

349

Chemical speciation and equilibria of some nucleic acid compounds and their iron(III) complexes.  

PubMed

The pH effect on electronic absorption spectra of some biologically active nucleic acid constituents have been studied at room temperature and the mechanism of ionization was explained. These compounds are of two categories (pyrimidines: [barbital; 5,5'-diethyl-barbituric acid], [SBA; 4,6-dihydroxy-2-mercapto-pyrimidin], [NBA; 5-nitro-2,4,6(1H,3H,5H)-pyrimidine trione] and [TU; 2,3-dihydro-2-thioxo-pyrimidin-4(1H)-one]) and (purines: [adenine; 6-amino purine], its [Schiff bases derived from adenine-acetylacetone; (Z)-4-(7H-purin-6-ylimino)pentan-2-one) and adenine-salicylaldehyde; 2-((7H-purin-6-ylimino) methyl) phenol] and its [Azo derived from adenine-resorcinol; 4-((7H-purin-6-yl)-diazenyl) benzene-1,3-diol]. The phenomena of tautomerization assigned different tautomers. Different spectrophotometric methods are applied to evaluate the pK's values that explained with their molecular structures. The interaction of Fe(3+) with some selected pyrimidines (barbital, NBA and SBA) was explained using familiar six spectrophotometric methods. The data typified the existence of different absorbing species with the different stoichiometries 1:1, 1:2, 1:3 and 2:3. The stability constant of the complexes was computed. More approach was deduced to assign the existence of different species applying the distribution diagrams. PMID:22446776

Masoud, Mamdouh S; Abd El-Kaway, Marwa Y; Hindawy, Ahmed M; Soayed, Amina A

2012-06-15

350

Chemical speciation and equilibria of some nucleic acid compounds and their iron(III) complexes  

NASA Astrophysics Data System (ADS)

The pH effect on electronic absorption spectra of some biologically active nucleic acid constituents have been studied at room temperature and the mechanism of ionization was explained. These compounds are of two categories (pyrimidines: [barbital; 5,5'-diethyl-barbituric acid], [SBA; 4,6-dihydroxy-2-mercapto-pyrimidin], [NBA; 5-nitro-2,4,6(1H,3H,5H)-pyrimidine trione] and [TU; 2,3-dihydro-2-thioxo-pyrimidin-4(1H)-one]) and (purines: [adenine; 6-amino purine], its [Schiff bases derived from adenine-acetylacetone; (Z)-4-(7H-purin-6-ylimino)pentan-2-one) and adenine-salicylaldehyde; 2-((7H-purin-6-ylimino) methyl) phenol] and its [Azo derived from adenine-resorcinol; 4-((7H-purin-6-yl)-diazenyl) benzene-1,3-diol]. The phenomena of tautomerization assigned different tautomers. Different spectrophotometric methods are applied to evaluate the pK's values that explained with their molecular structures. The interaction of Fe3+ with some selected pyrimidines (barbital, NBA and SBA) was explained using familiar six spectrophotometric methods. The data typified the existence of different absorbing species with the different stoichiometries 1:1, 1:2, 1:3 and 2:3. The stability constant of the complexes was computed. More approach was deduced to assign the existence of different species applying the distribution diagrams.

Masoud, Mamdouh S.; Abd El-Kaway, Marwa Y.; Hindawy, Ahmed M.; Soayed, Amina A.

351

MD study of primary damage in L10 TiAl structural intermetallics  

NASA Astrophysics Data System (ADS)

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

Voskoboinikov, Roman E.

2013-05-01

352

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

PubMed

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 C(2)H(2) over a mixture of both SnO(2) and In(2)O(3) particles. Importantly, tetragonal ?-In(3)Sn and hexagonal ?-InSn(4) nanowires with diameters of less than 100 nm are selectively synthesized at different SnO(2) to In(2)O(3) weight ratios. CNTs may serve as cylindrical nanocontainers for continuous growth of liquid-phased In(1-x)Sn(x) 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. PMID:22728332

Jeong, Namjo; Yeo, Jeong-gu

2012-07-20

353

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

NASA Astrophysics Data System (ADS)

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

Saleh, Ibrahim Khalifa

354

Reactivity of compound II: electronic structure analysis of methane hydroxylation by oxoiron(IV) porphyrin complexes.  

PubMed

The methane hydroxylation reaction by a Compound II (Cpd II) mimic PorFe(IV)=O and its hydrosulfide-ligated derivative [Por(SH)Fe(IV)=O](-) is investigated by density functional theory (DFT) calculations on the ground triplet and excited quintet spin-state surfaces. On each spin surface both the ?- and ?-channels are explored. H-abstraction is invariably the rate-determining step. In the case of PorFe(IV)=O the H-abstraction reaction can proceed either through the classic ?-channel or through the nonclassical ?-channel on the triplet surface, but only through the classic ?-mechanism on the quintet surface. The barrier on the quintet ?-pathway is much lower than on the triplet channels so the quintet surface cuts through the triplet surfaces and a two state reactivity (TSR) mechanism with crossover from the triplet to the quintet surface becomes a plausible scenario for C-H bond activation by PorFe(IV)=O. In the case of the hydrosulfide-ligated complex the H-abstraction follows a ?-mechanism on the triplet surface: the ?* is too high in energy to make a ?-attack of the substrate favorable. The ?- and ?-channels are both feasible on the quintet surface. As the quintet surface lies above the triplet surface in the entrance channel of the oxidative process and is highly destabilized on both the ?- and ?-pathways, the reaction can only proceed on the triplet surface. Insights into the electron transfer process accompanying the H-abstraction reaction are achieved through a detailed electronic structure analysis of the transition state species and the reactant complexes en route to the transition state. It is found that the electron transfer from the substrate ?(CH) into the acceptor orbital of the catalyst, the Fe-O ?* or ?*, occurs through a rather complex mechanism that is initiated by a two-orbital four-electron interaction between the ?(CH) and the low-lying, oxygen-rich Fe-O ?-bonding and/or Fe-O ?-bonding orbitals of the catalyst. PMID:22946694

Rosa, Angela; Ricciardi, Giampaolo

2012-09-17

355

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

Klanjšek, M; Gradišek, A; Kocjan, A; Bobnar, M; Jegli?, P; Wencka, M; Jagli?i?, Z; Pop?evi?, P; Ivkov, J; Smontara, A; Gille, P; Armbrüster, M; Grin, Yu; Dolinšek, J

2012-02-29

356

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.

Klanjšek, M.; Gradišek, A.; Kocjan, A.; Bobnar, M.; Jegli?, P.; Wencka, M.; Jagli?i?, Z.; Pop?evi?, P.; Ivkov, J.; Smontara, A.; Gille, P.; Armbrüster, M.; Grin, Yu; Dolinšek, J.

2012-02-01

357

Quaternary borocarbides: New class of intermetallic superconductors  

NASA Technical Reports Server (NTRS)

Our 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. Our 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 our multiphase ThNi2B2C we 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, Chandan; Hossain, Zakir; Godart, C.; Levy-Clement, C.; Padalia, B. D.; Vijayaraghavan, R.

1995-01-01

358

Stereocontrolled [3 + 2] annulations with arene chromium tricarbonyl complexes: construction of spirocyclic compounds related to fredericamycin A.  

PubMed

[reaction: see text] An efficient method has been developed for the stereocontrolled construction of polycyclic and spirocyclic compounds, including the spirocyclic core of the antitumor agent fredericamycin A. The strategy involves a one-pot aldol addition/Brook rearrangement/cyclization sequence beginning from arene chromium tricarbonyl complexes and can formally be described as a [3 + 2] annulation. PMID:12049497

Moser, William H; Zhang, Jian; Lecher, Carl S; Frazier, Tracy L; Pink, Maren

2002-06-13

359

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

SciTech Connect

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 175 deg. C for 5 h) gold aluminide easily forms in gold ball bonds while formation of intermetallic compound is absent in case of copper ball bonds. An analysis of the atomic property of the elements bonded explains that atomic radii and electronegativity factors favor gold aluminide formation.

Murali, S.; Srikanth, N.; Vath, Charles J

2003-03-24

360

Evidence of the transition from ordered to disordered growth during rapid solidification of an intermetallic phase  

Microsoft Academic Search

The dendrite growth velocity during solidification is measured on liquid drops of the intermetallic compound Ni50Al50 undercooled by levitation up to 265 K. A sharp increase of the growth velocity is found at a critical undercooling DeltaT*≈250 K. In situ diffraction of synchrotron radiation on levitation-processed samples unambiguously shows a transition from ordered to disordered growth at DeltaT*. The sharp

H. Hartmann; D. Holland-Moritz; P. K. Galenko; D. M. Herlach

2009-01-01

361

Catalytic activity of Pt-based intermetallics for the hydrogen production—Influence of ionic activator  

Microsoft Academic Search

In continuous search for advanced electrocatalytic materials for the hydrogen evolution reaction (HER), based on transition metal series, two types of intermetallic compounds, TiPt and MoPt2, were investigated as cathode materials. Additionally, ionic activator (i.a.), the mixture of Na-molybdate and tris(ethylenediamine)Co(III) chloride, was in situ added into electrolyte, 6M aqueous potassium hydroxide solution. The objective was to qualitatively compare their

Milica P. Mar?eta Kaninski; Vladimir M. Nikoli?; Tanja N. Potkonjak; Branislav R. Simonovi?; Nebojša I. Potkonjak

2007-01-01

362

Crystal potential model for the description of crystalline electric field effects in rare earth metals and intermetallics  

NASA Astrophysics Data System (ADS)

A crystal potential model is suggested. It allows us to interpret crystalline electric field effects in optical, EPR, NMR, NGR and neutron spectroscopy measurements in rare earth metals and intermetallics. The crystal potential character and space distribution are discussed. The model is used for the theoretical interpretation of the effects of the crystalline field in the compound PrAl 3.

Orlov, V. G.

1986-10-01

363

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

364

Molecular complex-based dispersive liquid-liquid microextraction: analysis of polar compounds in aqueous solution.  

PubMed

A novel molecular complex-based dispersive liquid-liquid microextraction (DLLME) method was established via hydrogen bond interaction between the extractant and the analytes. In this approach, tri-n-butylphosphate (TBP), a Lewis base, was directly used, instead of the traditional water-immiscible organic solvents, as the extractant for DLLME. The phenols (p-benzenediol, m-benzenediol, o-benzenediol and phenol), which are typical Lewis acids, were successfully extracted from environmental aqueous samples. In addition, phase separation was achieved in a disposable polyethylene pipet with the open and narrow tip upside, for a collection of the above extractant layer, i.e. TBP. To achieve satisfactory extraction performance, several extraction parameters, such as type of extractant solvents, extractant volume, pH of sample solution, ionic strength of sample solution and extraction time, were optimized. Additionally, the proposed method was applied to environmental water samples. Under the optimized conditions, the limits of detection and limits of quantification for the phenols were 7-29 and 25-98 ?g/L, respectively. The calibration curves showed good linearity (r(2)?0.9961) over the investigated concentration range. The repeatability of the method was investigated by evaluating the intra- and inter-day precisions. The relative standard deviations (RSDs) obtained were lower than 11.2% and 13.9% at different concentration levels. The recoveries ranged from 83.2% to 117.8%, with RSDs less than 13.1%. The developed approach provides a new way to facilitate DLLME of organic polar compounds from aqueous solutions. Moreover, it enables a convenient collection of solvent less dense making use of a cheap and disposable polyethylene pipet. PMID:20887994

Hu, Xi-Zhou; Wu, Jian-Hong; Feng, Yu-Qi

2010-11-01

365

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; Díaz, Francesc; Aguiló, Magdalena; O'Dwyer, Colm

2012-12-01

366

Elastic Properties of the Intermetallic Compound ReSi 2  

Microsoft Academic Search

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

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

1998-01-01

367

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

368

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

369

Synthesis, characterization and antiglaucoma activity of a novel proton transfer compound and a mixed-ligand Zn(II) complex  

Microsoft Academic Search

A novel proton transfer compound, pyridin-2-ylmethanaminium 2,4-dichloro-5-sulfamoylbenzoate (1), and a mixed-ligand Zn(II) complex, bis(2,4-dichloro-5-sulfamoylbenzoate)(2-aminomethylpyridine)aquazinc(II) monohydrate (2), have been synthesized from the same free ligands, which are 2,4-dichloro-5-sulfamoylbenzoic acid (Hsba) and 2-aminomethylpyridine (amp). They have been characterized by elemental, spectral (1H NMR, IR and UV–vis.) and thermal analyses. Additionally, magnetic measurement and single crystal X-ray diffraction technique were applied to compound

Cengiz Yenikaya; Musa Sar?; Metin Bülbül; Halil ?lkimen; Hülya Çelik; Orhan Büyükgüngör

2010-01-01

370

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.

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

2014-01-01

371

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

PubMed

Novel mixed ligand bivalent copper complexes [Cu. L. A. ClO 4 ] 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)/2,2(1)-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

372

COMPLEXITY OF SOIL ORGANIC MATTER: AMS 14C ANALYSIS OF SOIL LIPID FRACTIONS AND INDIVIDUAL COMPOUNDS  

Microsoft Academic Search

Radiocarbon measurements of different lipid fractions and individual compounds, isolated from soil samples collected on 2 different agricultural long-term study sites, located in the rural area of Rotthalmünster (Germany) and in the city of Halle\\/Saale (Germany), were analyzed to obtain information about sources and the stability of soil organic matter (SOM). Different lipid compound classes were isolated by automated solvent

Janet Rethemeyer; Christiane Kramer; Gerd Gleixner; Guido L B Wiesenberg; Lorenz Schwark; Nils Andersen; Marie-J Nadeau; Pieter M Grootes

373

Arc Casting Intermetallic Alloy (Materials Preparation Center)  

ScienceCinema

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

374

Investigation of S-nitrosothiol formation in complex I and model compounds by FTIR spectroscopy  

Microsoft Academic Search

In addition to its role as a regulator of vascular tone, synaptic signalling and cellular defence, nitric oxide (NO) has been shown to inhibit complex I and cytochrome c oxidase of the respiratory electron transfer chain. It has been suggested that the mechanism by which NO inhibits complex I involves the formation of S-nitrosothiols on the complex which are deleterious

Doug Marshall

375

Complex mixture analysis of organic compounds in green coffee bean extract by two-dimensional NMR spectroscopy.  

PubMed

A complex mixture analysis by one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy was carried out for the first time for the identification and quantification of organic compounds in green coffee bean extract (GCBE). A combination of (1)H-(1)H DQF-COSY, (1)H-(13)C HSQC, and (1)H-(13)C CT-HMBC two-dimensional sequences was used, and 16 compounds were identified. In particular, three isomers of caffeoylquinic acid were identified in the complex mixture without any separation. In addition, GCBE components were quantified by the integration of carbon signals by use of a relaxation reagent and an inverse-gated decoupling method without a nuclear Overhauser effect. This NMR methodology provides detailed information about the kinds and amounts of GCBE components, and in our study, the chemical makeup of GCBE was clarified by the NMR results. PMID:20818806

Wei, Feifei; Furihata, Kazuo; Hu, Fangyu; Miyakawa, Takuya; Tanokura, Masaru

2010-11-01

376

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

377

NEUROTOXIC EFFECTS OF CONTROLLED EXPOSURE TO A COMPLEX MIXTURE OF VOLATILE ORGANIC COMPOUNDS  

EPA Science Inventory

Subjective reactions of discomfort, impaired air quality, irritation of mucosal membranes, and impaired memory have been reported in chemically sensitive subjects during exposure to volatile organic compounds (VOC's) found in new buildings. 6 normal healthy male subjects aged 18-...

378

Enantiospecificity of Chloroperoxidase-Catalyzed Epoxidation: Biased Molecular Dynamics Study of a Cis ?-Methylstyrene\\/Chloroperoxidase-Compound I Complex  

Microsoft Academic Search

Molecular dynamics simulations of an explicitly solvated cis-?-methylstyrene\\/chloroperoxidase-Compound I complex are performed to determine the cause of the high enantiospecificity of epoxidation. From the simulations, a two-dimensional free energy potential is calculated to distinguish binding potential wells from which reaction to 1S2R and 1R2S epoxide products may occur. Convergence of the free energy potential is accelerated with an adaptive biasing

Alexander N. Morozov; Cassian D'Cunha; Carlos A. Alvarez; David C. Chatfield

2011-01-01

379

NMR measurements in milled RE-TM(sub 2) compounds (RE=Gd and TM=Co, Fe).  

National Technical Information Service (NTIS)

Milled samples of the Laves phase intermetallic compounds Gd Fe(sub 2) and Gd CO(sub 2) were measured by NMR at 4.2 K. The milling was made from the crystalline intermetallic compounds, inside a cylindrical tool made of hard steel, under argon atmosphere,...

C. V. Tribuzy A. P. Guimaraes A. Biondo C. Larica K. M. B. Alves

1996-01-01

380

Molecular design of new magnetically active copper complexes with heteroaromatic schiff bases and azo compounds  

Microsoft Academic Search

Copper chelates with tridentate ligands containing pyridine or pyrazole ring at the azomethine or azo fragment were synthesized\\u000a by chemical electrochemical methods, and their structure was characterized by the EXAFS spectra. Thermal magnetochemical analysis\\u000a of the complexes revealed antiferromagnetic exchange interaction in all complexes. The exchange interaction parameter of the\\u000a complex containing an N-tosylamino group in the ortho position with

A. S. Burlov; A. I. Uraev; V. N. Ikorskii; S. A. Nikolaevskii; Yu. V. Koshchienko; I. S. Vasil’chenko; D. A. Garnovskii; V. G. Vlasenko; Ya. V. Zubavichus; L. N. Divaeva; G. S. Borodkin; A. D. Garnovskii

2008-01-01

381

Spectral studies and thermal analysis of new vanadium complexes of ethanolamine and related compounds  

NASA Astrophysics Data System (ADS)

The electronic absorption spectral behaviors of newly synthesized complexes of VIII, VIV and VO2+ with Ethanolamine, Diethanolamine and Triethanolamine were described. The complexes have been characterized by elemental analyses, magnetic moment measurements, IR and UV-Vis spectroscopy. Absorption spectra in seven different solvents were recorded. The solvatochromism was examined and discussed. Dipolar interactions between the solvent and the complexes were used to correlate the observed spectral shifts to solvent polarity. Some of the obtained complexes were studied by thermal analysis using DTA and TG techniques.

Masoud, Mamdouh S.; Ali, Alaa E.; Ahmed, Hytham M.; Mohamed, Essam A.

2013-10-01

382

Deformation-Induced Amorphization of Copper-Titanium Intermetallics  

NASA Astrophysics Data System (ADS)

Two methods of inducing amorphization in Cu-Ti intermetallic compounds by mechanical means have been investigated. Ingots of compositions Cu_{35}Ti _{65} and Cu_ {33.3}Ti_{66.7} were rapidly quenched into ribbons. The microstructure consisted largely of microcrystals in an amorphous matrix, which were either quenched in or grown by annealing. The ribbons were cold-rolled, which reduced their effective thickness by a factor of about 8. The status of the intermetallic compound CuTi_2 was monitored by x-ray diffraction and transmission electron microscopy (TEM). The crystals were found to amorphize as rolling progressed. This behavior was not reproduced in polycrystalline samples that had no amorphous matrix present initially. The presence of the amorphous phase is thus necessary for amorphization of the crystal: it eliminates the need to nucleate the new glass, and it prevents the ribbon from disintegrating at high deformation stages. It may also change the deformation mechanism that occurs in the crystals, retarding the onset of amorphization. Diffuse scattering in close-packed directions is similar to that seen in electron irradiation experiments. It is postulated that the chemical disorder present in antiphase boundaries caused by deformation raises the free energy of the crystal higher than that of the amorphous phase. Ingots of the same compound were worn against each other in a custom-built wear apparatus. The design eliminates iron contamination of the wear sample and requires relatively small quantities of material. Alteration of the surface structure was monitored by plane-view and cross -sectional TEM. Larger subsurface crystals exhibit diffuse scattering, similar to that found in the rolled samples. A wide range of grain sizes was observed, due to the inhomogeneous nature of the wear process. An unusual phase was observed at the surface, consisting of a nanometer-scale mixture of aligned nanocrystalline regions and disordered areas. Some amorphous phase is possibly present as well. It is postulated a combination of high unidirectional strain rates and small grain sizes forces the nanocrystals to accommodate deformation by disordering in one direction. Deformation in additional directions might presumably cause the structure to go completely amorphous.

Askenazy, Philip Douglas

383

Reactions of [NH3+*, H2O] with carbonyl compounds: a McLafferty rearrangement within a complex?  

PubMed

The reactions of the water solvated ammonia radical cation [NH(3)(+*), H(2)O] with a variety of aldehydes and ketones were investigated. The reactions observed differ from those of low energy aldehydes and ketones radical cations, although electron transfer from the keto compound to ionized ammonia is thermodynamically allowed within the terbody complexes initially formed. The main process yields an ammonia solvated enol with loss of water and an alkene. This process corresponds formally to a McLafferty fragmentation within a complex. With aldehydes, another reaction can take place, namely the transfer of the hydrogen from the CHO group to ammonia, leading to the proton bound dimer of ammonia and water, and to the NH(4)(+) cation. Comparison between the available experimental results leads to the conclusion that the McLafferty fragmentation occurs within the terbody complex initially formed, with no prior ligand exchange, the water molecule acting as a spectator partner. PMID:15234355

van der Rest, G; Jensen, L B; Abdel-Azeim, S; Mourgues, P; Audier, H E

2004-07-01

384

Intermetallics as advanced cathode materials in hydrogen production via electrolysis  

Microsoft Academic Search

Intermetallics phases along Mo–Pt phase diagram have been investigated as cathode materials for the production of hydrogen by electrolysis from water KOH solutions, in an attempt to increase the electrolytic process efficiency. These materials were compared with conventional cathodes (Fe and Ni), often used in the alkaline electrolysis, and also with the intermetallic Ti–Pt. An significant upgrade of the electrolytic

Dragica Lj. Stoji?; Tomislav D. Grozdi?; Milica P. Mar?eta Kaninski; Aleksandar D. Maksi?; Nataša D. Simi?

2006-01-01

385

SCB ignition of pyrotechnics, thermites and intermetallics  

Microsoft Academic Search

We investigated ignition of pyrotechnics, metal-fuel\\/metal-oxide compositions (thermites), and exothermic alloy compositions (intermetallics) using a semiconductor bridge (SCB). It was shown that these materials could be ignited at low energy levels with an appropriately designed SCB, proper loading density, and good thermal isolation. Materials tested included Al\\/CuO, B\\/BaCrOâ, TiH{sub 1.65}\\/KClOâ, Ti\\/KClOâ, Zr\\/BaCrOâ, Zr\\/CuO, Zr\\/FeâOâ, Zr\\/KClOâ, and 100-mesh Al\\/Pd. Firing set

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

1996-01-01

386

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

387

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

PubMed Central

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

2012-01-01

388

Complexation of amidated pectin with poly(itaconic acid) as a polycarboxylic polymer model compound.  

PubMed

Complexes based on amidated pectin (AP) and poly(itaconic acid) (PIA) were prepared by casting films from solutions of AP and PIA in different ratios with the pectin amount ranging from 10% to 90% by mass. The complexes were investigated by elemental analysis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry (TG). In all investigated ratios of AP/PIA glassy transparent films with a uniform structure were obtained. The results of elemental analysis confirmed the composition of the complexes, and FTIR spectroscopy has shown carboxylic and amide peak shifting, indicating complex formation between AP and PIA. Comparison of thermograms of AP/PIA films with different ratios of AP indicated that the increase of the amount of AP increases the thermal stability of the films by retarding the onset of the main degradation processes. PMID:21943549

Nesic, Aleksandra R; Trifunovic, Snezana S; Grujic, Aleksandar S; Velickovic, Sava J; Antonovic, Dusan G

2011-11-01

389

Electromigration effects on intermetallic growth at wire-bond interfaces  

NASA Astrophysics Data System (ADS)

At a bimetallic interface, excessive intermetallic growth can cause device failure. For each intermetallic phase, a direct current flowing normal to the interface can change its thickening rate, increasing the rate for current in one direction and decreasing it for the reverse direction. In this paper, we present electrical resistance measurements on single wire-bond/bond-pad interfaces under the influence of current. Resistance increases are correlated with the growth of intermetallics observed in cross section of the wire bonds, providing a sensitive probe of microstructural evolution. The form of resistance change is clearly altered under applied current and depends on polarity. The resistance changes demonstrate key aspects of the effects of electromigration on intermetallic growth, but a fully quantitative interpretation of the changes is hampered by the appearance of more than one intermetallic phase and by the development of voids.

Orchard, H. T.; Greer, A. L.

2006-11-01

390

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.

Wadley, Lyn; Hodgskiss, Tamaryn; Grant, Michael

2009-01-01

391

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

392

Blood Esterases as a Complex Biomarker for Exposure to Organophosphorus Compounds  

Microsoft Academic Search

The growing threat of international terrorism brings with it new scenarios for disaster. For example, in the case of toxic\\u000a organophosphorus compounds (OPs), it possible for terrorists to use known agents or inadvertently to produce highly toxic\\u000a OPs of unknown structure as the result of attacks on chemical plants or stockpiles of pesticides and other chemicals. Defending\\u000a against such agents

G. Makhaeva; E. Rudakova; N. Boltneva; L. Sigolaeva; A. Eremenko; I. Kurochkin; R. Richardson

393

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.

Peruško, D.; Petrovi?, S.; Stojanovi?, M.; Mitri?, M.; ?izmovi?, M.; Panjan, M.; Milosavljevi?, M.

2012-07-01

394

Compound heterozygosity for mutations in PAX6 in a patient with complex brain anomaly, neonatal diabetes mellitus, and microophthalmia.  

PubMed

We report on a patient with trisomy 21, microophthalmia, neonatal diabetes mellitus, hypopituitarism, and a complex structural brain anomaly who was a member of a large bilineal family with eye anomalies. The patient inherited a different mutation in PAX6 from each parent and is the only known living and second reported patient with compound heterozygosity for mutations in PAX6. PAX6 is a transcription factor involved in eye and brain development and has roles in pancreatic and pituitary development. Clinical evaluation of the propositus and his parents demonstrated the effects of mutations of differing severity in multiple individuals. PMID:19876904

Solomon, Benjamin D; Pineda-Alvarez, Daniel E; Balog, Joan Z; Hadley, Donald; Gropman, Andrea L; Nandagopal, Radha; Han, Joan C; Hahn, Jin S; Blain, Delphine; Brooks, Brian; Muenke, Maximilian

2009-11-01

395

Cold Sprayed Intermetallic Thermal Barrier Coatings  

NASA Astrophysics Data System (ADS)

Conventional thermal barrier coating (TBC) systems consist of a duplex structure with a metallic bond coat and a ceramic heat-isolative topcoat. Several recent research activities are concentrated on the development of improved multilayer bond coat and TBC materials. This study represents an investigation performed for the aluminum based bond coats, especially those with reduced thermal conductivities. Using alternative TBC materials, such as metal alloys and intermetallics, their processing methods can be further optimized to achieve the best thermal physical parameters. One example is the ten-layer system in which cold sprayed aluminum based intermetallics are synthesized. These systems demonstrated improved heat insulation and thermal fatigue capabilities compared to conventional TBC. The microstructures and properties of the laminar coatings were characterized by SEM, EDS, XRD; micromechanical and durability tests were performed to define the structure and coating formation mechanisms. Application prospects for HCCI engines are discussed. Fuel energy can be utilized more efficiently with the concept of low heat rejection engines with applied TBC.

Leshchinsky, Evgeny

396

Complexes of tris(pentafluorophenyl)boron with nitrogen-containing compounds: Synthesis, reactivity and metallocene activation  

Microsoft Academic Search

The strong Lewis acid tris(pentafluorophenyl)boron, B(C6F5)3, reacts with several nitrogen-containing Lewis bases (nitriles, amines, imines, pyridines, etc.) and also with non-basic substrates (such as pyrroles and indoles) producing in both cases the BN coordination adduct. With particular substrates (some tertiary amines, the imine tBu(Me)CNBn, N-methyl-pyrrole and -indole,) the 1:1 borane\\/N-compound reaction produces zwitterions where a new BC bond is generated.

Francesca Focante; Pierluigi Mercandelli; Angelo Sironi; Luigi Resconi

2006-01-01

397

Complex magnetic order in quasi-one-dimensional compound Ca 3CoIrO 6  

NASA Astrophysics Data System (ADS)

In the spin-chain compound Ca 3CoIrO 6 muon spin precession and relaxation spectra at temperatures above 100 K exhibit non-exponential behavior characteristic of a system of dynamic, disordered magnetic moments. On cooling below about 100 K the onset of spontaneous magnetic order is revealed via the presence of coherent oscillations in muon spin relaxation spectra taken in zero external field. This magnetic transition is attributed to the intra-chain ferromagnetic order. There is one more change in the ?SR signal associated with the spin-glass like freezing transition at Tf=30 K previously established by bulk susceptibility and neutron scattering data.

Sugiyama, Jun; Morris, Gerald D.; Nozaki, Hiroshi; Ikedo, Yutaka; Russo, Peter L.; Stubbs, Scott L.; Brewer, Jess H.; Ansaldo, Eduardo J.; Martin, Christine; Hébert, Sylvie; Maignan, Antoine

2009-04-01

398

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

ERIC Educational Resources Information Center

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

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

2009-01-01

399

Metal complexes with N-(2-pyridylmethyl)iminodiacetate: from discrete polynuclear compounds to 1D coordination polymers.  

PubMed

The reactions of M(ClO(4))(2).6H(2)O (M = Mn(2+), Co(2+) and Ni(2+)) with N-(2-pyridylmethyl)-iminodiacetic acid (H(2)pmida) gave three discrete polynuclear complexes {Na[Mn(3)(pmida)(3)(H(2)O)(3)]}ClO(4) (), {Na[Co(3)(pmida)(3)(H(2)O)(3)](H(2)O)}ClO(4) () and [Co(H(2)O)(6)][Co(3)(pmida)(3)(H(2)O)(3)](2)(ClO(4))(2).4H(2)O () and two 1D polymers {[Co(pmida)(H(2)O)].H(2)O}(n) () and {[Ni(pmida)(H(2)O)].H(2)O}(n) (). All complexes were characterized by elemental analysis, infrared (IR) spectroscopy and single-crystal X-ray diffraction analysis. Complexes and show similar structures with an unprecedented trinuclear unit [M(3)(pmida)(3)(H(2)O)(3)] in which the three six-coordinated divalent metal ions are joined by three coplanar syn-anti bridging carboxylate groups of three ligands into a closed planar twelve-membered ring with one Na(+) ion located on the C(3) axis. Complex possesses two kinds of coordination units: mononuclear cation [Co(H(2)O)(6)](2+) and trinuclear unit [Co(3)(pmida)(3)(H(2)O)(3)]. The Co(2+) and Ni(2+) ions in complexes and , respectively, present distorted octahedral geometries and are bridged by anti-anti bridging carboxylate groups of the ligands to form 1D chains. Compounds display a structure variation from discrete polynuclear to 1D coordination polymer along Mn(ii), Co(ii) to Ni(ii), and a dependence of the formation of discrete compound or coordination polymer on the identity of the metal ion. The magnetic investigations of were also carried out. The negative Weiss constants and coupling constants obtained from two kinds of fitting models indicate the presence of dominant antiferromagnetic exchanges mediated by the syn-anti bridging carboxylate groups between the metal centers of three compounds. PMID:19565081

Chen, Zilu; Li, Yan; Jiang, Chunfang; Liang, Fupei; Song, You

2009-07-21

400

Integrated supercritical fluid extraction, bioassay and chemical screening methods for analyzing vapor-phase compounds of an environmental complex mixture: Diesel exhaust  

Microsoft Academic Search

The integration of bioassay and chemical analyses for vapor-phase compounds in environmental complex mixtures is a challenging process due to the volatility and the limited amounts of compounds collected and subsequently assayed. The advantage of an integrated approach is that the bioassay could aid in determining the most biologically active fractions for further chemical analyses. Previously, we reported on the

Norman Y. Kado; Robert A. Okamoto; Paul A. Kuzmicky; Christine J. Rathbun; Dennis P. H. Hsieh

1996-01-01

401

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

402

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

PubMed Central

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.

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

2014-01-01

403

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

404

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

USGS Publications Warehouse

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

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

2011-01-01

405

Lanthanide complexes with oda, ida, and nta: From discrete coordination compounds to supramolecular assemblies  

NASA Astrophysics Data System (ADS)

Lanthanide metal-organic frameworks have been receiving special attention for the last decade. The use of polydentate organic ligands has allowed the construction of interesting network topologies with many potential applications, based on the special characteristics of the 4f electrons. In this paper, the structural and thermodynamic properties of Ln(III) complexes with oxydiacetate, iminodiacetate, and nitrilotriacetate are critically reviewed. The presence of ligands able to act as a bridge promotes the formation of Ln-M polynuclear complexes with fascinating 3D structures, whose study is also included. Equilibrium data of these systems in aqueous solution have been collected, showing the relationship between the composition of the species in solution and the nuclearity in the solid state.

Kremer, Carlos; Torres, Julia; Domínguez, Sixto

2008-05-01

406

Acetalization of ?,?-unsaturated carbonyl compounds catalyzed by complexes of Pt(II)  

Microsoft Academic Search

A class of cationic diphosphine complexes of Pt(II) are sufficiently Lewis acidic to catalyze the acetalization of aldehydes and ketones. ?,?-Unsaturated substrates can be easily acetalized with ethylene glycol under mild conditions in high yield and avoiding side reactions leading to formation of undesired by-products arising from the nucleophilic addition to the carbon?carbon double bond conjugated to the carbonyl group.

Enrico Nieddu; Maurizio Cataldo; Francesco Pinna; Giorgio Strukul

1999-01-01

407

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

408

New 3,4-diaminobenzoic acid Schiff base compounds and their complexes: synthesis, characterization and thermodynamics.  

PubMed

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 (H3L(1)), 3,4-bis((E)-2-hydroxy-3-methoxybenzylideneamino)benzoic acid (H3L(2)) and 3,4-bis((E)-5-bromo-2-hydroxybenzylideneamino)benzoic acid (H3L(4)). Additionally, a tetradentate Schiff base ligand 3,4-bis((E)-2-hydroxybenzylideneamino)benzoic acid (H3L(3)) 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, (1)H 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 0.1M (NaClO4), at 25 °C in dimethylformamide (DMF) as a solvent. PMID:24309180

Mohammadi, Khosro; Niad, Mahmood; Jafari, Tahereh

2014-03-25

409

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

NASA Astrophysics Data System (ADS)

First-principles, density-functional studies of several intermetallic borides of the general type M2M'Ru 5-nRh nB 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 3 d 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.

Burghaus, Jens; Dronskowski, Richard; Miller, Gordon J.

2009-10-01

410

Reactions of N-phenyl-o-semiquinonediimine complexes of nickel and platinum with carbonyl-containing low-valence iron and rhenium compounds  

Microsoft Academic Search

The reactions of o-semiquinonediimine complexes M[o-(NH)(NPh)C6H4]2 (M = Ni (1) or Pt (2)) with carbonyl-containing iron and rhenium compounds were studied. The reactions of complexes 1 or 2 with Fe(CO)5 afforded the Fe2(CO)6[µ-(NH)(NPh)C6H4] complex (3) containing the bridging N-phenyl-o-phenylenediamide ligand in high yield. The reaction of the Re(CO)2(NO)Cl2(thf) complex with complex 2 gave rise to the unusual mononuclear rhenium(iii) complex,

A. V. Reshetnikov; M. O. Talismanova; A. A. Sidorov; S. E. Nefedov; I. L. Eremenko; I. I. Moiseev

2001-01-01

411

Structural transitions in RNi(10)Si(2) intermetallics.  

PubMed

Intermetallic compounds of the type RFe(10)Si(2) and RCo(10)Si(2) crystallize in the ThMn(12) structure (space group I4/mmm) whilst the heavy rare earth series RNi(10)Si(2) crystallize in a maximal subgroup of I4/mmm, P4/nmm. Reported here are neutron powder diffraction investigations for TbNi(10)Si(2) and ErNi(10)Si(2) which show that the P4/nmm structure undergoes a high temperature order-disorder phase transition at approximately 930?°C above which the ordered Ni and Si fractions revert to a random distribution on 4d and 4e sites. The volume expansion has been tracked in detail via the temperature dependence of the lattice parameters, whilst the temperature dependence of the thermal expansion coefficients ?(11), ?(33) and ?(volume) has been determined from the lattice parameters. Associated with the order-disorder transition is a transition associated with a displacement of the R ion along the c-axis. Both transitions are of second order and the critical exponent associated with the order-disorder and displacive transitions, ? = 0.31, is in excellent agreement with the exponent determined for the three-dimensional Ising model. PMID:21817452

Moze, O; Kockelmann, W A; Hofmann, M; Cadogan, J M; Ryan, D H; Buschow, K H J

2009-03-25

412

Crystal growth of Gd 7-xY xPd 3 intermetallics  

NASA Astrophysics Data System (ADS)

Recently, the single crystals of the intermetallic compounds Gd 7-xY xPd 3 were grown by the Czochralski method from a levitated melt. They grew in a single hexagonal phase of theTh 7Fe 3 type with the ratio c/ a=0.63. Electronic structure, transport and magnetic properties of a Gd 3Y 4Pd 3 crystal belonging to the series Gd 7-xY xPd 3 have been measured along the principal crystallographic directions. It was found that Gd 3Y 4Pd 3 orders ferromagnetically at 197 K. All measured physical properties show a strong anisotropy.

Talik, E.; Klimczak, M.; Winiarski, A.; Tro?, R.

2008-04-01

413

Evidence of the transition from ordered to disordered growth during rapid solidification of an intermetallic phase  

NASA Astrophysics Data System (ADS)

The dendrite growth velocity during solidification is measured on liquid drops of the intermetallic compound Ni50Al50 undercooled by levitation up to 265 K. A sharp increase of the growth velocity is found at a critical undercooling ?T*?250 K. In situ diffraction of synchrotron radiation on levitation-processed samples unambiguously shows a transition from ordered to disordered growth at ?T*. The sharp interface model is extended to describe the transition from ordered to disordered dendrite growth by taking into account the velocity dependence of the order parameter and the kinetic growth coefficient.

Hartmann, H.; Holland-Moritz, D.; Galenko, P. K.; Herlach, D. M.

2009-08-01

414

Formation of nearly void-free Cu3Sn intermetallic joints using nanotwinned Cu metallization  

NASA Astrophysics Data System (ADS)

Cu3Sn intermetallic compounds (IMCs) are more resistant to fracture than solders. In addition, the Cu3Sn IMCs are more conductive than the solders. In this study, we manufactured Cu3Sn IMCs to serve as a joint using electroplated nanotwinned Cu as a metallization layer to react with pure Sn at 260 °C and 340 °C. The results show that there were almost no Kirkendall voids generated inside the Cu3Sn layer. In addition, the kinetics of the Cu3Sn growth was analyzed to predict the time needed to form the Cu3Sn joint.

Chiu, Wei-Lan; Liu, Chien-Min; Haung, Yi-Sa; Chen, Chih

2014-04-01

415

Intermetallic Formation of Copper Pillar With Sn–Ag–Cu for Flip-Chip-On-Module Packaging  

Microsoft Academic Search

Copper pillar interconnects are a popular interposing option due to the advantages of small pillar size and good thermal and electrical performance, making copper pillar interconnects very useful for high-frequency and high-density flip-chip-on-module (FCOM) packages. However, the challenges associated with the technology include controlling the formation of brittle intermetallic compounds (IMC) and weak interfaces during heat-related processes, and preventing copper

Mark Huang; Ong Gee Yeow; Chia Yong Poo; Tom Jiang

2008-01-01

416

Crystalline Electric Fields and the Magnetic Ground State for the Heusler Intermetallic YbRh2Pb  

SciTech Connect

We have synthesized an intermetallic compound with a distorted Heusler structure, YbRh2Pb. We present a study of the magnetic, thermal, and transport properties. Heat capacity measurements revealed that YbRh2Pb magnetically orders below TN=0.57 K from a paramagnetic state with substantial crystal electric field splitting. Magnetic field further splits the ground state, which leads to the suppression of magnetic order in YbRh2Pb.

Sokolov,D.; Kim, M.; Aronson, M.; Henderson, C.; Stephens, P.

2008-01-01

417

High temperature erosion properties of arc-sprayed coatings using various cored wires containing Ti–Al intermetallics  

Microsoft Academic Search

Three Ti–Al series intermetallic compounds, TiAl3, TiAl, and Ti3Al, were utilized to prepare cored wires, which were then used to form coatings on low carbon steel substrates by a supersonic arc spraying process. High temperature erosion (HTE) properties of the coatings were determined in a laboratory elevated temperature erosion tester. The results show that the HTE resistance of the coatings

Shao-Guang Liu; Jin-Ming Wu; Sheng-Cai Zhang; Shu-Jie Rong; Zhi-Zhang Li

2007-01-01

418

Thermomechanical processing of plasma sprayed intermetallic sheets  

DOEpatents

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Hajaligol, Mohammad R. (Midlothian, VA); Scorey, Clive (Cheshire, CT); Sikka, Vinod K. (Oak Ridge, TN); Deevi, Seetharama C. (Midlothian, VA); Fleischhauer, Grier (Midlothian, VA); Lilly, Jr., A. Clifton (Chesterfield, VA); German, Randall M. (State College, PA)

2001-01-01

419

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

420

Novel dimetal bridging carbene complexes derived from a terminal carbonyl dimetal compound. Syntheses, structures and reactivities of 7H-indene-coordinated diiron bridging carbene complexes.  

PubMed

Pentacarbonyl-7H-indenediiron, [Fe2(CO)5(eta3,eta5-C9H8)] (1), reacts with aryllithium, ArLi (Ar = C6H5, p-C6H5C6H4), followed by alkylation with Et3OBF4 to give novel 7H-indene-coordinated diiron bridging alkoxycarbene complexes [Fe2{mu-C(OC2H5)Ar}(CO)4(eta4,eta4-C9H8)] (2, Ar = C6H5; 3, Ar = p-C6H5C6H4). Complexes 2 and 3 react with HBF4.Et2O at low temperature to yield cationic bridging carbyne complexes [Fe2(mu-CAr)(CO)4(eta4,eta4-C9H8)]BF4 (4, Ar = C6H5; 5, Ar = p-C6H5C6H4). Cationic 4 and 5 react with NaBH4 in THF at low temperature to afford diiron bridging arylcarbene complexes [Fe2{mu-C(H)Ar}(CO)4(eta4,eta4-C9H8)] (6, Ar = C6H5; 7, Ar = p-C6H5C6H4). The similar reactions of 4 and 5 with NaSC6H4CH3-p produce the bridging arylthiocarbene complexes [Fe2{mu-C(Ar)SC6H4CH3-p}(CO)4(eta4,eta4-C9H8)] (8, Ar = C6H5; 9, Ar = p-C6H5C6H4). Cationic 4 and 5 can also react with anionic carbonylmetal compounds Na[M(CO)5(CN)] (M = Cr, Mo, W) to give the diiron bridging aryl(pentacarbonylcyanometal)carbene complexes [Fe2{mu-C(Ar)NCM(CO)5}(CO)4(eta4,eta4-C9H8)] (10, Ar = C6H5, M = Cr; 11, Ar = p-C6H5C6H4, M = Cr; 12, Ar = C6H5, M = Mo; 13, Ar = p-C6H5C6H4, M = Mo; 14, Ar = C6H5, M = W; 15, Ar = p-C6H5C6H4, M = W). Interestingly, in CH2Cl2 solution at room temperature complexes 10-15 were transformed into the isomerized 7H-indene-coordinated monoiron complexes [Fe(CO)2(eta5-C9H8)C(Ar)NCM(CO)5] (16, Ar = C6H5, M = Cr; 17, Ar = p-C6H5C6H4, M = Cr; 18, Ar = C6H5, M = Mo; 19, Ar = p-C6H5C6H4, M = Mo; 20, Ar = C6H5, M = W; 21, Ar = p-C6H5C6H4, M = W), while complex 3 was converted into a novel ring addition product [Fe2{C(OC2H5)C6H4C6H5-p-(eta2,eta5-C9H8)}(CO)5] (22) under the same conditions. The structures of complexes 2, 6, 8, 14, 18 and 22 have been established by X-ray diffraction studies. PMID:16967119

Zhang, Lei; Sun, Jie; Zhu, Huping; Xu, Qiang; Tsumori, Nobuko; Chen, Jiabi

2006-09-28

421

High-temperature refractory metal-intermetallic composites  

NASA Astrophysics Data System (ADS)

In this article, toughness, oxidation, and rupture behaviors of present-generation refractory metal-intermetallic composites are compared to the performance requisites necessary to make these materials a competitive choice for the jet engine turbine environment of the future.

Jackson, M. R.; Bewlay, B. P.; Rowe, R. G.; Skelly, D. W.; Lipsitt, H. A.

1996-01-01

422

Theoretical energy release of thermites, intermetallics, and combustible metals.  

National Technical Information Service (NTIS)

Thermite (metal oxide) mixtures, intermetallic reactants, and metal fuels have long been used in pyrotechnic applications. Advantages of these systems typically include high energy density, impact insensitivity, high combustion temperature, and a wide ran...

S. H. Fischer M. C. Grubelich

1998-01-01

423

?-Brass polyhedral core in intermetallics: the nanocluster model.  

PubMed

Using the TOPOS program package, 26-atom nanoclusters of the ?-brass (Cu5Zn8) type (0@4@22 or 0@8@18) were found in 5918 crystal structures of cubic intermetallics. The nanocluster models were built for all the intermetallics using a recently developed algorithm implemented into TOPOS. The relations of the structures based on the 0@4@22 core are explored as a result of migration of atoms between different shells of the nanoclusters. It is shown that the 0@4@22 nanoclusters frequently occur as building units of intermetallics of different composition and structure type. Regularities in chemical composition of 702 ?-brass-type nanoclusters were found within both the nanoclusters approach (multishell structure) and the nested-polyhedra model. A database containing all topological types of ?-brass nanoclusters is created with which one can search for the corresponding atomic configuration in any intermetallics. PMID:24083847

Pankova, Arina A; Blatov, Vladislav A; Ilyushin, Gregory D; Proserpio, Davide M

2013-11-18

424

Laves intermetallics in stainless steel-zirconium alloys.  

National Technical Information Service (NTIS)

Laves intermetallics have a significant effect on properties of metal waste forms being developed at Argonne National Laboratory. These waste forms are stainless steel-zirconium alloys that will contain radioactive metal isotopes isolated from spent nucle...

D. P. Abraham S. M. McDeavitt J. W. Richardson

1997-01-01

425

Results on powder injection molding of Ni[sub 3]Al and application to other intermetallic compositions  

SciTech Connect

Net forming processes are under development to allow affordable production of intermetallic components. Powder injection molding (PIM) mav be employed for the production of complex-shaped intermetallic geometries. Proper choice of powder parameters and processing conditions can lead to the formation of fullv dense structures through pressure-less sintering. In this study, Ni[sub 3]Al with 0.04 wt.-% boron has been successfully injection molded and sintered to full density. A yield strength of 340 MPa, ultimate tensile strength (UTS) of 591 MPa, and 8% elongation were attained for injection molded and sintered tensile bars. Powder characteristics and sintering behavior are given for the nickel aluminide employed in this study to highlight the powder attributes needed for injection molding. Molding parameters, debinding and sintering schedules, along, with mechanical properties are presented to indicate the viability of PIM for intermetallics. This approach based on the understanding of key powder characteristics and use of the reactive synthesis powder process mav be extended to the successful injection molding of other intermetallic systems.

Cooper, R.M.

1992-01-01

426

Results on powder injection molding of Ni{sub 3}Al and application to other intermetallic compositions  

SciTech Connect

Net forming processes are under development to allow affordable production of intermetallic components. Powder injection molding (PIM) mav be employed for the production of complex-shaped intermetallic geometries. Proper choice of powder parameters and processing conditions can lead to the formation of fullv dense structures through pressure-less sintering. In this study, Ni{sub 3}Al with 0.04 wt.-% boron has been successfully injection molded and sintered to full density. A yield strength of 340 MPa, ultimate tensile strength (UTS) of 591 MPa, and 8% elongation were attained for injection molded and sintered tensile bars. Powder characteristics and sintering behavior are given for the nickel aluminide employed in this study to highlight the powder attributes needed for injection molding. Molding parameters, debinding and sintering schedules, along, with mechanical properties are presented to indicate the viability of PIM for intermetallics. This approach based on the understanding of key powder characteristics and use of the reactive synthesis powder process mav be extended to the successful injection molding of other intermetallic systems.

Cooper, R.M.

1992-12-31

427

Quasi-one-dimensional magnons in an intermetallic marcasite  

SciTech Connect

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

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

2012-01-01

428

The formation and growth of intermetallics in composite solder  

Microsoft Academic Search

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

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

1993-01-01

429

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

SciTech Connect

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

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

1984-05-29

430

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

SciTech Connect

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

Krismer, B.; Hoppe, A.

1984-05-01

431

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

432

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

PubMed

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

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

2013-12-01

433

Low coordinate germanium(II) and tin(II) hydride complexes: efficient catalysts for the hydroboration of carbonyl compounds.  

PubMed

This study details the first use of well-defined low-valent p-block metal hydrides as catalysts in organic synthesis. That is, the bulky, two-coordinate germanium(II) and tin(II) hydride complexes, L(†)(H)M: (M = Ge or Sn, L(†) = -N(Ar(†))(SiPr(i)3), Ar(†) = C6H2{C(H)Ph2}2Pr(i)-2,6,4), are shown to act as efficient catalysts for the hydroboration (with HBpin, pin = pinacolato) of a variety of unactivated, and sometimes very bulky, carbonyl compounds. Catalyst loadings as low as 0.05 mol % are required to achieve quantitative conversions, with turnover frequencies in excess of 13?300 h(-1) in some cases. This activity rivals that of currently available catalysts used for such reactions. PMID:24524219

Hadlington, Terrance J; Hermann, Markus; Frenking, Gernot; Jones, Cameron

2014-02-26

434

Effects of cross-linking, capsule wall thickness, and compound hydrophobicity on aroma release from complex coacervate microcapsules.  

PubMed

Microcapsules were produced by complex coacervation with a gelatin-gum acacia wall and medium-chain-triglyceride core. Dry capsules were partially rehydrated and then loaded with model aroma compounds covering a range of volatility, hydrophobicity, and molecular structure. An experimental design was prepared to evaluate the effects of cross-linking, wall/core ratio, and volatile load level on aroma release from capsules in a hot, aqueous environment. The real-time release on rehydration was measured by monitoring the headspace of a vessel containing the capsules to proton transfer reaction mass spectrometry (PTR-MS). Data collected showed no effects of cross-linking or wall/core ratio on volatile release in hot water for any of the volatiles studied. When comparing real-time release of the prepared coacervates to a spray-dried equivalent, there was no difference in the release from hot water but the release was slower when coacervates were added to ambient-temperature water. We found volatile release to be primarily determined by compound partition coefficients (oil/water and water/air) and temperature. PMID:19199587

Leclercq, Segolene; Milo, Christian; Reineccius, Gary A

2009-02-25

435

Intermetallic phase formation in thin solid-liquid diffusion couples  

SciTech Connect

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

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

1994-08-01

436

Intermetallic alloys: patterns and complexity. Final technical report  

SciTech Connect

This report summarizes the research accomplishment of the P.I. and her collaborators. The major findings are (a) in the area of ordering in metallic alloys, the interplay between chemical and structural short-range order and (b) in the area of glassy dynamics in frustrated spin models. In the context of alloys, the development of a theoretical framework for incorporating the correlation between chemical and structural degrees of freedom has been a major accomplishment. The work on frustrated spin models has had a major impact on the understanding of the glass transition.

Chakraborty, Bulbul

2001-11-07

437