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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

Making NiTi intermetallic compound coating using laser plasma complex spraying  

SciTech Connect

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

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

1996-12-31

3

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

4

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

PubMed

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

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

2014-01-31

5

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

6

New twisted intermetallic compound superconductor: A concept  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

7

A family of ductile intermetallic compounds.  

PubMed

Stoichiometric intermetallic compounds have always been touted for their attractive chemical, physical, electrical, magnetic and mechanical properties, but few practical uses have materialized because they are brittle at room temperature. Here we report on a large family of fully ordered, stoichiometric binary rare-earth intermetallic compounds with high ductility at room temperature. Although conventional wisdom calls for special conditions, such as non-stoichiometry, metastable disorder or doping to achieve some ductility in intermetallic compounds at room temperature, none of these is required in these unique B2 rare-earth compounds. Ab initio calculations of YAg, YCu and NiAl crystal defect energies support the observed deformation modes of these intermetallics. PMID:12942069

Gschneidner, Karl; Russell, Alan; Pecharsky, Alexandra; Morris, James; Zhang, Zhehua; Lograsso, Thomas; Hsu, David; Lo, C H Chester; Ye, Yiying; Slager, Aaron; Kesse, David

2003-09-01

8

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

9

Radiation-induced amorphization of intermetallic compounds  

NASA Astrophysics Data System (ADS)

In the present paper, important results of our recent computer simulation of radiation-induced amorphization in the ordered compounds CuTi and Cu4Ti3 are summarized. The energetic, structural, thermodynamic and mechanical responses of these intermetallics during chemical disordering, point-defect production and heating were simulated, using molecular dynamics and embedded-atom potentials. From the atomistic details obtained, the critical role of radiation-induced structural disorder in driving the crystalline-to-amorphous phase transformation is discussed.

Lam, N. Q.; Sabochick, M. J.; Okamoto, P. R.

1994-06-01

10

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

11

Magnetic phase transitions in layered intermetallic compounds  

NASA Astrophysics Data System (ADS)

Magnetic, magnetoelastic, and magnetotransport properties have been studied for the RMn2Si2 and RMn6Sn6 (R is a rare earth metal) intermetallic compounds with natural layered structure. The compounds exhibit wide variety of magnetic structures and magnetic phase transitions. Substitution of different R atoms allows us to modify the interatomic distances and interlayer exchange interactions thus providing the transition from antiferromagnetic to ferromagnetic state. Near the boundary of this transition the magnetic structures are very sensitive to the external field, temperature and pressure. The field-induced transitions are accompanied by considerable change in the sample size and resistivity. It has been shown that various magnetic structures and magnetic phase transitions observed in the layered compounds arise as a result of competition of the Mn-Mn and Mn-R exchange interactions.

Mushnikov, N. V.; Gerasimov, E. G.; Rosenfeld, E. V.; Terent'ev, P. B.; Gaviko, V. S.

2012-10-01

12

Roles of Titanium-Intermetallic Compound Layer  

NASA Astrophysics Data System (ADS)

Four different configurations have been tested: Al-Cu, Ti/Al-Cu, Al-Cu/Ti, and Ti/Al-Cu/Ti to evaluate the possible contributions of Ti-intermetallic compound layer(s) to enhancement of the lifetime to failure. Basically, the proposed mechanisms can be classified into two groups: shunting effect and effects limited to changes in Al-Cu conducting layer(s). A resistance monitoring technique was adopted to supplement lifetime measurement to separate these two effects. By correlating the first resistance jump (spike) to the happening of a complete open across Al-Cu layer, it was found that the shunting effect contributes to enhancement of the lifetime by 4 times in Ti/Al-Cu, 2 times in Al-Cu/Ti, and 2 times in Ti/Al-Cu/Ti. A Ti underlayer was found to contribute mainly the shunting effect. However, from drift velocity measurements and failure mode analysis, it is possible to deduce that a Ti overlayer contributes not only the shunting effect but also another effect that acts to diminish the grain boundary mass transport rate by a factor of about 76. It is believed that the latter effect is a consequence of the high compressive yield stength conferred by the Ti-intermetallic compound overlayer to the Al-Cu layer. Finally, an important non-destructive technique, based on the characteristic x-rays generated by energetic electrons, to characterize the mass divergences in multilayer interconnects, was developed in this research, called SMEISIS, representing Simultaneous Multiple Elements Intensity Scanning of Interconnecting Stripes. This technique was proved to be capable of revealing detail about the shapes, nature, and location of mass divergence that cannot be revealed by thermal wave image technique and that requires time consuming multiple sectioning in TEM and SEM methods.

Lee, Chii-Chang

13

Laser surface modification of intermetallic compounds  

NASA Astrophysics Data System (ADS)

The rare earth compound Terfenol-D (Tb(x)Dy(1-x)Fe(y), where x = 0.3 and y = 1.95) has highly magnetostrictive strain properties, but is very brittle and can be difficult to manufacture into functional components. A study was conducted to investigate the effects of laser surface modification of this intermetallic compound in order to determine if the rapid solidification following laser melting could produce a surface with improved toughness. The effects of various pulsed Nd:Y-Al garnet laser process parameters on the resultant surface pool diameter, penetration, and quality were studied experimentally. Individual spots were made on a carefully prepared butt joint at a mean laser power of 180 W. Conduction mode and keyhole mode pools were observed, and the quality of the specimens was poor. Experiments at 60 W and 180 W laser power were also conducted on bulk material. Different processing approaches were used, including manipulating focal position, temporal pulse shaping, using multiple pulses per shot, and preheating the specimens. Surface quality was improved in specimens processed with a temporal pulse shape consisting of a gentle pre-pulse followed by the balance of energy, and by specimens preheated to 150 and 450 C. Multiple pulses per shot on preheated (150 C) specimens also improved surface quality.

Graham, M. P.; Kerr, H. W.; Weckman, D. C.

1992-02-01

14

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

15

THE PREPARATION AND IDENTIFICATION OF SOME INTERMETALLIC COMPOUNDS OF POLONIUM  

Microsoft Academic Search

ABS>A micro technique for the preparation of intermetallic polonium ; compounds is described. Several polonides of the form MPo were prepared in this ; way and investigated by x-ray-powder diffraction; they include those of Be, Mg, ; Ca, Sr, Ba, Zn, Cd, Hg, and Pb. All these polonides, with the exception of Mg ; and Hg, were found to be

W. G. Witteman; A. L. Giorgi; D. T. Vier

1960-01-01

16

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

17

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

18

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

19

Enthalpies of formation of the Al–Ni intermetallic compounds  

Microsoft Academic Search

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

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

2004-01-01

20

Frustrated magnetic moments in RNiAl intermetallic compounds  

Microsoft Academic Search

Magnetic order in rare-earth-based intermetallic compounds of the series RNiAl (R ? Pr, Nd, Tb, Dy, Ho) is investigated by means of neutron diffraction and susceptibility measurements. Nearest neighbours of the rare earths form a triangular lattice in the hexagonal crystal structure. Due to antiferromagnetic coupling in the a-b plane this gives rise to frustration of one-third of the magnetic

G. Ehlers; H. Maletta

1997-01-01

21

Magnetism and superconductivity of uranium and intermetallic compounds  

SciTech Connect

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

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

2001-01-01

22

Magnetic field controlled FZ single crystal growth of intermetallic compounds  

NASA Astrophysics Data System (ADS)

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

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

2005-02-01

23

NUCLEAR ORIENTATION EXPERIMENTS ON CERIUM INTERMETALLIC COMPOUNDS  

E-print Network

ordered, that Sn3Ce is a Kondo lattice and that further experiments must be performed in order to confirm that the compound Al2Ce is well ordered down to 5 mK and that Al3Ce appears as a Kondo lattice [2] [3]. From represents the ideal case of a Kondo lattice described in refe- rences [3-5]. Thus we have performed N

Paris-Sud XI, Université de

24

EOS, thermodynamic, and structural-mechanical properties of intermetallic compounds  

SciTech Connect

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). Several classes of binary intermetallic compounds have important potential application as high temperature structural materials because of their high melting temperature, low density, and high strength, but their use is limited by their poor low temperature ductility and fracture toughness. The goal of this project was to further the development of techniques for performing ab-initio calculations of the electronic, structural, and elastic properties of these materials in an investigation of the relation between structure, composition, and mechanical properties of intermetallics. Materials properties to be addressed in these calculations included the equation of state (EOS), defect structure energetics, and elastic constants and phonons. Major accomplishments included calculations of stacking fault and twin energies in layered TiAl, structural stability in binary and ternary Ti-Al-Nb compounds, and point defect energies and elastic moduli of Laves phase intermetallics.

Wills, J.M.; Straub, G.; Albers, R.C.

1998-12-31

25

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

26

Statistically based assessment of formation enthalpy for intermetallic compounds  

NASA Astrophysics Data System (ADS)

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

Zhang, R. F.; Rajan, K.

2014-09-01

27

Isomerization of diacetoxybutenes on intermetallic compounds of palladium and rhodium  

SciTech Connect

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

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

1992-12-31

28

The Shock Hugoniot of the Intermetallic Compound Ni3Al  

SciTech Connect

The behaviour of the intermetallic compound, Ni3Al under shock loading conditions has been measured. The Hugoniot Elastic Limit occurs at ca. 530 MPa, which converts to a 1-D yield stress of 273 MPa, in agreement with quasi-static data. In contrast, the ductility at shock-induced strain-rates appears much reduced when compared to lower strain-rates. The Hugoniot in terms of shock velocity and particle velocity suggests that Ni3Al is more compressible than pure nickel. This is in agreement with the greater stiffnesses in nickel, measured using ultrasonic techniques.

Knapp, I.; Millett, J. C. F.; Meziere, Y. J. E. [Defence Academy of the United Kingdom, Cranfield University, Shrivenham, Swindon, SN6 8LA (United Kingdom); Gray, G. T. III [Los Alamos National Laboratory, Los Alamos, New Mexico, 87545 (United States); Bourne, N. K. [University of Manchester, Sackville Street, Manchester, M60 1QD (United Kingdom)

2006-07-28

29

Characterization of intermetallic compounds in Cu-Al ball bonds: Layer growth, mechanical properties and oxidation  

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; O. O'Halloran; R. Rongen

2011-01-01

30

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

Microsoft Academic Search

The polar intermetallic compound Ba5Ti12Sb19+x (x?0.2) has been synthesized by reaction of the elements. Single-crystal X-ray diffraction analysis revealed that it adopts a new structure type (Ba5Ti12Sb19.102(6), space group P43¯m, Z=2, a=12.4223(11)Å, V=1916.9(3)Å3). The set of Ba and Sb sites corresponds to the structure of Cu9Al4, a ?-brass type with a primitive cell. A complex three-dimensional framework of Ti atoms,

Haiying Bie; Arthur Mar

2009-01-01

31

Hydrogen Ordering in Hexagonal Intermetallic AB5 Type Compounds  

NASA Astrophysics Data System (ADS)

Intermetallic compounds AB5 type (A = rare-earth atoms, B = transition metal) are known to store reversibly large amounts of hydrogen and as that are discussed in this work. It was shown that the alloy cycling stability can be significantly improved by employing the so-called non-stoichiometric compounds AB5+x and that is why analysis of change of structure turned out to be interesting. A tendency for ordering of hydrogen atoms is one of the most intriguing problems for the unsaturated hydrides. The symmetry analysis method in the frame of the theory of space group and their representation gives opportunity to find all possible transformations of the parent structure. In this work symmetry analysis method was applied for AB5+x structure type (P6/mmm parent symmetry space group). There were investigated all possible ordering types and accompanying atom displacements in positions 1a, 2c, 3g (fully occupied in stoichiometric compounds AB5), in positions 2e, 6l (where atom B could appear in non-stoichiometric compounds) and also 4h, 6m, 6k, 12n, 12o, which could be partly occupied by hydrogen as a result of hydrides. An analysis was carried out of all possible structures of lower symmetry, following from P6/mmm for we k=(0, 0, 0). Also the way of getting the structure described by the P63mc space group with double cell along the z-axiswe k=(0, 0, 0.5), as it is suggested in the work of Latroche et al. is discussed by the symmetry analysis. The analysis was obtained by computer program MODY. The program calculates the so-called basis vectors of irreducible representations of a given symmetry group, which can be used for calculation of possible ordering modes.

Sikora, W.; Kuna, A.

2008-04-01

32

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

33

Formation of intermetallic compound coating on magnesium AZ91 cast alloy  

NASA Astrophysics Data System (ADS)

This study describes an intermetallic compound coating formed on AZ91 Mg cast alloy. The Al sputtered on AZ91 cast alloy reacted with substrate during a short period of heat treatment at 435°C, resulting in the formation of a continuous intermetallic compound layer. The short period treatment has the advantage of minimizing the negative effect on the microstructure of substrate and the mechanical properties, comparing with the reported diffusion coatings. DSC measurement and examination on the cross-section of Al sputtered samples show that local melting occurred along the Al/substrate interface at the temperature range between 430~435°C. The formation mechanism of intermetallic compound coating is proposed in terms of the local melting at Al/substrate interface. The salt water immersion test showed significant improvement in corrosion resistance of the intermetallic compound coated AZ91 cast alloy compared with the as-cast alloys.

Zhu, Tianping; Gao, Wei

2009-08-01

34

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

35

Preparation of a Ti-Ni intermetallic compound by using a drop shaft  

SciTech Connect

A Ti-Ni intermetallic compound could be formed rapidly from Ti and Ni powder compact with SHS process. Microgravity experiments using a drop shaft are carried out. This report shows the effect of microgravity or high gravity on formability of an intermetallic compound. It is concluded that the specimen forms a porous and nearly amorphous alloy by rapid cooling under microgravity, but with rapid cooling under high gravity after microgravity, the specimen forms a uniform and dense structure with better crystallinity.

Suzuki, Y.; Shimokawa, K.; Ueda, Y.; Nagao, J. [Hokkaido National Industrial Research Inst., Sapporo, Hokkaido (Japan)

1996-10-01

36

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

37

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: I4¯m2, 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

38

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

39

Mapping the 'materials gene' for binary intermetallic compounds—a visualization schema for crystallographic databases  

NASA Astrophysics Data System (ADS)

This paper provides a new approach for mapping the relative stability of intermetallic compounds. We quantitatively assess the collective role of numerous chemical and bonding parameters that govern the stability of these compounds (which we call 'genes') using the principles of information entropy. It is shown that one can establish a quantitative scaling parameter, in terms of Shannon entropy, that permits one to map the relative contributions of these parameters on to a single map. This new 'structure map' provides a means of exploring a multivariate array of attributes associated with structural stability and of discerning the efficacy of classical classification mappings for crystal chemistry. We used a binary AB2 intermetallics database as a platform for developing a classification scheme of phase stability based on the concept of Shannon information entropy. We have integrated a metric of information entropy into a recursive partitioning classifier for projecting high-dimensional data manifolds on to a low-dimensional structure map, hence providing a new visualization scheme of complex and high-dimensional crystallographic data sets.

Kong, Chang Sun; Villars, Pierre; Iwata, Shuichi; Rajan, Krishna

2012-01-01

40

Annealing Effect on the Intermetallic Compound Formation of Cold Sprayed Fe/Al Composite Coating  

NASA Astrophysics Data System (ADS)

A Fe/Al composite coating was prepared by cold spraying using an iron-aluminium powder mixture with a Fe/Al atomic ratio of 1:1. The effect of annealing temperature on the intermetallic compound formation in the cold-sprayed Fe/Al coating was investigated. The as-sprayed and annealed coatings were characterized by x-ray diffraction (XRD), and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy. Results showed that intensive particle deformation on impact promoted the Fe2Al5 intermetallic compound formation at a low annealing temperature of 450 °C and this intermetallic layer firstly appeared along some intimate contact regions at the aluminium-iron boundaries. The amount of the Fe2Al5 intermetallic compound increased and no other intermetallic compound phases appeared when the annealing temperature was raised from 450 to 600 °C. Some cracks developed in the Fe2Al5 intermetallic layer when the coating was annealed at 600 °C and the possible causes leading to evolution of cracks are discussed.

Wang, Hong-Tao; Li, Chang-Jiu; Ji, Gang-Chang; Yang, Guan-Jun

2012-06-01

41

Microwave assisted combustion synthesis of non-equilibrium intermetallic compounds.  

PubMed

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

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

2010-01-01

42

The role of intermetallic compounds in lead-free soldering  

Microsoft Academic Search

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

Paul G. Harris; Kaldev S. Chaggar

1998-01-01

43

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

44

XMCD study of RFe 11Ti intermetallic compounds  

NASA Astrophysics Data System (ADS)

We present a systematic X-ray Magnetic Circular Dichroism (XMCD) study performed at the Fe K-edge of the RFe 11Ti intermetallic materials. We have investigated the contribution of the rare-earth sublattice to the dichroism of the transition metal. The existence of a magnetic contribution of the rare-earth has been identified and isolated from the whole spectrum. This contribution is found to be related to the rare-earth moment even when one is looking at the Fe K-edge absorption.

Laguna-Marco, M. A.; Chaboy, J.; Sánchez, M. C.; Maruyama, H.; Kawamura, N.; Suzuki, M.

2004-05-01

45

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

Microsoft Academic Search

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

Jicheng Zhou; Jinbo Zhu; Jianwu Yan

2008-01-01

46

Rare-earth zircons and intermetallic compounds in megagauss-fields: investigation of new magnetic phenomena  

NASA Astrophysics Data System (ADS)

Magnetic phenomena of different material systems were studied in ultrahigh magnetic fields generated by the single-turn coil technique. We report on level crossing effects occurring in rare-earth zircons RXO 4 (R=rare-earth metal, X=P,V) and field-induced magnetic phase transitions in the rare-earth intermetallic compounds RMn 2Ge 2.

Kirste, A.; Kolmakova, N. P.; Hansel, S.; Mueller, H.-U.; von Ortenberg, M.

2004-04-01

47

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

Microsoft Academic Search

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

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

1996-01-01

48

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

SciTech Connect

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

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

2010-01-15

49

Ba5Ti12Sb19+x, a polar intermetallic compound with a stuffed gamma-brass structure  

Microsoft Academic Search

The polar intermetallic compound Ba5Ti12Sb19+x (x<=0.2) has been synthesized by reaction of the elements. Single-crystal X-ray diffraction analysis revealed that it adopts a new structure type (Ba5Ti12Sb19.102(6), space group P43¯m, Z=2, a=12.4223(11) Å, V=1916.9(3) Å3). The set of Ba and Sb sites corresponds to the structure of Cu9Al4, a gamma-brass type with a primitive cell. A complex three-dimensional framework of

Haiying Bie; Arthur Mar

2009-01-01

50

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

SciTech Connect

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

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

1996-06-01

51

Magnetocaloric Effect in the Intermetallic Compound Gd3Ni8Al  

NASA Astrophysics Data System (ADS)

The magnetic properties and magnetocaloric effect of the polycrystalline Gd3Ni8Al intermetallic compound are studied in this paper. Powder X-ray diffraction shows that the alloy is CeNi3-type single-phase structure. The magnetic measurements indicate that the compound is ferromagnetic and undergoes a second-order phase transition at 62 K. The maximum of magnetic entropy change reaches 11 J/kg K for the field change from 0 to 50 kOe and the refrigerant capacity of the titled compound is found to be 4.8×102 J/kg.

Wang, M. X.; Fu, H.; Zheng, Q.; Tang, J.

2012-10-01

52

Electrochemical performance of nanostructured amorphous Co 3Sn 2 intermetallic compound prepared by a solvothermal route  

Microsoft Academic Search

A nanostructured amorphous Co3Sn2 intermetallic compound was prepared by a solvothermal route. The microstructure and the electrochemical performance were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), galvanostatic cycling, and ex situ XRD. It was found that the as-prepared material is in nanoscale and is amorphous. The amorphous Co3Sn2 shows a first specific capacity of 363mAhg?1 compared to 92mAhg?1

J. Xie; X. B. Zhao; G. S. Cao; J. P. Tu

2007-01-01

53

Magnetic and magnetocaloric properties of rare earth intermetallic compound DyCoNi  

NASA Astrophysics Data System (ADS)

Magnetic and magnetocaloric properties of Laves phase rare earth intermetallic compound DyCoNi (cubic, MgCu2-type) have been studied. Magnetization data reveal a ferromagnetic transition at ˜68 K (TC). Magnetocaloric effect has been estimated in terms isothermal magnetic entropy change using field dependent magnetization data taken at various temperatures around TC. The maximum isothermal magnetic entropy change (-?Sm) is found to be ˜ 15.5 J/kg-K near TC for 7 T field change.

Mondal, Rajib; Chelvane, J. Arout; Nirmala, R.

2012-06-01

54

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

Microsoft Academic Search

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

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

2003-01-01

55

Growth of Intermetallic Compounds in Thermosonic Copper Wire Bonding on Aluminum Metallization  

Microsoft Academic Search

Interface evolution caused by thermal aging under different temperatures and durations was investigated by means of scanning\\u000a electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that approximately 30-nm-thick and discontinuous\\u000a Cu-Al intermetallic compounds (IMCs) were present in the initial bonds before aging. Cu-Al IMCs grew under thermal aging with\\u000a increasing aging time. The growth kinetics of the

Hui Xu; Changqing Liu; Vadim V. Silberschmidt; Zhong Chen

2010-01-01

56

Preparation of Cu9Al4 Intermetallic Compound Films as a Metallization Material for LSI Technology  

NASA Astrophysics Data System (ADS)

The intermetallic compound film of Cu9Al4 was prepared by cosputtering at substrate temperatures below 300°C. The prepared film is structurally quite stable up to about 700°C, showing little change in X-ray diffraction pattern. The film with well-textured polycrystalline grains has a low electrical resistivity of 13 ??-cm. It is revealed that the films obtained have sufficiently promising properties well applicable as metallization material for large-scale integrated circuits.

Noya, Atsushi; Sasaki, Katsutaka

1991-04-01

57

Preparation of Cu9Al4 Intermetallic Compound Films as a Metallization Material for LSI Technology  

Microsoft Academic Search

The intermetallic compound film of Cu9Al4 was prepared by cosputtering at substrate temperatures below 300°C. The prepared film is structurally quite stable up to about 700°C, showing little change in X-ray diffraction pattern. The film with well-textured polycrystalline grains has a low electrical resistivity of 13 muOmega-cm. It is revealed that the films obtained have sufficiently promising properties well applicable

Atsushi Noya; Katsutaka Sasaki

1991-01-01

58

Evolution of Cu\\/Al Intermetallic Compounds in the Copper Bump bonds during Aging Process  

Microsoft Academic Search

Growth of Cu\\/Al intermetallic compounds (IMCs) at the interface between the copper bond and the Al metallization pad would increase the contact resistance and degrade the bond reliabilities. In this study, the thermosonic copper bump bonds were aged at 250degC for 1 to 196 hours. Then the evolution of Cu\\/Al IMCs was investigated. Three IMC layers with different colors were

Yaiiliong Tian; Chunjin Hang; Chunqing Wang; Y. Zhou

2007-01-01

59

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

60

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

PubMed

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

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

2014-11-01

61

Electric field gradients at Ta in Zr and Hf inter-metallic compounds  

NASA Astrophysics Data System (ADS)

Here we calculate the electric field gradient (EFG) at the nucleus of the substitutional Ta impurity site in Zr 2T and Hf 2T (T=Cu, Ag, Au, and Pd) C11 b inter-metallic compounds. We use the ab initio FP-LAPW method as embodied in the Wien97 code in a super-cell approach and include lattice relaxations around the impurity. Our results are compared with EFG values inferred from measurements of the quadrupole coupling constants at the 111Ta probe in these compounds performed with the time differential perturbed angular correlation (TDPAC) technique. We also performed EFG calculations for the pure inter-metallic compounds. Through the comparison of theoretical and experimental EFGs in these cases, we elucidate the role played by the Ta probe in the TDPAC measurements of Hf and Zr compounds. Our results show that, although the EFGs at the Hf site are very similar to the EFGs at the Ta impurity, there is no direct correlation between the Zr and Ta EFGs.

Terrazos, L. A.; Petrilli, H. M.; Marszalek, M.; Saitovitch, H.; Silva, P. R. J.; Blaha, P.; Schwarz, K.

2002-03-01

62

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

PubMed

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

Berns, Veronica M; Fredrickson, Daniel C

2014-10-01

63

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

PubMed

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

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

2015-02-01

64

Determining factor of median diameter in intermetallic compound nanoparticles prepared by pulsed wire discharge  

NASA Astrophysics Data System (ADS)

The preparation of NiAl intermetallic compound nanoparticles was carried out by pulsed wire discharge (PWD) using twisted pure Ni and Al wires in N2 ambient gas with varying number of turns of the wire (Nt), energy ratio (K), and ambient gas pressure (P). From the voltage and current waveforms during the wire heating, the energy deposition ratio up to the voltage peak (Kp) was calculated. It increased with an increase in Nt to 0.4 turns/mm and with increases in K and P. Under all the conditions, with an increase in Kp, the Ni composition ratio of the prepared particles (CNi) became closer to that of the wire (= 51.2 mol %). Furthermore, the collection rate (Rc) increased and the median particle diameter (d50) decreased. In particular, the change in d50 due to the change in Nt was not predicted by the relationship of d50 and Dth in our previous report. Single-phase NiAl intermetallic compound nanoparticles were successfully prepared under the condition in which Nt is 0.4 turns/mm, K is 3.4, and P is 100 kPa, where relatively high value of Kp was obtained. From these results, Kp was determined to be an important factor that determines the composition, collection rate, and median diameter of intermetallic compound nanoparticles synthesized by PWD using different kinds of twisted wires under various experimental conditions. This may be because of the selective wire heating in high-resistance parts that are associated with the introduction of lattice defects and/or necks by overwinding.

Nagasawa, Shinobu; Koishi, Tetsuya; Tokoi, Yoshinori; Suzuki, Tsuneo; Nakayama, Tadachika; Suematsu, Hisayuki; Niihara, Koichi

2014-02-01

65

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

66

Fe-Containing Intermetallic Compounds As Catalysts of Methane Conversion with Carbon Dioxide  

NASA Astrophysics Data System (ADS)

Systems based on iron and aluminum were studied in methane conversion with carbon dioxide. The systems were prepared by the method of self-propagating high-temperature synthesis. Massive iron did not exhibit noticeable catalytic activity in methane conversion with carbon dioxide. The deactivation of iron-containing intermetallic compounds was shown to occur because of the formation of the FeC and FeO phases, which screened the active centers of the catalyst surface. The suggestion was made that the active center of the dissociative adsorption of methane was the ?-Fe phase, which existed at the working temperature of methane conversion with carbon dioxide.

Galaktionova, L. V.; Arkatova, L. A.; Kurina, L. N.; Gorbunova, E. I.; Belousova, V. N.; Naiborodenko, Yu. S.; Kasatskii, N. G.; Golobokov, N. N.

2008-02-01

67

Thermochemistry of the intermetallic compounds RuTi, RuZr, and RuHf  

NASA Astrophysics Data System (ADS)

The standard enthalpies of formation of the Intermetallic compounds RuTi, RuZr, and RuHf have been determined by high temperature mixing calorimetry at 1400 K. The following values of ? Hf are reported: RuTi: -153.9 ± 7.4 kJ mol-1; RuZr: -137.3 ± 6.8 kJ mol-1; RuHf: -183.5 ±10.4 kJ mol-1. Since there are no experimental data for these compounds in the literature, comparisons are made with predicted and estimated values. The new data also are compared with recent results reported by the authors for the corresponding equiatomic alloys of Pd and Rh with Ti, Zr, and Hf. This comparison indicates that RuTi is significantly more exothermic than inferred from the systematic trend(s) shown by the other compounds studied.

Topor, Letitia; Kleppa, O. J.

1988-04-01

68

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

69

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

NASA Astrophysics Data System (ADS)

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

Booth, Corwin

2013-03-01

70

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

71

Characterization of second-phase plates in a Gd5Ge3 intermetallic compound  

SciTech Connect

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

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

2013-05-16

72

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

73

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

NASA Astrophysics Data System (ADS)

The crystallization behavior of iron-containing intermetallic compounds in industrial grade 319 aluminum alloy has been investigated by means of thermal analysis and metallography. In the absence of manganese, the iron compound crystallizes in the ? phase, at all cooling rates ranging from 0.1 °C/s to 20 °C/s under normal casting temperatures (750 °C). However, when the melt is superheated to a high temperature (about 200 to 300 degrees above the liquidus temperature), the iron compound crystallizes in the ? phase at high cooling rates. This is due to the fact that ? alumina, which forms at low melt temperatures (?750 °C), acts as a nucleus for crystallization of ? phase. When the melt is superheated to high temperature (?85O °C), the ? alumina transforms to a alumina. This is a poor nucleus for the ?-phase crystallization, and as a result, a phase forms. The importance of nucleation and growth undercooling for the crystallization of iron compounds is highlighted. In the presence of manganese, the iron compound crystallizes in a phase at low cooling rates and in both the ? and ? phases at high cooling rates. This reverse crystallization behavior is explained in terms of phase diagram relationships.

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

1994-08-01

74

Intermetallic Compounds Formed in Sn-20In-2.8Ag Solder BGA Packages with Ag/Cu Pads  

NASA Astrophysics Data System (ADS)

The interfacial reactions in a Sn-20In-2.8Ag solder ball grid array (BGA) package with immersion Ag surface finish are investigated. After reflow, the Ag thin film dissolves quickly into the solder matrix, and scallop-shaped intermetallic layers, with compositions of (Cu0.98Ag0.02)6(In0.59Sn0.41)5, appear at the interfaces between Sn-20In-2.8Ag solder ball and Cu pad. No evident growth of the (Cu0.98Ag0.02)6(Sn0.59In0.41)5 intermetallic compounds was observed after prolonged aging at 100 °C. However, the growth accelerated at 150 °C, with more intermetallic scallops floating into the solder matrix. The intermetallic thickness versus the square root of reaction time ( t 1/2) shows a linear relation, indicating that the growth of intermetallic compounds is diffusion-controlled. Ball shear tests show that the strength of Sn-20In-2.8Ag solder joints after reflow is 4.4 N, which increases to 5.18 N and 5.14 N after aging at 100 and 150 °C, respectively.

Jain, C. C.; Wang, S. S.; Huang, K. W.; Chuang, T. H.

2009-03-01

75

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

76

Structure and phase composition of alloyed intermetallic compound Ni3Al after annealing and high-temperature creep  

NASA Astrophysics Data System (ADS)

The structure and phase composition of a VKNA-25 alloy based on the Ni3Al intermetallic compound, produced by directional solidification, and alloyed with rare-earth metals are studied in the following two states: after annealing at 1100°C and after creep at 1100°C.

Vershinina, T. N.; Golosova, O. A.; Kolobov, Yu. R.; Povarova, K. B.

2011-05-01

77

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

NASA Astrophysics Data System (ADS)

We present an atomistic approach aimed at determining the free energy gliq of binary alloy liquids, a quantity which governs the thermodynamics of phase transformations and whose evaluation has long been a challenge to modeling methods. Our approach, illustrated here for a metallic system model NiZr, combines two methods: the quasiharmonic approximation, applied for some existing (real or hypothetical) intermetallic compounds, and the liquid-solid coexistence conditions. The underlying equations for gliq are solved by means of a subregular-solution approximation. We demonstrate the high reliability of our calculated free energies in determining the phase diagram of a binary system and describing quantitatively the growth kinetics. The latter issue is illustrated by linking molecular dynamics simulations to phase-field modeling with regard to directional solidification and melting in a two-phase system [NixZr1-x]liq-Zrcryst out of chemical equilibrium.

Guerdane, M.

2014-02-01

78

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

79

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

80

Growth of Intermetallic Compounds in Thermosonic Copper Wire Bonding on Aluminum Metallization  

NASA Astrophysics Data System (ADS)

Interface evolution caused by thermal aging under different temperatures and durations was investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that approximately 30-nm-thick and discontinuous Cu-Al intermetallic compounds (IMCs) were present in the initial bonds before aging. Cu-Al IMCs grew under thermal aging with increasing aging time. The growth kinetics of the Cu-Al IMCs was correlated to the diffusion process during aging; their combined activation energy was estimated to be 1.01 eV. Initially, Al-rich Cu-Al IMCs formed in the as-bonded state and early stage of aging treatment. Cu9Al4 was identified by selected-area electron diffraction (SAD) as the only type of Cu-Al IMC present after thermal aging at 250°C for 100 h; this is attributed to the relatively short supply of aluminum to the interfacial reaction.

Xu, Hui; Liu, Changqing; Silberschmidt, Vadim V.; Chen, Zhong

2010-01-01

81

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

82

Observation of superconductivity in the intermetallic compound ?-IrSn4  

NASA Astrophysics Data System (ADS)

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{\\lambda }}_{e-p h}=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.

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

2013-04-01

83

Ab initio calculations of B2 type RHg (R = Ce, Pr, Eu and Gd) intermetallic compounds  

NASA Astrophysics Data System (ADS)

Spin polarized ab initio calculations have been carried out to study the structural, electronic, elastic and thermal properties of RHg (R = Ce, Pr, Eu and Gd) intermetallic compounds in B2 structure. The calculations have been performed by using both generalized gradient approximation (GGA) and local spin density approximation (LSDA). The calculated value of lattice constant (a0) for these compounds with GGA is in better agreement with the experimental data than those with LSDA. Bulk modulus (B), first-order pressure derivative of bulk modulus and magnetic moment (?B) are also presented. The energy band structure and electron density of states show the occupancy of 4f states for light as well as heavy rare earth atom. The elastic constants are predicted from which all the related mechanical properties like Poisson's ratio (?), Young's modulus (E), shear modulus (GH) and anisotropy factor (A) are calculated. The ductility or brittleness of these compounds is predicted from Pugh's rule (B/GH) and Cauchy pressure (C12 - C44). The Debye temperature (?D) is estimated from the average sound velocity, which have not been calculated and measured yet.

Devi, Hansa; Pagare, Gitanjali; Jain, Ekta; Sanyal, Sankar P.

2014-11-01

84

Ab Initio Calculations of Curie Temperature of Intermetallic Compounds Gd2Fe17-xGax  

NASA Astrophysics Data System (ADS)

Intermetallic compounds R2Fe17 are perspective for applications as permanent magnets. Technologically these systems must have Curie temperature Tc much higher than room temperature and preferably have easy axis anisotropy. At the moment highest Tc among stoichiometric R2Fe17 materials is 476 K, which is not high enough. There are two possibilities to increase Tc [1]: substitution of Fe ions with non-magnetic elements or introduction of light elements into interstitial positions. In this work we have focused our attention on substitution scenario. Curie temperature increase is observed experimentally in Gd2Fe17-xGax (x = 3) compounds. In the framework of the LSDA+U approach electronic structure and magnetic properties of the compounds with x = 0,3,6 were calculated. Ab initio exchange interaction parameters within the Fe sublattice for all nearest Fe ions were obtained. Employing the theoretical values of exchange parameters Curie temperatures Tc of Gd2Fe17-xGax within mean-field theory were estimated. Obtained values of Tc agree well with experiment.

Kokorina, E. E.; Medvedev, M. V.; Nekrasov, I. A.

2011-06-01

85

The role of rotation speed on intermetallic compounds formation and mechanical behavior of friction stir welded brass\\/aluminum 1050 couple  

Microsoft Academic Search

In this paper, the intermetallic compounds formation during dissimilar friction stir welding of brass to aluminum 1050 and its effect on the mechanical behavior of joint were studied. Scanning Electron Microscopy (SEM), Energy dispersive spectroscopy analysis (EDS) and X-ray Diffraction analysis were used to characterize intermetallics. In addition, tensile tests and microhardness measurements were performed to evaluate mechanical properties. The

A. Esmaeili; H. R. Zareie Rajani; M. Sharbati; M. K. Besharati Givi; M. Shamanian

2011-01-01

86

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

87

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

88

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

89

Physical properties and magnetic structure of the intermetallic CeCuBi2 compound  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

90

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

91

Theoretical investigation of the hydrogenation induced atomic rearrangements in palladium rich intermetallic compounds MPd3 (M = Mg, In, Tl)  

NASA Astrophysics Data System (ADS)

Based on results from density-functional calculations we present an interesting and unusual mechanism for a structural change in a certain class of intermetallic compounds that can be induced through hydrogen absorption. Through an atomic rearrangement, palladium-rich intermetallic compounds MPd3 (M = Mg, In, Tl) can change the structure from a tetragonal ZrAl3 or TiAl3 type to a cubic AuCu3 type structure. Within the density-functional calculations we study a possible reaction pathway via a gliding of atomic layers with and without the presence of hydrogen. Subsequently, we argue that H-Pd interactions can be held responsible for the structural change upon hydrogen uptake, and that entropic and packing effects can explain the existence of the lower-symmetric structures in the absence of hydrogen.

Kunkel, N.; Sander, J.; Louis, N.; Pang, Y.; Dejon, L. M.; Wagener, F.; Zang, Y. N.; Sayede, A.; Bauer, M.; Springborg, M.; Kohlmann, H.

2011-07-01

92

Synthesis of ultrafine particles of intermetallic compounds by the vapor-phase magnesium reduction of chloride mixtures: Part I. Titanium aluminides  

Microsoft Academic Search

A new chemical synthesis process for the preparation of intermetallic compounds has been developed. It involves the vapor-phase\\u000a reduction of mixtures of constituent metal chlorides by magnesium vapor to produce intermetallic compounds in the form of\\u000a fine powder. The advantages of the process include (a) the use of inexpensive raw materials, (b) low reaction temperatures,\\u000a and (c) products in the

H. Y. Sohn; S. Paldey

1998-01-01

93

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

94

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

95

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

96

Effect of Loading Stress on the Growth of Cn/Sn Intermetallic Compounds at High Temperatures  

NASA Astrophysics Data System (ADS)

Fabrication of reliable solder joints is crucial in microelectronics. In this study we tested solder joints under different loads and temperature-controlled conditions to investigate the effect of external stress on the growth of interfacial Cu/Sn intermetallic compounds (IMCs). Test specimens were prepared by electroplating a layer of Sn (25 ?m thick) on a copper substrate. Samples were then clamped in a micromechanical testing apparatus integrated within a furnace. Experiments were performed by using load feedback control to ensure a constant load of 25, 50, or 100 MPa at a constant temperature of 200°C for periods of 24, 72, or 120 h. We then compared samples that underwent stress with those that did not to elucidate the effect of stress and aging on the formation of IMCs. Our results indicate that the presence of external stress affects the formation of Cu/Sn IMCs, including the speed of formation and the resulting thickness. Moreover, the micrographic structure of IMCs formed under external stress varied substantially depending on the amount of stress applied.

Cheng, Ya-Chi; Wang, Yu-Ting; Hsu, Feng-Chih; Lu, Fang-Ching; Wu, Chung-Lin; Lin, Ming-Tzer

2015-01-01

97

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

NASA Astrophysics Data System (ADS)

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

Wu, Ming

98

Activation energy of self-diffusion along symmetric tilt grain boundaries <111> in the Ni3Al intermetallic compound  

NASA Astrophysics Data System (ADS)

Activation energy of self-diffusion along symmetric tilt grain boundaries <111> in the Ni3Al inter-metallic compound has been calculated depending on the temperature and misorientation angle. For comparison, two types of potentials of interatomic interaction have been used: pair Morse potentials and multi-particle Cleri-Rosato potentials. It has been shown that the activation energy of grain-boundary diffusion increases with temperature on applying the additional diffusion mechanisms. Three temperature ranges with various activation energies have been found.

Kharina, E. G.; Starostenkov, M. D.; Poletaev, G. M.; Rakitin, R. Yu.

2011-05-01

99

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

100

Enthalpies of formation of Cd–Pr intermetallic compounds and thermodynamic assessment of the Cd–Pr system  

PubMed Central

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

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

2014-01-01

101

The effect of microstructures on mechanical behaviors of Ti2AlNb intermetallic compounds  

SciTech Connect

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

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

1992-03-01

102

Growth of CuAl intermetallic compounds in Cu and Cu(Pd) wire bonding  

Microsoft Academic Search

In this study, Cu wire bonds are aged at 150, 175, 250, and 350 o C for time ranging from 5 min to 2000 h. The top temperature of 350 o C is chosen to have the fastest kinetics, while maintaining the same types of stable intermetallics (IMCs) according to the Al-Cu binary phase diagram. Two types of Cu wire

Y. H. Lu; Y. W. Wang; B. K. Appelt; Y. S. Lai; C. R. Kao

2011-01-01

103

Magnetic Order and Spin Reorientations of R-Gallium (R = gadolinium, dysprosium, holmium and erbium) Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

The magnetic structures and spin reorientations of RGa (R = Gd, Dy, Ho and Er) intermetallic compounds have been investigated using neutron powder diffraction and rare earth Mössbauer spectroscopy. The aim has been to determine the magnetic structures of these compounds before and after their spin reorientation transitions and to understand the role of the crystal field and exchange interactions in the spin reorientation mechanism. The results have been compared with those found from previous single-crystal susceptibility measurements on RGa and the recent 119Sn Mössbauer spectroscopy work on Sn-doped RGa compounds. The magnetic structures obtained at low temperatures are a simple collinear ferromagnetic in DyGa, canted ferromagnetic in HoGa and a non-collinear ferromagnetic in GdGa. The spin reorientation in ErGa was also observed by 166Er Mössbauer spectroscopy. These results show that both the crystal field and exchange interactions play an important role in the reorientation mechanism.

Susilo, Resta

104

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

NASA Astrophysics Data System (ADS)

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

Xiao, Lin; Wang, Ning

2015-01-01

105

Competing magnetic interactions in the intermetallic compound Ho2Mn3Si5  

NASA Astrophysics Data System (ADS)

The compound Ho2Mn3Si5 exhibits multiple magnetic transitions: (i) an ordering at ˜78 K, (ii) a second magnetic transition at ˜16 K, and (iii) an anomaly at ˜4 K. Its paramagnetic Curie temperature is found to be small but positive. Assuming a free ion effective paramagnetic moment of 10.6?B for Ho3+ ion, the effective paramagnetic moment per Mn in this compound is calculated to be 1.73?B, which indicates the itinerant nature of Mn d electrons. The various transitions in magnetization data are perhaps due to the ordering of rare earth and Mn moments. The magnetization at 2 K in applied fields of up to 7 T has linear field dependence, indicating dominant antiferromagnetic interactions in the system. Neutron diffraction studies point to a complex amplitude modulated incommensurate magnetic structure at 9 K.

Nirmala, R.; Morozkin, A. V.; Lamsal, Jagat; Chu, Z.; Sankaranarayanan, V.; Sethupathi, K.; Yamamoto, Y.; Hori, H.; Yelon, W. B.; Malik, S. K.

2009-04-01

106

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

107

Structural and magnetic properties of ErCo4.5Ge0.5 intermetallic compound  

NASA Astrophysics Data System (ADS)

We report on the structural and magnetic properties of ErCo4.5Ge0.5 intermetallic compound. This phase crystallize in the hexagonal CaCu5-type structure with P6/mmm space group. Neutron powder diffraction experiments demonstrate that the Ge atoms preferentially occupy the 3g crystallographic site of the CaCu5 structure. The Ge for Co substitution induces a dramatic decrease of the magnetic ordering temperature down to 785 K. The ErCo4.5Ge0.5 compound exhibit a compensation temperature at 100 K where the magnetization of the two sublattices Er and Co cancel out. The influence of Ge for Co substitution on the magnetic properties is discussed.

Colin, C. V.; Isnard, O.

2010-05-01

108

Structure comparison between Th2Zn17-type and TbCu7-type Sm Fe intermetallic compounds and their nitrides by means of 57Fe-Mössbauer spectroscopy  

NASA Astrophysics Data System (ADS)

Samarium iron intermetallic compounds were prepared by a melt spinning method with low and high wheel speeds, which resulted in a Th2Zn17-type and a TbCu7-type structure, respectively. Structure comparison between these types was investigated for Sm Fe intermetallic compounds and their nitrides by 57Fe-Mössbauer spectroscopy.

Sakai, Yoichi; Omatsuzawa, Ryo; Sakazaki, Iwao; Suzuki, Sayaka; Hashino, Hayato; Saito, Takanobu; Iriyama, Takahiko

2005-11-01

109

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

110

Valence behavior of Eu-ions in intermetallic compound Ce 0.5 Eu 0.5 Pd 3 B 0.5  

NASA Astrophysics Data System (ADS)

We have studied the valence behavior of rare-earth ions, in particular Eu-ions, in a cubic intermetallic compound Ce0.5Eu0.5Pd3B0.5 which is a homogeneous solid solution of two mixed-valent compounds CePd 3 and EuPd3B. Results of 151Eu Mössbauer spectroscopic measurements show that two different valence states, i.e., divalent- and trivalent-like states of Eu-ions exist in the compound. The possible reason for the observed heterogeneous valency vis- á- vis the variation in the chemical environment and the number of nearest-neighbor B atoms surrounding the Eu-ions has been discussed. Our results demonstrate that B incorporation in such Eu-based cubic intermetallic compounds leads to a situation where heterogeneous-valence state of Eu-ions is an energetically favorable ground state.

Pandey, Abhishek; Mazumdar, Chandan; Ranganathan, R.; Raghavendra Reddy, V.; Gupta, Ajay

2011-12-01

111

HRTEM of dislocation cores and thin-foil effects in metals and intermetallic compounds.  

PubMed

Examples of the observation and analysis of dislocation cores and dislocation fine structure in metals and intermetallics using high resolution transmission electron microscopy are discussed. Specific examples include the 60 degrees dislocations in aluminum, a011 edge dislocations in NiAl, and screw dislocations in Ni3Al. The effect of the thin TEM foils on the structure and imaging of these dislocations is discussed in light of embedded atom method calculations for several configurations and coupled with image simulations. Some generalizations based on these calculations are discussed. These analyses enables determination of the spreading or decomposition of the edge component of the cores, both in and out of the glide plane, which can have significant implications for the modeling of macroscopic behavior. PMID:16646008

Mills, M J; Baluc, N L; Sarosi, P M

2006-05-01

112

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

113

L1{sub 2} (Al,Cr){sub 3}Ti-based two-phase intermetallic compounds. 1: Plastic deformation behavior  

SciTech Connect

A number of recent works on intermetallic compounds in the Ti-Al system have concentrated on gamma-based TiAl, but Al{sub 3}Ti is especially attractive because of its low density and good oxidation resistance. However, Al{sub 3}Ti, with a low-symmetry tetragonal D0{sub 22} structure, exhibits less than 1% compressive strain in the temperature range of 298 K to 893 K, for which the primary deformation mode is ordered twinning. Therefore, its brittleness limits its practical application as a structural material. More recently, much work has been conducted on the transformation of crystal structure through the addition of ternary alloying elements to improve the ductility of Al{sub 3}Ti. In this study, the plastic deformation behavior of two-phase intermetallic compounds consisting of mainly L1{sub 2} phase and the second phases in Al-Ti-Cr system was investigated. As in the case of {alpha}{sub 2}/{gamma} two-phase TiAl compounds, the possibility of ductilizing two-phase intermetallic compounds based on L1{sub 2}-type (Al,Cr){sub 3}Ti was examined. The influence of pore formation, ingot cast structure and second phase morphology on ductility of the alloy was also examined.

Park, J.Y.; Wee, D.M. [KAIST, Taejon (Korea, Republic of). Dept. of Materials Science and Engineering] [KAIST, Taejon (Korea, Republic of). Dept. of Materials Science and Engineering; Oh, M.H. [Kumoh National Univ. of Technology, Kumi (Korea, Republic of). Dept. of Materials Science and Engineering] [Kumoh National Univ. of Technology, Kumi (Korea, Republic of). Dept. of Materials Science and Engineering; Miura, S.; Mishima, Y. [Tokyo Inst. of Technology, Yokohama (Japan)] [Tokyo Inst. of Technology, Yokohama (Japan)

1997-04-01

114

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

115

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

NASA Astrophysics Data System (ADS)

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

Nath, Jyotishman; Mallik, Sabuj; Borah, Anil

2015-01-01

116

Estimation of the effective parameter of spinorbital interaction of electrons in intermetallic Er-In system compounds from the kinetic and magnetic properties  

NASA Astrophysics Data System (ADS)

Normal, R 0 and anomalous, R S components of the Hall coefficient are determined from the results of experimental investigations of temperature dependences of the Hall coefficient, magnetic susceptibility, and specific electrical resistance for intermetallic Er2In, ErIn, and Er3In5 compounds. Effective parameters of spinorbital interaction ?SO of intermetallic compounds are calculated from anomalous components RS of the Hall coefficient and specific electrical resistance. The results calculated for the band parameters and effective parameters of spin-orbital interaction ?SO for Er-In system intermetallides coincide by orders of magnitude with the results obtained in [4,7,8] from the optical spectra of pure rare-earth metals.

Kuvandikov, O. K.; Hamraev, N. S.; Razhabov, R. M.; Éshkulov, A. A.

2012-05-01

117

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

SciTech Connect

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

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

2012-01-15

118

Enhancement of high temperature thermoelectric properties of intermetallic compounds based on a Skutterudite IrSb 3 and a half-Heusler TiNiSb  

Microsoft Academic Search

Phonon glass and electron crystal (PGEC) thermoelectric materials have been expected to be a new class of thermoelectric materials for high temperature applications. Among the efforts to optimize the high temperature thermoelectric properties of various PGEC thermoelectric materials, recent experimental works on the Skutterudite IrSb3 and half-Heusler TiNiSb intermetallic compounds are presented herein by which the material design concept for

S. W Kim; Y. Kimura; Y. Mishima

2004-01-01

119

Neutron scattering study of the quasi-elastic spectral width in CeMg, CeMg3 and NdMg3 intermetallic compounds  

E-print Network

.20H 1. Introduction. Pure cerium and some cerium intermetallic com- pounds are known to exhibit much smaller and the magnetic properties close to those of the trivalent ion, are considered as Kondo cerium compounds CeMg3 [9], CeO.5LaO.5Mg3, CeO.5 Y 0.5Mg3, CeMg [10], Ceo.2Lao.8Mg, Ceo.2 Y o.sMg [11

Paris-Sud XI, Université de

120

Auger Electron Spectroscopy Study on the Stability of the Interface between Deposited Cu9Al4 Intermetallic Compound Film and Si  

Microsoft Academic Search

The interaction of deposited Cu9Al4 intermetallic compound film with a silicon substrate is studied by Auger electron spectroscopy. Although the incorporation of silicon into the Cu9Al4 film with low concentration level is observed, the interface is stable up to the annealing temperature of 700°C without forming aluminum spikes or a copper silicide layer. It is revealed that Cu9Al4 film is

Atsushi Noya; Katsutaka Sasaki; Shirou Ohtaka; Nobuyuki Sasao

1991-01-01

121

Formation and morphology of the intermetallic compounds formed at the 91Sn–8.55Zn–0.45Al lead-free solder alloy\\/Cu interface  

Microsoft Academic Search

Formation and morphology of the intermetallic compounds (IMCs) formed at the 91Sn–8.55Zn–0.45Al lead-free solder alloy\\/Cu interface has been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED). The XRD analysis indicates that the ?-Cu5Zn8 IMC is found at the solder\\/Cu interface in the as-wetted sample. When heat treated at 423K for 100

Moo-Chin Wang; Shan-Pu Yu; Tao-Chih Chang; Min-Hsiung Hon

2005-01-01

122

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

123

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

124

Mathematical and experimental investigation of the self-propagating high-temperature synthesis (SHS) of TiAl3 and Ni3Al intermetallic compounds  

Microsoft Academic Search

One-dimensional mathematical modeling was used to describe the self-propagating high-temperature synthesis (SHS) process for preparing TiAl3 and Ni3Al intermetallics. The kinetic parameters (activation energies and pre-exponential factors) for the two compounds were obtained by matching experimental measurement and the numerical solution. The results thus obtained were compared with rate parameters obtained using different methods. The activation energy was 483 and

H. Y. Sohn; X. Wang

1996-01-01

125

Formation of a multimodal grain structure and its influence on the strength and the ductility of the intermetallic compound Ni3Al  

NASA Astrophysics Data System (ADS)

The results of studying the plastic deformation of the product of high-temperature synthesis on the grain structure, the strength, and the ductility of the intermetallic compound Ni3Al are presented. Plastic deformation forms a multimodal grain structure in Ni3Al. The multimodal grain structure contains of submicron multigrains. The volume fraction of multigrains increases and the strength and the ductility of synthesized Ni3Al increase with the strain.

Ovcharenko, V. E.; Psakh'e, S. G.; Boyangin, E. N.

2014-04-01

126

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

PubMed

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

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

2014-06-16

127

First-principles calculations on temperature-dependent elastic constants of rare-earth intermetallic compounds: YAg and YCu  

NASA Astrophysics Data System (ADS)

We present the temperature-dependent elastic constants of two ductile rare-earth intermetallic compounds YAg and YCu with CsCl-type B2 structure by using a first-principles approach. The elastic moduli as a function of temperature are predicted from the combination of static volume-dependent elastic constants obtained by the first-principles total-energy method with density-functional theory and the thermal expansion obtained by the first-principles phonon calculations with density-functional perturbation theory. The comparison between our calculated results and the available experimental data for Ag and Cu provides good agreements. In the calculated temperature 0-1000 K, the elastic constants of YAg and YCu follow a normal behavior with temperature that those decrease with increasing temperature, and satisfy the stability conditions for B2 structures. The Cauchy pressure for YAg and YCu as a function of temperature is also discussed, and our results mean that YAg and YCu become more ductile while increasing temperature.

Wang, Rui; Wang, Shaofeng; Wu, Xiaozhi; Yao, Yin

2011-10-01

128

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

129

Formation of intermetallic compound layer in multi-laminated Ni-(TiB2/Al) composite sheets during annealing treatment.  

PubMed

Solid-state reactive diffusion between Ni and Al was investigated during annealing at 650°C by employing multi-laminated Ni-(TiB(2)/Al) composite sheets. In multi-laminated Ni-(TiB(2)/Al) composite sheets annealed up to 5min NiAl(3) was the only phase observed in the diffusion zone, and Ni(2)Al(3) appeared after longer annealing time. Most grains of Ni(2)Al(3) showed equiaxed morphology rather than columnar microstructures like NiAl(3), due to the low concentration gradients of Al and Ni at the Ni/NiAl(3) interface. The preferential formation of this intermetallic compound NiAl(3) in multi-laminated Ni-(TiB(2)/Al) composite sheets was predicted using an effective heat of formation model. The present work indicated that both Ni and Al interdiffused, and the formation of NiAl(3) was a reaction-diffusion process. PMID:23266224

Wang, Q W; Fan, G H; Geng, L; Zhang, J; Zhang, Y Z; Cui, X P

2013-02-01

130

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

SciTech Connect

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

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

1991-04-30

131

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

132

The magnetic and electronic structures of several rare earth-transition metal intermetallic compounds  

NASA Astrophysics Data System (ADS)

The crystallographic and magnetic properties of the LaNi5--x Fex (1 ? x ? 1.4) and LaNi5--xMn x (x = 0, 1, 1.5, and 2) compounds have been studied by x-ray and neutron diffraction, SQUID and Mossbauer spectroscopy (LaNi 5--xFex only). All of the samples crystallized in the hexagonal CaCu5-type structure with space group P6/mmm. Both Fe and Mn atoms preferentially occupy the 3g site in these compounds. The LaNi 5--xFex samples exhibit ferromagnetic properties for x ? 1.2. The different magnetic behavior observed in LaNi4Fe suggests the coexistence of both short and long range magnetic ordering. The magnetic structure of LaNi5--xMnx for x = 1.5 and 2 is described by a ferrimagnetic model. A ferromagnetic model gives the best fit of the neutron diffraction data for LaNi4Mn. Calculations of the nearest-neighbor environments suggest that the difference between the magnetic structures of LaNi5--xMnx is due to the Mn dilution. The electronic structures of the LaNi5--xFe x compounds with x = 1 and 2 have been modeled by the orthogonalized linear combination of atomic orbitals (OLCAO) method. Calculations of magnetic moments, total energy, which is related to the preference of Fe occupying the 3g site, and total density of states are consistent with the results from SQUID measurements, neutron diffraction data, and Mossbauer spectroscopy. The spin-polarized photoemission measurements did not provide quality data due to a sample magnetization problem caused by the low remanence of the samples. Spin-independent photoemission spectra for YCo5, NdCo5, and LaNi3.65Fe1.35 are presented.

Tai, Chiu-Ying

133

Crystal structure of the inter-metallic compound SrCdPt.  

PubMed

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

Gulo, Fakhili; Köhler, Jürgen

2014-12-01

134

Composition dependence of Ni magnetic moment in Ni Mn-based Heusler-type intermetallic compounds  

NASA Astrophysics Data System (ADS)

Ni2MnGa, a promising candidate of magnetic shape memory, and its derivatives Ni2MnIn and Ni2MnSn are studied by soft X-ray magnetic circular dichroism. It is revealed that Ni2MnGa has the largest Ni 3d partial density of states just above the Fermi level among these three compounds. It is also shown to have the largest ratio of Ni 3d magnetic moment relative to that of Mn.

Imada, S.; Yamasaki, A.; Kanomata, T.; Muro, T.; Sekiyama, A.; Suga, S.

2007-03-01

135

Crystal structure of the inter­metallic compound SrCdPt  

PubMed Central

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

Gulo, Fakhili; Köhler, Jürgen

2014-01-01

136

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

137

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

PubMed

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

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

2014-05-01

138

Electrocatalytic Formation and Inactivation of Intermetallic Compounds in Electrorefining of Silicon  

NASA Astrophysics Data System (ADS)

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

Olsen, Espen; Rolseth, Sverre; Thonstad, Jomar

2010-08-01

139

Thermal transport in the intermetallic compound CeNi4Cr  

NASA Astrophysics Data System (ADS)

Electrical resistivity, thermopower (TEP), thermal conductivity and the thermoelectric figure of merit are studied for the CeNi4Cr compound, which has been previously suggested to be a fluctuating valence system with a tendency to the increase of the effective mass at low temperatures. The analysis of the thermoelectric properties confirms such a possibility and provides characteristic parameters like the Debye temperature, Fermi energy and the position of the f band. Both the thermopower and the magnetic part of the electrical resistivity could be analyzed within a similar model assuming a narrow f-band of the Lorentzian form near the Fermi energy. The thermal conductivity shows that the phonon contribution exceeds the electronic one below 220 K.

Toli?ski, T.

2011-11-01

140

Strong hybridization of 4f states of heavy rare earths in intermetallic compounds  

NASA Astrophysics Data System (ADS)

Strong hybridization between 4f states of heavy rare earths (RE’s) and valence states was found in TbRh, TbPd, and DyPd. The resonant photoemission (PE) spectra taken in the region of the RE 4d?4f excitation threshold reveal splittings of the Tb 8S7/2 and Dy 7F6 components of the PE final-state multiplets if they overlap in energy the transition-metal 4d-derived valence bands of the compounds. The phenomenon is described quantitatively in the framework of the single-impurity Anderson model applied usually for the description of Ce systems. The reported results are of high importance for understanding electronic properties of heavy lanthanide systems including magnetic materials relevant for technological applications.

Molodtsov, S. L.; Kucherenko, Yu.; Vyalikh, D. V.; Behr, G.; Starodubov, A.; Laubschat, C.

2003-11-01

141

Hydrogenation-Induced Insulating State in the Intermetallic Compound LaMg2Ni  

NASA Astrophysics Data System (ADS)

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

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

2005-02-01

142

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

SciTech Connect

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

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

2013-02-15

143

Investigations of the (R)nickel germanide intermetallic compounds by X-ray resonant magnetic scattering  

NASA Astrophysics Data System (ADS)

The x-ray magnetic scattering (XRMS) intensities of the Gd, Tb, Dy, Ho, Er, and Tm L2,3 edges were investigated using two isostructural samples [Gd1/4Tb1/4Dy1/4Ho 1/4]Ni2Ge2 and [Gd1/3Er1/3Tm 1/3]Ni2Ge2 in order to elucidate systematics in the underlying resonance process. Taken together with theoretical linearized augmented planewave (LAPW) calculations employing LDA + U, we found that the XRMS intensity at the heavy rare-earth L edges is strongly related to the 4f-5d exchange interaction and that the branching ratio arises from the effects of spin orbit coupling in the 5d band. For Gd, the 4f-5 d exchange interaction is large and dominant over not only the spin orbit coupling but also other interactions. Therefore, the XRMS intensity of Gd L3 and L2 edges most closely reflects the state of 4f moments. In the pure GdNi2Ge2 compound, large antiferromagnetic (AFM) domains were found, comparable to the x-ray beam size. Single domain scattering was measured carefully with a very small beam size for various azimuth angles and temperatures. From this measurement, a second transition at 16 K in bulk measurements was identified as a transformation from a collinear squared-up structure at high temperature, to a tilted helical structure below 16 K. Since the XRMS scattering cross-section is strongly dependent on the magnetic moment direction, the AFM domain structure was imaged by the XRMS intensity. From single domain scattering data, the ratio of the spin moments in the collinear and the spiral structure of GdNi2Ge2 at the second magnetic transition temperature were derived and used to estimate the magnetic anisotropy energy of Gd. Surprisingly, the estimated magnetic anisotropy energy of Gd in this compound is much higher than that of pure Gd metal (about a order of magnitude). This is expected to be the effect of the anisotropy in 5d conduction band. More theoretical study is necessary to understand this observation.

Kim, Jong-Woo

2005-11-01

144

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

145

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

146

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

147

Kinetics of intermetallic compound formation at 91Sn–8.55Zn–0.45Al lead-free solder alloy\\/Cu interface  

Microsoft Academic Search

The kinetics of intermetallic compounds (IMCs) formation at the 91Sn–8.55Zn–0.45Al lead-free solder alloy\\/Cu substrate interface during soldering and subsequent aging have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM) and electron diffraction (ED). From the XRD results, ?-Cu5Zn8 and Cu6Sn5 are found in the eutectic 91Sn–8.55Zn–0.45Al solder alloy\\/copper interface, but

Moo-Chin Wang; Shan-Pu Yu; Tao-Chih Chang; Min-Hsiung Hon

2004-01-01

148

Auger Electron Spectroscopy Study on the Stability of the Interface between Deposited Cu9Al4 Intermetallic Compound Film and Si  

NASA Astrophysics Data System (ADS)

The interaction of deposited Cu9Al4 intermetallic compound film with a silicon substrate is studied by Auger electron spectroscopy. Although the incorporation of silicon into the Cu9Al4 film with low concentration level is observed, the interface is stable up to the annealing temperature of 700°C without forming aluminum spikes or a copper silicide layer. It is revealed that Cu9Al4 film is a useful material to realize a stable interface when employed as a metallization material for silicon devices.

Noya, Atsushi; Sasaki, Katsutaka; Ohtaka, Shirou; Sasao, Nobuyuki

1991-04-01

149

The influence of modifying admixtures on the catalytic properties of the Ni3Al intermetallic compound in the conversion of methane with carbon dioxide  

NASA Astrophysics Data System (ADS)

Catalytic systems based on the Ni3Al intermetallic compound and modified with niobium and chromium were studied in methane reforming with carbon dioxide. The catalysts were prepared under self-propagating high-temperature synthesis conditions. The phase composition of the catalytic systems was studied by X-ray diffraction. The catalytic activity of the samples increased as the concentration of modifying admixtures decreased and was maximum at 2% concentrations of Nb and Cr. The scanning electron microscopy data showed that the catalytic systems experienced substantial structural changes, which caused catalytic activity loss with time.

Arkatova, L. A.; Kurina, L. N.; Galaktionova, L. V.

2009-04-01

150

The modification of Ni3Al intermetallic compound with chromium and tungsten for carbon dioxide reforming of methane to synthesis gas  

NASA Astrophysics Data System (ADS)

Catalytic systems based on the Ni3Al intermetallic compound and modified with chromium and tungsten were studied in carbon dioxide reforming of methane. The catalysts were prepared by the self-propagating high-temperature synthesis method. The phase composition of the catalytic systems was determined by X-ray diffraction. The catalytic activity of the samples increased as the concentration of dopants decreased and was maximum at 2 wt % Cr and W. Scanning electron microscopy studies showed that the catalytic system underwent substantial structural changes responsible for catalytic activity loss with time.

Arkatova, L. A.; Kurina, L. N.

2010-01-01

151

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

152

La9Sb16Br3 and Ce9Sb16Cl3: stars and stripes in rare earth halide and intermetallic compounds.  

PubMed

The title compounds were synthesized from Ln, LnX(3) (Ln = La, Ce; X = Cl, Br), and Sb under an Ar atmosphere at 950 degrees C. They crystallize in the space group P6(3)/m (No. 176) with lattice constants a = 21.232(5) and 20.862(2) Angstroms and c = 4.323(2) and 4.2728(7) Angstroms for La(9)Sb(16)Br(3) and Ce(9)Sb(16)Cl(3), respectively. The solids are the most metal-rich members in the reduced rare earth metal halide family and contain partial structures which are characteristic of reduced halides and intermetallic phases. These are the [Ln(6)X(6)](infinity) hexagon stars, Sb-centered [Ln(3)Sb](infinity) trigonal prismatic columns, and stripes of Sb square meshes. Computational analysis indicates that their electronic structure is valence-precise in the reduced halide part, but electron-deficient in the intermetallic part. Susceptibility and resistivity measurements reveal the metallic nature of the compounds. PMID:15877452

Zheng, Chong; Mattausch, Hansjürgen; Simon, Arndt

2005-05-16

153

Magnetic structure of R2CoGa8 (R = Gd, Tb, and Dy): Structural tuning of magnetic properties in layered Ga-based intermetallic compounds  

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 spin structure with a magnetic propagation vector ??= (1/2,1/2,1/2) and a Néel temperature of approximately 20, 28.5, and 15.2 K for R = Gd, Tb, and Dy, respectively. The critical exponent ? obtained from the temperature dependence of the magnetic peaks suggest a three-dimensional universality class for the three compounds. Comparing the simulated and integrated intensities we conclude that the magnetic moment direction is in the ab plane for the Gd2CoGa8 compound and parallel to the c axis for the Tb2CoGa8 and Dy2CoGa8 compounds. The evolution of the magnetic properties of the R2CoGa8 series for R = Gd-Tm is discussed taking into account the indirect Ruderman-Kittel-Kasuya-Yoshida interaction and crystalline-electric field effects. The comparison between the reported magnetic properties of the Ga-based compounds with those for the In-based isostructural family reveals differences in their exchange couplings that contribute to the understanding of the role of the f-electron magnetism in these classes of materials.

Mardegan, J. R. L.; Adriano, C.; Vescovi, R. F. C.; Faria, G. A.; Pagliuso, P. G.; Giles, C.

2014-03-01

154

Growth Kinetics of Cu-Sn Intermetallic Compounds at Interface of 80Sn-20Pb Electrodeposits and Cu Based Leadframe Alloy, and Its Influence on the Fracture Resistance to 90°-Bending  

NASA Astrophysics Data System (ADS)

Electrodeposits of 80Sn-20Pb were formed on a Cu-based leadframe alloy from organic sulfonate solutions under different plating conditions, and were then aged at 100 to 180°C to examine the effects of the microstructure of electrodeposits on the growth kinetics of the Cu-Sn intermetallic layer formed at the electrodeposit/substrate interface, and the resultant influence on the fracture resistance of the electrodeposits under bending. The Cu-Sn intermetallic compound layers [? (Cu3Sn) + ? (Cu6Sn5)] increase linearly in thickness with the square root of aging time. However, the growth rate of the intermetallic compounds layer exhibits significant differences depending on the deposition condition; it is fastest in an extremely fine elecrodeposit formed using pulse current in a bath without any grain refiner, but is slowest in that formed using dc current in a bath with grain refiner, in spite of an equivalent grain size in both electrodeposits. This is due primarily to the inhibiting effects of the grain refiner remaining at grain boundaries of the electrodeposit on the diffusion of Sn across the intermetallic compounds/electrodeposit interface. The occurrence frequency and the degree of opening of surface cracks, formed when the aged samples are subjected to the 90°-bending test, are found to be associated with the growth rate of the intermetallic compound layer and the ductility of the electrodeposit. For samples aged under the same conditions, the sample electrodeposited from the solution containing grain refiner shows the highest resistance to surface cracking during the 90°-bending test due to the lower growth rate of its intermetallic layer and the higher ductility of the electrodeposit compared with those of other samples.

Suh, Min-Suk; Kwon, Hyuk-Sang

2000-10-01

155

Intermetallic compounds formed during the reflow and aging of Sn-3.8Ag-0.7Cu and Sn-20In-2Ag-0.5Cu solder ball grid array packages  

NASA Astrophysics Data System (ADS)

After reflow of Sn-3.8Ag-0.7Cu and Sn-20In-2Ag-0.5Cu solder balls on Au/Ni surface finishes in ball grid array (BGA) packages, scallop-shaped intermetallic compounds (Cu0.70Ni0.28Au0.02)6Sn5 (IM1a) and (Cu0.76Ni0.24)6(Sn0.86In0.14)5 (IM1b), respectively, appear at the interfaces. Aging at 100°C and 150°C for Sn-3.8Ag-0.7Cu results in the formation of a new intermetallic phase (Cu0.70Ni0.14Au0.16)6Sn5 (IM2a) ahead of the former IM1a intermetallics. The growth of the newly appeared intermetallic compound, IM2a, is governed by a parabolic relation with an increase in aging time, with a slight diminution of the former IM1a intermetallics. After prolonged aging at 150°C, the IM2a intermetallics partially spall off and float into the solder matrix. Throughout the aging of Sn-20In-2Ag-.5Cu solder joints at 75°C and 115°C, partial spalling of the IM1b interfacial intermetallics induces a very slow increase in thickness. During aging at 115°C for 700 h through 1,000 h, the spalled IM1b intermetallics in the solder matrix migrate back to the interfaces and join with the IM1b interfacial intermetallics to react with the Ni layers of the Au/Ni surface finishes, resulting in the formation and rapid growth of a new (Ni0.85Cu0.15)(Sn0.71In0.29)2 intermetallic layer (IM2b). From ball shear tests, the strengths of the Sn-3.8Ag-0.7Cu and Sn-20In-2Ag-0.5Cu solder joints after reflow are ascertained to be 10.4 N and 5.4 N, respectively, which drop to lower values after aging.

Cheng, M. D.; Chang, S. Y.; Yen, S. F.; Chuang, T. H.

2004-03-01

156

Thermoelectric properties of FeGa3-type narrow-bandgap intermetallic compounds Ru(Ga,In)3: Experimental and calculational studies  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of polycrystalline binary narrow-bandgap intermetallic RuGa3 and RuIn3 compounds have been investigated in the temperature range from 373 K to 973 K. These compounds exhibit semiconductor-like transport properties with large Seebeck coefficients of -560 ?V/K and 280 ?V/K at 373 K for RuGa3 and RuIn3, respectively. The Seebeck coefficient of RuGa3 changed rapidly from large negative to large positive values around 500 K, which is consistent with our calculation based on the full-potential-linearized-augmented-plane-wave method. In contrast, RuIn3 is a p-type material at its operating temperature. The dimensionless figures of merit ZT of pure compounds reached maximum values of 0.13 and 0.17 at about 973 K and 773 K, respectively. The potential maximum ZT value was evaluated using the Boltzmann transport equation and can exceed unity by electron- or hole-doping for both compounds. By substituting Co for Ru in RuIn3, n-type thermoelectric materials (ZTmax = 0.10 at 473 K) were obtained. We suggest that ZT will be enhanced by further effective electron-doping.

Takagiwa, Y.; Kitahara, K.; Matsubayashi, Y.; Kimura, K.

2012-06-01

157

First-principles calculations of the mechanic and vibration properties of AgRE (RE = Ho, Er, Tm) intermetallic compounds under pressure  

NASA Astrophysics Data System (ADS)

First-principles calculations are used to investigate the structural, elastic and vibration properties of the binary intermetallic compounds AgRE (RE = Ho, Er, Tm) with a B2 (CsCl) structure using density functional theory. The calculated structural parameters, the bulk modulus and its derivative with respect to pressure are in good agreement with experimental and numerical data. Additionally, the negative energy of formation of AgRE (RE = Ho, Er, Tm) with a B2 structure is examined. The independent second order elastic constants and their related properties, which are essential for mechanical stability, are investigated under pressure (0–60 GPa). The phonon spectra and phonon density of states are also discussed. All calculated phonon modes for AgRE (RE = Ho, Er) are positive in the phonon dispersion diagrams.

Mogulkoc, Y.; Ciftci, Y. O.; Colakoglu, K.; Deligoz, E.

2015-02-01

158

Magnetic properties and structure of nonstoichiometric rare-earth transition-metal intermetallic compounds TbNi2Mn x (0 ? x ? 1.5)  

NASA Astrophysics Data System (ADS)

Crystal structure, magnetization, coercive force, magnetic susceptibility, and anisotropic magnetostriction of nonstoichiometric rare-earth transition-metal intermetallic compounds TbNi2Mn x (0 ? x ? 1.5) have been studied. The samples with x ? 1 have an fcc structure, whereas TbNi2Mn1.25 has a rhombohedral structure of the PuNi3 type. It has been found that the magnetic ordering temperature increases sharply when manganese is added. As the Mn concentration grows, the magnetization and the magnetostriction decrease monotonically, while the coercive force increases. The experimental data obtained have been interpreted on the assumption that a partial substitution of manganese for terbium in TbNi2Mn x leads to local distortions of the crystal field acting on Tb ions, to the appearance of a local uniaxial random anisotropy, and to the formation of a noncollinear magnetic structure in the terbium sublattice.

Mushnikov, N. V.; Gaviko, V. S.; Gerasimov, E. G.; Terent'ev, P. B.; Tkach, I. A.

2010-09-01

159

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

160

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

161

First-principles calculations of phonon and thermodynamic properties of AlRE (RE = Y, Gd, Pr, Yb) intermetallic compounds  

NASA Astrophysics Data System (ADS)

The phonon and thermodynamic properties of aluminum-rare-earth (AlRE, RE = Y, Gd, Pr, Yb) intermetallics with B2-type structure are investigated by performing density functional theory and density functional perturbation theory calculations within the quasiharmonic approximation. The phonon spectra and phonon density of states, including the phonon partial density of states and total density of states, are discussed. Our results demonstrate that the density of states is mostly composed of Al states at high frequency. The temperature dependences of various quantities such as thermal expansion, heat capacities at constant volume and pressure, the isothermal bulk modulus and the entropy are obtained. The electronic contribution to specific heat is discussed, and the present results show that the thermal electronic excitation affecting the thermal properties is inessential.

Wang, Rui; Wang, Shaofeng; Wu, Xiaozhi; Lan, Mingjian; Song, Tingting

2012-03-01

162

Radiation-induced amorphization of ordered intermetallic compounds CuTi, CuTi2, and Cu4Ti3: A molecular-dynamics study  

NASA Astrophysics Data System (ADS)

Solid-state amorphization resulting from the introduction of chemical disorder and point defects in the ordered intermetallic compounds CuTi, CuTi2, and Cu4Ti3 was investigated, with use of the isobaric-isothermal molecular-dynamics method in conjunction with embedded-atom potentials. Antisite defects were produced by randomly exchanging Cu and Ti atoms, and vacancies and interstitials were created by removing atoms at random from their normal sites and inserting atoms at random positions in the lattice, respectively. The potential energy, volume expansion, and pair-correlation function were calculated as functions of the numbers of atom exchanges and point defects. The results indicated that, although both chemical disordering and point-defect introduction increased the system energy and volume, the presence of point defects was essential to trigger the crystalline-to-amorphous transition. By comparing the pair-correlation function calculated after the introduction of point defects with that of the quenched liquid alloy, the critical damage dose (in dpa, displacements per atom) for amorphization was estimated for each compound: ~0.7 dpa for CuTi, ~0.5 dpa for CuTi2, and ~0.6 dpa for Cu4Ti3. At the onset of amorphization, the volume expansions were found to be ~1.9%, ~3.7%, and ~1.7% for these respective compounds. In general, the results obtained in the present work are in good agreement with experimental observations.

Sabochick, Michael J.; Lam, Nghi Q.

1991-03-01

163

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

164

Spectroscopic characterization of intermetallic catalysts and correlations with methanation activity and laser mass spectrometry of organic compounds  

SciTech Connect

Spectroscopic techniques such as electron spectroscopy for chemical analysis (ESCA), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), ion scattering spectroscopy (ISS), scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX) were used to characterize a number of intermetallic catalytic systems: Th/sub x/Ni/sub y/, Th/sub x/Co/sub y/ and Th Ni/sub x/Fe/sub 5-x/. The results are discussed in relation to methanation activity. Laser mass spectra (LMS) obtained for diquaternary ammonium salts do not show emission of doubly charged molecular ions. Instead, characteristic ions are formed by dehydrogenation (M-H)/sup +/ or dealkylation (M-CH/sub 3/)/sup +/ from the dication. In the case where coulombic repulsion between the two positive charges in the molecule is large, the charge separation process, M/sup 2 +/ ..-->.. M/sub 1//sup +/ + M/sub 2//sup +/, is favored over dehydrogenation and dealkylation. Emission of cluster ions occurs during laser irradiation of substituted pyridines even at threshold laser power density. The clusters generated include dimers and trimers, and appear in both positive ion and negative ion laser mass spectra.

Dang, T.A.

1983-01-01

165

The influence of long range order on fatigue crack initiation in an FeCo-V intermetallic compound  

SciTech Connect

A detailed analysis of both surface and subsurface damage accumulation in polycrystalline FeCo-2 vol pct is presented, and the observations are compared to those made on another ordered intermetallic, Ni3Al. Warm worked rods of FeCo-2-percent V were obtained from a commercial source. The alloy was annealed at 1000 C, and water quenched to produce the disordered condition. Ordering was accomplished by slow cooling to 25 C. The critical temperature for long-range order is 720 C. Cycling under strain control in air resulted in improved fatigue lives when samples were tested in the ordered condition. Cycling in a vacuum produced a small improvement in fatigue lives in both the ordered and disordered conditions. A distinct difference in cyclic hardening was noted between ordered and disordered FeCo-V. Hardening was more rapid in the ordered condition. TEM revealed that disordered material contained only unit dislocations, while ordered specimens contained superlattice dislocations. 9 refs.

Stoloff, N.S.; Choe, S.J.; Rajan, K. (Rensselaer Polytechnic Institute, Troy, NY (United States))

1992-01-01

166

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

167

Massive spalling of Cu-Zn and Cu-Al intermetallic compounds at the interface between solders and Cu substrate during liquid state reaction  

NASA Astrophysics Data System (ADS)

The interfacial intermetallic compound (IMC) formation between Cu substrate and Sn-3.8Ag-0.7Cu-X (wt.%) solder alloys has been studied, where X consists of 0-5% Zn or 0-2% Al. The study has focused on the effect of solder volume as well as the Zn or Al concentration. With low solder volume, when the Zn and Al concentrations in the solder are also low, the initial Cu-Zn and Al-Cu IMC layers, which form at the solder/substrate interface, are not stable and spall off, displaced by a Cu6Sn5 IMC layer. As the total Zn or Al content in the system increases by increasing solder volume, stable CuZn or Al2Cu IMCs form on the substrate and are not displaced. Increasing concentration of Zn has a similar effect of stabilizing the Cu-Zn IMC layer and also of forming a stable Cu5Zn8 layer, but increasing Al concentration alone does not prevent spalling of Al2Cu. These results are explained using a combination of thermodynamic- and kinetics-based arguments.

Kotadia, H. R.; Panneerselvam, A.; Mokhtari, O.; Green, M. A.; Mannan, S. H.

2012-04-01

168

The effect of intermetallic compound evolution on the fracture behavior of Au stud bumps joined with Sn-3.5Ag solder  

NASA Astrophysics Data System (ADS)

The microstructure and joint properties of Au stud bumps joined with Sn-3.5Ag solder were investigated as functions of flip chip bonding temperature and aging time. Au stud bumps were bonded on solder-onpad (SOP) at bonding temperature of 260°C and 300°C for 10 s, respectively. Aging treatment was carried out at 150°C for 100 h, 300 h, and 500 h, respectively. After flip chip bonding, intermetallic compounds (IMCs) of AuSn, AuSn2, and AuSn4 were formed at the interface between the Au stud bump and Sn-3.5Ag solder. At a bonding temperature of 300°C, AuSn2 IMC clusters, which were surrounded by AuSn4 IMCs, were observed in the Sn-3.5Ag solder bump. After flip chip bonding, bonding strength was approximately 220.5mN/bump. As aging time increased, the bonding strength decreased. After 100 h of aging treatment, the bonding strength of the joint bonded at 300°C was lower than that bonded at 260°C due to the fast growth rate of the AuSn2 IMCs. The main failure modes were interface fractures between the AuSn2 IMCs and AuSn4 IMCs, fractures through the AuSn2 IMCs and pad lift. Initial joint microstructures after flip chip bonding strongly affected the bonding strengths of aged samples.

Lee, Young-Kyu; Ko, Yong-Ho; Kim, Jun-Ki; Lee, Chang-Woo; Yoo, Sehoon

2013-01-01

169

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

170

Growth Behavior of Intermetallic Compounds in Cu/Sn3.0Ag0.5Cu Solder Joints with Different Rates of Cooling  

NASA Astrophysics Data System (ADS)

The growth behavior of intermetallic compounds (IMC) in Cu/Sn3.0Ag0.5Cu solder joints, including the interfacial Cu6Sn5 layer and Ag3Sn, and Cu6Sn5 in the solder, were investigated when different cooling methods—quenched water, cooling in air, and cooling in a furnace after reflow—were used. For the solder joint quenched in water, no obvious Cu6Sn5 or Ag3Sn was detected in the solder, and the thickness of interfacial Cu6Sn5 layer was slightly thinner than that of the joint cooled in air. On the basis of results from scanning electron microscopy and energy-dispersive spectrometry, a mechanism is proposed for growth of IMC in Sn3.0Ag0.5Cu solder during solidification. The rate of cooling has a substantial effect on the morphology and size of Ag3Sn, which evolved into large plate-like shapes when the joint was cooled slowly in a furnace. However, the morphology of Ag3Sn was branch-like or particle-like when the joint was cooled in air. This is attributed to re-growth of Ag3Sn grains via substantial atomic diffusion during the high-temperature stage of furnace cooling.

Yang, Linmei; Zhang, Z. F.

2015-01-01

171

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

E-print Network

BY IRRADIATION Arthur T.Motta1 , Lawrence M. Howe2 and Paul R. Okamoto3 1.Dept. of Nuclear Engineering keV electron irradiation until amorphous to study the change in the dose (amorphization) of intenietallic compounds under irradiation has elicited great interest ever since it was first

Motta, Arthur T.

172

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

173

Relationship between XMCD and molecular field in rare-earth (R) transition-metal (T) intermetallic compounds  

NASA Astrophysics Data System (ADS)

This work reports an x-ray magnetic circular dichroism (XMCD) study performed at the rare-earth L2,3 edges in several rare-earth transition-metal RT2 compounds (T = Fe, Co and Al). The transition metal contributes to the XMCD of the rare earth recorded at the L2 edge while no influence is detected at the L3 edge. This contribution shows the same spectral shape for both light and heavy rare earths and its amplitude reflects the sign and the magnitude of the magnetic moment of the transition metal. The results here presented point out that this contribution is associated with the molecular field due to the transition metal acting at the rare-earth sites.

Chaboy, J.; Laguna-Marco, M. A.; Piquer, C.; Maruyama, H.; Kawamura, N.

2007-10-01

174

Behavior of carboxylic acids upon complexation with beryllium compounds.  

PubMed

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

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

2014-07-31

175

Low-Temperature Synthesis Routes to Intermetallic Superconductors  

SciTech Connect

Over the past few years, our group has gained expertise at developing low-temperature solution-based synthetic pathways to complex nanoscale solids, with particular emphasis on nanocrystalline intermetallic compounds. Our synthetic capabilities are providing tools to reproducibly generate intermetallic nanostructures with simultaneous control over crystal structure, composition, and morphology. This DOE-funded project aims to expand these capabilities to intermetallic superconductors. This could represent an important addition to the tools that are available for the synthesis and processing of intermetallic superconductors, which traditionally utilize high-temperature, high-pressure, thin film, or gas-phase vacuum deposition methods. Our current knowledge of intermetallic superconductors suggests that significant enhancements could result from the inherent benefits of low-temperature solution synthesis, e.g. metastable phase formation, control over nanoscale morphology to facilitate size-dependent property studies, robust and inexpensive processability, low-temperature annealing and consolidation, and impurity incorporation (for doping, stoichiometry control, flux pinning, and improving the critical fields). Our focus is on understanding the superconducting properties as a function of synthetic route, crystal structure, crystallite size, and morphology, and developing the synthetic tools necessary to accomplish this. This research program can currently be divided into two classes of superconducting materials: intermetallics (transition metal/post transition metal) and metal carbides/borides. Both involve the development and exploitation of low-temperature synthesis routes followed by detailed characterization of structures and properties, with the goal of understanding how the synthetic pathways influence key superconducting properties of selected target materials. Because of the low-temperature methods used to synthesize them and the nanocrystalline morphologies of many of the products, the superconductors and their nanocrystalline precursors are potentially amenable to inexpensive and large-scale solution-based processing into wires, coatings, films, and templated or patterned structures with nanoscale and microscale features. Also, because of the new synthetic variables that play a key role in the low-temperature formation of intermetallics, the possibility exists to discover new superconductors.

Schaak, Raymond E

2008-01-08

176

Contrasts in Structural and Bonding Representations among Polar Intermetallic Compounds. Strongly Differentiated Hamilton Populations for Three Related Condensed Cluster Halides of the Rare-Earth Elements  

SciTech Connect

The crystal and electronic structures of three related R{sub 3}TnX{sub 3} phases (R = rare-earth metal, Tn = transition metal, X = Cl, I) containing extended mixed-metal chains are compared and contrasted: (1) Pr{sub 3}RuI{sub 3} (P2{sub 1}/m), (2) Gd{sub 3}MnI{sub 3} (P2{sub 1}/m), and (3) Pr{sub 3}RuCl{sub 3} (Pnma). The structures all feature double chains built of pairs of condensed R{sub 6}(Tn) octahedral chains encased by halogen atoms. Pr{sub 3}RuI{sub 3} (1) lacks significant Ru-Ru bonding, evidently because of packing restrictions imposed by the large closed-shell size of iodine. However, the vertex Pr2 atoms on the chain exhibit a marked electronic differentiation. These are strongly bound to the central Ru (and to four I), but very little to four neighboring Pr in the cluster according to bond populations, in contrast to Pr2-Pr 'bond' distances that are very comparable to those elsewhere. In Gd{sub 3}MnI{sub 3} (2), the smaller metal atoms allow substantial distortions and Mn-Mn bonding. Pr{sub 3}RuCl{sub 3} (3), in contrast to the iodide (1), can be described in terms of a more tightly bound superstructure of (2) in which both substantial Ru-Ru bonding and an increased number of Pr-Cl contacts in very similar mixed-metal chains are favored by the smaller closed-shell contacts of chlorine. Local Spin Density Approximation (LSDA) Linearized Muffin-Tin Orbital (LMTO)-ASA calculations and Crystal Orbital Hamilton Population (COHP) analyses show that the customary structural descriptions in terms of condensed, Tn-stuffed, R-R bonded polyhedral frameworks are poor representations of the bonding in all. Hamilton bond populations (-ICOHP) for the polar mixed-metal R-Tn and the somewhat smaller R-X interactions account for 75-90% of the total populations in each of these phases, together with smaller contributions and variations for R-R and Tn-Tn interactions. The strength of such R-Tn contributions in polar intermetallics was first established or anticipated by Brewer. The rare-earth-metal atoms are significantly oxidized in these compounds.

Gupta, Shalabh; Meyer, Gerd; Corbett, John D.

2010-10-01

177

Contrasts in structural and bonding representations among polar intermetallic compounds. Strongly differentiated Hamilton populations for three related condensed cluster halides of the rare-earth elements.  

PubMed

The crystal and electronic structures of three related R(3)TnX(3) phases (R = rare-earth metal, Tn = transition metal, X = Cl, I) containing extended mixed-metal chains are compared and contrasted: (1) Pr(3)RuI(3) (P2(1)/m), (2) Gd(3)MnI(3) (P2(1)/m), and (3) Pr(3)RuCl(3) (Pnma). The structures all feature double chains built of pairs of condensed R(6)(Tn) octahedral chains encased by halogen atoms. Pr(3)RuI(3) (1) lacks significant Ru-Ru bonding, evidently because of packing restrictions imposed by the large closed-shell size of iodine. However, the vertex Pr2 atoms on the chain exhibit a marked electronic differentiation. These are strongly bound to the central Ru (and to four I), but very little to four neighboring Pr in the cluster according to bond populations, in contrast to Pr2-Pr "bond" distances that are very comparable to those elsewhere. In Gd(3)MnI(3) (2), the smaller metal atoms allow substantial distortions and Mn-Mn bonding. Pr(3)RuCl(3) (3), in contrast to the iodide (1), can be described in terms of a more tightly bound superstructure of (2) in which both substantial Ru-Ru bonding and an increased number of Pr-Cl contacts in very similar mixed-metal chains are favored by the smaller closed-shell contacts of chlorine. Local Spin Density Approximation (LSDA) Linearized Muffin-Tin Orbital (LMTO)-ASA calculations and Crystal Orbital Hamilton Population (COHP) analyses show that the customary structural descriptions in terms of condensed, Tn-stuffed, R-R bonded polyhedral frameworks are poor representations of the bonding in all. Hamilton bond populations (-ICOHP) for the polar mixed-metal R-Tn and the somewhat smaller R-X interactions account for 75-90% of the total populations in each of these phases, together with smaller contributions and variations for R-R and Tn-Tn interactions. The strength of such R-Tn contributions in polar intermetallics was first established or anticipated by Brewer. The rare-earth-metal atoms are significantly oxidized in these compounds. PMID:20886870

Gupta, Shalabh; Meyer, Gerd; Corbett, John D

2010-11-01

178

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

179

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

180

Challenges in intermetallics: synthesis, structural characterization, and transitions.  

PubMed

Intermetallics that contain rare-earth elements are particularly interesting because of their temperature- and pressure-dependent structural and physical transitions that make them potential candidates for magnetic applications. This article highlights synthetic routes and structural characterization advancements used to investigate intermetallic materials. Experimental and theoretical examples of three intermetallic structure types--ThCr(2)Si(2), Heusler and Laves--are discussed to present a historical review and to illustrate the grand challenges in unravelling structure-property relationships of intermetallic compounds. PMID:22986914

Macaluso, Robin T; Greve, Benjamin K

2012-12-21

181

Removal of cyanides by complexation with ferrous compounds  

SciTech Connect

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

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

1995-12-31

182

Complex Dynamics of Compound Vesicles in Linear Flow  

NASA Astrophysics Data System (ADS)

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

Levant, Michael; Steinberg, Victor

2014-04-01

183

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

184

Magnetic anisotropy and molecular assembling in d complex cation–f complex anion type coordination compounds  

Microsoft Academic Search

The system [Fe(bpca)2][Er(NO3)4(H2O)2] (1) (Hbpca=bis(2-pyridil-carbonyl) amine) is a complex cation–complex anion type coordination compound consisting of distinct d and f units, interlinked by hydrogen bonds. Particularly, the association of f-type complex anions in dimers is remarked and discussed. The energy decomposition analyses based on DFT calculations offered supplementary insight into the coordination effects at the lanthanide ions and the hydrogen

Marilena Ferbinteanu; Fanica Cimpoesu; Takashi Kajiwara; Masahiro Yamashita

2009-01-01

185

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

186

Waste-Heat-Driven Cooling Using Complex Compound Sorbents  

NASA Technical Reports Server (NTRS)

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

Rocketfeller, Uwe; Kirol, Lance; Khalili, Kaveh

2004-01-01

187

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

PubMed Central

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

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

2013-01-01

188

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

189

Rare-earth orbital contribution to the Fe K-edge x-ray magnetic circular dichroism in rare-earth transition-metal intermetallic compounds  

NASA Astrophysics Data System (ADS)

We present a systematic x-ray magnetic circular dichroism (XMCD) study performed at the Fe K-edge of the RFe11Ti intermetallic materials (R, rare earth). We have investigated the contribution of the rare-earth sublattice to the dichroism of the transition metal. The existence of a magnetic contribution of the rare earth has been identified and isolated from the whole spectrum. This contribution is found to be related to the rare-earth moment even when one is looking at the Fe K-edge absorption. The contribution of the rare earths to the total XMCD signal has been extracted for both pure and hydride derivatives, showing the decrease of the rare-earth magnetic moment upon hydrogen absorption.

Chaboy, J.; Laguna-Marco, M. A.; Sánchez, M. C.; Maruyama, H.; Kawamura, N.; Suzuki, M.

2004-04-01

190

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

PubMed

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

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

2010-08-01

191

Thermal stability of new zinc acetate-based complex compounds  

Microsoft Academic Search

New zinc acetate based complex compounds (of general formula Zn(CH3COO)2·1?2L·nH2O) containing one or two molecules of urea, thiourea, coffeine and phenazone were prepared namely: Zn(CH3COO)2·2.5H2O, Zn(CH3COO)2·2u·0.5H2O, Zn(CH3COO)2·tu·0.5H2O, Zn(CH3COO)2·2tu, Zn(CH3COO)2·cof·2.5H2O, Zn(CH3COO)2·2cof·3.5H2O, Zn(CH3COO)2·2phen·1.5H2O.\\u000a \\u000a The compounds were characterized by IR spectroscopy, chemical analysis and thermal analysis. Thermal analysis showed that\\u000a no changes in crystallographic modifications of the compounds take place during (heating in

K. Gydryovft; V. Balek

1993-01-01

192

Exposure profiling of reactive compounds in complex mixtures.  

PubMed

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

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

2013-11-16

193

Nanocrystalline intermetallics and alloys  

Microsoft Academic Search

Nanocrystalline intermetallics and alloys are novel materials with high surface areas which are potential low-cost and high-performance\\u000a catalysts. Here, we report a general approach to the synthesis of a large variety of nanocrystalline intermetallics and alloys\\u000a with controllable composition, size, and morphology: these include Au-, Pd-, Pt-, Ir-, Ru-, and Rh-based bi- or tri-metallic\\u000a nanocrystals. We find that only those

Dingsheng Wang; Qing Peng; Yadong Li

2010-01-01

194

Short-range order of undercooled melts of PdZr2 intermetallic compound studied by X-ray and neutron scattering experiments  

NASA Astrophysics Data System (ADS)

The short-range order in undercooled melts of the intermetallic Zr2Pd glass-forming alloy is investigated by combining electrostatic levitation (ESL) with high-energy X-ray diffraction and neutron diffraction. Experimentally determined structure factors are measured and analyzed with respect to various structures of short-range order. The comparative X-ray and neutron scattering experiments allow for investigations of topological and chemical short-range order. Based on these studies, no preference of a specific short-range order is found for the liquid Zr2Pd glass-forming alloy, even in the metastable state of the deeply undercooled melt. This is in agreement with an earlier report from X-ray diffraction and molecular-dynamics studies of a Zr75.5Pd24.5 liquid, which showed a broad distribution of cluster types. The results for the Zr2Pd liquid are discussed with respect to the glass-forming ability of this melt.

Klein, S.; Holland-Moritz, D.; Herlach, D. M.; Mauro, N. A.; Kelton, K. F.

2013-05-01

195

Electronic and magnetic properties of the rare earth intermetallic compounds RRu 4Sn 6 (R=Nd, Sm, Gd, Tb, Dy and Ho)  

NASA Astrophysics Data System (ADS)

A number of compounds of structural formula RRu 4Sn 6 (R=rare-earth element) have previously been reported to form in the tetragonal crystal structure with space group I4¯2m. In this structure the R atoms are well isolated from each other. We embarked on this study to investigate the physical properties and to compare with earlier results obtained on the strongly correlated, low charge-carrier density compound CeRu 4Sn 6. Here we report our results of crystallographic, electrical resistivity, and magnetic studies on this family of compounds. In contrast to the behaviour in CeRu 4Sn 6, magnetic ordering is evident at low temperatures in the compounds with R=Sm, Gd, and Dy, as is evidenced by well-resolved anomalies in the temperature dependence of the electrical resistivity and static magnetic susceptibility.

Koch, N. E.; Strydom, A. M.

196

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

197

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

198

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

199

Study of Crystal-field Effects in Rare-earth (RE) - Transition-metal Intermetallic Compounds and in RE-based Laser Crystals  

NASA Astrophysics Data System (ADS)

Rare-earth (RE) based compounds and alloys are of great interest both for their fundamental physical properties and for applications. In order to tailor the required compounds for a specific task, one must be able to predict the energy level structure and transition intensities for any magnetic ion in any crystalline environment. The crystal-field (CF) analysis is one of the most powerful theoretical methods to deal with the physics of magnetic ions. In the present work, this technique is used to analyze peculiar physical properties of some materials employed in the production of new-generation solid-state laser and high-performance permanent magnets.

Magnani, Nicola

2003-09-01

200

SrAu 0.5Pt 0.5 and CaAu 0.5Pt 0.5, analogues to the respective Ba compound, but featuring purely intermetallic behaviour  

NASA Astrophysics Data System (ADS)

Both, SrAu 0.5Pt 0.5 and CaAu 0.5Pt 0.5, have been synthesized by reaction of corresponding mixtures of the pure elements at 1223 K in an argon atmosphere, and characterized by single-crystal X-ray analysis as well as by magnetic susceptibility and electric resistivity measurements. The new compounds crystallize in the CrB type of structure and thus are isostructural to BaAu 0.5Pt 0.5 (SrAu 0.5Pt 0.5: Cmcm; a = 4.262(1) Å; b = 11.435(3) Å; c = 4.632(1) Å; Z = 4; CaAu 0.5Pt 0.5: Cmcm; a = 3.9858(4) Å; b = 10.920(1) Å; c = 4.5249(5) Å; Z = 4). SrAu 0.5Pt 0.5 as well as CaAu 0.5Pt 0.5 are poor metallic conductors with ?300K = 0.95 m?.cm and ? 300K = 3.93 m?.cm, respectively, and featuring diamagnetic behaviour. According to ESCA measurements SrAu 0.5Pt 0.5 and CaAu 0.5Pt 0.5 both can be formulated as having intermetallic character, showing a negligible electron transfer from alkaline earth metals to the noble metals.

Saltykov, Vyacheslav; Nuss, Jürgen; Konuma, Mitsuharu; Jansen, Martin

2010-09-01

201

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

NSDL National Science Digital Library

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

Cruz Quiñones, Miguel

2005-08-17

202

The magnetic spin-reorientation transitions in the RGa (R=rare earth) intermetallic compounds studied by measurements of the hyperfine interactions of the 119Sn probe atoms  

NASA Astrophysics Data System (ADS)

The magnetic and electric hyperfine interactions of the probe nucleus 119Sn on the Ga site of the ferromagnetic rare-earth (R) gallium compounds RGa (R=Pr-Er) have been investigated by Mössbauer spectroscopy technique. For all of the compounds, the directions of the magnetic moments of the R 3+ ions have been determined as a function of temperature in the range from 5 K to TC. For NdGa, SmGa, HoGa, and ErGa compounds, the magnetic reorientation transitions due to the competition between the exchange interaction and the interaction with crystal field have been investigated. At high temperatures, when the electric interaction dominates, the orientation of the magnetic moments is unambiguously determined by the sign of the quadrupole moment of 4f shell of the R 3+ ion. With decreasing temperature, the magnetic moments rotate gradually from the bc-plane toward the crystallographic a-axis. In the temperature range 5 K? T<100 K, the ferromagnetic structure of the GdGa compound is noncollinear. At 5 K the magnetic moments of the Gd 3+ ions point in two distinct directions with respect to the crystallographic a-axis ( ?1?30° and ?2?60°).

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

2007-01-01

203

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

204

Effect of hydrogenation on the magnetic properties of the intermetallic compound Er2Fe14B with single-crystal and nanocrystalline structures  

NASA Astrophysics Data System (ADS)

Hydrogenated single crystals Er2Fe14Bh x with different hydrogen contents are grown and their magnetic properties are studied for the first time. It is established that both the Curie temperature and the temperature of the spin-reorientation phase transition increase with an increase in the hydrogen content. In the Er2Fe14B single crystal, the contributions of the rare-earth metal and iron sublattices to the magnetic anisotropy decrease upon hydrogenation. However, their compensation occurs at a temperature higher than that in the initial compound Er2Fe14B due to the enhancement of the Fe-Fe and R-Fe exchange interactions. The effect of hydrogenation on the magnetic characteristics of the Er2Fe14B compound with a nanocrystalline structure is investigated. It is revealed that the hydrogenation leads to an increase in the coercive force and the residual magnetization of these alloys.

Tereshina, E. A.; Tereshina, I. S.; Nikitin, S. A.; Burkhanov, G. S.; Chistyakov, O. D.; Telegina, I. V.; Belousova, V. A.; Palewski, T.; Drulis, H.

2008-01-01

205

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

206

The effect of Co doping on the magnetic, hyperfine and transport properties of the metamagnetic LaFe11.44Al1.56 intermetallic compound  

NASA Astrophysics Data System (ADS)

The influence of Co doping on the hyperfine, structural, magnetic and transport properties of La(Fe1-xCox)11.44Al1.56 (x = 0, 0.04, 0.08 and 0.12) compounds was investigated by Mössbauer spectroscopy, x-ray diffraction, magnetization and electric resistivity measurements. Stabilization of the NaZn13 structure by Al atoms was also investigated in Co undoped samples and a relatively large amount of ? -Fe segregated phase was observed for Al content lower than 0.10, which indicate a solubility limit for Al substitution. The Mössbauer spectra indicate that Fe atoms see a chemically disordered environment, which is related to the presence of substitutional Al and/or Co atoms. The electric field gradient value at the Fe sites of the compounds is not affected by the Al substitution, with a quadrupole splitting value of 0.44 mm s-1. The compound magnetic ordering temperature varies from 195 to 360 K and can be set according to the Co content. An enhancement of the Fe effective magnetic moment with increasing Co doping has also been observed. The applied magnetic field induces antiferromagnetic (AFM) to ferromagnetic (FM) phase transition, with a field value depending on the Co concentration, and is about 5 T for x = 0 and about 0.5 T for x = 0.04. A second magnetic phase transition occurs on cooling to low temperatures from an AFM to a spin-glass-like (SGL) state for x = 0. A possibly reentrant SGL state may occur from the FM state for x = 0.04. For x > 0.04, the compounds behave as FM for measuring field of 0.04 T.

Proveti, J. R.; Passamani, E. C.; Larica, C.; Gomes, A. M.; Takeuchi, A. Y.; Massioli, A.

2005-05-01

207

Intermetallic compounds with near Zintl phase behavior: RE2Zn3Ge6 (RE = La, Ce, Pr, Nd) grown from liquid indium.  

PubMed

A series of compounds has been discovered while investigating reactions of rare earth, transition metals, and Ge in excess indium. These compounds, RE2Zn3Ge6 (RE = La, Ce, Pr, Nd), are isostructural, crystallizing in the orthorhombic space group Cmcm with lattice parameters a = 5.9691(9) angstroms, b = 24.987(4) angstroms, and c = 5.9575(9) angstroms for La2Zn3Ge6, a = 5.9503(5) angstroms, b = 24.761(2) angstroms, and c = 5.9477(5) angstroms for the Ce analogue, a =5.938(2) angstroms, b = 24.708(8) angstroms, and c = 5.936(2) angstroms for Pr2Zn3Ge6, and a = 5.9094(7) angstroms, b = 24.619(3) angstroms, and c = 5.9063(5) angstroms for the Nd analogue. The structure is composed of PbO-like ZnGe layers and ZnGe4 cage layers and is related to the Ce4Zn8Ge(11-x) structure type. The bonding in the system can be rationalized using the Zintl concept resulting in a material that is expected to be a valence precise semiconductor, although its behavior is more consistent with it being a semimetal, making it an intermediate case. The results of band structure calculations and magnetic measurements of these compounds are discussed. PMID:16296820

Salvador, James R; Bilc, Daniel; Gour, Jeffrey R; Mahanti, Subhendra D; Kanatzidis, Mercouri G

2005-11-28

208

Analysis of three structurally related antiviral compounds in complex with human rhinovirus 16  

E-print Network

Analysis of three structurally related antiviral compounds in complex with human rhinovirus 16 Contributed by Michael G. Rossmann, November 1, 1999 Rhinoviruses are a frequent cause of the common cold of such compounds, complexed with rhinovirus serotypes 14, 16, 1A, and 3, previously have been examined. Three

Rossmann, Michael G.

209

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

E-print Network

Crystalline electric fields and the magnetic ground state of the novel Heusler intermetallic YbRh2 intermetallic compound with a distorted Heusler structure, YbRh2Pb. We present a study of the magnetic, thermal effects as well as phenomena related to the magnetic ordering. The Heusler compounds are an especially

Aronson, Meigan

210

Equiatomic intermetallic compounds YTX (T = Ni, Ir; X = Si, Ge, Sn, Pb): a systematic study by ??Y solid state NMR and ¹¹?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

211

Low-temperature large reversible magnetocaloric effects of ErNi1-xCuxAl (x = 0.2, 0.5, 0.8) intermetallic compounds  

NASA Astrophysics Data System (ADS)

The magnetic properties and magnetocaloric effects of the ErNi1-xCuxAl (x = 0.2, 0.5, 0.8) compounds have been studied. The sample with x = 0.2 is found to be antiferromagnetic below the Néel temperature of TN = 4.6 K, while the sample x = 0.5 is simply ferromagnetic with a Curie temperature of TC = 5.8 K. In contrast, the sample x = 0.8 exhibits a short-range magnetic order, as revealed by AC magnetic measurements, and the transition temperature is 5.5 K. Large magnetic entropy change (?S) without hysteresis losses has been observed around the transition temperature for all the samples. The ?S displays a peak between 4 K and 10 K, and the maximal values of ?S are -22.6, -25.9, and -24.8 J/kg K for the field changes of 0-5 T, corresponding to the compositions of x = 0.2, x = 0.5, and x = 0.8, respectively. The large ?S value as well as no hysteresis loss indicate that ErNi1-xCuxAl can be alternative candidates for magnetic refrigerant working at low temperature (<10 K).

Wang, L. C.; Dong, Q. Y.; Lu, J.; Shao, X. P.; Mo, Z. J.; Xu, Z. Y.; Sun, J. R.; Hu, F. X.; Shen, B. G.

2013-12-01

212

Magnetic and magnetocaloric properties of the new rare-earth-transition-metal intermetallic compound Gd3Co29Ge4B10  

NASA Astrophysics Data System (ADS)

The compounds Gd3-xYxCo29Ge4B10 (x = 0, 0.5, 1.0, 1.5, and 3.0), Gd3Co29Al4B10, and Gd3Co29Al4B10 were synthesized by arc melting, and their magnetic properties investigated as a function of temperature and applied magnetic field. X-ray measurements showed primarily single-phase samples with the tetragonal crystal structure P4/nmm. It was found that Gd3Co29Ge4B10 orders ferromagnetically at TC = 212 K and shows a compensation point at 128 K, indicating a ferrimagnetic ordering of the Co and Gd moments. An entropy change of -?S = 0.5 J/kgK was observed in a 5-T field at TC for this sample, while a change in sign for this quantity was observed both at the maximum value of magnetization (around 200 K) and then again at the compensation point. Substitution of Y for Gd in Gd3Co29Ge4B10 does not affect the Curie temperature, but shifts the compensation point to lower temperatures. This indicates that a decrease in Gd concentration does not affect the d-d exchange interaction, but has a pronounced effect on the f-d exchange interaction.

Hill, P.; Dubenko, Igor; Samanta, Tapas; Quetz, Abdiel; Ali, Naushad

2012-04-01

213

The influence of spontaneous and field induced spin reorientation transitions on the magnetocaloric properties in rare earth intermetallic compounds: Application to TbZn  

NASA Astrophysics Data System (ADS)

We report a theoretical investigation on the magnetocaloric properties of the cubic CsCl-type TbZn compound. Two successive peaks in the magnetocaloric quantities are observed and attributed to different types of phase transitions. For the magnetic field applied in the ?110? direction, the first peak is ascribed to a spontaneous first-order spin reorientation transition (SRT) at T1=63 K, and the second one to the ferroparamagnetic phase transition. The application of an external magnetic field of 2 T along this direction leads to a tablelike behavior in the magnetocaloric quantities (?ST and ?TS) as a consequence of two successive second-order SRTs at TSR1=71 K and at TSR2=160 K. Applying a magnetic field of 5 T suppress the flat behavior but a high refrigeration capacity of 352 J/kg is predicted in a wide temperature range from 62 to 258 K. When the magnetic field is applied along the ?100? direction an inverse magnetocaloric effect is observed in the temperature range below T1. The system was studied throughout a Hamiltonian that takes into account the Zeeman, exchange, and crystal field interactions.

de Sousa, V. S. R.; Plaza, E. J. R.; von Ranke, P. J.

2010-05-01

214

Complex flow mechanisms in compound meandering channels with overbank flow  

Microsoft Academic Search

Turbulence and secondary flow measurements were undertaken using a two-component laser-Doppler anemometer in meander channels with straight flood plain banks. The most interesting feature of the compound meandering channel flow was found to be the behaviour of the secondary flow. The difference in direction of rotation of the flow before and after inundation at a bend section was confirmed by

K. Shiono; Y. Muto

1998-01-01

215

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

216

Pentamethylcyclopentadienyl and cyclopentadienyl tantalum and niobium calixarene compounds and their water and acetonitrile inclusion complexes  

SciTech Connect

Several niobium and tantalum pentamethylcyclopentadienyl or cyclopentadienyl calixarene complexes were prepared and structurally characterized. The cavity in these compounds is of an appropriate geometry to receive small molecules such as water or acetonitrile. X-ray diffraction and Fenske-Hall calculations were used in the consideration of the structure of these compounds.

Acho, J.A.; Doerrer, L.H.; Lippard, S.J. [Massachusetts Institute of Technology, Cambridge, MA (United States)

1995-05-10

217

Intermetallic generators of alkali metal with a seal  

Microsoft Academic Search

A design of an alkali metal generator with a working substance in the form of intermetallic compound AnMem the surface of which is covered by a protective layer Me (A — alkali metal, Me — an element, the vapour pressure of which under the deposition temperatures is ?- 108 and more times lower than the vapour pressure of the component

KA Chuntonov; VV Mansurov

1996-01-01

218

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

SciTech Connect

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

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

2010-01-27

219

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

220

Complex magnetic behavior in the novel Kondo lattice compound CeRhSn3  

NASA Astrophysics Data System (ADS)

We report the magnetic and transport properties of a new ternary intermetallic compound, CeRhSn3, using magnetic susceptibility, magnetization, specific heat, electrical resistivity, muon-spin relaxation (?SR) and neutron diffraction investigations. The dc magnetic susceptibility data reveal two magnetic phase transitions at 0.9 and 4 K. The overall behavior of dc susceptibility and magnetization indicates a ferrimagnetic-type phase transition near 4 K. The specific heat data also exhibit sharp ?-type anomalies at 1 and 4 K. The behavior of the specific heat anomaly under the application of a magnetic field suggests that the 1 K transition is probably related to a transition from a ferri- to a ferromagnetic state. The low temperature specific heat exhibits an enhanced Sommerfeld coefficient ? (~100 mJ mol - 1 K - 2) due to the formation of a moderate heavy fermion state. The resistivity of CeRhSn3 demonstrates an interplay between the RKKY and Kondo interactions which is further modified by the presence of the crystal electric field. Interestingly, the resistivity of the nonmagnetic reference compound, LaRhSn3, is found to increase with decreasing temperature. Further, the onset of long-range magnetic order below 1 K is confirmed from our ?SR study on CeRhSn3. However, the 4 K transition is not detected in the ?SR and low temperature neutron diffraction data. Analysis of the dc magnetic susceptibility data within the framework of a two-sublattice model of ferrimagnetism supports the ferrimagnetic-type transition at 4 K in CeRhSn3. We have observed an unusual frequency dependence of the peak near 4 K in the ac susceptibility, which shows that the transition temperature shifts toward the lower temperature side with increasing frequency.

Anand, V. K.; Adroja, D. T.; Hillier, A. D.; Kockelmann, W.; Fraile, A.; Strydom, A. M.

2011-07-01

221

Complex magnetic behavior in the novel Kondo lattice compound CeRhSn?.  

PubMed

We report the magnetic and transport properties of a new ternary intermetallic compound, CeRhSn?, using magnetic susceptibility, magnetization, specific heat, electrical resistivity, muon-spin relaxation (?SR) and neutron diffraction investigations. The dc magnetic susceptibility data reveal two magnetic phase transitions at 0.9 and 4 K. The overall behavior of dc susceptibility and magnetization indicates a ferrimagnetic-type phase transition near 4 K. The specific heat data also exhibit sharp ?-type anomalies at 1 and 4 K. The behavior of the specific heat anomaly under the application of a magnetic field suggests that the 1 K transition is probably related to a transition from a ferri- to a ferromagnetic state. The low temperature specific heat exhibits an enhanced Sommerfeld coefficient ? (~100 mJ mol?¹ K?²) due to the formation of a moderate heavy fermion state. The resistivity of CeRhSn? demonstrates an interplay between the RKKY and Kondo interactions which is further modified by the presence of the crystal electric field. Interestingly, the resistivity of the nonmagnetic reference compound, LaRhSn?, is found to increase with decreasing temperature. Further, the onset of long-range magnetic order below 1 K is confirmed from our ?SR study on CeRhSn?. However, the 4 K transition is not detected in the ?SR and low temperature neutron diffraction data. Analysis of the dc magnetic susceptibility data within the framework of a two-sublattice model of ferrimagnetism supports the ferrimagnetic-type transition at 4 K in CeRhSn?. We have observed an unusual frequency dependence of the peak near 4 K in the ac susceptibility, which shows that the transition temperature shifts toward the lower temperature side with increasing frequency. PMID:21673393

Anand, V K; Adroja, D T; Hillier, A D; Kockelmann, W; Fraile, A; Strydom, A M

2011-07-13

222

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

223

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

224

Natural products as starting points for the synthesis of complex and diverse compounds.  

PubMed

Covering: up to 2013. Natural products and their derivatives are used as treatments for numerous diseases. Many of these compounds are structurally complex, possessing a high percentage of sp(3) hybridized carbons and multiple stereogenic centers. Due to the difficulties associated with the isolation of large numbers of novel natural products, lead discovery efforts over the last two decades have shifted toward the screening of less structurally complex synthetic compounds. While there have been many success stories from these campaigns, the modulation of certain biological targets (e.g. protein-protein interactions) and disease areas (e.g. antibacterials) often require complex molecules. Thus, there is considerable interest in the development of strategies to construct large collections of compounds that mimic the complexity of natural products. Several of these strategies focus on the conversion of simple starting materials to value-added products and have been reviewed elsewhere. Herein we review the use of natural products as starting points for the generation of complex compounds, discussing both early ad hoc efforts and a more recent systematization of this approach. PMID:24219884

Morrison, Karen C; Hergenrother, Paul J

2014-01-01

225

Intermetallics for structural applications  

SciTech Connect

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

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

1995-09-01

226

Electroanalytical chemistry of complex compounds of 2,2'-dipyridyl and 1,10-phenanthroline  

Microsoft Academic Search

Complex compounds of 2,2'-dipyridyl and 1,10-phenanthroline are useful in various electroanalytical methods (extraction voltammetry, direct and indirect variants of potentiometry and coulometry, amperometric and conductometric titration). Most promising at the present time is the use of the electrocatalytic properties of complexes of 2,2'-dipyridyl and 1,10-phenanthroline with transition elements. The combination of specific properties of these catalytic systems with the possibilities

G. V. Prokhorova; E. A. Osipova; P. K. Agasyan; V. I. Fadeeva

1987-01-01

227

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

228

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. PMID:21912588

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

2011-01-01

229

Two new hybrid compounds assembled from Keggin-type polyoxometalates and transition metal coordination complexes  

NASA Astrophysics Data System (ADS)

Two new hybrid compounds based on Keggin-type polyoxometalates: {[PMo 12O 40][Ni( Phen) 2(H 2O)] 2}·K·2OH - ( 1) and [Cd 2( Phen) 4Cl 2][HPW 12O 40]·H 2O ( 2) ( Phen=1,10-phenanthroline), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Compound 1 exhibits a 1-D chain structure constructed from Pseudo-Keggin polyoxometalate bi-supported transition metal coordination complexes linked by K + ions. Compound 2 contains Pseudo-Keggin polyoxoanions [HPW 12O 40] 2- and novel metal-chloride-ligand coordination complexes [Cd 2( Phen) 4Cl 2] 2+.

Wang, Yan; Zou, Bo; Xiao, Li-Na; Jin, Ning; Peng, Yu; Wu, Feng-Qing; Ding, Hong; Wang, Tie-Gang; Gao, Zhong-Min; Zheng, Da-Fang; Cui, Xiao-Bing; Xu, Ji-Qing

2011-03-01

230

Electroanalytical chemistry of complex compounds of 2,2'-dipyridyl and 1,10-phenanthroline  

SciTech Connect

Complex compounds of 2,2'-dipyridyl and 1,10-phenanthroline are useful in various electroanalytical methods (extraction voltammetry, direct and indirect variants of potentiometry and coulometry, amperometric and conductometric titration). Most promising at the present time is the use of the electrocatalytic properties of complexes of 2,2'-dipyridyl and 1,10-phenanthroline with transition elements. The combination of specific properties of these catalytic systems with the possibilities of modern polarographic instrumentation allows us to markedly reduce the detection limit and to enhance the selectivity of the techniques for determining a number of metals. Electrochemical methods are irreplaceable in the study of the oxidation-reduction properties of complexes of transition elements with 2,2'-dipyridyl and 1,10-phenanthroline; using them, important characteristic regularities have been established in the field of coordination chemistry of these compounds.

Prokhorova, G.V.; Osipova, E.A.; Agasyan, P.K.; Fadeeva, V.I.

1987-10-20

231

Electrocatalytic addition reaction of bromide compounds and activated olefins on nickel(II) tetraazamacrocyclic complex-modified graphite felt electrode  

Microsoft Academic Search

Electrocatalytic addition reaction of bromide compounds and activated olefins was studied using a nickel(II) tetraazamacrocyclic complex-modified graphite felt (GF) electrode. The modified GF electrode was observed a catalytic current in the presence of bromide compound by cyclic voltammetry. A preparative electrocatalytic addition reaction of bromide compounds and activated olefins was successfully achieved on the modified GF electrode with an adequate

Yoshitomo Kashiwagi; Chikara Kikuchi; Futoshi Kurashima; Tetsuya Ono

2007-01-01

232

Two new hybrid compounds assembled from Keggin-type polyoxometalates and transition metal coordination complexes  

SciTech Connect

Two new hybrid compounds based on Keggin-type polyoxometalates: {l_brace}[PMo{sub 12}O{sub 40}][Ni(Phen){sub 2}(H{sub 2}O)]{sub 2{r_brace}}.K.2OH{sup -} (1) and [Cd{sub 2}(Phen){sub 4}Cl{sub 2}][HPW{sub 12}O{sub 40}].H{sub 2}O (2) (Phen=1,10-phenanthroline), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Compound 1 exhibits a 1-D chain structure constructed from Pseudo-Keggin polyoxometalate bi-supported transition metal coordination complexes linked by K{sup +} ions. Compound 2 contains Pseudo-Keggin polyoxoanions [HPW{sub 12}O{sub 40}]{sup 2-} and novel metal-chloride-ligand coordination complexes [Cd{sub 2}(Phen){sub 4}Cl{sub 2}]{sup 2+}. -- Graphical abstract: Two new hybrid compounds based on different Keggin-type polyoxometalates have been hydrothermally synthesized and characterized by IR, UV-Vis, XPS, XRD, elemental analysis and single crystal X-ray diffraction analysis. Display Omitted Research highlights: {yields} Two hybrids based on Pseudo-Keggin polyanions and metal coordination complexes. {yields} 1-D structure formed by polyanion bisupported metal coordination units linked by K{sup +}. {yields} A metal-chloride-ligand coordination complex [Cd{sub 2}(Phen){sub 4}Cl{sub 2}]{sup 2+}. {yields} A hybrid based on polyanions and metal-chloride-ligand coordination complexes.

Wang Yan, E-mail: jlccwxz@163.co [College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130023 (China); Zou, Bo, E-mail: doctorz@jlu.edu.c [College of Chemistry, Jilin University, Changchun 130023 (China); Xiao Lina, E-mail: xiaolina2009@163.co [College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130023 (China); Jin Ning, E-mail: generalman948@163.co [China-Japan Union Hospital of Jilin University, Changchun (China); Peng Yu, E-mail: jlu5@163.co [College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130023 (China); Wu Fengqing, E-mail: fqwu@mail.jlu.edu.c [College of Chemistry, Jilin University, Changchun 130023 (China); Ding Hong, E-mail: dinghong@jlu.edu.c [College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130023 (China); Wang Tiegang, E-mail: Wangtg@mail.jlu.edu.c [College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130023 (China); Gao Zhongmin, E-mail: gaozm@jlu.edu.c [College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130023 (China); Zheng Dafang, E-mail: zhengdf@mail.jlu.edu.c [College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130023 (China); Cui Xiaobing, E-mail: cuixb@mail.jlu.edu.c [College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130023 (China); Xu Jiqing, E-mail: xjq@mail.jlu.edu.c [College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130023 (China)

2011-03-15

233

Interstitial and substitutional solute effects in intermetallics  

SciTech Connect

This volume addresses recent developments in the understanding of the effects of interstitial and substitutional solute atoms on the physical and mechanical properties of intermetallic compounds. Topics discussed include the theory, modeling, and experimental verification of such effects as static and dynamic strain aging, the Portevin-le Chatelier effect, solid solution hardening behavior, dislocation-solute interactions, and related topics such as the amelioration of environmental embrittlement by various solutes. Topics covered include: (1) Vacancy-solute interactions in FeAl-based alloys; (2) Static and dynamic strain aging in microalloyed NiAl-based alloys; (3) Design fundamentals for Gamma TiAl alloys; and (4) Strain rate sensitivity of Cr-stabilized cubic titanium trialuminides.

Baker, I.; Noebe, R.D.; George, E.P. (eds.)

1998-01-01

234

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

235

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

PubMed Central

Abstract Significance: Despite advances made in the treatment of cancer, a significant number of patients succumb to this disease every year. Hence, there is a great need to develop new anticancer agents. Recent Advances: Emerging data show that malignant cells have a greater requirement for iron than normal cells do and that proteins involved in iron import, export, and storage may be altered in cancer cells. Therefore, strategies to perturb these iron-dependent steps in malignant cells hold promise for the treatment of cancer. Recent studies show that gallium compounds and metal-thiosemicarbazone complexes inhibit tumor cell growth by targeting iron homeostasis, including iron-dependent ribonucleotide reductase. Chemical similarities of gallium(III) with iron(III) enable the former to mimic the latter and interpose itself in critical iron-dependent steps in cellular proliferation. Newer gallium compounds have emerged with additional mechanisms of action. In clinical trials, the first-generation-compound gallium nitrate has exhibited activity against bladder cancer and non-Hodgkin's lymphoma, while the thiosemicarbazone Triapine® has demonstrated activity against other tumors. Critical Issues: Novel gallium compounds with greater cytotoxicity and a broader spectrum of antineoplastic activity than gallium nitrate should continue to be developed. Future Directions: The antineoplastic activity and toxicity of the existing novel gallium compounds and thiosemicarbazone-metal complexes should be tested in animal tumor models and advanced to Phase I and II clinical trials. Future research should identify biologic markers that predict tumor sensitivity to gallium compounds. This will help direct gallium-based therapy to cancer patients who are most likely to benefit from it. Antioxid. Redox Signal. 00, 000–000. PMID:22900955

Antholine, William E.

2013-01-01

236

Hydrogen-bonded inclusion compounds with reversed polarity: anionic metal-complexes and cationic organic linkers.  

PubMed

Synthesized and structurally characterized is a new series of soft-host frameworks assembled by charge-assisted hydrogen bonds between an anionic metal complex (MC) and cationic organic linkers (OL), specifically [Co(en)(ox)(2)](-) and diprotonated 4,4'-bipyridinium (H(2)bpy) or 1,2-bis(4-pyridinium)ethylene (H(2)bpye). While frameworks built of cationic complexes and anionic organic linkers are already well-known, the seven new compounds described here represent the first series of frameworks with reversed polarity, that is, made of anionic complexes and cationic organic linkers. The compounds have a general formula [OL][MC](2)·n(guest), where the guest molecules 4,4'-biphenol (bp), 4-methoxyphenol (mp), 1,4-dimethoxybenzene (dmb), 1,6-dimethoxynaphtalene (dmn), and 4-nitroanisole (na). Structurally the compounds can be described as pillared-layer frameworks with layers constructed of MC anions and linked together by hydrogen-bonded cationic OL pillars. The guest molecules occupy the galleries between the pillars while their steric, electronic, and ?-? and hydrogen-bonding capabilities influence the overall structure of the soft frameworks. PMID:22085246

Prakash, M Jaya; Sevov, Slavi C

2011-12-19

237

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

PubMed

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

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

2014-09-01

238

Crystal structure of the intermetallics produced by a calcium hydride method  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

239

Structures and physical properties of R2TX3 compounds  

NASA Astrophysics Data System (ADS)

Rare-earth compounds have been an attractive subject based on the unique electronic structures of the rare-earth elements. Novel ternary intermetallic compounds R2TX3 (R = rare-earth element or U, T = transition-metal element, X = Si, Ge, Ga, In) are a significant branch of this research field due to their complex and intriguing physical properties, such as magnetic order at low temperature, spin-glass behavior, Kondo effect, heavy fermion behavior, and so on. The unique physical properties of R2TX3 compounds are related to distinctive electronic structures, crystal structures, microinteraction, and external environment. Most R2TX3 compounds crystallize in AlB2-type or derived AlB2-type structures and exhibit many similar properties. This paper gives a concise review of the structures and physical properties of these compounds. Spin glass, magnetic susceptibility, resistivity, and specific heat of R2TX3 compounds are discussed.

Pan, Zhi-Yan; Cao, Chong-De; Bai, Xiao-Jun; Song, Rui-Bo; Zheng, Jian-Bang; Duan, Li-Bing

2013-05-01

240

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

E-print Network

the measured dichroism integrated along the emitted energies, and the radius of the cerium ion in differentStudy of bulk ground state properties of cerium intermetallics by linear dichroism in 4f resonant resonant inelastic X-ray scattering in the M5 region of intermetallic compounds of cerium (CeRh2, CePd3, Ce

Marcon, Marco

241

Effect of fat nature and aroma compound hydrophobicity on flavor release from complex food emulsions.  

PubMed

Complex food emulsions containing either hydrogenated palm kernel oil (vegetable fat) or anhydrous milk fat (animal fat) were flavored by using different aroma compounds. The fats differed by their fatty acid and triacylglycerol compositions and by their melting behavior, while the aroma compounds (ethyl butanoate, ethyl hexanoate, methyl hexanoate, mesifurane, linalool, diacetyl, cis-3-hexen-1-ol, and gamma-octalactone) differed by their hydrophobicity. Application of differential scanning calorimetry to fat samples in bulk and emulsified forms indicated differences in the ratio of solid-to-liquid between temperatures ranging from 10 to 35 degrees C. Solid-phase microextraction coupled with GC-MS analysis indicated that flavor release from food emulsions containing animal or vegetable fat differed depending on both the fat nature and flavor compound hydrophobicity. The release of diacetyl was higher for emulsions containing animal fat, whereas the release of esters was higher for emulsions containing vegetable fat. The release of cis-3-hexenol, linalool, gamma-octalactone, and mesifurane (2,5-dimethyl-4-methoxy-(2H)-furan-3-one) was very similar for the two fatty systems. The above results were discussed not only in terms of aroma compound hydrophobicity, but also in terms of structural properties of the emulsions as affected by the lipid source. PMID:15453696

Relkin, Perla; Fabre, Marjorie; Guichard, Elisabeth

2004-10-01

242

The Ba 4d-4f giant dipole resonance in complex Ba/Si compounds  

NASA Astrophysics Data System (ADS)

The shape of the Ba 4d-4f giant dipole resonance is studied for Ba atoms embedded inside complex Si networks covering structures consisting of Si nanocages and nanotubes, i.e. the clathrate Ba8Si46, the complex compound BaSi6, and the semiconducting BaSi2. Here, non-resonant x-ray Raman scattering is used to investigate confinement effects on the shape of the giant resonance in the vicinity of the Ba NIV, V-edge. The distinct momentum transfer dependence of the spectra is analyzed and discussed. The measurements are compared to calculations of the giant resonance within time-dependent local density approximation in the dipole limit. No modulation of the giant resonance’s shape for Ba atoms confined in different local environments was observed, in contrast to the calculations. The absence of such shape modulation for complex Ba/Si compounds is discussed providing important implications for further studies of giant resonance phenomena utilizing both theory and experiment.

Sahle, Ch J.; Sternemann, C.; Sternemann, H.; Tse, J. S.; Gordon, R. A.; Desgreniers, S.; Maekawa, S.; Yamanaka, S.; Lehmkühler, F.; Wieland, D. C. F.; Mende, K.; Huotari, S.; Tolan, M.

2014-02-01

243

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.

2002-11-01

244

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

245

Complex N-acetyl-L-cysteine compounds with biometals as self-defense factors of biological system  

Microsoft Academic Search

We studied the effects of complex N-acetyl-L-cysteine compounds with transitional biometals on the inflammatory and adaptation\\u000a reactions. Some compounds were superior to known antihypoxants and actoprotectors and exhibited significant antiinflammatory\\u000a activity.

A. V. Evseev; V. L. Kovalyova; I. A. Krylov; E. A. Parfyonov

2006-01-01

246

compounds  

NASA Astrophysics Data System (ADS)

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

Shah, N. A.

2014-10-01

247

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

SciTech Connect

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

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

2007-07-27

248

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

249

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

250

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

PubMed Central

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

Mazurek, Monica A

2002-01-01

251

Complex-compound heat pump: Topical report on phase 1 results  

NASA Astrophysics Data System (ADS)

A gas-fired heat pump using complex compound chemisorption media and ammonia refrigerant is being developed. Complex compounds are advantageous because they adsorb large amounts of refrigerant (up to 80 percent of the adsorbent dry weight), exhibit vapor pressure independent of refrigerant concentration, can be made to adsorb very rapidly, and can be formulated to have different vapor pressures. The heat pump being developed has three stages, each using a different formulation. Multiple stages are used to increase efficiency, giving cooling COPs near one. Heating-mode operation at ambient temperatures of -20 F and below can also be achieved. The report presents results from Phase 1 of the development project. Phase 1 efforts focused on generation of engineering data to ensure that no major obstacles would be met in future development, and to provide data necessary for design of a breadboard system. Work included the following: (1) optimization of the sorbers internal heat and mass transfer hardware to maximize sorption rates and minimize cost, (2) qualification of sorbent media with respect to stability and corrosion, (3) estimation of manufacturing and operating costs, and (4) development of preliminary designs for heat pump and AC systems.

Rockenfeller, U.; Kirol, L. D.; Dooley, W. T.; Langeliers, J.; Sarkisian, P.

1992-08-01

252

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

SciTech Connect

The authors conducted tests with the water flea (Daphnia magna) to compare the bioaccumulation of compounds presented alone with the bioaccumulation of these same compounds when they were presented within a complex coal liquid, water-soluble fraction. Phenol and aniline were used as representative compounds because they are highly soluble, moderately toxic, and common to many fossil fuel liquid products and corresponding wastes. The tests were primarily designed to aid in development of predictive models relating to the transport and fate of components from complex mixtures in aquatic biota.

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

1986-07-01

253

Copper Complexation Screen Reveals Compounds with Potent Antibiotic Properties against Methicillin-Resistant Staphylococcus aureus  

PubMed Central

Macrophages take advantage of the antibacterial properties of copper ions in the killing of bacterial intruders. However, despite the importance of copper for innate immune functions, coordinated efforts to exploit copper ions for therapeutic interventions against bacterial infections are not yet in place. Here we report a novel high-throughput screening platform specifically developed for the discovery and characterization of compounds with copper-dependent antibacterial properties toward methicillin-resistant Staphylococcus aureus (MRSA). We detail how one of the identified compounds, glyoxal-bis(N4-methylthiosemicarbazone) (GTSM), exerts its potent strictly copper-dependent antibacterial properties on MRSA. Our data indicate that the activity of the GTSM-copper complex goes beyond the general antibacterial effects of accumulated copper ions and suggest that, in contrast to prevailing opinion, copper complexes can indeed exhibit species- and target-specific activities. Based on experimental evidence, we propose that copper ions impose structural changes upon binding to the otherwise inactive GTSM ligand and transfer antibacterial properties to the chelate. In turn, GTSM determines target specificity and utilizes a redox-sensitive release mechanism through which copper ions are deployed at or in close proximity to a putative target. According to our proof-of-concept screen, copper activation is not a rare event and even extends to already established drugs. Thus, copper-activated compounds could define a novel class of anti-MRSA agents that amplify copper-dependent innate immune functions of the host. To this end, we provide a blueprint for a high-throughput drug screening campaign which considers the antibacterial properties of copper ions at the host-pathogen interface. PMID:24752262

Haeili, Mehri; Moore, Casey; Davis, Christopher J. C.; Cochran, James B.; Shah, Santosh; Shrestha, Tej B.; Zhang, Yaofang; Bossmann, Stefan H.; Benjamin, William H.

2014-01-01

254

Suppressors made from intermetallic materials  

DOEpatents

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

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

2014-11-04

255

Vibrational signatures of isotopic impurities and complexes in II-VI compound semiconductors  

NASA Astrophysics Data System (ADS)

In II-VI compound semiconductors, we have used a comprehensive Green's function theory to study the vibrational properties of isotopic defects and to ascertain the microstructure of complex centers involving dopants and intrinsic impurities. The phonons generated by a realistic lattice-dynamical model for the host materials are integrated in simulating the Green's functions to help explicate the observed localized vibrational modes (LVMs) for various defect centers. Contrary to the distinct force constants required for isolated defects, the isotopic shift of LVMs has offered strong revelations for inflexible ‘impurity-host’ interactions in each isotopic defect. In compound semiconductors a unique force variation correlation with bond covalency is proposed providing corrections to the nearest-neighbor (NN) force constants for the closest mass isoelectronic and impurities carrying static charges. The articulation is extremely useful for defining perturbations and for analyzing the infrared absorption data on LVMs of complex defect centers. In corroboration with experiments, the Green's functions theory of impurity modes in Li-doped CdTe:Al (ZnSe:Al) has established second NN LiCd(Zn)-AlCd(Zn) pairs indicating the passivation of group-I acceptors via interaction with group-III elements as donors. The proposal of an antisite complex model AlZn-ZnSe-AlZn for the X center is consistent with the existing absorption results on impurity modes and is equally justified by theoretical considerations—making it the more likely identity for the native defect compensating neighboring AlZn donors in ZnSe.

Talwar, Devki N.; Feng, Zhe Chuan; Yang, Tzuen-Rong

2012-05-01

256

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

257

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

258

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

259

Reactive sintering of NiâAl intermetallic alloys under compressive stress  

Microsoft Academic Search

Synthesis of the Ni-25% at. Al intermetallic compound by the thermal explosion mode subject to the application of compressive stress was systematically investigated. The stress was applied prior to the reaction. It was proved that the compressive stress had a profound effect on the reaction, as well as the densification. At a relative low stress, a full reaction could be

K. H. Wu; C. T. Liu

1992-01-01

260

Reactive sintering of Ni[sub 3]Al intermetallic alloys under compressive stress  

Microsoft Academic Search

Synthesis of the Ni-25% at. Al intermetallic compound by the thermal explosion mode subject to the application of compressive stress was systematically investigated. The stress was applied prior to the reaction. It was proved that the compressive stress had a profound effect on the reaction, as well as the densification. At a relative low stress, a full reaction could be

K. H. Wu; C. T. Liu

1992-01-01

261

Growth and properties of intermetallics formed during thermal aging of Cu-Al ball bonds  

Microsoft Academic Search

To mimic the growth of intermetallic compounds during and after copper ball bonding, diffusion couples of aluminum and copper were made, annealed at high temperature and chemically analyzed. Two types of couples were investigated: 1) a piece of copper and of aluminum in mechanical contact at a specified temperature 2) a galvanic deposited layer of copper on aluminum. Both types

G. H. M. Gubbels; M. H. M. Kouters; O. O'Halloran; R. Rongen

2010-01-01

262

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

263

A technique for rapid characterization of intermetallics and interfaces  

Microsoft Academic Search

The production, testing and characterization of intermetallics is expensive and time consuming. In view of the wide range of intermetallics which need to be explored, the development of rapid and simple methods for classifying intermetallics is of importance. In the current work we will describe a method of producing layered or graded materials containing a sequence of intermetallics by controlled

D. Moreno; J. Garrett; J. D. Embury

1999-01-01

264

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

265

Magnetic Exchange Interactions of Quaternary Intermetallic Superconductors  

NASA Astrophysics Data System (ADS)

The magnetic exchange interaction constants J_ex^par for parallel to the c-axis (H//c) in quarternary intermetallic superconductors, RNi_2B_2C (R = rare earth elements), were estimated by substituting the anisotropic Weiss-temperatures (for magnetic field, H , parallel or perpendicular to c-axis), where J_ex^per(for H is perpendicular to c-axis) of R^+3 ions sublattice in RNi_2B_2C is assumed by that of Ho^+3 ions one. The magnetic susceptibility, i , showed the Curie-Weiss behavior at the high tempearture regions and two different Weiss-temperatures. From the high-temperature series expansion of i(T)¡¯s and the anisotropic Weiss temperatures, the magnetic exchange interaction constant J_ex^par of each R^+3 ions sublattice in RNi_2B_2C (R= Tm, Er, Ho, Dy, and Tb)were obtained. The magnetic ordering in these compounds at high temperature regions will be compared with the previous crystalline electric field effect results.

Lee, W. C.

2003-03-01

266

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

267

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

268

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

269

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

SciTech Connect

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

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

1995-03-01

270

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

271

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

272

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

273

PURY: a database of geometric restraints of hetero compounds for refinement in complexes with macromolecular structures.  

PubMed

The number and variety of macromolecular structures in complex with ;hetero' ligands is growing. The need for rapid delivery of correct geometric parameters for their refinement, which is often crucial for understanding the biological relevance of the structure, is growing correspondingly. The current standard for describing protein structures is the Engh-Huber parameter set. It is an expert data set resulting from selection and analysis of the crystal structures gathered in the Cambridge Structural Database (CSD). Clearly, such a manual approach cannot be applied to the vast and ever-growing number of chemical compounds. Therefore, a database, named PURY, of geometric parameters of chemical compounds has been developed, together with a server that accesses it. PURY is a compilation of the whole CSD. It contains lists of atom classes and bonds connecting them, as well as angle, chirality, planarity and conformation parameters. The current compilation is based on CSD 5.28 and contains 1978 atom classes and 32,702 bonding, 237,068 angle, 201,860 dihedral and 64,193 improper geometric restraints. Analysis has confirmed that the restraints from the PURY database are suitable for use in macromolecular crystal structure refinement and should be of value to the crystallographic community. The database can be accessed through the web server http://pury.ijs.si/, which creates topology and parameter files from deposited coordinates in suitable forms for the refinement programs MAIN, CNS and REFMAC. In the near future, the server will move to the CSD website http://pury.ccdc.cam.ac.uk/. PMID:19020347

Andrejasic, Miha; Praaenikar, Jure; Turk, Dusan

2008-11-01

274

Intermetallic phases in Al-Mn alloys  

Microsoft Academic Search

The intermetallic phases present in high-purity and commercial purity Al-Mn alloys (up to 2% Mn) in as-cast and heat-treated conditions were extracted electrolytically in 10% HCl in methanol solution and identified by X-ray diffraction. As iron is known to increase the coarse cast-intermetallic particles and to cause refinement of the grain size after recrystallization, different amounts of iron (up to

Aruna Bahadur

1988-01-01

275

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

PubMed Central

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

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

2013-01-01

276

Functionalized 13-crown-4, 14-crown-4, 15-crown-4, and 16-crown-4 compounds: synthesis and lithium ion complexation  

SciTech Connect

Seven novel (benzyloxy)methyl-substituted crown ethers with four ring oxygens and 13-, 14-, 15-, and 16-membered polyether rings are synthesized and their lithium and sodium cation-binding abilities are assessed by solvent extraction of the aqueous alkali metal picrates. Strongest lithium ion complexation is observed with ((benzyloxy)methyl)-14-crown-4 compounds. 28 references, 1 figure, 2 tables.

Czech, B.P.; Babb, D.A.; Son, B.; Bartsch, R.A.

1984-12-14

277

Functionalized 13-crown-4, 14-crown-4, 15-crown-4, and 16-crown-4 compounds: synthesis and lithium ion complexation  

Microsoft Academic Search

Seven novel (benzyloxy)methyl-substituted crown ethers with four ring oxygens and 13-, 14-, 15-, and 16-membered polyether rings are synthesized and their lithium and sodium cation-binding abilities are assessed by solvent extraction of the aqueous alkali metal picrates. Strongest lithium ion complexation is observed with ((benzyloxy)methyl)-14-crown-4 compounds. 28 references, 1 figure, 2 tables.

B. P. Czech; D. A. Babb; B. Son; R. A. Bartsch

1984-01-01

278

High-confidence mapping of chemical compounds and protein complexes reveals novel aspects of chemical stress response in yeastw  

E-print Network

High-confidence mapping of chemical compounds and protein complexes reveals novel aspects of chemical stress response in yeastw Thiago M. Venancio,*a S. Balajiab and L. Aravind*a Received 16th June.1039/b911821g Chemical genetics in yeast has shown great potential for clarifying the pharmacology

279

Petroporphyrins The most abundant and problematic metal compounds in crude oil exist as organic complexes of vanadium  

E-print Network

Petroporphyrins ­The most abundant and problematic metal compounds in crude oil exist as organic of porphyrins is critical for developing petroleum upgrading processes, as well as linking crude oil to source routine analytical techniques due to the increased complexity associated with heavy crudes. Atmospheric

McQuade, D. Tyler

280

Preparative separation of structurally related and racemic hydroxyl-containing compounds through the formation of crystalline molecular complexes  

NASA Astrophysics Data System (ADS)

The published data concerning the development of the methods for preparative separation of structurally related and racemic hydroxyl-containing organic compounds through the formation of crystalline molecular complexes are generalised. Special attention is focused on the resolution of racemic alcohols and phenols into enantiomers.

Kurilov, D. V.; Vinogradov, M. G.

2008-07-01

281

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

282

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

PubMed

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

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

2015-02-10

283

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

PubMed Central

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

Zhao, Yanchuan; Swager, Timothy M.

2014-01-01

284

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

PubMed

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

Zhao, Yanchuan; Swager, Timothy M

2013-12-18

285

Advanced ordered intermetallic alloy deployment  

SciTech Connect

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

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

1997-04-01

286

Cancer cell cytotoxicity of cyclometalated compounds obtained with osmium(II) complexes.  

PubMed

A library of 29 organoosmium compounds has been built up with known and novel cyclometalated compounds obtained with C-N, N(?)C(?)N, and C(?)N(?)N ligands. All compounds have been tested for their in vitro cytotoxic properties against A172, a tumor cell line derived from a human glioblastoma, this affording a contrasted picture of the activities of the compounds gathered in this study. Some compounds displayed good to excellent activities, some of them showing IC50 in the nanomolar range. The level of activity was tentatively correlated to several physicochemical properties of the compounds such as their E(0)1/2(Os(III/II)) redox potential and their lipophilicity (log Po/w). A parallel with related ruthenium derivatives was tentatively proposed. PMID:23427955

Boff, Bastien; Gaiddon, Christian; Pfeffer, Michel

2013-03-01

287

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

288

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

289

Preparation and properties of the Ni-Al/Fe-Al intermetallics composite coating produced by plasma cladding  

NASA Astrophysics Data System (ADS)

A novel approach to produce an intermetallic composite coating was put forward. The microstructure, microhardness, and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) analysis, microhardness test, and ball-on-disc wear experiment. XRD results indicate that some new phases FeAl, Fe0.23Ni0.77Al, and Ni3Al exit in the composite coating with the Al2O3 addition. SEM results show that the coating is bonded with carbon steel metallurgically and exhibits typical rapid directional solidification structures. The Cr7C3 carbide and intermetallic compounds co-reinforced composite coating has a high average hardness and exhibits an excellent wear resistance under dry-sliding wear test compared with the Cr7C3 carbide-reinforced composite coating. The formation mechanism of the intermetallic compounds was also investigated.

Zhang, Li-Min; Liu, Bang-Wu; Sun, Dong-Bai

2011-12-01

290

The intra-annular acylamide chelate-coordinated compound: The keto-tautomer of metal (II) milrinone complex  

NASA Astrophysics Data System (ADS)

In the presence of N, N'-dimethyllformamide (DMF), two isostructural metal (II)-milrinone complexes formulated as M(C 12H 8N 3O) 2 (M = Co 1 and Ni 2) have been synthesized and characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. The two compounds crystallize in the tetragonal system, chiral space group P4 32 12. They exhibit similar two dimensional (2D) square grid-like framework, in which milrinone acts as a ditopic ligand with its terminal pyridine and intra-annular acylamide groups covalently bridging different metal centers. The intra-annular acylamide ligand shows a chelate-coordinated mode. Compounds 1 and 2 are stable under 200 °C. Compound 3 formulated as (C 12H 9N 3O) 4·H 2O was obtained in the presence of water, the water molecule in the structure leads to the racemization of compound 3 and it crystallizes in the monoclinic system, non-chiral space group P2 1/ c. Milrinone exhibits a keto-form in the three compounds and compounds 1- 3 exhibit different photoluminescence properties.

Gong, Yun; Liu, Jinzhi; Tang, Wang; Hu, Changwen

2008-03-01

291

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

PubMed Central

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

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

2014-01-01

292

25Mg NMR site analysis in metals and intermetallics.  

PubMed

Nuclear magnetic resonance (NMR) of the low abundance and low gyromagnetic ratio isotope (25)Mg, I=5/2, 2.606MHz/T, 10% abundant, is shown here to provide an informative probe for phase identification, site symmetry and site multiplicity of the intermetallic compounds which occur as strengthening precipitate phases in lightweight alloys. The intermetallics discussed here, Mg(17)Al(12), MgZn(2), Mg(2)Al(3) and Al(2)CuMg, are the final equilibrium precipitate phases in a number of Mg- and Al-based heat-treatable alloys. The (25)Mg spectra of Mg in Al-10at%Mg alloy show the progressive precipitation of Mg(2)Al(3) from Mg in solid solution as a function of annealing time at 150 degrees C. Also reported are (25)Mg spectra for CuMg(2), Mg(44)Al(15)Zn(41) and Mg(2)Sn, along with the counter atom (67)Zn and (63)Cu NMR spectra for MgZn(2) and CuMg(2). All spectra are simulated to determine nuclear interaction parameters and confirm site occupancy. PMID:19307108

Bastow, T J; Celotto, S

2009-07-01

293

New intermetallics YbAu2In4 and Yb2Au3In5.  

PubMed

The intermetallic compounds YbAu(2)In(4) and Yb(2)Au(3)In(5) were obtained as single crystals in high yield from reactions run in liquid indium. Single crystal X-ray diffraction data of YbAu(2)In(4) showed that it crystallizes as a new structure type in the monoclinic space group P2(1)/m and lattice constants a = 7.6536(19) Å, b = 4.5424(11) Å, c = 9.591(2) Å and ? = 107.838(4)°. The YbAu(2)In(4) compound is composed of a complex [Au(2)In(4)](3-) polyanionic network in which the rare-earth ions are embedded. Yb(2)Au(3)In(5) crystallizes in the polar space group Cmc2(1) with the Y(2)Rh(3)Sn(5) type structure and lattice constants a = 4.5351(9) Å, b = 26.824(5) Å, and c = 7.4641(15) Å. The gold and indium atoms define a complex three-dimensional [Au(3)In(5)] network with a broad range of Au-In (2.751(2) Å-3.0518(16) Å) and In-In (3.062(3) Å-3.3024(19) Å) distances. Magnetic susceptibility measurements of YbAu(2)In(4) revealed a transition at 25 K. Below the transition, the susceptibility of YbAu(2)In(4) follows Curie-Weiss behavior with an effective paramagnetic moment of 0.79 ?(B)/Yb. Magnetic susceptibility measurements on Yb(2)Au(3)In(5) show a mixed valent ytterbium and the magnetic moment within the linear region (<100 K) of 1.95 ?(B)/Yb. Heat capacity data for YbAu(2)In(4) and Yb(2)Au(3)In(5) give Debye temperatures of 185 and 153 K, respectively. PMID:20961134

Sebastian, C Peter; Salvador, James; Martin, Joshua B; Kanatzidis, Mercouri G

2010-11-15

294

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-...

295

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

Microsoft Academic Search

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

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

1999-01-01

296

Behavior of aluminum oxide, intermetallics and voids in Cu–Al wire bonds  

Microsoft Academic Search

Nanoscale interfacial evolution in Cu–Al wire bonds during isothermal annealing from 175°C to 250°C was investigated by high resolution transmission electron microscopy (HRTEM). The native aluminum oxide film (?5nm thick) of the Al pad migrates towards the Cu ball during annealing. The formation of intermetallic compounds (IMC) is controlled by Cu diffusion, where the kinetics obey a parabolic growth law

H. Xu; C. Liu; V. V. Silberschmidt; S. S. Pramana; T. J. White; Z. Chen; V. L. Acoff

2011-01-01

297

Combustion synthesis of LiGa and LiAl intermetallic alloys  

NASA Astrophysics Data System (ADS)

LiAl and LiGa intermetallic alloys have been synthesized using the simultaneous combustion mode of combustion synthesis. LiAl intermetallic is potentially suitable as a temper alloy for producing aluminum-lithium alloys and as an anodic material for high-energy batteries. LiGa can be used as a reduction alloy to recover valuable reactive metals from molten salt effluent in actinide recovery technology. The effects of particle size, preignition heating rate, and theoretical green density on the ignition and combustion temperatures have been studied in an effort to more precisely control the synthesis reaction of these intermetallics. A lithium particle size of -20 /xm was found to be suitable when the combustion synthesis reaction was conducted at a high heating rate (>1.0 cC/s) and a moderate green density (55 to 65 pct theoretical). Preignition diffusion is suggested as the cause for low exothermic heat release at high green densities. A combustion temperature above the melting point of the LiGa intermetallic compound can be achieved under optimized conditions. However, the exothermicity and, therefore, the adiabatic temperature is too low for either LiAl or LiGa to be produced by the propagating mode of combustion synthesis.

Pritchett, S. R.; Mishra, B.; Moore, J. J.

1995-02-01

298

Dissolution of iron intermetallics in Al-Si Alloys through nonequilibrium heat treatment  

NASA Astrophysics Data System (ADS)

Conventional heat treatment techniques in Al-Si alloys to achieve optimum mechanical properties are limited to precipitation strengthening processes due to the presence of second-phase particles and spheroidization of silicon particles. The iron intermetallic compounds present in the microstructure of these alloys are reported to be stable, and they do not dissolve during conventional (equilibrium) heat treatments. The dissolution behavior of iron intermetallics on nonequilibrium heat treatment has been investigated by means of microstructure and mechanical property studies. The dissolution of iron intermetallics improves with increasing solution temperature. The addition of manganese to the alloy hinders the dissolution of iron intermetallics. Nonequilibrium heat treatment increases the strength properties of high iron alloys until a critical solution temperature is exceeded. Above this temperature, a large amount of liquid phase is formed as a result of interdendritic and grain boundary melting. The optimum solution treatment temperature for Al-6Si-3.5Cu-0.3Mg-lFe alloys is found to be between 515 °C and 520 °C.

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

1995-08-01

299

Iron d-band occupancy in NiAl intermetallics  

NASA Astrophysics Data System (ADS)

Iron when sitting at Al sites in intermetallic NiAl has been shown to expand the lattice and produce an unusual solid solution softening effect. First-principles calculations predict that an Fe atom develops a large magnetic moment and an expanded effective atomic size when it occupies a site on the Al-sublattice(1). In this study, electron energy loss spectroscopy was used to examine the magnetic characteristics of Fe substituted on the Ni and Al sites in the B2 ordered NiAl compound. We have found a higher L-edge branching ratio for Fe when on the Al site compared to Fe on the Ni site. This corresponds to an enhanced magnetic moment of Fe confirming the theoretical predication. (1) C.T. Liu, C.L. Fu, L.M.Pike and D.S. Easton, Acta Materialia 50 3203 (2002).

Chisholm, M. F.; Fu, C. L.; Liu, C. T.

2003-03-01

300

Hydrogen solubility in zirconium intermetallic second phase particles  

NASA Astrophysics Data System (ADS)

The enthalpies of solution of H in Zr binary intermetallic compounds formed with Cu, Cr, Fe, Mo, Ni, Nb, Sn and V were calculated by means of density functional theory simulations and compared to that of H in ?-Zr. It is predicted that all Zr-rich phases (formed with Cu, Fe, Ni and Sn), and those phases formed with Nb and V, offer lower energy, more stable sites for H than ?-Zr. Conversely, Mo and Cr containing phases do not provide preferential solution sites for H. In all cases the most stable site for H are those that offer the highest coordination fraction of Zr atoms. Often these are four Zr tetrahedra but not always. Implications with respect to H-trapping properties of commonly observed ternary phases such as Zr(Cr, Fe)2, Zr2(Fe, Ni) and Zr(Nb, Fe)2 are also discussed.

Burr, P. A.; Murphy, S. T.; Lumley, S. C.; Wenman, M. R.; Grimes, R. W.

2013-11-01

301

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

302

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

SciTech Connect

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

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

2010-12-15

303

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

304

Synthesis and characterization of nanocrystalline binary and ternary intermetallic compounds  

E-print Network

bromide DSC Differential scanning calorimetry EDS Energy dispersive x-ray spectroscopy Fcc Face centered cubic Hcp Hexagonal close packed ICP-MS Inductively coupled plasma ? mass spectrometry Oe Oersted PVP Polyvinylpyrrolidone SAED Selected area....99%), and poly(vinylpyrrolidone) (PVP; MW = 40000, 114 mg) were added to 25 mL of distilled, deionized water (NANOpure, 18.2 M?). (Note that water was the only solvent used in the synthesis of these materials.) After the mixture was stirred for at least 30 min...

Leonard, Brian Matthew

2009-05-15

305

Magnetization processes in rare earth intermetallic compound DyCu  

NASA Astrophysics Data System (ADS)

We have investigated the temperature dependence of magnetic susceptibility ? and elastic constant cB, c?, and c44 of DyCu (Pmbar3m) at the temperatures between 2 K and 300 K in order to evaluate the exchange and quadrupole interaction coefficients by using a mean-field approximation. The following results are obtained; (i) ? shows the Curie-Weiss behavior in the paramagnetic phase, meaning that the 4f electrons are well localized. (ii) c44 in the paramagnetic phase shows small softening at temperatures near TN while cB and c? do not. This result indicates that the dominant components of quadrupole moment are Oyz, Ozx and Oxy in the ?5 symmetry. (iii) The estimated exchange and quadrupole interaction coefficients are determined to be (J1+2J2)S2/kB=-79 K and (G1+2G2)Q2/kB=-45 K, respectively. (iv) We propose the magnetic structure models of field-induced phases, and calculate the critical fields of magnetization processes in the [0 0 1], [1 1 0] and [1 1 1] directions by using above values of interaction coefficients. The calculated values are in agreement with the experimental ones.

Kakeshita, Tomoyuki; Terai, Tomoyuki; Sonomura, Hirosuke; Yasui, Motoyoshi; Kida, Takanori; Hagiwara, Masayuki

2013-07-01

306

ESCA studies of methanation catalysts derived from intermetallic compounds  

SciTech Connect

ESCA measurements have been performed on several catalysts: (1) MNi/sub 5/(M = Th, U, or Zr), which under reaction conditions convert to Ni/MO/sub 2/; (2) Ni/ThO/sub 2/ prepared by conventional means; and (3) ThCo/sub 5/ which converts during reaction to Co/ThO/sub 2/. All except the conventionally formed Ni/ThO/sub 2/ show surfaces rich in the transition metal, accounting for the high methanation activity of these materials. The ESCA results show that the surface of the Ni/ThO/sub 2/ conventionally formed catalyst is very low in Ni, thus providing an explanation of its weak catalytic activity. Exposure of the MNi/sub 5/ systems to H/sub 2/ or mixtures of H/sub 2/ and CO enhances the surface enrichment of Ni. This ascribed to the strong interactions between Ni and H or CO.

Chin, R.L.; Elattar, A.; Wallace, W.E.; Hercules, D.M.

1980-10-30

307

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

308

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

309

SUPERCONDUCTIVITY OF TECHNETIUM ALLOYS AND COMPOUNDS  

Microsoft Academic Search

The superconducting transition temperatures of Mo- Tc alloys are ; reported. Critical field measurements of a 50 atomic per cent alloy indicate ; that it might be a promising material for superconducting magnets. The ; similarity of Tc and Re with respect to alloy and intermetallic compound ; formation is noted. The superconducting transition temperatures of the compounds ; ZrTcâ

V. B. Compton; E. Corenzwit; J. P. Maita; B. T. Matthias; F. J. Morin

1961-01-01

310

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

SciTech Connect

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

Chow, Tina Kuo Fung

1992-05-01

311

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

EPA Science Inventory

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

312

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

313

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

314

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

E-print Network

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

Paris-Sud XI, Université de

315

NMR Solution Structure of the Antitumor Compound PT523 and NADPH in the Ternary Complex with Human Dihydrofolate Reductase †  

Microsoft Academic Search

: The antitumor compound PT523 [NR-(4-amino-4-deoxypteroyl)-N#-hemiphthaloyl-L-ornithine]was found to have an inhibition constant (K i ) of 0.35 ( 0.10 pM against human dihydrofolate reductase(hDHFR), 15-fold lower than that of the classical antifolate drug methotrexate (MTX). The structure ofPT523 bound to hDHFR and hDHFR-NADPH was investigated using multinuclear NMR techniques.NMR data indicate that the binary complex has two distinct conformations in

Jason M. Johnson; Elizabeth M. Meiering; Joel E. Wright; Jorge Pardo; Andre Rosowsky; Gerhard Wagner

1997-01-01

316

The use of x-ray absorption spectroscpy for analysis of coordination and configuration in complex compounds  

NASA Astrophysics Data System (ADS)

Cu and Ni x-ray absorption spectra of complex compounds with ligands of the 1,2-dithiolate type with the binucleating ligand 3,5-bis(2-pyridyl)pyrazolate and of tetrachlorocuprates(II) and hexachlorodicuprates(II) with cations containing N-H bonds have been recorded using synchrotron radiation. The sensitivity of X-ray absorption ner edge fine structure (XANES) to the local electronic and stereochemical properties is analysed. Reversible thermochromism in the x-ray region has been found due to square-planar/tetrahedral change of the [CuCl4]2- and the [Cu2Cl6]2- anions.

Szargan, R.; Hallmeier, K.-H.; Meisel, A.; Pantelouris, M.; Hormes, J.; Fröba, M.; Metz, W.; Beyer, L.

1990-12-01

317

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

PubMed

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

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

2007-05-01

318

Investigation of Y6Mn23 and YMn12 intermetallic alloys under high hydrogen pressure  

NASA Astrophysics Data System (ADS)

Among three intermetallic compounds existing in Y-Mn system the YMn2 and Y6Mn23 can easily form interstitial hydrides while for YMn12 existence of hydride has never been reported. At moderate hydrogen pressure YMn2 and Y6Mn23 transform into YMn2H4.5 and Y6Mn23H25 respectively. At high hydrogen pressure the YMn2 (C15 or C14 parent structure) forms a unique YMn2H6 (s.g. Fm3m) complex hydride of fluorite structure in which one Mn atom Mn(1) and Y randomly occupy the 8c sites while second manganese (Mn2) in position 4a forms complex anion with 6 hydrogen atoms located in positions 24e. Formation of YMn2H6 independently of the structure of parent phase (C14 or C15) as well as occupation of the same site (8c) by Y and Mn(1) atoms suggested that also Y6Mn23 and YMn12 could transform into YMn2H6 - type hydride in which suitable number of Y atoms will be substituted by Mn(1) in the 8c positions. This assumption was confirmed by exposing R6Mn23 and RMn12 to 1 GPa of hydrogen pressure at 1000C. Formation of (RxMn2-x)MnH6 (where x = 18/29 or 3/13 for R6Mn23 and RMn12 hydrides respectively) was confirmed by XRD. Hydrogen concentration in both R6Mn23 and RMn12 based hydrides reached H/Me = 2 thus value two times higher than in R6Mn23H25.

Filipek, S. M.; Sato, R.; Kuriyama, N.; Tanaka, H.; Takeichi, N.

2010-03-01

319

The cholesterol lowering properties of the complex compound simvastatin with glycyrrhizic acid (simvaglyzin) in experimental models  

Microsoft Academic Search

A molecular complex of simvastatin (SV) and glycyrrhizic acid (GA) (at their ratio of 1 : 4) has been synthesized. The complex\\u000a named “simvaglyzin” (SVG) was stable in aqueous and aqueous-alcohol solutions at GA concentrations exceeding 0.2 mM. In vitro\\u000a SVG acted as an uncompetitive inhibitor of 3-hydroxy-3-methyl-glutaryl-CoA (3-HMG-CoA) reductase (Ki of 94 nM). Appearance\\u000a of this inhibitory activity is

V. A. Vavilin; N. F. Salakhutdinov; Yu. I. Ragino; N. E. Polyakov; M. B. Taraban; T. V. Leshina; E. M. Stakhneva; V. V. Lyakhovich; Yu. P. Nikitin; G. A. Tolstikov

2008-01-01

320

Circular dichroism sensing of chiral compounds using an achiral metal complex as probe.  

PubMed

Coordination of a chiral substrate to (meso-salen)cobalt(II) nitrate and subsequent oxidation generates a Co(III) complex exhibiting a strong chiroptical readout that is attributed to spontaneous substrate-to-ligand chirality imprinting. The characteristic circular dichroism (CD) response of the (salen)cobalt complex can be used for enantiomeric analysis of a variety of chiral substrates based on a simple CD measurement at low concentration and without additional purification steps. This chirality sensing approach has potential for high-throughput enantiomeric excess (ee) screening applications and minimizes solvent waste production. PMID:24839183

Irfanoglu, Burcin; Wolf, Christian

2014-08-01

321

Transient liquid phase bonding of intermetallics  

Microsoft Academic Search

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

Yimin Guan

1998-01-01

322

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

PubMed

Inclusion complexes of estragole (ES) as pure compound and as main component of basil and tarragon essential oils (EOs) with ?-cyclodextrin (?-CD), ?-cyclodextrin (?-CD), hydroxypropyl-?-cyclodextrin (HP-?-CD), randomly methylated-?-cyclodextrin (RAMEB), a low methylated-?-cyclodextrin (CRYSMEB) and ?-cyclodextrin (?-CD) were characterized. Formation constants (Kf) of the complexes were determined in aqueous solution by nonlinear regression analysis using static headspace gas chromatography (SH-GC) and UV-visible spectroscopy. Solid inclusion complexes were prepared by the freeze-drying method for different CD:ES molar ratios and were characterized by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). Inclusion complexes formation allowed the controlled release of ES. Moreover, increased DPPH radical scavenging activity and photostability of ES and ES containing EOs (ESEOs) were observed in the presence of CDs. These findings suggest that encapsulation with CDs could be an efficient tool to improve the use of ES and ESEOs in aromatherapy, cosmetic and food fields. PMID:25542121

Kfoury, Miriana; Auezova, Lizette; Ruellan, Steven; Greige-Gerges, Hélène; Fourmentin, Sophie

2015-03-15

323

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

324

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

325

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

326

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

327

Evaluations of an Enhanced Total Hydrocarbon Analyzer With Complex Mixtures of Volatile Organic Compounds  

NASA Technical Reports Server (NTRS)

From the earliest manned missions, the volatile organic compound (VOC) content of spacecraft air has been a concern because of a much greater potential for contamination than air in most terrestrial settings. First, the volume of air is small compared to the mass of man- made materials comprising the interior furnishings of the spacecraft. These man-made materials offgas VOCs trapped during manufacture. Second, the nitrogen fraction of the air is recycled. Any VOCs not scrubbed out with charcoal filters or aqueous condensate (mainly water expired by the crew) will accumulate in the air. Third, the crew emits metabolic VOCs. Fourth, experimental payloads can also offgas or accidentally release a VOC; in fact a major organic constituent of the atmosphere is the disinfectant isopropanol released from swabs used in medical experiments.

Cross, John H.; Limero, Thomas F.; James, John T.; Breach, James; Hinton, Mark

1995-01-01

328

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

329

Anion complexation, transport and structural studies of a series of bis-methylurea compounds.  

PubMed

A new family of bis-methylureas () have been synthesised and their ability to bind anions both in solution and in the solid state and to transport them through lipid membrane have been studied. From the solid state studies it has emerged that various conformations can be adopted by the receptors allowing the isolation of complexes of different stoichiometries (from 1?:?1 to 1?:?3). The transport studies highlighted the possibility to use bis-methylureas to mediate Cl(-) transport across membranes. PMID:25500633

Olivari, Martina; Montis, Riccardo; Karagiannidis, Louise E; Horton, Peter N; Mapp, Lucy K; Coles, Simon J; Light, Mark E; Gale, Philip A; Caltagirone, Claudia

2015-01-20

330

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

E-print Network

is that transition metals can be found in silicon as either interstitial or substitutional species, point defect complexes e.g., interstitial-substitutional pairs , or single-metal silicide precipitates, such as Cu3Si; revised manuscript received 12 May 2006; published 8 June 2006 We report the observation of an alloy phase

331

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

SciTech Connect

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

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

2003-01-15

332

Magnetic Exchange Interactions of Quaternary Intermetallic Superconductors  

Microsoft Academic Search

The magnetic exchange interaction constants J_ex^par for parallel to the c-axis (H\\/\\/c) in quarternary intermetallic superconductors, RNi_2B_2C (R = rare earth elements), were estimated by substituting the anisotropic Weiss-temperatures (for magnetic field, H , parallel or perpendicular to c-axis), where J_ex^per(for H is perpendicular to c-axis) of R^+3 ions sublattice in RNi_2B_2C is assumed by that of Ho^+3 ions one.

W. C. Lee

2003-01-01

333

Towards crystal structure prediction of complex organic compounds--a report on the fifth blind test.  

PubMed

Following on from the success of the previous crystal structure prediction blind tests (CSP1999, CSP2001, CSP2004 and CSP2007), a fifth such collaborative project (CSP2010) was organized at the Cambridge Crystallographic Data Centre. A range of methodologies was used by the participating groups in order to evaluate the ability of the current computational methods to predict the crystal structures of the six organic molecules chosen as targets for this blind test. The first four targets, two rigid molecules, one semi-flexible molecule and a 1:1 salt, matched the criteria for the targets from CSP2007, while the last two targets belonged to two new challenging categories - a larger, much more flexible molecule and a hydrate with more than one polymorph. Each group submitted three predictions for each target it attempted. There was at least one successful prediction for each target, and two groups were able to successfully predict the structure of the large flexible molecule as their first place submission. The results show that while not as many groups successfully predicted the structures of the three smallest molecules as in CSP2007, there is now evidence that methodologies such as dispersion-corrected density functional theory (DFT-D) are able to reliably do so. The results also highlight the many challenges posed by more complex systems and show that there are still issues to be overcome. PMID:22101543

Bardwell, David A; Adjiman, Claire S; Arnautova, Yelena A; Bartashevich, Ekaterina; Boerrigter, Stephan X M; Braun, Doris E; Cruz-Cabeza, Aurora J; Day, Graeme M; Della Valle, Raffaele G; Desiraju, Gautam R; van Eijck, Bouke P; Facelli, Julio C; Ferraro, Marta B; Grillo, Damian; Habgood, Matthew; Hofmann, Detlef W M; Hofmann, Fridolin; Jose, K V Jovan; Karamertzanis, Panagiotis G; Kazantsev, Andrei V; Kendrick, John; Kuleshova, Liudmila N; Leusen, Frank J J; Maleev, Andrey V; Misquitta, Alston J; Mohamed, Sharmarke; Needs, Richard J; Neumann, Marcus A; Nikylov, Denis; Orendt, Anita M; Pal, Rumpa; Pantelides, Constantinos C; Pickard, Chris J; Price, Louise S; Price, Sarah L; Scheraga, Harold A; van de Streek, Jacco; Thakur, Tejender S; Tiwari, Siddharth; Venuti, Elisabetta; Zhitkov, Ilia K

2011-12-01

334

The magnesium-rich intermetallics Ir 3.30(1)Mg 17.96(4)In 0.74(4) and Ir 3Mg 17.1(1)In 1.9(1)  

NASA Astrophysics Data System (ADS)

Phase analytical investigations in the system magnesium-iridium-indium revealed the magnesium-rich intermetallics Ir 3.30(1)Mg 17.96(4)In 0.74(4) and Ir 3Mg 17.1(1)In 1.9(1). The samples were prepared from the elements via induction melting in glassy carbon crucibles in a water-cooled sample chamber and subsequent annealing. Both intermetallics were investigated by X-ray powder and single-crystal diffraction: C2/ c, Z=4, a=979.1(1), b=2197.4(2), c=848.2(1) pm, ?=105.79(1)°, wR2=0.0434, 3076 F2 values, 108 variables for Ir 3.30(1)Mg 17.96(4)In 0.74(4), and a=983.39(8), b=2211.4(2), c=849.55(7) pm, ?=105.757(6)°, wR2=0.0487, 3893 F2 values, and 115 variables for Ir 3Mg 17.1(1)In 1.9(1). Both compounds show solid solutions. In Ir 3.30(1)Mg 17.96(4)In 0.74(4), the indium site shows an occupancy by 69.9(4)% In+30.1(4)% Ir, and one magnesium site has a small mixed occupancy with indium, while nine atomic sites in Ir 3Mg 17.1(1)In 1.9(1) show Mg/In mixing with indium occupancies between 1.2(3)% and 14.8(3)%. The relatively complex crystal structure is of a new type. It can be explained by a packing of coordination number 10 and 12 polyhedra around the iridium atoms. The crystal chemical peculiarities and chemical bonding in both intermetallics is briefly discussed.

Hlukhyy, Viktor; Pöttgen, Rainer

2005-01-01

335

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

PubMed

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

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

2014-06-28

336

Determination of thermodynamic and thermo-elastic properties for ductile B2-DyCu intermetallics using molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

The thermodynamic and thermo-elastic properties of ductility intermetallic compounds DyCu with B2 structure are investigated with molecular dynamics. The calculated structural properties are in reasonable agreement with the available experimental and previously calculated data. At 300 K, the heat capacity of DyCu is 23.93 J mol-1 K-1. At the whole range 0-900 K, the elastic constants decrease with increasing temperature, and satisfy the stability criterions for DyCu compound. The value of B/G ratio for DyCu is greater than 1.75 implying the DyCu intermetallics are ductile, and increases with elevating temperature. Our results mean that the ductility of DyCu can be improved by increasing temperature.

Wu, Yurong; Xu, Longshan; Hu, Wangyu

2015-02-01

337

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

338

Process for synthesizing compounds from elemental powders and product  

DOEpatents

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

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

1993-12-14

339

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

340

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

341

The dissolution behavior of Ni–Ni\\/Al intermetallic electrode in Li\\/K = 62\\/38 mixed molten carbonate  

Microsoft Academic Search

A Ni3Al intermetallic compound was added to the cathode to decrease the solubility of Ni in a Li\\/K eutectic molten salt. The solubility of Ni\\/Ni3Al used as a cathode was examined by measuring the concentrations of Ni and Al ions in alkali metal carbonate. The electrolyte consisted of a mixture of lithium carbonate and potassium carbonate (62Li2CO3–38K2CO3) at 650°C. A

Yun-Sung Kim; Hun-Seok Jung; Hyun-Jung Park; Jun Heok Lim

2010-01-01

342

Lanthanide-to-lanthanide energy-transfer processes operating in discrete polynuclear complexes: can trivalent europium be used as a local structural probe?  

PubMed

This work, based on the synthesis and analysis of chemical compounds, describes a kinetic approach for identifying intramolecular intermetallic energy-transfer processes operating in discrete polynuclear lanthanide complexes, with a special emphasis on europium-containing entities. When all coordination sites are identical in a (supra)molecular complex, only heterometallic communications are experimentally accessible and a Tb ? Eu energy transfer could be evidenced in [TbEu(L5)(hfac)6] (hfac = hexafluoroacetylacetonate), in which the intermetallic separation amounts to 12.6?Å. In the presence of different coordination sites, as found in the trinuclear complex [Eu3(L2)(hfac)9], homometallic communication can be induced by selective laser excitation and monitored with the help of high-resolution emission spectroscopy. The narrow and non-degenerated character of the Eu((5)D0 ? (7)F0) transition excludes significant spectral overlap between donor and acceptor europium cations. Intramolecular energy-transfer processes in discrete polynuclear europium complexes are therefore limited to short distances, in agreement with the Fermi golden rule and with the kinetic data collected for [Eu3(L2)(hfac)9] in the solid state and in solution. Consequently, trivalent europium can be considered as a valuable local structural probe in discrete polynuclear complexes displaying intermetallic separation in the sub-nanometric domain, a useful property for probing lanthanido-polymers. PMID:25099883

Zaïm, Amir; Eliseeva, Svetlana V; Guénée, Laure; Nozary, Homayoun; Petoud, Stéphane; Piguet, Claude

2014-09-15

343

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

PubMed Central

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

Porco, David; Bedos, Anne; Deharveng, Louis

2010-01-01

344

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

345

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

EPA Science Inventory

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

346

Decomposition of intermetallics during high-energy ball-milling  

Microsoft Academic Search

The decomposition behavior of FeSn, CoSn and CoIn2 intermetallics under high-energy ball-milling has been investigated using X-ray diffraction, calorimetric and magnetization measurements. Upon milling a large amount of the FeSn intermetallic decomposes into Fe5Sn3 and FeSn2, where the average grain size of the product phases stays nearly constant with milling-time. Similar observations are made for the CoSn intermetallic, which decomposes

Y. S. Kwon; P. P. Choi; J. S. Kim; D. H. Kwon; K. B. Gerasimov

2007-01-01

347

Titanium aluminide intermetallic alloys with improved wear resistance  

SciTech Connect

The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

2014-07-08

348

The emission characteristics and the related malodor intensities of gaseous reduced sulfur compounds (RSC) in a large industrial complex  

NASA Astrophysics Data System (ADS)

In this study, the concentrations of major reduced sulfur compounds (RSC: H 2S, CH 3SH, DMS, CS 2 and DMDS) were determined from various emission sources located within the Ban-Wall (BW)/ Si-Hwa (SH) industrial complex in Ansan city, Korea. The measurement data were obtained from a total of 202 individual points at 77 individual companies during 2004-2005. The highest RSC concentration levels came most dominantly from H 2S (300 (mean) and 0.86 ppb (median)) followed by CS 2, while the results of CH 3, DMS, and DMDS are notably lower at the mean concentration levels of a few ppb. These data were evaluated further after being grouped into two different classification schemes: 9 industry sectors and 9 processing unit types. The strongest emissions of RSC, when evaluated among different industry sectors, are generally found from such industry types as leather, food, paper/pulp, as well as waste/sewage related ones. In contrast, when these RSC data are compared across different processing units, the highest values were seen most frequently from such units as junction boxes, aeration tanks, and settling tanks. The assessment of data in terms of relative contribution to malodor intensity showed that H 2S and CH 3SH are more important than others. The overall results of the present study suggest that information combining RSC speciation and types of anthropogenic activities may be used to distinguish the patterns of odorous pollution in areas affected by strong source processes.

Kim, Ki-Hyun; Jeon, Eui-Chan; Choi, Ye-Jin; Koo, Youn-Seo

349

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

350

Co–Sn intermetallic phases and their formation at the Co\\/Sn interface studied with perturbed angular correlation (PAC) method  

Microsoft Academic Search

Cobalt–tin intermetallic compounds of different stoichiometries were studied by means of the perturbed angular correlation (PAC) technique. The hyperfine interaction parameters for 111Cd probes in the crystal lattices of CoSn2 and Co3Sn2 were determined. A T3\\/2 temperature dependence of the electric field gradient (EFG) in CoSn2 compound was found. Due to the thermal interdiffusion in a bilayer Co\\/Sn sample the

P Wodniecki; B Wodniecka; A Kuli?ska; A. Z Hrynkiewicz

1998-01-01

351

Superconductivity of Technetium Alloys and Compounds  

Microsoft Academic Search

The superconducting transition temperatures of Mo-Tc alloys are reported. Critical field measurements of a 50 atomic percent alloy indicate that it might be a promising material for superconducting magnets. The similarity of Tc and Re with respect to alloy and intermetallic compound formation is noted. The superconducting transition temperatures of the compounds ZrTc6 and NbTc3 are 9.7°K and 10.5°K, respectively.

V. B. Compton; E. Corenzwit; J. P. Maita; B. T. Matthias; F. J. Morin

1961-01-01

352

High-temperature ordered intermetallic alloys IV; Proceedings of the 4th MRS Symposium, Boston, MA, Nov. 27-30, 1990  

SciTech Connect

The present conference discusses topics in the fields of alloying theory and phase stability, microstructural defects, alloy mechanical properties, alloy design and processing, corrosion, and multiphase materials and composites. Attention is given to phase stability and the role of ternary additions on the electronic and mechanical properties of Al intermetallics, ternary alloying of refractory intermetallics, phase-diagram relationships in the Ti-Al-V system, a model of yield behavior in Ni3Al alloys, dislocation structures and anomalous yielding in ordered alloys, deformation and ductility in Al3Ti-based alloys, and the microstructure of TiBe12. Also discussed are deformation mechanisms and solid-solution strengthening in ordered alloys, the cyclic deformation of B2 aluminides, hydrogen embrittlement of FeAl and Fe3Al, the electronic structure of planar faults in TiAl, advances in gamma-Ti aluminide intermetallics, the microstructure of rapidly solidified Nb3Al-X ribbons, the oxidation behavior of advanced intermetallic compounds, and the processing/property relationships of intermetallic-matrix composites.

Johnson, L.A.; Pope, D.P.; Stiegler, J.O. (GE Aircraft Engines, Cincinnati, OH (United States) Pennsylvania, University, Philadelphia, (United States) Oak Ridge National Laboratory, TN (United States))

1991-01-01

353

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

354

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

355

The role of thiol and nitrosothiol compounds in the nitric oxide-forming reactions of the iron-N-methyl-d-glucamine dithiocarbamate complex.  

PubMed Central

The object of the present study is to investigate whether the physiologically dominant thiol compounds such as GSH and cysteine or their nitrosothiol compounds affect the formation of the iron- N -methyl-D-glucamine dithiocarbamate [(MGD)(2)Fe(2+)]-nitric oxide complex. The present study provided experimental evidence that physiological concentrations of GSH (approx. 5 mM) and L-cysteine (approx. 0.5 mM) accelerated the formation of the (MGD)(2)Fe(2+)-NO complex from nitrite by two and three times respectively. The rate constants for the reduction of (MGD)(3)Fe(3+) to (MGD)(2)Fe(2+) by GSH and cysteine were calculated as 1.3 and 2.0x10(2) M(-1).s(-1) respectively. Furthermore, depletion of GSH was demonstrated in PC12 cells, and thiol compounds enhanced the formation of reactive oxygen species by the (MGD)(2)Fe(2+) complex by accelerating its redox turnover. The main effect of the physiological concentration of thiols was the reduction of (MGD)(3)Fe(3+). S -nitrosoglutathione spontaneously reacted with (MGD)(2)Fe(2+) to produce the (MGD)(2)Fe(2+)-NO complex with a 1:2 stoichiometry. In fact, (MGD)(2)Fe(2+) was as good an indicator of nitrosothiols as it was of NO itself. The present study elucidates the difficulties of utilizing the (MGD)(2)Fe(2+) complex for the quantification of NO in biological samples, especially in vivo. PMID:12141947

Tsuchiya, Koichiro; Kirima, Kazuyoshi; Yoshizumi, Masanori; Houchi, Hitoshi; Tamaki, Toshiaki; Mason, Ronald P

2002-01-01

356

Determination of 13C/12C isotopic ratios of biogenic organometal(loid) compounds in complex matrixes.  

PubMed

Methylated metal(loid) compounds are formed in the environment by abiotic as well as enzymatically catalyzed transfer of a methyl group. Due to the increased mobility and toxicity in comparison to the inorganic precursors, the investigation of the formation process is of high relevance. Though the natural abundance carbon isotope ratio can give important insights toward their origin as well as the biochemical methyl transfer process, so far, these species have not been investigated by carbon isotope ratio mass spectrometry (IRMS). This is due to the analytical challenge to precisely determine the natural isotope distribution of trace amounts of metal(loid)-bound carbon in complex organic matrixes. To overcome this problem, we tested the concept of selective derivatization of nonvolatile organometal(loid)s by hydride generation (HG) followed by purge and trap (P-T) enrichment, heart-cut gas chromatography (hcGC), and subsequent analysis by GC/IRMS. Parameter optimization of HG/P-T/hcGC was conducted using online coupling to element-sensitive ICPMS (inductively coupled plasma mass spectrometry) detection. The purity of the HG/P-T/hcGC fraction was verified by GC/MS. For the model substance trimethylarsine oxide (TMAsO), an excellent agreement of the delta(13)C-value analyzed by HG/P-T/hcGC-GC/IRMS was achieved in comparison to the bulk delta(13)C-value, which shows that no significant isotope fractionation occurred during hydride generation and subsequent separation. The optimized method showed good reproducibility and a satisfying absolute detection limit of 4.5 microg TMAsO (1.2 microg(carbon)). This method was applied to the analysis of TMAsO in compost. The low delta(13)C value of this compound (-48.38 +/- 0.41 per thousand) indicates that biomethylation leads to significant carbon fractionation. HG/P-T/hcGC-GC/IRMS is a promising tool for investigation of the biomethylation process in the environment. PMID:19476388

Wuerfel, Oliver; Diaz-Bone, Roland A; Stephan, Manuel; Jochmann, Maik A

2009-06-01

357

On the intermetallic corrosion of Cu-Al wire bonds  

Microsoft Academic Search

A detailed description of the Cu-Al wire bond interface is presented, which can possibly explain the often observed corrosion failures in humidity reliability tests. Using micro-structural analysis techniques, it is shown that the unstressed interface contains up to three intermetallic phases, where the Cu-rich phases are located at the Cu-ball interface. Upon humidity stress test only the high-Cu containing intermetallic

Tim Boettcher; Michael Rother; Stefan Liedtke; Mandy Ullrich; Marc Bollmann; Andreas Pinkernelle; Daniel Gruber; H.-J. Funke; M. Kaiser; Kan Lee; M. Li; K. Leung; T. Li; M. L. Farrugia; O. O'Halloran; M. Petzold; B. Ma?rz; R. Klengel

2010-01-01

358

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

359

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

SciTech Connect

We present the first study of intermolecular interactions between nitrous oxide (N{sub 2}O) and three representative aromatic compounds (ACs): phenol, cresol, and toluene. The infrared spectroscopic experiments were performed in a Ne matrix and were supported by high-level quantum chemical calculations. Comparisons of the calculated and experimental vibrational spectra provide direct identification and characterization of the 1:1 N{sub 2}O-AC complexes. Our results show that N{sub 2}O is capable of forming non-covalently bonded complexes with ACs. Complex formation is dominated by dispersion forces, and the interaction energies are relatively low (about ?3 kcal mol{sup ?1}); however, the complexes are clearly detected by frequency shifts of the characteristic bands. These results suggest that N{sub 2}O can be bound to the amino-acid residues tyrosine or phenylalanine in the form of ? complexes.

Cao, Qian [Department of Chemistry, P.O. Box 55, University of Helsinki, Helsinki FI-00014 (Finland) [Department of Chemistry, P.O. Box 55, University of Helsinki, Helsinki FI-00014 (Finland); School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Gor, Gennady Y., E-mail: ggor@princeton.edu [Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Krogh-Jespersen, Karsten [Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903 (United States)] [Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903 (United States); Khriachtchev, Leonid [Department of Chemistry, P.O. Box 55, University of Helsinki, Helsinki FI-00014 (Finland)] [Department of Chemistry, P.O. Box 55, University of Helsinki, Helsinki FI-00014 (Finland)

2014-04-14

360

Magnetism and phase stability of R(Co,M)7 pseudobinary intermetallics with TbCu7-type structure  

NASA Astrophysics Data System (ADS)

Pseudobinary RCo7-xMx intermetallic compounds with TbCu7-type structure have been synthesized, and their structural and magnetic properties have been investigated using powder x-ray diffraction and magnetic measurements. Based upon the structural analysis, the stabilized element M occupies the 2e or the 3g position depending on its electronegativity. RCo7-xMx compounds exhibit ferromagnetic order with high Curie temperature. In addition, the uniaxial magnetocrystalline anisotropy is observed in SmCo7-xMx intermetallics. The magnetic moments have been investigated using a modified magnetic valence model with the equation ?Zm?=±xRZmR+xTZmT+2Nsp??ixi, where the magnetic moment contributed by 4f transition metal is corrected from its chemical valence numbers of rare earth in the original magnetic valence model to the theoretical value of gJ?BJ. It is also assumed that the nonmagnetic metal has no contribution to the moment. The corrected model can also be used to calculate the moments of the other strong ferromagnetic intermetallics such as R -(T,M) 1:5, 2:17, and R2Fe14B, etc. This model could estimate and even predict the moments as long as the composition of the ferromagnetic alloy is known.

Guo, Yongquan; Feng, Weicun; Li, Wei; Luo, Jun; Liang, Jingkui

2007-01-01

361

Steric effects on uranyl complexation: synthetic, structural, and theoretical studies of carbamoyl pyrazole compounds of the uranyl(VI) ion.  

PubMed

New bifunctional pyrazole based ligands of the type [C(3)HR(2)N(2)CONR'] (where R = H or CH(3); R' = CH(3), C(2)H(5), or (i)C(3)H(7)) were prepared and characterized. The coordination chemistry of these ligands with uranyl nitrate and uranyl bis(dibenzoyl methanate) was studied with infrared (IR), (1)H NMR, electrospray-mass spectrometry (ES-MS), elemental analysis, and single crystal X-ray diffraction methods. The structure of compound [UO(2)(NO(3))(2)(C(3)H(3)N(2)CON{C(2)H(5)}(2))] (2) shows that the uranium(VI) ion is surrounded by one nitrogen atom and seven oxygen atoms in a hexagonal bipyramidal geometry with the ligand acting as a bidentate chelating ligand and bonds through both the carbamoyl oxygen and pyrazolyl nitrogen atoms. In the structure of [UO(2)(NO(3))(2)(H(2)O)(2)(C(5)H(7)N(2)CON {C(2)H(5)}(2))(2)], (5) the pyrazole ligand acts as a second sphere ligand and hydrogen bonds to the water molecules through carbamoyl oxygen and pyrazolyl nitrogen atoms. The structure of [UO(2)(DBM)(2)C(3)H(3)N(2)CON{C(2)H(5)}(2)] (8) (where DBM = C(6)H(5)COCHCOC(6)H(5)) shows that the pyrazole ligand acts as a monodentate ligand and bonds through the carbamoyl oxygen to the uranyl group. The ES-MS spectra of 2 and 8 show that the ligand is similarly bonded to the metal ion in solution. Ab initio quantum chemical studies show that the steric effect plays the key role in complexation behavior. PMID:22471744

Das, Debasish; Kannan, Shanmugaperumal; Maity, Dilip K; Drew, Michael G B

2012-04-16

362

Reactivity of tracheal smooth muscles in albino rats with experimental diabetes mellitus treated with a new complex compound of oxovanadium (IV) and isonicotinic acid hydrazide.  

PubMed

We studied functional properties of tracheal smooth muscle cells in rats with diabetes mellitus. Reactivity of tracheal smooth muscles increased in rats with experimental alloxan-induced diabetes mellitus. A new complex compound of oxovanadium (IV) and isonicotinic acid hydrazide affected reactivity of tracheal smooth muscles in albino rats with experimental type I diabetes mellitus. This new organic vanadium-containing compound reduced contractility of tracheal smooth muscles in rats and potentiated relaxation of smooth muscle cells in the trachea in response to exogenous nitric oxide. PMID:12937677

Khafiz'yanova, R Kh; Minnebaev, M M; Gallyamov, R M; Latypov, R S; Gosmanov, A R; Aleeva, G N

2003-06-01

363

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

SciTech Connect

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

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

1984-10-01

364

Multiconfigurational nature of 5f orbitals in uranium and plutonium intermetallics  

PubMed Central

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

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

2012-01-01

365

Transient liquid phase bonding of intermetallics  

NASA Astrophysics Data System (ADS)

The present work was undertaken to examine the applicability of transient liquid phase bonding to structural intermetallics. This research was based on an investigation of the mechanisms governing microstructural development in the joint and adjacent substrates during the joining process. The bonding systems investigated included polycrystalline NiAl/Cu/Ni, polycrystalline NiAl/Cu/superalloys (Martin-Marietta (MM)-247, Inconel (IN) 718 and Nimonic 90), single-crystal NiAl (with 1.5 at % Hf) joined to MM-247 using different filler metals (Cu foil, powder filler metal and electro-plated thin Cu film), and martensitic NiAl joined with martensitic NiTi using Cu foil and specially designed powder filler metals. In polycrystalline NiAl/Cu/Ni bonds, the mechanism of isothermal solidification is considered. Changes in the microstructure of the bond centerline due to element redistribution are discussed. The precipitation of both L1sb2 type gammasp' and B2 type beta phase at the joint centerline is investigated. The formation of martensitic L1sb0 type NiAl is also examined. The mechanical properties of the joints are investigated using shear strength and microhardness tests. In TLP bonding of polycrystalline NiAl with MM-247, both the epitaxial growth of the beta phase NiAl into the joint and the formation of non-epitaxial beta-phase layers are considered. The formation of second-phases, including the gammasp' phase, carbides, and sigma-phase intermetallics is also examined. Bond-line and adjacent substrate microstructures for the NiAl/Cu/MM-247 bonds are correlated with joint mechanical properties determined by room temperature shear testing. Single-crystal NiAl (1.5 at % Hf)/Cu/MM-247 joints are examined and compared with polycrystalline NiAl/Cu/MM247 joints. The effect of Hf on the microstructure of joints is investigated. The influence of different filler metals (i.e., wide-gap powder filler metal and electro-plated thin film filler metal) on the joining process is also considered. In TLP bonding of martensitic NiAl with martensitic NiTi, the formation Ti depletion region was observed while using Cu foil as the filler metal. Alternative filler metals were successfully used to solve this problem. According to the experimental results, standard TLP bonding models cannot be applied to the bonding systems in this research. The influence of second phase formation on TLP models is discussed.

Guan, Yimin

366

X-ray diffraction study of the phase purity, order, and texture of ductile B2 intermetallics  

SciTech Connect

Representatives (AgY, CuY, AgEr, CuDy, MgY and MgCe) of the newly discovered family of ductile stoichiometric B2 intermetallic (metal-rare-earth element, MR) compounds were characterized by X-ray diffraction, to determine if their anomalous ductility is related to an exceptional level of phase purity, lack of chemical ordering or a strong crystallographic texture. Brittle NiAl served as an anti-type in this study. We found that all of the rare-earth compounds, except MgY, have a significant volume fraction (-5-20vol.%) of second phases (M{sub 2}R intermetallics and R{sub 2}O{sub 3} oxides), which has not been reported in previous studies of these materials. The most ductile of observed MR compounds, AgY, is highly ordered. A moderate texture was observed in AgY, which may explain its higher ductility (using polycrystal modeling) as compared to other MR compounds. However, the intrinsic polycrystalline ductility of these compounds in the randomly textured state (like that observed in CuY) still has no specific, definitive explanation.

Mulay, Rupalee [University of Virginia; Wollmershauser, J.A. A. [University of Virginia; Heisel, M A [University of Virginia; Bei, Hongbin [ORNL; Russell, A M [Iowa State University; Agnew, S R [University of Virginia

2010-01-01

367

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

368

Thermal stress effects in intermetallic matrix composites  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

369

Bulk and defect properties of ordered intermetallics  

SciTech Connect

First-principles calculations based on the local-density-functional theory have been used to investigate the factors governing strength of ordered intermetallic alloys. Unlike Ni{sub 3}Al, calculated elastic constants and shear fault energies indicate anomalous yield strength behavior is not likely to occur in Ni{sub 3}Si. This suggests the inadequacy of cross-slip-pinning model to explain the strength anomaly in the L1{sub 2} structure. For strongly ordered NiAl, the defect structure is dominated by two types of defects -- monovacancies on the Ni sites and substitutional antisite defects on the Al sites. By contrast, for Ni{sub 3}Al, absence of structural vacancies and deviations from stoichiometry are accommodated by substitutional antisite defects on both sublattices. Intrinsic strengthening mechanisms in TiAl are discussed in terms of calculated elastic constants and shear fault energies. Because of reduced fault energies at the {gamma}/{alpha}{sub 2} interface, slip and twinning contribute significantly to high shear deformation of the lamellar structure.

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

1993-12-31

370

Transport properties calculated from complex energy Fermi surface and Boltzmann approach: Example of TiFe1-xNixSb half-Heusler compound  

NASA Astrophysics Data System (ADS)

The Green function Korringa-Kohn-Rostoker methodology with the coherent potential approximation was used to calculate complex energy band structure. In the framework of Boltzmann approach life time and velocity of electron were determined on complex energy Fermi surface. Then electron transport properties as temperature dependent Seebeck coefficient, residual resistivity were investigated. Calculations were performed with several approximations, compared and demonstrated for the TiFe1-xNixSb half-Heusler compound that experimentally revealed tunable electron transport properties, i.e. a metal-semiconductor-metal crossover and change in sign of thermopower.

Kutorasinski, K.; Tobola, J.; Kaprzyk, S.

2012-06-01

371

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

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

372

Strength and ductility of L1{sub 2}-based intermetallics. Final report  

SciTech Connect

For the first time a complete and systematic study has been made of the strength and ductility of the L1{sub 2}-based intermetallic compounds Ni{sub 3}X (X=Al,Ga,Ge,Ga), w/wo boron and w/wo notches. Variables included grain size, boron concentration, deviation from stoichiometry, temperature, strain rate, and notch geometry. Approaches included tensile, compression, hardness and Bauchinger tests; optical microscopy; scanning, transmission and high-resolution scanning-transmission electron microscopy; and numerical modeling. The hypothesis tested was that the increase in ductility induced by boron is caused largely by an increase in the accommodation of slip at grain boundaries. The results and interpretations were published in 41 papers. Every result obtained over the course of the study is consistent with this hypothesis. Indeed, every result obtained by other investigators on the same alloy systems is also consistent with the hypothesis. Thus, we conclude the study by saying that the grain boundary accommodation of slip is a major factor in accounting for the beneficial effect of boron on the strength and ductility of Ni{sub 3}X-based L1{sub 2} intermetallics.

Schulson, E. M.

2002-01-18

373

Observations of a dynamical-to-kinematic diffraction transition in plastically deformed polycrystalline intermetallic YCu  

SciTech Connect

Unlike most intermetallic compounds, polycrystalline YCu, a B2 (CsCl-type) intermetallic, is ductile at room temperature. The mechanisms for this behavior are not fully understood. In situ neutron diffraction was used to investigate whether a stress-induced phase transformation or twinning contribute to the ductility; however, neither mechanism was found to be active in YCu. Surprisingly, this study revealed that the intensities of the diffraction peaks increased after plastic deformation. It is thought that annealing the samples created nearly perfect crystallinity, and subsequent deformation reduced this high degree of lattice coherency, resulting in a modified mosaic structure that decreased or eliminated the extinction effect. Analysis of changes in diffraction peak intensity showed a region of primary plasticity that exhibits significant changes in diffraction behavior. Fully annealed samples initially contain diffracting volumes large enough to follow the dynamical theory of diffraction. When loaded beyond the yield point, dislocation motion disrupts the lattice perfection, and the diffracting volume is reduced to the point that diffraction follows the kinematic theory of diffraction. Since the sample preparation and deformation mechanisms present in this study are common in numerous material systems, this dynamical to kinematic diffraction transition should also be considered in other diffraction experiments. These measurements also suggest the possibility of a new method of investigating structural characteristics. (C) 2014 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.

Williams, Scott H. [Ames Laboratory; Brown, Donald W. [Los Alamos National Laboratory; Clausen, Bjorn [Los Alamos National Laboratory; Russell, Alan [Ames Laboratory; Gschneidner Jr., Karl A. [Ames Laboratory

2014-03-01

374

Influence of pH and counteranion on the structure of tropolonato-lead(II) complexes: structural and infrared characterization of formed lead compounds.  

PubMed

Reactions of tropolone with lead(II) trifluoromethanesulfonate, perchlorate, and nitrate in water/methanol mixtures at pH below 1.0 lead to the formation of three different polymeric lead(II) complexes, [Pb(trop)(CF3SO3)(H2O)]n (1), [Pb3(trop)4(ClO4)2]n (2), and [Pb2(trop)2(NO3)2(CH3OH)]n (3), respectively. On the other hand, if the reactions are performed at pH above 2.0, the dimeric compound [Pb(trop)2]2 (4) is obtained independently of the lead(II) salt used, as long as lead(II) does not form any strong complexes with the counterion. The crystal structures of these compounds have been determined by single-crystal X-ray diffraction. The structure of solid tetrakis(tropolonato)lead(IV), Pb(trop)4 (5), has been studied by means of the EXAFS technique because it was not possible to obtain sufficiently large single crystals. In the polymeric structures, the counterions are coordinated to the lead(II) ions and act as bridges. The tropolonato ligand behaves as a chelating agent and a tri- or tetraconnective bridge. The total coordination number of the lead(II) ion is five in compound 4, seven in 1 and 3, and eight in 2, and the lead(IV) ion in 5 is eight-coordinated. The 6s2 lone electron pair on the lead(II) ion seems to be stereochemically active in all lead(II) complexes studied. All compounds have been characterized by IR spectroscopy as well. PMID:17474735

Lyczko, Krzysztof; Starosta, Wojciech; Persson, Ingmar

2007-05-28

375

Intermetallic alloy welding wires and method for fabricating the same  

DOEpatents

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

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

1996-01-01

376

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

377

Complex magnetoelastic properties in the frustrated kagome-staircase compounds (Co1-xNix)3V2O8  

Microsoft Academic Search

High-resolution heat-capacity and thermal-expansion measurements on single crystals of the kagome-staircase compounds (Co1-xNix)3V2O8 are presented. The parent compounds Co3V2O8 and Ni3V2O8 undergo a sequence of first- and second-order magnetic phase transitions. The low-temperature (T<=40 K) magnetic entropy evolves monotonically with the doping content x from the full value expected for Ni2+ S=1 magnetic moments in Ni3V2O8 to only half the

Q. Zhang; W. Knafo; P. Adelmann; P. Schweiss; K. Grube; N. Qureshi; Th. Wolf; H. V. Löhneysen; C. Meingast

2011-01-01

378

Intermetallic crystal structures as foams. Beyond frank-kasper.  

PubMed

In many intermetallic structures, the atoms and bonds divide space into tilings by tetrahedra. The well-known Frank-Kasper phases are examples. The dual tilings divide space into a tiling by polyhedra that is topologically a foam. The number of faces of the dual polyhedron corresponds to the atom coordination number in the direct structure, and face sharing by adjacent polyhedra corresponds to bonds in the direct structure. A number of commonly occurring intermetallic crystal structures are shown as their duals. A major advantage of this alternative mode of depiction is that coordination of all of the atoms can be seen simultaneously. PMID:25247234

Bonneau, Charlotte; O'Keeffe, Michael

2015-02-01

379

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

SciTech Connect

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

Chow, Tina Kuo Fung.

1992-05-01

380

Facile route for the preparation of ordered intermetallic Pt3Pb-PtPb core-shell nanoparticles and its enhanced activity for alkaline methanol and ethanol oxidation  

NASA Astrophysics Data System (ADS)

Pt3Pb(core)-PtPb(shell) intermetallic compound nanoparticles (NPs) were synthesized on carbon black (CB) by converting nanocrystalline Pt to an ordered intermetallic compound with the reduction of Pb ions. The Pt3Pb-PtPb core-shell NPs were characterized by analyzing their crystal structures with powder X-ray diffraction (pXRD), hard X-ray photoemission spectroscopy (HX-PES), and transmission electron microscopy (TEM). The synthesized NPs exhibited enhanced catalytic activity and relatively stable cycle performance towards methanol (MeOH) and ethanol (EtOH) oxidation in an alkaline aqueous solution. The improved catalytic performance of the Pt3Pb-PtPb core-shell NPs might be attributed to both the enhancement of EtOH dehydrogenation and the higher concentration of surface OHads at lower potential on the modified PtPb surface in the Pt3Pb-PtPb core-shell NPs.

Gunji, Takao; Tanabe, Toyokazu; Jeevagan, Arockiam John; Usui, Sho; Tsuda, Takashi; Kaneko, Shingo; Saravanan, Govindachetty; Abe, Hideki; Matsumoto, Futoshi

2015-01-01

381

Metal complexes of ONO donor Schiff base ligand as a new class of bioactive compounds: synthesis, characterization and biological evolution.  

PubMed

Present work reviews that, the synthesis of (E)-N'-((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide [L] ligand and their metal complexes. The colored complexes were prepared of type [M(2+)L]X2, where M(2+)=Mn, Co, Ni, Cu, Sr and Cd, L=(7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide, X=Cl(-). Ligand derived from the condensation of 8-formyl-7-hydroxy-4-methylcoumarin and benzohydrazide in the molar ratio 1:1 and in the molar ratio 1:2 for metal complexes have been prepared. The chelation of the ligand to metal ions occurs through the both oxygen groups, as well as the nitrogen atoms of the azomethine group of the ligand. Reactions of the Schiff base ligand with Manganese(II), Cobalt(II), Nickel(II), Copper(II), Strontium(II), and Cadmium(II) afforded the corresponding metal complexes. The structures of the obtained ligand and their respective metal complexes were elucidated by infra-red, elemental analysis, Double beam UV-visible spectra, conductometric measurements, magnetic susceptibility measurements and also thermochemical studies. The metal complex exhibits octahedral coordination geometrical arrangement. Schiff base ligand and their metal complexes were tested against antioxidants, antidiabetic and antimicrobial activities have been studied. The Schiff base metal complexes emerges effective ?-glucosidase inhibitory activity than free Schiff base ligand. PMID:24858195

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

2014-10-15

382

A method to rank order water soluble compounds according to their toxicity using Caenorhabditis elegans, a Complex Object Parametric Analyzer and Sorter, and axenic liquid media.  

PubMed

Complex Object Parametric Analyzer and Sorter (COPAS) parameters Time of Flight (TOF) and Extinction (EXT) were utilized to assess growth and development in Caenorhabditis elegans exposed to (in order of decreasing toxicity) sodium arsenite, sodium fluoride, caffeine, valproic acid, sodium borate or DMSO in C. elegans Habitation Medium (CeHM) for 72h. Using multivariate statistical modeling and unique sub sampling procedures mean p-value ratios were calculated for each compound. Comparison of mean p-value ratios and/or the percent change in mean-p value ratios to controls were utilized to assess test compound toxicity. Using this assay 5 of the 6 compounds tested (83.3%) were correctly ranked according to their toxicity based on oral rat LD50 data. Test compounds were ranked from most toxic to least toxic as follows: sodium arsenite, sodium fluoride, sodium borate, valproic acid, caffeine and DMSO. Sodium borate was found to be more toxic than caffeine and valproic acid in this bioassay. This study suggests that axenic liquid culture may be used to expose large numbers of nematodes to water soluble toxicants and the COPAS parameters TOF and EXT may be used as functional biomarkers to assess a toxin's effect on growth and development in C. elegans. PMID:19162123

Sprando, Robert L; Olejnik, Nicholas; Cinar, Hediye Nese; Ferguson, Martine

2009-04-01

383

Synthesis of cerium rich intermetallics using molten metal eutectics  

NASA Astrophysics Data System (ADS)

Metal eutectic fluxes are useful for exploratory synthesis of new intermetallic phases. In this work the use of cerium/transition metal eutectics such as: Ce/Co, Ce/Ni, and Ce/Fe have yielded many new synthetically and magnetically complex phases. Structural units that were previously observed in phases grown in La/Ni eutectic reactions have also been observed in new structures and analogs grown from cerium/transition metal eutectics. These structural units include a main group element coordinated by 9 rare-earth atoms (such as the Al Ce9 clusters seen in Ce31.0(2)Fe11.8(5)Al6.5(6) B13C4), trigonal planar FeC3 units (also seen in Ce31.0(2)Fe11.8(5)Al6.5(6)B 13C4), iron clusters capped by light elements (Fe4C 6 frustrated tetrahedral in Ce21Fe8M7C 14, and larger Fe clusters in Ce33Fe14B25 C34). Variants of these building blocks were observed in Ce10Co2B7C16 with square Co units and chains of B and C connected to them, Fe2C8 units observed in Ce7Fe2C9, and FeC4 observed in Ce4FeGa0.85Al0.15C4 and Ce4FeAlC4. Two new phases were grown from Ce/Fe eutectic, Ce33Fe 14B25C34 and Ce33Fe13B 18C34 which exhibits very similar structures, but significantly different magnetic behavior. Structurally these two phases are similar. Both crystallize in the Im-3m space group, but differ by the centering of the Fe clusters. Ce33Fe14B25C34 contains Fe clusters centered by B atoms and Al doped on the Fe2 site. In Ce33Fe13B18C34, the Fe cluster is a perfect cuboctahedron. Ce33Fe14B25 C34 exhibits mixed valent behavior of cerium at 75K and no magnetic moment on iron, where-as Ce33Fe13B18C 34 exhibits tetravalent cerium and its iron clusters undergo a ferromagnetic transition at 180K. Another borocarbide, Ce10Co2B7C 16 was synthesized from Ce/Co eutectic flux. This structure features squares of Co surrounded by chains of C and B and a sea of cerium atoms. Temperature dependent magnetic susceptibility measurements at 1 Tesla were fit to a modified Curie-Weiss law and a moment per Ce was calculated to be 2.70microB. Field dependent data were collected at 200K and 2K. Paramagnetic behavior dominated at 200K and at 2K, ferromagnetic behavior was observed. XPS measurements were used to confirm that Ce is in the 3+ oxidation state. Intermetallics containing different Fe clusters (Y5Mg 5Fe4AlSi, La6Fe10Al3Si, Ce21Fe8Al7-xSixC12, and Ce33Fe13.1Al1.1B24.8C 34) were explored as potential catalysts for conversion of methane to Carbon Nanotubes (CNT). Different growth temperatures were explored. At 690ºC, Ce33Fe14B25C34 catalyzed the growth of single walled carbon nanotubes, Ce21Fe8Al7-x SixC12 multiwalled carbon nanotubes, and all other structures did not catalyze the growth of CNT.

Tucker, Patricia Christine

384

Rare earth transition metal magnesium compounds—An overview  

NASA Astrophysics Data System (ADS)

Intermetallic rare earth-transition metal-magnesium compounds play an important role as precipitations in modern light weight alloys and as host materials for hydrogen storage applications. Recent results on the crystal chemistry, the chemical bonding peculiarities, physical properties, and hydrogenation behavior of these materials are reviewed.

Rodewald, Ute Ch.; Chevalier, Bernard; Pöttgen, Rainer

2007-05-01

385

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

PubMed

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

Wadley, Lyn; Hodgskiss, Tamaryn; Grant, Michael

2009-06-16

386

arXiv:cond-mat/0310369v227Oct2003 Magnetotransport in Single Crystal Half-Heusler Compounds  

E-print Network

arXiv:cond-mat/0310369v227Oct2003 Magnetotransport in Single Crystal Half-Heusler Compounds K, it was demonstrated in the early 1990's that a subset of the half-Heusler compounds, with the generic formula RNX (R of single crystal samples, which we report here. Many intermetallic compounds form in the Heusler structure

Aronson, Meigan

387

General one-step self-assembly of isostructural intermetallic Co(II)(3)Ln(III) cubane aggregates.  

PubMed

A new family of Co/rare-earth intermetallic cubane aggregates [Co3Ln(hmp)4(OAc)5H2O] (Ln = Dy, Ho, Er, Tm, Yb, Y) have been synthesized by self-assembly. Single-crystal X-ray diffraction analysis revealed that they are remarkably isostructural in showing a common [Co3Ln] core. Magnetic studies showed that the Dy, Er, Tm, Yb, and Y complexes are ferromagnetic. The Dy complex exhibits the largest magnetocaloric effect (-?Sm = 12.58 J kg(-1) K(-1)), which can be attributed to the large magnetic density of Dy(III). PMID:23106491

Wang, Pei; Shannigrahi, Santiranjan; Yakovlev, Nikolai L; Hor, T S Andy

2012-11-19

388

Gold(III) N-heterocyclic carbene complexes mediated synthesis of ?-enaminones from 1,3-dicarbonyl compounds and aliphatic amines.  

PubMed

A series of gold(III) N-heterocyclic carbene complexes [1-(R(1))-3-(R(2))imidazol-2-ylidene]AuBr(3) [R(1) = i-Pr, R(2) = CH(2)Ph (1c); R(1) = mesityl, R(2) = CH(2)Ph (2c); R(1) = i-Pr, R(2) = CH(2)COt-Bu (3c), and R(1) = t-Bu, R(2) = CH(2)COt-Bu (4c)] act as effective precatalysts in the synthesis of ?-enaminones from 1,3-dicarbonyl compounds and primary amines under ambient conditions. Specifically the 1c-4c complexes efficiently catalyzed the condensation of a variety of cyclic as well as acyclic 1,3-dicarbonyl compounds, namely, acetyl acetone, benzoylacetone, 2-acetylcyclopentanone, and ethyl-2-oxocyclopentanecarboxylate with primary aliphatic amines, viz., methylamine, ethylamine, n-propylamine, i-propylamine, and n-butylamine, yielding ?-enamines at room temperature. Interestingly enough, the more electrophilic gold(III) 1c-4c complexes exhibited superior activity in comparison to the gold(I) counterparts 1b-4b. A comparison along a representative 4a-c series further underscored the importance of gold in the reaction as both the gold(I) 4b and gold(III) 4c complexes were more effective than the silver analogue 4a. The density functional theory (DFT) study revealed that the strong ?-donating nature of the N-heterocyclic carbene ligand results in a strong C(carbene)-Au(III) interaction in the 1c-4c complexes. PMID:21254751

Samantaray, Manoja K; Dash, Chandrakanta; Shaikh, Mobin M; Pang, Keliang; Butcher, Ray J; Ghosh, Prasenjit

2011-03-01

389

Antiferromagnetism, structural instability and frustration in intermetallic AFe4X2 systems  

NASA Astrophysics Data System (ADS)

Magnetic systems with reduced dimensionality or frustration attract strong interest because these features lead to an increase of quantum fluctuations and often result in unusual properties. Here, we present a detailed study of the magnetic, thermodynamic, and structural properties of the intermetallic AFe4X2 compounds (A=Sc,Y,Lu,Zr; X=Si,Ge) crystallizing in the ZrFe4Si2 structure type. Our results evidence that these compounds cover the whole regime from frustrated AFM order up to an AFM quantum critical point. Susceptibility ?(T), specific heat, resistivity, and T-dependent XRD measurements were performed on polycrystalline samples. In all compounds we observed a Curie-Weiss behavior in ?(T) at high T indicating a paramagnetic moment of about 3?B/Fe. Magnetic and structural transitions as previously reported for YFe4Ge2 occur in all compounds with trivalent A. However, transition temperatures, nature of the transition as well as the relation between structural and magnetic transitions change significantly with the A element. Low TN's and large ?CW/TN ratios confirm the relevance of frustration. The results are analyzed and discussed with respect to electronic, structural and magnetic instabilities applying DFT calculations.

Rosner, Helge; Bergmann, Christoph; Weber, Katharina; Kraft, Inga; Mufti, N.; Klauss, Hans-Henning; Dellmann, T.; Woike, T.; Geibel, Christoph

2013-03-01

390

High temperature creep behavior of oxide dispersion strengthened NiAl intermetallics  

SciTech Connect

The intermetallic compound NiAl is a promising candidate material for high-temperature applications, provided its creep strength can be raised by some strengthening strategy. Oxide-dispersion strengthened (ODS) NiAl has been produced by powder-metallurgical methods and its creep behavior at temperatures up to 1,723 K (1,450 C) has been studied. Exceptional creep properties, with high stresses and stress sensitivities when compared to dispersoid-free NiAl, are found, which confirms the effectiveness of dispersion strengthening in this material. The creep behavior is interpreted in the light of creep models. Detachment-controlled models satisfactorily describe the deformation in coarse-grained ODS-NiAl, but modifications are necessary for fine-grained material. In technical terms, ODS-NiAl recommends itself as a strong, light and oxidation-resistant high-temperature alloy for applications up to 1,700 K.

Arzt, E.; Grahle, P. [Univ. of Stuttgart (Germany)] [Univ. of Stuttgart (Germany)

1998-05-01

391

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

392

Anti-Inflammatory Compounds as Ligands in Metal Complexes as Revealed in X-Ray Structural Studies  

Microsoft Academic Search

The papers which report on the crystal structures of the metal complexes containing anti-inflammatory drugs used to cure humans and other animals are critically reviewed and analyzed to search for the major structural-characteristics both for the coordination spheres and the ligand moieties. Even though this is not an exhaustive review, it appears that metal complexes of non-steroidal anti-inflammatory drugs (NSAID)

Renzo Cini

2000-01-01

393

Metal–salen complexes as efficient catalysts for the oxygenation of heteroatom containing organic compounds—synthetic and mechanistic aspects  

Microsoft Academic Search

The metal–salen complexes (metal=Mn, Cr, Fe, Ru, Co, V and Ti) find widespread use as efficient catalysts for the selective oxygenation of organic sulfides, sulfoxides and aromatic amines. The active oxidant can be generated from the metal–salen ion using PhIO, H2O2, t-BuO2H and ClO? as the oxygen source. The catalytic activity of these complexes can be finely tuned by introducing

Natarajan S. Venkataramanan; Gopi Kuppuraj; Seenivasan Rajagopal

2005-01-01

394

New insights in the cellular processing of platinum antitumor compounds, using fluorophore-labeled platinum complexes and digital fluorescence microscopy  

Microsoft Academic Search

The cellular distribution and processing pathways of two platinum compounds, modeling the antitumor drug cisplatin (cDDP) in human osteosarcoma (U2-OS) cells is reported. A [Pt(en)Cl2] entity has been covalently linked to a carboxyfluorescein diacetate (CFDA) moiety and to a dinitrophenyl (DNP) moiety. The two different constructs were administered to living cell cultures that were analyzed using digital fluorescence microscopy. The

Chris Molenaar; Jan-Maarten Teuben; Robert J. Heetebrij; Hans J. Tanke; Jan Reedijk

2000-01-01

395

Synthesis and Characterization of Aluminum–Zirconium Intermetallic Composites  

Microsoft Academic Search

The search for composite materials comes from a necessity of improving properties of conventional materials. The reaction synthesis process frequently gives products with some level of porosity that may be improved through the use of hot pressing routes. The combination of aluminum and zirconia in controlled conditions has led to a metal matrix composite with a dispersion of intermetallics, especially

Giovane Azevedo; Dagoberto Brandão Santos

2000-01-01

396

Role of intermetallic phases in localized corrosion of AA5083  

Microsoft Academic Search

The presence of intermetallic inclusions very often plays a crucial role for the susceptibility of different aluminium alloys to localized corrosion attack. The intimate details of localized corrosion of 5083 aluminium alloy have been studied in the present work. Local techniques such as scanning Kelvin probe force microscopy, in situ atomic force microscopy, scanning electron microscopy coupled with energy dispersive

Kiryl A. Yasakau; Mikhail L. Zheludkevich; Sviatlana V. Lamaka; Mario G. S. Ferreira

2007-01-01

397

Identifying Transition Metal Contribution to the Rare-Earth L2-Edge XMCD Spectra in R-T Intermetallics  

NASA Astrophysics Data System (ADS)

We report on a transition metal contribution to the rare-earth L2-edge XMCD spectrum of intermetallic rare-earth — transition metal compounds (R-T). The shape and location of this contribution is independent on both the specific rare-earth and the specific 3d metal in the compound. The evolution of the signal with the 3d content indicates that the signal is proportional to the number of T neighboring atoms around the absorbing R atom. In addition, comparison between Fe and Co Laves compounds indicates that the signal also resembles the magnetic moment of the T metal. Comparison with other R:T series shows that the presence of a T contribution is not a particularity of Laves phases but a general result.

Laguna-Marco, M. A.; Chaboy, J.; Piquer, C.; Maruyama, H.; Ishimatsu, N.; Kawamura, N.

2007-02-01

398

Operation of a two-stage treatment train for the remediation of volatile organic compounds (VOCs) from a complex air stream  

SciTech Connect

The use of aqueous biological systems to remove contaminants from waste streams has been well documented. However, in complex waste streams containing compounds of varying chemical properties, the use of only one type of treatment system may not be the best alternative. When treating a complex waste stream, the use of treatment trains, or coupled systems, may be advantageous when compared with any single technology. The purpose of this project was to design and operate a treatment train for the effective removal and biodegradation of a complex mixture of VOCs with varying chemical properties. A bench-scale system was designed consisting of a liquid bioreactor coupled to a biofilter for removal of acetone, methanol, methyl ethyl ketone, naphthalene, alpha-pinene, and toluene. The liquid bioreactor contained an aqueous medium and an inert solid support (polystyrene bioballs) which immobilized a characterized microbial population. The biofiltration portion of the system utilized the same microbial inoculum, but employed Douglas fir bark as its solid support. As the air stream bubbled into the liquid bioreactor, the VOCs were made available to the bacteria for destruction in the aqueous medium or on the polystyrene solid support. The fugitive VOCs from the liquid bioreactor were then subsequently treated by the biofiltration unit. The six-compound VOC mixture was added to the air stream via in-line syringe pump injection. Concentrations of the VOC mixture in the main influent air stream, the effluent air stream from the liquid bioreactor, the aqueous medium in the liquid bioreactor, and the effluent air stream from the biofilter were monitored on a regular basis via an on-line gas chromatograph with a flame ionization detector (GC-FID). Successful biodegradation of the complex VOC mixture was accomplished with this treatment train, the average total VOC removal efficiency being 96.2% ({+-}2.6).

Manninen, M.R.; Kleinheinz, G.T.; Niemi, B.A.; Hose, J.T.

1999-07-01

399

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

400

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

NASA Astrophysics Data System (ADS)

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

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

401

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

PubMed

Coordination compounds having formulae [AsPh4][Ln(NMA)4] (1(Ln)), Ln(NMA)3(tppo)2 (2(Ln)), Ln(NMA)3(bipyO2) (3(Ln)), Ln(NMA)3(phen) (4(Ln)) and Ln(NMA)3(terpy) (5(Ln)) (Ln = Y and some lanthanides; NMA = conjugate base of nitromalonaldehyde; tppo = triphenylphosphine oxide; bipyO2 = 2,2'-bipyridine-N,N'-dioxide; phen = 1,10-phenanthroline; terpy = 2,2':6',2''-terpyridine) were synthesized and characterized and X-ray diffraction data were collected for [AsPh4][Y(NMA)4] (1(Y)). The neutral europium derivatives showed appreciable luminescence in the solid state upon excitation with UV light and photoluminescence measurements were carried out. These compounds were used as dopants for the preparation of luminescent poly(methyl methacrylate). Luminescent polyvinylpyrrolidone samples were obtained by reacting the pure polymer with water solutions containing NMA and trivalent europium ions. PMID:24873972

Bortoluzzi, Marco; Bianchin, Elena; Roppa, Stefania; Bertolasi, Valerio; Enrichi, Francesco

2014-07-14

402

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

PubMed

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

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

2014-09-01

403

Superconductivity in the Heusler family of intermetallics  

NASA Astrophysics Data System (ADS)

Several physical properties of the superconducting Heusler compounds, focusing on two systems (Sc, Y, Lu)Pd2Sn and APd2M, where A = Hf, Zr and M = Al, In, are summarized and compared. The analysis of the data shows the importance of the electron-phonon coupling for superconductivity in this family. We report the superconducting parameters of YPd2Sn, which has the highest Tc among all known Heusler superconductors.

Klimczuk, T.; Wang, C. H.; Gofryk, K.; Ronning, F.; Winterlik, J.; Fecher, G. H.; Griveau, J.-C.; Colineau, E.; Felser, C.; Thompson, J. D.; Safarik, D. J.; Cava, R. J.

2012-05-01

404

Hyperfine interactions in R x Gd1 - x Fe3 intermetallics R = Tb, Y  

NASA Astrophysics Data System (ADS)

The structural and magnetic properties of rare earth iron intermetallic compounds Tb x Gd1- x Fe3 and Y x Gd1- x Fe3 ( x = 0. 0, 0. 1, 0. 2, 0. 4, 0. 5, 0. 6, 0. 8, 1. 0) was studied by X-ray diffraction, the 57Fe Mössbauer effect and SQUID measurements. All investigated compounds crystallize in the rhombohedral PuNi3-type of crystal structure. The investigation of magnetic properties of R x Gd1- x Fe3 proved their ferrimagnetic behavior. The Curie temperature of the investigated compounds decreases with the increase of R concentration from 721K (GdFe3) to 655K (TbFe3) and 533K (YFe3). The saturation magnetic moment MS in the R x Gd 1- x Fe3 system increase with x parameter. The Mössbauer spectra are analyzed using four sextets, corresponding to three crystallographically (b, c, h) and four magnetically (b, c, h1, h2) inequivalent sites for iron. The mean hyperfine magnetic field increases with increase of the Gd concentration

Ka?zio?ka-Gawe?, M.; Bajorek, A.

2014-04-01

405

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

SciTech Connect

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

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

2012-01-01

406

Suitability of dye–clay complexes for removal of non-ionic organic compounds from aqueous solutions  

Microsoft Academic Search

Aqueous sorption of phenol, atrazine and naphthalene was measured on complexes formed from Na-montmorillonite (Fischer bentonite) and the organic cationic dyes crystal violet and rhodamine-B. Sorption isotherms were found to be non-linear. This agrees well with the rigid nature of the dye–clay organic coverage, which provides a finite surface for adsorption. High values of organic carbon-normalized distribution coefficients reached 20,000–25,000

Mikhail Borisover; Ellen R. Graber; Fernando Bercovich; Zev Gerstl

2001-01-01

407

A diffraction based study of the deformation mechanisms in anomalously ductile B2 intermetallics  

NASA Astrophysics Data System (ADS)

For many decades, the brittle nature of most intermetallic compounds (e.g. NiAl) has been the limiting factor in their practical application. Many B2 (CsCl prototypical structure) intermetallics are known to exhibit slip on the <001>{110} slip mode, which provides only 3 independent slip systems and, hence, is unable to satisfy the von Mises (a.k.a. Taylor) criterion for polycrystalline ductility. As a result, inherent polycrystalline ductility is unexpected. Recent discovery of a number of ductile B2 intermetallics has raised questions about possible violation of the von Mises criterion by these alloys. These ductile intermetallic compounds are MR (metal (M) combined with a rare earth metal or group IV refractory metal (R)) alloys and are stoichiometric, ordered compounds. Single crystal slip trace analyses have only identified the presence of <100>{011} or <100>{010} slip systems. More than 100 other B2 MR compounds are known to exist and many of them have already been shown to be ductile (e.g., CuY, AgY, CuDy, CoZr, CoTi, etc.). Furthermore, these alloys exhibit a large Bauschinger effect. The present work uses several diffraction based techniques including electron back scattered diffraction (EBSD), X-ray diffraction (XRD) and in-situ neutron diffraction; in conjunction with scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical testing, and crystal plasticity modeling, to elucidate the reason for ductility in select B2 alloys, explore the spread of this ductility over the B2 family, and understand the Bauschinger effect in these alloys. Several possible explanations (e.g., slip of <111> dislocations, strong texture, phase transformations and twinning) for the anomalous ductility were explored. An X-ray diffraction based analysis ruled out texture, phase purity and departure from order as explanations for the anomalous ductility in MR alloys. In-situ neutron diffraction and post deformation SEM, EBSD, and TEM were unable to detect any evidence for phase transformations in CoTi and CoZr. Also, post deformation characterization did not reveal any evidence of twinning. However, TEM based g·b analysis and EBSD based in-grain misorientation axis (IGMA) analysis showed that beyond a transition in the strain hardening behavior in CoTi, slip modes involving dislocations with <110> and <111> Burgers vectors are activated. The slip of such dislocations can reduce stress concentrations that could otherwise lead to premature fracture, thus providing a satisfying explanation for the anomalous ductility of CoTi and related compounds, like CoZr. Dislocation self-energy calculations accounting for elastic anisotropy suggest that the choice of slip direction in these alloys is mobility-, rather than source-, limited. The reach of this "ductilizing effect" over B2 alloys was explored by producing, characterizing, and testing a number of simple metal-rare earth metal compounds, namely MgY, MgNd and MgCe. MgR intermetallics with the B2 structure were found to be brittle and exhibit a cleavage type fracture indicating that the ductilizing effect is not as widespread as was initially thought. MgY and MgNd were found to primarily cleave along the {100} planes, while MgCe was found to cleave on the {111} planes. A large Bauschinger effect was observed in several of the anomalously ductile B2 compounds, such that the material actually begins to yield in the reverse direction on unloading. When only the primary slip mode <100>{011} is active in CoZr (prior to a transition in strain hardening), the buildup of intergranular stresses is large and is chiefly responsible for the observed Bauschinger effect. However, past the aforementioned transition in strain hardening, the effect of intergranular stresses diminishes. The results demonstrate that the activation of hard, secondary slip modes causes the internal strains to develop more uniformly among the grains, thus reducing the intergranular stresses which cause the Bauschinger effect. Crystal plas

Mulay, Rupalee Prashant

408

Gd2Au2Cd : A Mo2FeB2 -type intermetallic with ferromagnetic ordering and spin glass anomalies  

NASA Astrophysics Data System (ADS)

The ternary intermetallic compound Gd2Au2Cd , synthesized by reaction of the elements via inductive melting, is studied for its structural and physical properties. Gd2Au2Cd crystallizes with the Mo2FeB2 type (an ordered derivative of U3Si2 structure), space group P4/mbm . The magnetic measurements (ac and dc susceptibility) establish magnetic ordering (To) at 110K and have been confirmed by both transport (resistivity ? ;) and calorimetric (heat capacity, C ) measurements. ac susceptibility measurements indicate “spin-glass” type anomalies below To . The nature of magnetic ordering and the low-temperature behavior in this compound have been investigated in detail.

Rayaprol, S.; Pöttgen, R.

2006-06-01

409

Cyclometalated iridium(III) complexes containing hydroxide/chloride ligands: isolation of heterobridged dinuclear iridium(III) compounds containing ?-OH and ?-pyrazole ligands.  

PubMed

The reaction of the cyclometalated chloro-bridged iridium(III) dimers [(ppy)(2) Ir(?-Cl)](2) (ppyH = 2-phenyl pyridine) and [(tpy)(2)Ir(?-Cl)](2) (tpyH = 2-p-tolylpyridine) with 3,5-diphenylpyrazole (Ph(2)PzH) in the presence of sodium methoxide resulted in the formation of heterobridged dimers [(ppy)(2)Ir(?-OH)(?-Ph(2)Pz)Ir(ppy)(2)] (1) and [(tpy)(2)Ir(?-OH)(?-Ph(2)Pz)Ir(tpy)(2)] (2). Interestingly, the reaction of [(ppy)(2)Ir(?-Cl)](2) with 3(5)-methyl-5(3)-phenylpyrazole (PhMePzH) afforded both a heterobridged dimer, [(ppy)(2)Ir(?-OH)(?-PhMePz)Ir(ppy)(2)] (3), and the monomer [(ppy)(2)Ir(PhMePz)Cl] (4). The compound [(ppy)(2)Ir(PhMePz)OH] (5) containing a terminal OH was obtained in a hydrolysis reaction involving 4, sodium methoxide, and PhMePzH. Complexes 1-5 were characterized by X-ray crystallography and electrospray ionization high-resolution mass spectrometry. All of the complexes are luminescent at room temperature in their dichloromethane solutions. The luminescence of the dinuclear complexes is characterized by a single structureless band centered at ?(max) = 550 nm (1 and 3) and 546 nm (2). The emission spectra of the mononuclear complexes 4 and 5 display vibronic structures with their ?(max) values at 497 nm (4) and 513 nm (5). In each case, the main emission bands are accompanied by shoulder bands at 526 (4) and 534 nm (5). The quantum yields, calculated with reference to [Ir(ppy)(2)(bpy)]PF(6) (?(CH(3)CN) = 0.0622), range from 0.11 to 0.17 for the dinuclear complexes and 0.045 to 0.048 for the mononuclear complexes. The lifetimes of the emission are in the microsecond region, suggesting the phosphorescent nature of the emission. Density functional theory (DFT) and time-dependent DFT calculations were performed on complexes 1 and 4 in the ground state to gain insight into the structural, electronic, and photophysical properties. Electrochemical studies on complexes 1-3 showed the presence of two consecutive one-electron-oxidation processes, assigned as the stepwise oxidation of the two Ir(III) centers, i.e., Ir(III)-Ir(III)/Ir(III)-Ir(IV) and Ir(III)-Ir(IV)/Ir(IV)-Ir(IV) couples, respectively. The monomers displayed single-oxidation peaks. No reduction process was observed within the solvent cathodic potential limit. PMID:23013461

Chandrasekhar, Vadapalli; Mahanti, Bani; Bandipalli, Priyanka; Bhanuprakash, Kotamarthi

2012-10-15

410

Grain boundary intermetallic phases in alloy 718  

Microsoft Academic Search

A nickel base superalloy which is widely used in power generation applications, Alloy 718, was studied by analytical electron microscopy in order to elucidate the development of the complex microstructure which is produced during a typical multistage thermal treatment. The distribution of delta, gamma (double prime), gamma (prime) and Laves phases was found to be strongly dependent on aging treatment.

M. G. Burke; M. K. Miller

1990-01-01

411

Grain boundary intermetallic phases in alloy 718  

NASA Astrophysics Data System (ADS)

A nickel base superalloy which is widely used in power generation applications, Alloy 718, was studied by analytical electron microscopy in order to elucidate the development of the complex microstructure which is produced during a typical multistage thermal treatment. The distribution of delta, gamma (double prime), gamma (prime) and Laves phases was found to be strongly dependent on aging treatment.

Burke, M. G.; Miller, M. K.

412

Iridium complex catalyzed germylative coupling reaction between alkynes and iodogermanes--a new route to alkynylgermanium and alkynylgermasilicon compounds.  

PubMed

The new reaction of terminal alkynes with iodogermanes proceeding in the presence of an Ir(I)-complex [{Ir(?-Cl)(CO)2}2] (I) and NEt((i)Pr)2, as a hydrogen iodide acceptor, leads to the formation of functionalized alkynylgermanes. This reaction occurs via direct activation of the C(sp)-H bond in the starting alkyne. Detailed stoichiometric experiments using [Ir(cod)(CCPh)(PCy3)] (IVa) and iodogermane were performed and resulted in a proposal of a reasonable mechanism for the germylative coupling reaction between alkynes and iodogermanes. PMID:25286331

Rzonsowska, Monika; Kownacki, Ireneusz; Dudziec, Beata; Marciniec, Bogdan

2014-11-28

413

Volatilizable Biogenic Organic Compounds (VBOCs) with two dimensional Gas Chromatography-Time of Flight Mass Spectrometry (GC × GC-TOFMS): sampling methods, VBOC complexity, and chromatographic retention data  

NASA Astrophysics Data System (ADS)

Two dimensional gas chromatography (GC × GC) with detection by time-of-flight mass spectrometry (TOFMS) was applied in the rapid analysis of air samples containing highly complex mixtures of volatilizable biogenic organic compounds (VBOCs). VBOC analytical methodologies are briefly reviewed, and optimal conditions are discussed for sampling with both adsorption/thermal desorption (ATD) cartridges and solid-phase microextraction (SPME) fibers. Air samples containing VBOC emissions from leaves of two tree species (Cedrus atlantica and Calycolpus moritzianus) were obtained by both ATD and SPME. The optimized gas chromatographic conditions utilized a 45 m, 0.25 mm I.D. low-polarity primary column (DB-VRX, 1.4 ?m film) and a 1.5 m, 0.25 mm I.D. polar secondary column (StabilwaxTM, 0.25 ?m film). Excellent separation was achieved in a 36 min temperature programmed GC × GC chromatogram. Thousands of VBOC peaks were present in the sample chromatograms; hundreds of tentative identifications by NIST mass spectral matching are provided. Very few of the tentatively identified compounds are currently available as authentic standards. Minimum detection limit values for a 5 l ATD sample were 3.5 pptv (10 ng m-3) for isoprene, methyl vinyl ketone, and methacrolein, and ~1.5 pptv (~10 ng m-3) for monoterpenes and sesquiterpenes. Kovats-type chromatographic retention index values on the primary column and relative retention time values on the secondary column are provided for 21 standard compounds and for 417 tentatively identified VBOCs. 19 of the 21 authentic standard compounds were found in one of the Cedrus atlantica SPME samples. In addition, easily quantifiable levels of at least 13 sesquiterpenes were found in an ATD sample obtained from a branch enclosure of Calycolpus moritzianus. Overall, the results obtained via GC × GC-TOFMS highlight an extreme, and largely uncharacterized diversity of VBOCs, consistent with the hypothesis that sesquiterpenes and other compounds beyond the current list of typically determined VBOC analytes may well be important contributors to global atmospheric levels of organic particulate matter.

Pankow, J. F.; Luo, W.; Melnychenko, A. N.; Barsanti, K. C.; Isabelle, L. M.; Chen, C.; Guenther, A. B.; Rosenstiel, T. N.

2012-02-01

414

Volatilizable biogenic organic compounds (VBOCs) with two dimensional gas chromatography-time of flight mass spectrometry (GC × GC-TOFMS): sampling methods, VBOC complexity, and chromatographic retention data  

NASA Astrophysics Data System (ADS)

Two dimensional gas chromatography (GC × GC) with detection by time-of-flight mass spectrometry (TOFMS) was applied in the rapid analysis of air samples containing highly complex mixtures of volatilizable biogenic organic compounds (VBOCs). VBOC analytical methodologies are briefly reviewed, and optimal conditions are discussed for sampling with both adsorption/thermal desorption (ATD) cartridges and solid-phase microextraction (SPME) fibers. Air samples containing VBOC emissions from leaves of two tree species (Cedrus atlantica and Calycolpus moritzianus) were obtained by both ATD and SPME. The optimized gas chromatographic conditions utilized a 45 m, 0.25 mm I.D. low-polarity primary column (DB-VRX, 1.4 ?m film) and a 1.5 m, 0.25 mm I.D. polar secondary column (Stabilwax® 0.25 ?m film). Excellent separation was achieved in a 36 min temperature programmed GC × GC chromatogram. Thousands of VBOC peaks were present in the sample chromatograms; hundreds of tentative identifications by NIST mass spectral matching are provided. Very few of the tentatively identified compounds are currently available as authentic standards. Method detection limit values for a 5 l ATD sample were 3.5 pptv (10 ng m-3) for isoprene, methyl vinyl ketone, and methacrolein, and ~1.5 pptv (~10 ng m-3) for monoterpenes and sesquiterpenes. Kovats-type chromatographic retention index values on the primary column and relative retention time values on the secondary column are provided for 21 standard compounds and for 417 tentatively identified VBOCs. 19 of the 21 authentic standard compounds were found in one of the Cedrus atlantica SPME samples. In addition, easily quantifiable levels of at least 13 sesquiterpenes were found in an ATD sample obtained from a branch enclosure of Calycolpus moritzianus. Overall, the results obtained via GC × GC-TOFMS highlight an extreme, and largely uncharacterized diversity of VBOCs, consistent with the hypothesis that sesquiterpenes and other compounds beyond the current list of typically determined VBOC analytes may well be important contributors to global atmospheric levels of organic particulate matter.

Pankow, J. F.; Luo, W.; Melnychenko, A. N.; Barsanti, K. C.; Isabelle, L. M.; Chen, C.; Guenther, A. B.; Rosenstiel, T. N.

2011-06-01

415

193 nm ultraviolet photodissociation mass spectrometry for the structural elucidation of lipid A compounds in complex mixtures.  

PubMed

Here we implement ultraviolet photodissociation (UVPD) in an online liquid chromatographic tandem mass spectrometry (MS/MS) strategy to support analysis of complex mixtures of lipid A combinatorially modified during development of vaccine adjuvants. UVPD mass spectrometry at 193 nm was utilized to characterize the structures and fragment ion types of lipid A from Escherichia coli, Vibrio cholerae, and Pseudomonas aeruginosa using an Orbitrap mass spectrometer. The fragment ions generated by UVPD were compared to those from collision induced dissociation (CID) and higher energy collision dissociation (HCD) with respect to the precursor charge state. UVPD afforded the widest array of fragment ion types including acyl chain C-O, C-N, and C-C bond cleavages and glycosidic C-O and cross ring cleavages, thus providing the most comprehensive structural analysis of the lipid A. UVPD exhibited virtually no dependence on precursor ion charge state and was best at determining lipid A structure including acyl chain length and composition, giving it an advantage over collision based methods. UVPD was incorporated into an LC-MS/MS methodology for the analysis of a number of structural variants in a complex mixture of combinatorially engineered Escherichia coli lipid A. PMID:24446701

O'Brien, John P; Needham, Brittany D; Henderson, Jeremy C; Nowicki, Emily M; Trent, M Stephen; Brodbelt, Jennifer S

2014-02-18

416

Complex Physiology and Compound Stress Responses during Fermentation of Alkali-Pretreated Corn Stover Hydrolysate by an Escherichia coli Ethanologen  

PubMed Central

The physiology of ethanologenic Escherichia coli grown anaerobically in alkali-pretreated plant hydrolysates is complex and not well studied. To gain insight into how E. coli responds to such hydrolysates, we studied an E. coli K-12 ethanologen fermenting a hydrolysate prepared from corn stover pretreated by ammonia fiber expansion. Despite the high sugar content (?6% glucose, 3% xylose) and relatively low toxicity of this hydrolysate, E. coli ceased growth long before glucose was depleted. Nevertheless, the cells remained metabolically active and continued conversion of glucose to ethanol until all glucose was consumed. Gene expression profiling revealed complex and changing patterns of metabolic physiology and cellular stress responses during an exponential growth phase, a transition phase, and the glycolytically active stationary phase. During the exponential and transition phases, high cell maintenance and stress response costs were mitigated, in part, by free amino acids available in the hydrolysate. However, after the majority of amino acids were depleted, the cells entered stationary phase, and ATP derived from glucose fermentation was consumed entirely by the demands of cell maintenance in the hydrolysate. Comparative gene expression profiling and metabolic modeling of the ethanologen suggested that the high energetic cost of mitigating osmotic, lignotoxin, and ethanol stress collectively limits growth, sugar utilization rates, and ethanol yields in alkali-pretreated lignocellulosic hydrolysates. PMID:22389370

Schwalbach, Michael S.; Tremaine, Mary; Marner, Wesley D.; Zhang, Yaoping; Bothfeld, William; Higbee, Alan; Grass, Jeffrey A.; Cotten, Cameron; Reed, Jennifer L.; da Costa Sousa, Leonardo; Jin, Mingjie; Balan, Venkatesh; Ellinger, James; Dale, Bruce; Kiley, Patricia J.

2012-01-01

417

Complex physiology and compound stress responses during fermentation of alkali-pretreated corn stover hydrolysate by an Escherichia coli ethanologen.  

PubMed

The physiology of ethanologenic Escherichia coli grown anaerobically in alkali-pretreated plant hydrolysates is complex and not well studied. To gain insight into how E. coli responds to such hydrolysates, we studied an E. coli K-12 ethanologen fermenting a hydrolysate prepared from corn stover pretreated by ammonia fiber expansion. Despite the high sugar content (?6% glucose, 3% xylose) and relatively low toxicity of this hydrolysate, E. coli ceased growth long before glucose was depleted. Nevertheless, the cells remained metabolically active and continued conversion of glucose to ethanol until all glucose was consumed. Gene expression profiling revealed complex and changing patterns of metabolic physiology and cellular stress responses during an exponential growth phase, a transition phase, and the glycolytically active stationary phase. During the exponential and transition phases, high cell maintenance and stress response costs were mitigated, in part, by free amino acids available in the hydrolysate. However, after the majority of amino acids were depleted, the cells entered stationary phase, and ATP derived from glucose fermentation was consumed entirely by the demands of cell maintenance in the hydrolysate. Comparative gene expression profiling and metabolic modeling of the ethanologen suggested that the high energetic cost of mitigating osmotic, lignotoxin, and ethanol stress collectively limits growth, sugar utilization rates, and ethanol yields in alkali-pretreated lignocellulosic hydrolysates. PMID:22389370

Schwalbach, Michael S; Keating, David H; Tremaine, Mary; Marner, Wesley D; Zhang, Yaoping; Bothfeld, William; Higbee, Alan; Grass, Jeffrey A; Cotten, Cameron; Reed, Jennifer L; da Costa Sousa, Leonardo; Jin, Mingjie; Balan, Venkatesh; Ellinger, James; Dale, Bruce; Kiley, Patricia J; Landick, Robert

2012-05-01

418

193 nm Ultraviolet Photodissociation Mass Spectrometry for the Structural Elucidation of Lipid A Compounds in Complex Mixtures  

PubMed Central

Here we implement ultraviolet photodissociation (UVPD) in an online liquid chromatographic tandem mass spectrometry (MS/MS) strategy to support analysis of complex mixtures of lipid A combinatorially modified during development of vaccine adjuvants. UVPD mass spectrometry at 193 nm was utilized to characterize the structures and fragment ion types of lipid A from Escherichia coli, Vibrio cholerae, and Pseudomonas aeruginosa using an Orbitrap mass spectrometer. The fragment ions generated by UVPD were compared to those from collision induced dissociation (CID) and higher energy collision dissociation (HCD) with respect to the precursor charge state. UVPD afforded the widest array of fragment ion types including acyl chain C–O, C–N, and C–C bond cleavages and glycosidic C–O and cross ring cleavages, thus providing the most comprehensive structural analysis of the lipid A. UVPD exhibited virtually no dependence on precursor ion charge state and was best at determining lipid A structure including acyl chain length and composition, giving it an advantage over collision based methods. UVPD was incorporated into an LC–MS/MS methodology for the analysis of a number of structural variants in a complex mixture of combinatorially engineered Escherichia coli lipid A. PMID:24446701

2015-01-01

419

Structures of KcsA in complex with symmetrical quaternary ammonium compounds reveal a hydrophobic binding site.  

PubMed

Potassium channels allow for the passive movement of potassium ions across the cell membrane and are instrumental in controlling the membrane potential in all cell types. Quaternary ammonium (QA) compounds block potassium channels and have long been used to study the functional and structural properties of these channels. Here we describe the interaction between three symmetrical hydrophobic QAs and the prokaryotic potassium channel KcsA. The structures demonstrate the presence of a hydrophobic pocket between the inner helices of KcsA and provide insight into the binding site and blocking mechanism of hydrophobic QAs. The structures also reveal a structurally hidden pathway between the central cavity and the outside membrane environment reminiscent of the lateral fenestration observed in sodium channels that can be accessed through small conformational changes in the pore wall. We propose that the hydrophobic binding pocket stabilizes the alkyl chains of long-chain QA molecules and may play a key role in hydrophobic drug binding in general. PMID:25093676

Lenaeus, Michael J; Burdette, Dylan; Wagner, Tobias; Focia, Pamela J; Gross, Adrian

2014-08-19

420

Grain boundary intermetallic phases in alloy 718  

SciTech Connect

A nickel base superalloy which is widely used in power generation applications, Alloy 718, has been studied by analytical electron microscopy in order to elucidate the development of the complex microstructure which is produced during a typical multistage thermal treatment. The distribution of {delta}, {gamma}{double prime}, {gamma}{prime} and Laves phases was found to be strongly dependent on aging treatment. 7 refs., 5 figs.

Burke, M.G. (Westinghouse Electric Corp., Pittsburgh, PA (USA). Science and Technology Center); Miller, M.K. (Oak Ridge National Lab., TN (USA))

1990-01-01

421

Molecularly Imprinted Polymers for Selective Analysis of Chemical Warfare Surrogate and Nuclear Signature Compounds in Complex Matrices  

SciTech Connect

This paper describes the preparation and evaluation of molecularly imprinted polymers (MIPs) that display specificity toward diisopropyl methylphosphonate (DIMP) and tributyl phosphate (TBP). Polymer activity was assessed by solid-phase extraction and high-performance liquid chromatography experiments. Both DIMP- and TBP-specific MIPs selectively retained their targets relative to a nonimprinted control. Proof-of-principle experiments demonstrated highly selective analysis of the targets from fortified complex matrix samples (diesel fuel, gasoline, and air extract concentrate). The retained MIP fractions gave near quantitative recovery of the target analytes with very low matrix background content. The same fraction from the control sorbent was less pure and recovered only about half of the analyte.

Harvey, Scott D.

2005-08-01

422

Site preference, magnetism and lattice vibrations of intermetallics Lu2Fe17-xTx (T=Cr, Mn, Ru)  

NASA Astrophysics Data System (ADS)

We present an atomistic study on the phase stability, site preference and lattice constants of the rare earth intermetallics Lu2Fe17-xTx (T=Cr, Mn, Ru). The calculated preferential occupation site of ternary element T is found to be the 4f site. The order of site preference is given as 4f, 12k, 12j and 6g for Lu2Fe17-xTx. The calculated lattice parameters are corresponding to the experimental results. We have calculated the magnetic moments of Lu2Fe17-xTx compounds. Results show that the calculated total magnetic moment of Lu2Fe17 compound is M=37.34 ?B/f.u. In addition, the total and partial phonon densities of states are evaluated first for these complicated structures.

Li, Jin-Chun; Qian, Ping; Zhang, Zhen-Feng; Yuan, Xiao-Jian; Wang, Yi-Wen; Shen, Jiang; Chen, Nan-Xian

2013-05-01

423

Activated charcoal-mediated RNA extraction method for Azadirachta indica and plants highly rich in polyphenolics, polysaccharides and other complex secondary compounds  

PubMed Central

Background High quality RNA is a primary requisite for numerous molecular biological applications but is difficult to isolate from several plants rich in polysaccharides, polyphenolics and other secondary metabolites. These compounds either bind with nucleic acids or often co-precipitate at the final step and many times cannot be removed by conventional methods and kits. Addition of vinyl-pyrollidone polymers in extraction buffer efficiently removes polyphenolics to some extent, but, it failed in case of Azadirachta indica and several other medicinal and aromatic plants. Findings Here we report the use of adsorption property of activated charcoal (0.03%–0.1%) in RNA isolation procedures to remove complex secondary metabolites and polyphenolics to yield good quality RNA from Azadirachta indica. We tested and validated our modified RNA isolation method across 21 different plants including Andrographis paniculata, Aloe vera, Rosa damascena, Pelargonium graveolens, Phyllanthus amarus etc. from 13 other different families, many of which are considered as tough system for isolating RNA. The A260/280 ratio of the extracted RNA ranged between 1.8-2.0 and distinct 28S and 18S ribosomal RNA bands were observed in denaturing agarose gel electrophoresis. Analysis using Agilent 2100 Bioanalyzer revealed intact total RNA yield with very good RNA Integrity Number. Conclusions The RNA isolated by our modified method was found to be of high quality and amenable for sensitive downstream molecular applications like subtractive library construction and RT-PCR. This modified RNA isolation procedure would aid and accelerate the biotechnological studies in complex medicinal and aromatic plants which are extremely rich in secondary metabolic compounds. PMID:23537338

2013-01-01

424

New benzo[h]quinoline-based ligands and their pincer Ru and Os complexes for efficient catalytic transfer hydrogenation of carbonyl compounds.  

PubMed

New benzo[h]quinoline ligands (HCN'N) containing a CHRNH2 (R=H (a), Me (b), tBu (c)) function in the 2-position were prepared starting from benzo[h]quinoline N-oxide (in the case of ligand a) and 2-chlorobenzo[h]quinoline (for ligands b and c). These compounds were used to prepare ruthenium and osmium complexes, which are excellent catalysts for the transfer hydrogenation (TH) of ketones. The reaction of a with [RuCl2(PPh3)3] in 2-propanol at reflux afforded the terdentate CN'N complex [RuCl(CN'N)(PPh3)2] (1), whereas the complexes [RuCl(CN'N)(dppb)] (2-4; dppb=Ph2P(CH2)4PPh2) were obtained from [RuCl2(PPh3)(dppb)] with a-c, respectively. Employment of (R,S)-Josiphos, (S,R)-Josiphos*, (S,S)-Skewphos, and (S)-MeO-Biphep in combination with [RuCl2(PPh3)3] and ligand a gave the chiral derivatives [RuCl(CN'N)(PP)] (5-8). The osmium complex [OsCl(CN'N)(dppb)] (12) was prepared by treatment of [OsCl2(PPh3)3] with dppb and ligand a. Reaction of the chloride 2 and 12 with NaOiPr in 2-propanol/toluene afforded the hydride complexes [MH(CN'N)(dppb)] (M=Ru 10, Os 14), through elimination of acetone from [M(OiPr)(CN'N)(dppb)] (M=Ru 9, Os 13). The species 9 and 13 easily reacted with 4,4'-difluorobenzophenone, via 10 and 14, respectively, affording the corresponding isolable alkoxides [M(OR)(CN'N)(dppb)] (M=Ru 11, Os 15). The complexes [MX(CN'N)(P2)] (1-15) (M=Ru, Os; X=Cl, H, OR; P=PPh3 and P2=diphosphane) are efficient catalysts for the TH of carbonyl compounds with 2-propanol in the presence of NaOiPr (2 mol %). Turnover frequency (TOF) values up to 1.8x10(6) h(-1) have been achieved using 0.02-0.001 mol % of catalyst. Much the same activity has been observed for the Ru--Cl, --H, --OR, and the Os--Cl derivatives, whereas the Os--H and Os--OR derivatives display significantly lower activity on account of their high oxygen sensitivity. The chiral Ru complexes 5-8 catalyze the asymmetric TH of methyl-aryl ketones with TOF approximately 10(5) h(-1) at 60 degrees C, up to 97 % enatiomeric excess (ee) and remarkably high productivity (0.005 mol % catalyst loading). High catalytic activity (TOF up to 2.2x10(5) h(-1)) and enantioselectivity (up to 98 % ee) have also been achieved with the in-situ-generated catalysts prepared from [MCl2(PPh3)3], (S,R)-Josiphos or (S,R)-Josiphos*, and the benzo[h]quinoline ligands a-c. PMID:18803204

Baratta, Walter; Ballico, Maurizio; Baldino, Salvatore; Chelucci, Giorgio; Herdtweck, Eberhardt; Siega, Katia; Magnolia, Santo; Rigo, Pierluigi

2008-01-01

425

Local decomposition induced by dislocation motions inside tetragonal Al2Cu compound: slip system-dependent dynamics  

PubMed Central

Dislocations in a crystal are usually classified into several independent slip systems. Motion of a partial dislocation in monometallic crystals may remove or create stacking fault characterized with a partial of a lattice translation vector. However, it is recently known that motion of partial dislocations in complex structure, such as that inside an intermetallic Al2Cu compound, lead to a local composition deviation from its stoichiometric ratio and the resultant structure collapse. Here we report such a local decomposition behaviors are strongly dependent on slip system of dislocations. Under applied external stress, we have studied dislocation motion behaviors in the three independent slip systems of [001](110), [100]() and [110]() within tetragonal Al2Cu crystal by using molecular dynamics method. We found dislocation motions in all these slip systems result in local decomposition but their physical details differ significantly. PMID:24196169

Chen, D.; Ma, X. L.

2013-01-01

426

Effect of gallium and refractory metal substitution in 3:29 intermetallic permanent magnetic materials  

NASA Astrophysics Data System (ADS)

The search for high temperature permanent magnetic materials in recent years has led to the study of the 3:29 rare-earth transition metal intermetallic compounds. These materials have shown great promise due to their high magnetization, Curie temperature and anisotropy. They have been limited in their coercivity. The ability to tailor the microstructure of these materials particularly in the nanoscale will help harness the coercivity and have far reaching applications. In addition, their Curie temperature and magnetic anisotropy can be improved by optimizing the alloy compositions. In this thesis, we present the effect of the substitution of Co, Ga and refractory metals in Pr3Fe27.5Ti1.5 on the magnetic properties. Co was substituted to improve the Curie temperature. Ga has no magnetic but helped to serve as a grain refiner which in turn increased the anisotropy. Amorphous and nanocrystalline grains formed by melt-spinning the Ga alloys. Co and refractory metal substitutions improved the Curie temperature and anisotropy significantly. From crystal field calculations, the easy magnetization directions have been predicted for different 3:29 rare-earth substitution compounds.

Kuchimanchi, Sirisha

427

Coupling solid-phase microextraction with ambient mass spectrometry using surface coated wooden-tip probe for rapid analysis of ultra trace perfluorinated compounds in complex samples.  

PubMed

Coupling solid-phase microextraction (SPME) with ambient mass spectrometry using surface coated wooden-tip probe was achieved for the first time and applied in the analysis of ultra trace perfluorinated compounds (PFCs) in complex environmental and biological samples. We modified n-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride on the surface of sharp wooden tip via silanization to form a novel SPME probe, which was then used for highly selective enrichment of PFCs from complex matrices and applied as a solid substrate to induce electrospray ionization for mass spectrometric analysis. The porous structural surface together with the dual extraction mechanisms (reversed phase adsorption and ion exchange adsorption) demonstrated that the SPME probe has an outstanding enrichment capacity, enhancing sensitivity by approximately 4000-8000 folds for the detection in aqueous samples, and 100-500-fold in whole blood and milk samples. The method showed good linearity, with correlation coefficient values (r(2)) of no less than 0.9931 for eight target PFCs. The limits of detection and qualification of the eight PFCs were 0.06-0.59 and 0.21-1.98 ng/L, respectively. Quantification of real samples was achieved by isotope internal standard calibration curve method or isotope dilution method, and ultratrace levels of PFCs present in lake water, river water, whole blood, and milk samples had been successfully detected and qualified. PMID:25354323

Deng, Jiewei; Yang, Yunyun; Fang, Ling; Lin, Li; Zhou, Haiyun; Luan, Tiangang

2014-11-18

428

MCM-41-supported oxo-vanadium(IV) complex: a highly selective heterogeneous catalyst for the bromination of hydroxy aromatic compounds in water.  

PubMed

An ecofriendly solid catalyst has been synthesized by anchoring vanadium(IV) into organically modified MCM-41. First, the surface of Si-MCM-41 was modified with 3-aminopropyl-triethoxysilane (3-APTES), the amine group of which upon condensation with ortho-hydroxy-acetophenone affords a N(2)O(2)-type Schiff base moiety in the mesoporous matrix. The Schiff base moieties were used to anchor oxo-vanadium(IV) ions. The prepared catalyst has been characterized by UV-vis, IR spectroscopy, small-angle X-ray diffraction (SAX), nitrogen sorption, and transmission electron microscopy (TEM) studies. It is observed that the mesostructure has not been destroyed in the multistep synthesis procedure, as evidenced by SAX and TEM measurements. The catalyst has shown unprecedented high conversion as well as para selectivity toward the bromination of hydroxy aromatic compounds using aqueous 30% H(2)O(2)/KBr in water. The reaction proceeds according to the stoichiometric ratio, and the monobrominated product was obtained as the major product using a stoichiometric amount of the bromine source. The immobilized complex does not leach or decompose during the catalytic reactions, showing practical advantages over the free metal complex. PMID:22026477

Bhunia, Susmita; Saha, Debraj; Koner, Subratanath

2011-12-20

429

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

Microsoft Academic Search

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

Frank Stepniak

2001-01-01

430

EVOLUTION OF OXIDE SCALES ON FeAl GRADE 3 INTERMETALLIC F. Pedraza1  

E-print Network

EVOLUTION OF OXIDE SCALES ON FeAl GRADE 3 INTERMETALLIC ALLOY F. Pedraza1 , J.L. Grosseau-Poussard2@univ-lr.fr Abstract The ODS FeAl Grade 3 intermetallic alloy have been shown to develop