Note: This page contains sample records for the topic complex intermetallic compounds from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
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

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

SciTech Connect

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

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

1995-04-01

3

Intermetallic Compounds of Extreme Stability.  

National Technical Information Service (NTIS)

The ideas of the Engel-Brewer Correlation have been used to choose a class of intermetallic compounds as possible refractory materials. Calorimetric experiments clearly show that ZrPt3 and HfPt3 are the most thermodynamically stable intermetallics known. ...

J. Carloni J. Wu P. Ficalora V. ikrishnan

1971-01-01

4

Oxidation of advanced intermetallic compounds  

Microsoft Academic Search

Intermetallic compounds with low densities and high melting temperatures are prime structural material candidates for advanced heat engines. The close link between crystal structure and mechanical properties has led the search for new cubic pseudo-binary transition metal aluminides. Compositing leads the way for improved mechanical properties of refractory metal silicides. In all cases there is a strong competition for oxide

N. S. Bornstein

1993-01-01

5

Oxygen stabilized zirconium vanadium intermetallic compound  

DOEpatents

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

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

1982-01-01

6

THERMAL EXPANSION OF SEVERAL Sn-BASED INTERMETALLIC COMPOUNDS  

Microsoft Academic Search

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

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

1997-01-01

7

Atomic jumps in ordered intermetallic compounds  

Microsoft Academic Search

Information about elementary atomic jump in intermetallic compounds can be obtained by quasielastic Mssbauer spectroscopy, a microscopic method. High temperature 57Fe Mssbauer spectroscopy permits to separate jumps between various sublattices in non-Bravais lattice through measuring the angular dependence of diffusional line broadening. Results obtained from diffusion in B2 (FeAl) and DO3 (Fe3Si) structures and the effect of atomic disorder in

B. Sepiol

1993-01-01

8

Forging of FeAl intermetallic compounds  

SciTech Connect

Much activity has been concentrated on the development of intermetallic compounds with the aim of improving tensile ductility, fracture toughness and high notch sensitivity in order to develop an attractive combination of properties for high and low temperature applications. This paper reports experience in processing and forging of FeAl intermetallic of B2 type. During the experiments two different temperatures were employed, and the specimens were forged after annealing in air, 10{sup {minus}2} torr vacuum and argon. From the results it was learned that annealing FeAl in argon atmosphere prior to forging resulted in better deformation behavior than for the other two environments. For the higher forging temperature used in the experiments (700C), the as-cast microstructure becomes partially recrystallized.

Flores, O.; Juarez, J.; Campillo, B.; Martinez, L. [UNAM, Cuernavaca (Mexico). Lab. de Cuernavaca; Schneibel, J.H. [Oak Ridge National Lab., TN (United States)

1994-09-01

9

Mechanism of Diffusion in Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

10

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

11

Fibre-reinforced intermetallic compounds by physical vapour deposition  

Microsoft Academic Search

This paper describes work on SiC fibre-reinforced ?-Tial and MoSi2 intermetallic matrix composites (IMCs). Electron beam evaporation and vapour mixing were used to matrix-coat SiC fibre with a thick layer of intermetallic compound, and these coated fibres were successfully fabricated into IMCs. Intermetallic compounds have attractive properties for high-temperature structural applications and have been the subject of much research effort

Miriam Wood; Malcolm Ward-Close

1995-01-01

12

First-principles studies of Al-Ni intermetallic compounds  

SciTech Connect

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

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

2009-10-15

13

Gas-phase modification of rare-earth intermetallic compounds  

SciTech Connect

Recent work concerning the interstitial modification of permanent magnet alloys based on rare-earth iron intermetallic compounds is reviewed. The crystal structure of the new materials is discussed, then the thermodynamic and statistical aspects of the low-temperature interstitial modification process are considered. Finally, reaction kinetics and thermal stability of the new compounds are discussed and future prospects assessed.

Skomski, R.; Coey, J.M.D. (Trinity College, Dublin (Ireland))

1993-04-01

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

Thermochemical Investigations on Intermetallic UMe sub 3 Compounds (Me=Ru,Rh,Pd).  

National Technical Information Service (NTIS)

The subject of this thesis is the determination of the thermodynamic properties of the intermetallic compounds of uranium with the light platinum metals, ruthenium, rhodium and palladium. These intermetallics are formed as very stable compounds during fis...

G. Wijbenga

1981-01-01

16

Low Temperature Studies of Heavy Electron Intermetallic Compounds  

Microsoft Academic Search

The heavy fermion systems are a class of intermetallic compounds, the most remarkable property of which is the very large electronic contribution to the specific heat. At low temperatures, the specific heat of heavy fermion systems is usually two to three orders of magnitude larger than that of ordinary metals, and they behave like systems with very heavy quasiparticles. Their

Chao Jin

1993-01-01

17

The Reflectance of the Intermetallic Compounds Nial and Coal.  

National Technical Information Service (NTIS)

The reflectivities at normal incidence of samples of the intermetallic compounds NiAl and CoAl are presented in the photon energy region from 0.5 to 6.0 eV. The data and their interpretation are compared with those of Sambongi, Hagiwara and Yamadaya (J. P...

D. A. Kiewit J. Rechtien J. O. Brittain

1966-01-01

18

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

National Technical Information Service (NTIS)

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

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

2004-01-01

19

CO2 laser welding of titanium aluminide intermetallic compound  

Microsoft Academic Search

Titanium aluminide intermetallic compound is studied to find out good welding conditions using CO2 laser irradiation. In the experiment, we used the casting titanium aluminide containing iron, vanadium and boron with a thickness of 2 mm. We carried out bead-on-plate laser welding at various initial temperatures of specimens varied from room temperature to 873 [K] in inert gas environment filled

Gaku Kuwahara; Shigeru Yamaguchi; Kenzo Nanri; Masanori Ootani; Sachio Seto; Mikiya Arai; Tomoo Fujioka

2000-01-01

20

Intermetallic Compounds for High-Temperature Structural Use  

Microsoft Academic Search

The next generation of efficient turbines and engines will require materials that can withstand operating temperatures approaching 2000 degrees C. Intermetallic compounds with high melting temperatures are candidates for this application, but the obstacle of their limited ductility must first be overcome. Because the available data on these materials is limited, a survey of the effects of chemistry and crystal

A. I. Taub; R. L. Fleischer

1989-01-01

21

AN INVESTIGATION OF INTERMETALLIC COMPOUNDS FOR VERY HIGH TEMPERATURE APPLICATIONS  

Microsoft Academic Search

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

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

1959-01-01

22

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

Microsoft Academic Search

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.

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

1998-01-01

23

COMPUTER CONTROLLED CONTAINERLESS PROCESSING OF HIGH TEMPERATURE INTERMETALLIC COMPOUNDS  

Microsoft Academic Search

A containerless automated system for processing high temperature reactive intermetallic compounds from the liquid state has been developed. Single crystals 2.5 cm in diameter have been processed in various atmospheres from nearly turbulent liquids. The liquid is electromagnetically contained in such a fashion as to permit the propagation of the solidification interface to control the resulting dimensions and structure. The

R. D. Reviere; B. F. Oliver; D. D. Bruns

1989-01-01

24

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

25

Prediction of stable insulating intermetallic compounds  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

26

Magnetostriction and magnetic anisotropy in rare earth intermetallic compounds  

Microsoft Academic Search

An analysis of the magnetoelastic coupling and the magnetocrystalline anisotropy in rare earth intermetallic compounds has been undertaken on the basis of a microscopic description. Crystal electric field and exchange interaction have been considered as the main contribution to the free energy in order to explain the behaviour. Magnetostriction measurements on cubic (RAl2, RNi2) and uniaxial (RCo5 and R2Fe14B) compounds

M. R. Ibarra; A. del Moral

1990-01-01

27

INVESTIGATION OF INTERMETALLIC COMPOUNDS FOR VERY HIGH TEMPERATURE APPLICATIONS  

Microsoft Academic Search

Intermetallic beryllides from the systems Ta--Be, W-Be, and Hf--Be along ; with the disilicides of W, Ta, and Mo, were screened for compounds capable of ; serving as structural materials at temperatures above 2500 deg F. The compounds ; studied were TaBe. TaBe, HfBe, MoS\\/ sub 12\\/; , TaSi, and WSi. An investigation of the rates of oxidation of ;

J. Booker; R. M. Paine; A. J. Stonehouse

1960-01-01

28

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

29

Analysis of intermetallic compounds in lead-free solders  

Microsoft Academic Search

Intermetallic compounds (IMCs) are essential part of lead-free solders microstructure. In 96.5Sn3Ag0.5Cu (SAC305) solder is dominant element tin (Sn). But despite this Sn dominancy only 3% weight contain of silver (Ag) has influence on final structure of solid solder joint. Fundamental impact on strength properties of solder joint has also interaction between the solder and printed circuit board (PCB) pad.

A. Pietrikova; J. Durisin; J. Urbancik; J. Bansky

2009-01-01

30

Surface integrity on grinding of gamma titanium aluminide intermetallic compounds  

Microsoft Academic Search

Gamma-TiAl is an ordered intermetallic compound characterized by high strength to density ratio, good oxidation resistance, and good creep properties at elevated temperatures. However, it is intrinsically brittle at room temperature. This thesis investigates the potential for the use of grinding to process TiAl into useful shapes. Grinding is far from completely understood, and many aspects of the individual mechanical

Gregorio Roberto Murtagian

2004-01-01

31

High-strength, high-temperature intermetallic compounds  

Microsoft Academic Search

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

R. L. Fleischer

1987-01-01

32

Intermetallic compounds of the type MNi as methanation catalysts  

Microsoft Academic Search

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

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

1977-01-01

33

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

34

Intermetallic compoundsA new base for heat-resisting materials  

Microsoft Academic Search

1.Intermetallic compounds form a special class of inorganic compounds which is promising as a source of heat-resisting materials. They have many properties which are characteristic of metalsmechanical, physical, chemical, and others.2.Intermetallic compounds have higher melting points than their constituents, higher strength, and retain their heat resistance up to higher temperatures than metals and their solid solutions.3.Many intermetallic compounds have a

I. I. Kornilov

1967-01-01

35

Synthesis and Metallurgical Properties of Intermetallic Compounds.  

National Technical Information Service (NTIS)

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

G. W. Webb G. Arrhenius

1975-01-01

36

heats of formation of aluminum-cerium intermetallic compounds  

NASA Astrophysics Data System (ADS)

The formation heats of the intermetallic compounds of aluminum and cerium were studied using a differential direct isoperibol calorimeter. The composition and equilibrium state of the samples were confirmed by metallographic and X-ray analyses. For the various compounds, the ?Hform (for the reaction in the solid state at 300 K) was determined as follows (kJ/mol of atoms): Ce3Al: -27.0 2; CeAl: -46.0 3; CeAl2: -50.0 2; and Ce3Al11: -41.0 2. The results are discussed and compared with the values which can be found in literature.

Borzone, G.; Cacciamani, G.; Ferro, R.

1991-09-01

37

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 200-525C. 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

38

Quantum criticality in selected uranium intermetallic and organometallic compounds  

NASA Astrophysics Data System (ADS)

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

Nasreen, Farzana

39

Environmental effects on intermetallic compounds: A guide to the literature. Final report  

Microsoft Academic Search

This report is a guide to the literature on environmental effects on intermetallic compounds; primarily the aluminides of nickel, titanium, iron, and niobium. The guide relies heavily upon the proceedings of recent conferences. Brief technical discussions introduce the various topics and lead to specific sources of information. Various relevant review articles are also listed. Intermetallic compounds, Aluminides, Corrosion, Oxidation, Hydrogen

Isserow

1993-01-01

40

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

Microsoft Academic Search

The unusual high temperature properties of the ordered intermetallic compounds have made them highly desirable potential candidates for structural materials in the aerospace industry. However, the lack of ductility at ambient temperature in most of these intermetallic compounds has been the major obstacle in their applications. Very little is known about the cause of their brittleness and possible mechanisms of

Wayne Wei Lin

1991-01-01

41

Structural, Electronic and Mechanical Properties of High-Temperature Ordered Intermetallic Compounds  

Microsoft Academic Search

Although they are superior to the widely used superalloys in many aspects, the severe brittleness at ambient temperature observed in most intermetallic compounds has so far prevented their use as high temperature structural materials. To investigate the possibility of ductilizing intermetallic compounds, first principle total energy quantum mechanical calculations were employed to study the phase stability, electronic structure and mechanical

Tao Hong

1990-01-01

42

High Temperature Oxidation and Surface Modification of Binary Aluminide Intermetallic Compounds Using Ion Implantation of Oxygen  

Microsoft Academic Search

This work presents a novel approach to the modification of intermetallic compounds to achieve improved oxidation resistance. In order to bypass problems associated with the transient oxidation stage of alloys and intermetallic compounds, high-dose implants of oxygen are used to form a continuous oxygen saturated layer at room temperature. In order to study the implanted layer using secondary ion mass

Robert Joseph Hanrahan Jr.

1994-01-01

43

Development of New Cryocooler Regenerator Materials-Ductile Intermetallic Compounds  

SciTech Connect

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

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

2004-09-30

44

Effect of Reflow Profile on Intermetallic Compound Formation  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

45

CO2 laser welding of titanium aluminide intermetallic compound  

NASA Astrophysics Data System (ADS)

Titanium aluminide intermetallic compound is studied to find out good welding conditions using CO2 laser irradiation. In the experiment, we used the casting titanium aluminide containing iron, vanadium and boron with a thickness of 2 mm. We carried out bead-on-plate laser welding at various initial temperatures of specimens varied from room temperature to 873 [K] in inert gas environment filled with argon. We measured fused depth, bead width and Vickers hardness. As a result of experiments, welding speeds that allow full bead-on- plate welding to be possible were strongly by dependent on the initial temperature, 3000 [mm/min], initial temperature 873 [K], 2600 [mm/mm], initial temperature 673 [K], and 2000 [mm/min] with 300 [K]. Transverse crack-free welding was achieved, when initial temperature was at 873 [K].

Kuwahara, Gaku; Yamaguchi, Shigeru; Nanri, Kenzo; Ootani, Masanori; Seto, Sachio; Arai, Mikiya; Fujioka, Tomoo

2000-02-01

46

Ab Initio Study of Electronic and Magnetic Structure of Intermetallic RE5Ge3 Compounds  

NASA Astrophysics Data System (ADS)

A series of binary rare-earth metal germanides RE5Ge3 (RE = La, Ce, Pr and Nd) adopting the Mn5Si3-type hexagonal structure is studied. These intermetallic phases show a complex magnetic behavior. Using a modification of the local density approximation (LSDA + U) the magnetic and electronic properties of these compounds are calculated. The spin-orbit coupling (SOC) was included using a full relativistic basis. Besides the structural parameters, bonding characters, total and partial densities of state and band structures are analyzed and compared with the experimental findings.

Djermouni, M.; Belhadj, M.; Kacimi, S.; Zaoui, A.

47

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 435C, 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 430~435C. 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

48

Microstructure and tribological properties of TiCu 2Al intermetallic compound coating  

NASA Astrophysics Data System (ADS)

TiCu 2Al ternary intermetallic compound coating has been in situ synthesized successfully on pure Ti substrate by laser cladding. Tribological properties of the prepared TiCu 2Al intermetallic compound coating were systematically evaluated. It was found that the friction coefficient and wear rate was closely related to the normal load and sliding speed, i.e., the friction coefficient of the prepared TiCu 2Al intermetallic compound coating decreased with increasing normal load and sliding speed. The wear rate of the TiCu 2Al intermetallic compound coating decreased rapidly with increasing sliding speed, while the wear rate first increased and then decreased at normal load from 5 to 15 N.

Guo, Chun; Zhou, Jiansong; Zhao, Jierong; Wang, Linqian; Yu, Youjun; Chen, Jianmin; Zhou, Huidi

2011-04-01

49

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

SciTech Connect

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

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

1999-11-05

50

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

Microsoft Academic Search

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

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

1996-01-01

51

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

Microsoft Academic Search

In this paper, postannealing of cold-sprayed (CDGS) coatings for intermetallic compounds (IMC) in the matrix at low temperature\\u000a and dependences of types and dispersion characteristics of intermetallic compounds on spraying pressure condition were investigated.\\u000a The pressure prior to entering the gas heater was fixed at 0.7, 1.5, and 2.5MPa. The relatively soft Al has been coated at\\u000a low gas pressure

H. Lee; H. Shin; K. Ko

2010-01-01

52

Intermetallic compound formation at Cu-Al wire bond interface  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

53

Resonant ultrasound spectroscopy: Elastic properties of some intermetallic compounds  

Microsoft Academic Search

A novel nondestructive evaluation method, resonant ultrasound spectroscopy (RUS), is reviewed with an emphasis upon defining the elastic properties of intermetallic phases. The applications and advantages of RUS as compared to other conventional elastic constant measurement methods are explained. RUS has been employed to measure the elastic properties of single crystal and\\/or polycrystalline intermetallics, such as Laves phases (C15 HfV

F. Chu; D. J. Thoma; Y. He; S. A. Maloy; T. E. Mitchell

1996-01-01

54

AN INVESTIGATION OF INTERMETALLIC COMPOUNDS FOR VERY HIGH TEMPERATURE APPLICATIONS. Period covered : March 13, 1956 to March 12, 1957  

Microsoft Academic Search

Intermetallic compounds from thirty-five binary metallic systems were ; prepared, fabricated into oxidation-test specimens, and tested for oxidation ; resistance in dry air at 2300 F. Only high-melting (above 2550 F) compounds ; were studied. These included aluminides, beryllides, silicides, germanides, and ; zirconides, as well as numerous miscellaneous compounds. The intermetallic ; compounds or compositions which are shown to

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

1959-01-01

55

Microstructure and tribological properties of TiAg intermetallic compound coating  

NASA Astrophysics Data System (ADS)

TiAg intermetallic compound coating has been in situ synthesized successfully on pure Ti substrate by laser cladding using Ag powder as the precursor. It has been found that the prepared coating mainly comprised TiAg and Ti phases. The high resolution transmission electron microscopy results further conform the existence of TiAg intermetallic compound in the prepared coating. The magnified high resolution transmission electron microscopy images shown that the laser cladding coating contains TiAg nanocrystalline with the size of about 4 nm. Tribological properties of the prepared TiAg intermetallic compound coating were systematically evaluated. It was found that the friction coefficient and wear rate was closely related to the normal load and sliding speed, i.e., the friction coefficient of the prepared TiAg intermetallic compound coating decreased with increasing normal load and sliding speed. The wear rate of the TiAg intermetallic compound coating decreased rapidly with increasing sliding speed, while the wear rate increased as the normal load increased.

Guo, Chun; Chen, Jianmin; Zhou, Jiansong; Zhao, Jierong; Wang, Linqian; Yu, Youjun; Zhou, Huidi

2011-10-01

56

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

57

INVESTIGATION OF INTERMETALLIC COMPOUNDS FOR VERY HIGH TEMPERATURE APPLICATIONS  

Microsoft Academic Search

Three differert areas were studied in a continuing investigation of ; intermetallic beryllides and silicides for very high-temperature applications. ; The measured properties of TaBe were unaffected by minor ; variations in stoichiometry between 800 and 3000 deg F, whereas best results for ; WSi were obteined with a material slightiy deficient in tungsten. WSi\\/sub ; 2\\/ exhibited poorest oxidation

J. Booker; R. M. Paine; A. J. Stonehouse

1962-01-01

58

Surface integrity on grinding of gamma titanium aluminide intermetallic compounds  

NASA Astrophysics Data System (ADS)

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

Murtagian, Gregorio Roberto

59

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

Microsoft Academic Search

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

Ming Wu

1991-01-01

60

Magnetic anisotropy in intermetallic compounds containing both uranium and 3 d-metal  

NASA Astrophysics Data System (ADS)

Magnetic properties of intermetallic compounds containing both uranium and a 3 d metal (Fe, Co) are summarized and discussed. It was shown that the ordered magnetism of the U and 3 d-metal sublattices can coexist in the same compound (e.g. with 2-17 and 1-12 stoichiometries) even at room and elevated temperatures.

Andreev, A. V.; Tereshina, E. A.; Gorbunov, D. I.; antav, E.; ebek, J.; ?ek, M.; Homma, Y.; Shiokawa, Y.; Satoh, I.; Yamamura, T.; Komatsubara, T.; Watanabe, K.; Koyama, K.

2013-09-01

61

A study of nanoparticles in SnAg-based lead free solders for intermetallic compounds and drop test performance  

Microsoft Academic Search

Co, Ni, Pt, Al, P, Cu, Zn, Ge, Ag, In, Sb or Au including in Sn-Ag based lead free solders were evaluated to study if these nanoparticles can reduce the growth of intermetallic compounds after 4 time reflow processes and thermal aging. Also, these nanoparticles were studied if they can reduce the frequency of occurrence of intermetallic compound fractures in

M. Amagai

2006-01-01

62

DEVELOPMENT OF INTERMETALLIC COMPOUNDS FOR VERY HIGH TEMPERATURE APPLICATIONS. Quarterly Progress Report, May 1July 31, 1960  

Microsoft Academic Search

Progress in the development of intermetallic compounds between beryllium ; and certain transitional elements is described. Work was continued on mixed-; phase compositions in the Ta--Be and Zr-Be systems. The effect of impurities in ; raw materials and their disposition during process ing of intermetallic compounds ; is described. Modulus of rupture tests, hardness measurements, and thermal shock ; data

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

1960-01-01

63

REVIEW: Intermetallic compounds of rare earths and non-magnetic metals  

Microsoft Academic Search

A review is given of the physical properties, composition and crystal structure of intermetallic compounds formed between rare-earth elements and non-magnetic metals, with emphasis on the magnetic properties. Included are the properties of compounds in which the non-rare-earth component is a 4d or 5d transition element. Special consideration is given to the properties of pseudo-binary compounds. Results of magnetisation measurements,

K. Buschow

1979-01-01

64

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

Microsoft Academic Search

Intermetallic compounds based on the Laves phases NbCr2 and TiCr2 are of interest for high temperature applications. At temperatures where the high temperature strength and creep resistance of these compounds are excellent, their oxidation resistance is relatively poor. Beryllide compounds in the 3-Be, Ti-Be and Nb-Be systems (CrBe2, TiBel2, TiBez, NbBel2) on the other hand, exhibit excellent oxidation resistance even

R. J. Hanrahan; J. C. Cooley; W. L. Hults; D. J. Thoma; K. C. Chen

2001-01-01

65

Nuclear-Magnetic-Resonance Measurements in the Rare-Earth Group-VA Intermetallic Compounds  

Microsoft Academic Search

The temperature dependences, signs, and magnitudes of the phosphorus, arsenic, antimony, and bismuth nuclear-magnetic-resonance (NMR) Knight shifts in the NaCl-type rare-earth group-VA intermetallic compounds have been studied in detail for the temperature range of 1.5-600K. The Knight shifts in the nonmagnetic compounds, such as LaP, were found to be temperature-independent. For most of the magnetic compounds, such as GdP, the

E. D. Jones

1969-01-01

66

THE SHAPE, SIZE, AND GROWTH OF SOME INTERMETALLIC COMPOUNDS IN LIQUID BISMUTH  

Microsoft Academic Search

The shapes and sizes of particles of binary intermetallic compounds of ; uranium, thorium, cerium, zirconium, magnesium, calcium, struntium, barium, ; tellurium, and selenium with bismuth have been studied metallographically with ; respect to their made of preparation, ateer isothermal treatment in liquid ; bismuth, under changes in temperature, and on precipitation from solution. With ; the exception of MgBi,

P. J. Barton; G. W. Greenwood

1958-01-01

67

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

Microsoft Academic Search

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

Zhigang Xiao

1999-01-01

68

Acoustic emission behavior during tensile deformation of Ni 3Al intermetallic compound  

Microsoft Academic Search

Acoustic emission behavior during tensile deformation of single crystals and unidirectionally solidified specimens of Ni3Al intermetallic compound was studied. Mobile dislocation behavior in single crystals was investigated by measuring acoustic emission rms voltage. Using unidirectionally solidified specimens, effects of grain boundaries parallel to tensile axis on the acoustic emission behavior during tensile deformation of Ni3Al was examined. It was made

K. Yoshida; T. Saito; A. Zhu; H. Takagi; K. Sakamaki

1998-01-01

69

Use of combustion and thermal explosion for the synthesis of intermetallic compounds and their alloys  

Microsoft Academic Search

Methods of utilizing the heat evolving during reactions between components for the synthesis of intermetallic compounds and their alloys may vary depending on the character of the exothermic processes occurring in the metal powder mixtures employed. During the initiation of a reaction in some local volume of a substance heat is liberated in the reaction zone. This raises the temperature

V. I. Itin; A. D. Bratchikov; L. N. Postnikova

1980-01-01

70

Reliability studies of surface mount solder joints - effect of Cu-Sn intermetallic compounds  

Microsoft Academic Search

Cu-Sn intermetallic compounds (IMCs), formed at the interface between the solder and the copper substrate are found to play a dominant role in determining the thermal fatigue life of surface mount solder joints fabricated from a conventional infrared reflow process. In order to predict the growth of this IMC layer during the operating life of the solder joint and its

Alex C. K. So; Yan C. Chan

1996-01-01

71

Identification of Mechanical Properties of Intermetallic Compounds on Lead Free Solder  

Microsoft Academic Search

In this paper, we present methods for obtaining mechanical properties of silicon substrates and two intermetallic compounds (IMC) formed at the interfaces between lead-free solders and the copper and between leadfree solders and nickel substrates. To determine the mechanical properties of the silicon substrate, 255 um (100) and 306 um (110) thick silicon wafers were adopted. With proper sensor locations

Iting Tsai; Li Jung Tai; S. F. Yen; T. H. Chuang; R. Lo; T. Ku; Enboa Wu

2005-01-01

72

Fabrication and Investigation of Intermetallic Compound-Glassy Phase Composites having Tensile Ductility.  

National Technical Information Service (NTIS)

The purpose of this research was to produce in-situ ductile crystalline intermetallic compound-glassy composite materials with high strength and good plasticity. A range of composite specimens was prepared (Cu-Y, Y-Cu-Ag, Y-Cu-Al, Cu-Y-Ag, Mg-Cu-Y, Mg-Y-A...

D. Louzguine

2012-01-01

73

Heavy Ion Induced Damage and Disorder in Intermetallic Compounds with the B2 Structure.  

National Technical Information Service (NTIS)

Although the B2-type intermetallic compounds, NiAl, FeAl, NiTi and FeTi all maintained a high degree of order during irradiation, metastable phase formation was observed. Dislocation loops and network developed in NiAl and FeAl during irradiation and a ni...

J. L. Brimhall H. E. Kissinger

1984-01-01

74

Fundamental study about CO2 laser welding of titanium aluminide intermetallic compound  

Microsoft Academic Search

Titanium aluminide intermetallic compound is attracting attentions as heat-resistant and high-specific strength material in the next generation, especially, it is promising material in the field of aerospace components. Conventional machining process including welding, however, can be hardly applied due to its very low ductility. The objective of this study, as a first stage, is to find out paying attention to

Gaku Kuwahara; Shigeru Yamaguchi; Kenzo Nanri; Masanori Ootani; Masato Tetsuka; Sachio Seto; Mikiya Arai; Tomoo Fujioka

2000-01-01

75

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

76

C15 intermetallic compounds HfV{sub 2}+Nb  

SciTech Connect

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

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

1994-12-31

77

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

Microsoft Academic Search

The intermetallic compound (IMC) (or intermetallic phase layer) has a significant influence on the mechanical properties ofjoints between dissimilar metals obtained by thermal processes such as laser welding. Its formation is basically affected by thermal cycles in the joining or contact zone, where the IMC is formed. Within this study, the influence of the thermal cycle on the formation of

J. Fan; C. Thomy; F. Vollertsen

2011-01-01

78

Synthesis and Characterization of New Intermetallic Compounds for the grant entitled: Laser Processing of Advanced Magnetic Materials.  

National Technical Information Service (NTIS)

This six-month work is focused mainly on the properties of novel magnetic intermetallics. In the first project, we synthesized several 2:17 intermetallic compounds, namely Nd2Fe15Si2, Nd2Fe15Al2, Nd2Fe15SiAl and Nd2Fe15SiMn, as well as several 1:12 interm...

M. Sorescu

2003-01-01

79

REVIEW: Intermetallic compounds of rare-earth and 3d transition metals  

Microsoft Academic Search

A survey is given of the physical properties, composition and crystal structure of intermetallic compounds formed between rare-earth elements and 3d transition elements. Apart from binary compounds the results of pseudobinary series are also considered. The magnetic properties determined by the exchange interactions involving 4f as well as 3d electrons, are discussed together with experimental results available on magnetovolume effects

K. H. J. Buschow

1977-01-01

80

Similarities and differences in the physical properties of rare earth and uranium intermetallic compounds  

Microsoft Academic Search

The compounds exhibiting the tetragonal BaAl structure and its modifications represent one of the families of intermetallic systems that have turned out to be particularly numerous and interesting. Their general formula is RTX, where R = f elements (4f or 5f), T = transition metals (3d, 4d, 5d), and X = silicon or germanium. All these compounds have metallic behavior,

J. Etourneau; B. Chevalier

1992-01-01

81

Electron spin resonance of Nd3+ and Gd3+ in d-band intermetallic compounds  

Microsoft Academic Search

We report on the ESR of the rare-earth ions Nd3+, Gd3+, Er3+, and Yb3+ on powdered samples of various intermetallic compounds of AB2 cubic structure where B is a transition-metal ion belonging to the group VIII of the Periodic Table, and A is a nonmagnetic ion (La, Ce, Y). The resonance of the Nd3+ in these compounds originates within a

G. E. Barberis; D. Davidov; J. P. Donoso; C. Rettori; J. F. Suassuna; H. D. Dokter

1979-01-01

82

Computer simulations of disordering kinetics in irradiated intermetallic compounds  

NASA Astrophysics Data System (ADS)

Molecular-dynamics computer simulations of collision cascades in intermetallic Cu3Au, Ni3Al, and NiAl have been performed to study the nature of the disordering processes in the collision cascade. The choice of these systems was suggested by the quite accurate description of the thermodynamic properties obtained using embedded-atom-type potentials. Since melting occurs in the core of the cascades, interesting effects appear as a result of the superposition of the loss (and subsequent recovery) of the crystalline order and the evolution of the chemical order, both processes being developed on different time scales. In our previous simulations on Ni3Al and Cu3Au [T. Diaz de la Rubia, A. Caro, and M. Spaczr, Phys. Rev. B 47, 11 483 (1993)] we found a significant difference between the time evolution of the chemical short-range order (SRO) and the crystalline order in the cascade core for both alloys, namely the complete loss of the crystalline structure but only partial chemical disordering. Recent computer simulations in NiAl show the same phenomena. To understand these features we study the liquid phase of these three alloys and present simulation results concerning the dynamical melting of small samples, examining the atomic mobility, the relaxation time, and the saturation value of the chemical short-range order. An analytic model for the time evolution of the SRO is given.

Spaczr, M.; Caro, A.; Victoria, M.; Diaz de La Rubia, T.

1994-11-01

83

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

84

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

SciTech Connect

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

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

1989-02-01

85

Intermetallic compound layer growth kinetics in non-lead bearing solders  

SciTech Connect

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

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

1995-04-01

86

Magnetic properties and electronic structure of rare earth-transition metal intermetallic compounds  

Microsoft Academic Search

A model for the electronic structure of the RxMy intermetallic compounds is proposed in which the s electrons are spread over the crystal and the d states are mostly localized on the transition metal sites, the degree of localization varying from 3d to 4d and 5d. The authors distinguish between two cases: (i) magnetism driven by the localized f moments

A. A. Gomes; A. P. Guimaraes

1974-01-01

87

Magnetic and quadrupolar phase transitions in cubic rare-earth intermetallic compounds  

Microsoft Academic Search

A new analytical approach of the problem of magnetic and quadrupolar phase transitions in rare-earth intermetallic compounds is presented, in terms of single-ion susceptibilities and within the Landau theory: The coefficients of the free-energy expansion are simply related to several magnetic, strain, and quadrupolar crystal-field susceptibilities, the expression of which is given for any multilevel system. The analysis of sign

P. Morin; D. Schmitt

1983-01-01

88

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

Microsoft Academic Search

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

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

2004-01-01

89

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

Microsoft Academic Search

The atomic volume of an AxByCz ternary intermetallic compound can be calculated starting from volumes of some proper AB, AC and BC binary phases. The three methods by Colinet, Muggianu and Kohler, originally used to estimate thermodynamic quantities, and a new method here proposed, were tested to derive volume data in eight systems containing 91 ternary phases with the known

M. Pani; F. Merlo

2011-01-01

90

Crystal and magnetic structure of hexagonal RCo 4Al intermetallic compounds (R=Y and Pr)  

Microsoft Academic Search

We report on the structural and magnetic properties of the YCo4Al and PrCo4Al intermetallic compounds. Both phases crystallize in the hexagonal CaCu5-type structure with P6\\/mmm space group. Neutron powder diffraction experiments demonstrate that the Al atoms preferentially occupy the 3g crystallographic site of the CaCu5 structure. Al substitution in RCo5 induces remarkable changes of the magnetic properties: a drastic decrease

C Zlotea; O Isnard

2002-01-01

91

Effect of electromigration on intermetallic compound formation in Pb-free solder-Cu interfaces  

Microsoft Academic Search

The polarity effect of electromigration on intermetallic compound (IMC) formation at the cathode and the anode in solder lines has been investigated. The lines were formed by flowing molten lead-free solder SnAg3.8Cu0.7 into V-grooves etched on [001] silicon wafers, and two copper wires were used as electrodes. The V-groove solder line samples, with width of about 100 ?m and length

H. Gan; K. N. Tu

2002-01-01

92

Finite element based fatigue life estimation of the solder joints with effect of intermetallic compound growth  

Microsoft Academic Search

This paper develops an analysis procedure to study the effects of intermetallic compound (IMC) growth on the fatigue life of 63Sn37Pb (lead-rich)\\/96.5Sn3.5Ag (lead-free) solder balls for flip-chip plastic ball grid array packages under thermal cycling test conditions. In this analysis procedure, the thickness of the IMC increased with the number of thermal cycles, and was determined using the growth rate

Yung-Chuan Chiou; Yi-Ming Jen; Shih-Hsiang Huang

93

Magnetostriction and magnetism of rare earth intermetallic compounds: First principle study  

Microsoft Academic Search

Magnetism and magnetostriction of rare earth intermetallic compounds, GdCo2, GdFe2, NdCo2, SmCo2, and ErCo2, have been studied by using the first principles full-potential linearized augmented plane-wave method with the generalized gradient approximation. The calculated magnetostriction coefficients agree well with experiment. The itinerant electrons of transition metal elements are found to play a significant role in magnetoelastic coupling. The strong anisotropy

V. I. Gavrilenko; R. Q. Wu

2001-01-01

94

Modeling of interfacial intermetallic compounds in the application of very fine lead-free solder interconnections  

Microsoft Academic Search

Intermetallic compounds (IMCs) are formed between lead-free solders and base metals during soldering processes. The morphology\\u000a as well as the amount of the IMCs, in particular the interfacial IMCs, are important to mechanical performance of the solder\\u000a joints in their service environment. This is especially the case in state-of-art ultrafine-pitch wafer-level packaging, in\\u000a which solder joints could become as small

Zhiheng Huang; Paul P. Conway; Rongshan Qin

2009-01-01

95

The high temperature behavior of beryllide intermetallic compounds. [Studies up to 1,400C  

Microsoft Academic Search

The mechanical properties of four metal beryllide intermetallics were studied up to 1,400C. TaBe, NbBe, TiBe, and ZrBe were shown to be potential candidates for high temperature structural service. Microindentation and high temperature compression testing were employed to study the static and time dependent deformation of these low density compounds. The yield strength in compression and the microhardness values over

1992-01-01

96

Magnetic recording on FePt and FePtB intermetallic compound media  

Microsoft Academic Search

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

Ning Li; Bruce M. Lairson

1999-01-01

97

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

98

High-temperature atomic defect properties and diffusion processes in intermetallic compounds  

Microsoft Academic Search

Data on thermal vacancy formation in intermetallic compounds obtained from positron lifetime spectroscopy yield high effective formation enthalpies HFV in close-packed structures and low values in bcc-type structures which can be well understood theoretically. The vacancy migration enthalpy HMV could be determined at high temperatures for B2-FeAl by studying the equilibration process after temperature changes. As demonstrated here in a

H.-E. Schaefer; K. Frenner; R. Wrschum

1999-01-01

99

Palladiumgallium intermetallic compounds for the selective hydrogenation of acetylene  

Microsoft Academic Search

The intermetallic compounds PdGa and Pd3Ga7 are introduced as selective catalysts for the hydrogenation of acetylene. Single phase PdGa and Pd3Ga7 can readily be prepared by the appropriate thermal treatment of the stoichiometric mixtures of the corresponding elements. The initial low surface areas of the as-prepared materials can be increased by careful mechanical treatment without decomposition. Detailed investigations of PdGa

Jrgen Osswald; Rainer Giedigkeit; Rolf E. Jentoft; Marc Armbrster; Frank Girgsdies; Kirill Kovnir; Thorsten Ressler; Yuri Grin; Robert Schlgl

2008-01-01

100

Microstructure investigation in B2-phased Ni25Al40Fe intermetallic compound  

Microsoft Academic Search

To change the microstructures and improve the room-temperature ductility of B2-structured (β phase) NiAl intermetallic compound, macroalloying with iron was reported by referring previous literature. In the previous investigation on the Ni-25Al-xFe alloys (x is from 20 to 40 at.%), the alloy was prepared by bulk-processing because of convenience for structural application. Therefore, the significant segregation could not be avoided

Chun-Huei Tsau; Jason Shian-Ching Jang; Jin-Wei Yeh

1996-01-01

101

High temperature deformation of Ti(4648)Al2W intermetallic compounds  

Microsoft Academic Search

The high temperature deformation behavior of Ti46Al2W and Ti48Al2W intermetallic compounds have been investigated in isothermal compressive tests, performed at temperatures between 1000C and 1200C for strain rates between 10?3 and 10?1 s?1. The stressstrain curve during high temperature deformation exhibits a peak stress which is followed by a gradual decrease into a steady state stress with increasing the strain.

Hee Y. Kim; Woong H. Sohn; Soon H. Hong

1998-01-01

102

Mechanical properties of Ni 2CuSn intermetallic compounds at high temperatures  

Microsoft Academic Search

The present paper reports on the results of the investigation of tensile deformation of Ni2CuSn intermetallic compound samples prepared from as-cast ingot and from hot isostatically pressed material. The yield stress (defined at 0.2% plastic strain) has been investigated as a function of temperature and strain rate in the temperature range from 420 to 870 C. Both the yield stress

J. Mencl; J. Gtzov; P. Kratochvl; P. Luk?

1995-01-01

103

PdZn=Cu: Can an Intermetallic Compound Replace an Element?  

Microsoft Academic Search

An intermetallic compound, PdZn, exhibits a similar valence electron density of states as pure Cu, which has been confirmed by energy band calculation and X-ray photoelectron spectroscopy. The catalytic function was verified to be identical for PdZn and Cu. This explains the origin of the high selectivity of PdZn for the steam reforming of methanol (SRM), CH3OH+H2O-->3H2+CO2, a chemical reaction

An Pang Tsai; Satoshi Kameoka; Yasushi Ishii

2004-01-01

104

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

Microsoft Academic Search

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

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

1997-01-01

105

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

Microsoft Academic Search

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

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

1997-01-01

106

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

Microsoft Academic Search

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

Brje Johansson; Lars Nordstrm; Olle Eriksson; M. S. S. Brooks

1991-01-01

107

Orbital and spin polarizations of conduction electrons in rare-earth intermetallic compounds. Theory  

Microsoft Academic Search

Recent experiments on rare-earth intermetallic compounds have given us data on the contribution from conduction electrons to the magnetization and hyperfine fields at rare-earth nuclei. Analyses based on isotropic bilinear exchange interactions between the 4f and conduction electrons have not been able to explain the systematic variation of these contributions across the rare-earth series. To explain these variations it is

E. Belorizky; J. J. Niez; P. M. Levy

1981-01-01

108

Magneto-optical properties of U x Y 1? x Fe 10Si 2 intermetallic compounds  

Microsoft Academic Search

We studied the role of uranium 5f states at room temperature in optical and magneto-optical properties of uranium intermetallic compounds UxY1?xFe10Si2. The uranium atoms were observed to strongly enhance the magneto-optical effects from near infrared to ultraviolet spectral range. This shows on remarkable contribution of uranium 5f states even at room temperature, in spite of low number of 5f electrons

M. Kucera; P. Hasa

2007-01-01

109

Magnetic susceptibility and parameters of electronic structure of Al2REM (Gd, Dy, and Ho) intermetallic compounds at high temperatures  

Microsoft Academic Search

The magnetic susceptibility of Al2REM (REM = Gd, Dy, and Ho) intermetallic compounds is experimentally investigated by the Faraday method in a wide temperature interval (290-2000 K) in different magnetic fields (0.3-1.3 T). In the crystalline state, the temperature dependences of the susceptibility follow the generalized Curie-Weiss law. In the liquid phase, the magnetic susceptibility of these intermetallic compounds above

N. S. Uporova; S. A. Uporov; V. E. Sidorov

2011-01-01

110

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 4.8102 J/kg.

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

2012-10-01

111

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

112

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

SciTech Connect

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

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

2007-04-15

113

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

114

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

SciTech Connect

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

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

2011-05-15

115

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

SciTech Connect

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

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

1994-03-01

116

Electronic properties of Hf XY intermetallic compounds ( X = Si, Ge; Y = S, Se, Te)  

NASA Astrophysics Data System (ADS)

The electric field gradient (efg) parameters were calculated for the ternary system Hf XY ( X = Si, Ge; Y = S, Se, Te), using the full-potential linear augmented plane wave (LAPW) method applying the generalized gradient approximation (GGA). The major contribution to the efg value in these compounds comes from the p-p contribution next to the probe nucleus. The intermetallic compounds Hf XY ( X = Si, Ge; Y = S, Se, Te) show similar electronic properties. This similarity can be attributed to the resemblance of the crystallographic structure and the alike electronic structure of the X and Y ligand atoms, having two and four p-electrons in the external orbital, respectively.

Yaar, I.; Halevy, I.; Kahane, S.; Beck, A.; Berant, Z.

2007-04-01

117

155,157 Gd NMR study of GdNi intermetallic compounds  

Microsoft Academic Search

The spin-echo NMR technique was used to study the magnetic properties of the following intermetallic compounds of the GdNi series: Gd2Ni17, GdNi5, GdNi3, GdNi2 and GdNi, with 155Gd and 157Gd nuclei as local probes. These compounds have different crystal structures and order ferri- or ferromagnetically. The NMR measurements were performed at 4.2 and 1.5K. The NMR spectra were compared to

V. L. B de Jesus; I. S Oliveira; P. C Riedi; A. P Guimares

2000-01-01

118

Hydrogen occupancy in the RNi4Mg ( R=Y , La, Ce, and Nd) intermetallic compounds and hydrides  

NASA Astrophysics Data System (ADS)

We have investigated the effect of hydrogen on the electronic strtucture of the RNi4Mg ( R=Y , La, Ce, Pr, and Nd) intermetallics. By means of a two-step approach, the projected plane-wave and linearized plane-waves methods, we studied the hydrogen-insertion energetics on the intermetallic matrix and the H-vacancy formation in the hydride compound. We found that particular interstitial sites in the intermetallics are suitable to allocate hydrogen and form a solid solution. The effect of these interstitials on the electronic structure is discussed. In the other hand, the hydrogen-occupied sites in the hydride are found to be energetically equivalent.

Hahn-Herrera, Otto; Aburto, Andrea; Orgaz, Emilio

2009-10-01

119

Ab initio study of PrAg intermetallic compound  

NASA Astrophysics Data System (ADS)

In this work, a first-principles study on PrAg compound using the density functional theory implemented in the projector-augmented wave (PAW) method in the CsCl (B2) crystal structure has been performed. Based on the optimized structural parameter, which is in good agreement with experimental data, the electronic structure, elastic, thermodynamics and vibrational properties have been investigated. The temperature and pressure variations of volume, bulk modulus, thermal expansion coefficient, heat capacities, and Debye temperatures in wide pressure (0-30 GPa) and temperature ranges have also been predicted.

Kocak, B.; Ciftci, Y. O.; Colakoglu, K.; Deligoz, E.

2011-02-01

120

Low temperature properties of some Er-rich intermetallic compounds  

SciTech Connect

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

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

2004-09-30

121

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

PubMed

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

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

2009-03-18

122

Thermodynamic and structural changes of various intermetallic compounds during extended cycling in closed systems  

Microsoft Academic Search

The application-relevant AB5-type intermetallic compounds LmNi4.85Sn0.15, LmNi4.49Co0.1Mn0.205Al0.205 and LmNi4.08Mn0.62Al0.1Co0.2 underwent about 90?000 thermally induced hydrogen absorptiondesorption cycles in closed systems at different cycling temperatures and pressures. Depending on the individual rates of decay, regeneration procedures were carried out several times. After the half time and after the end of cycling additional experimental techniques were employed in order to determine possible

M Wanner; G Friedlmeier; G Hoffmann; M Groll

1997-01-01

123

Hard surfacing of TiAl intermetallic compound by plasma carburization  

Microsoft Academic Search

For an intermetallic compound such as TiAl to be used in various components, the wear resistance is very important. Recently, plasma carburization was performed on the fully lamellar cast alloy with Ti-33.5Al-1Nb-0.5Cr-0.5Si (mass%). The induced surface layer, 3 ?m in thickness, was a carbide, Ti2AlC, with a hardness that was higher than HV836 for a bearing steel AISI52100. The pin-on-disk

T. Noda; M. Okabe; S. Isobe

1996-01-01

124

Nd3+:YAG laser interaction with intermetallic compounds Hf2Rh and Hf2Co  

NASA Astrophysics Data System (ADS)

The results of an investigation of Nd3+:YAG laser interaction with the intermetallic compounds Hf2Rh and Hf2Co are presented. The analytical expression for the laser pulse power is determined. Reflection spectra over a wide infrared region are measured to obtain the principal mechanism of absorption. The samples and the laser damage are investigated by the Taylor-Hobson Talysurf with a diamond needle for roughness measurements, optical microscope, scanning electron microscope (SEM) and electron microprobe analyses, and the results obtained are presented and discussed. Attention is paid to the validity of some principal relations characterizing the evaluation of the interaction.

Ivanovic, N.; Sreckovic, M.; Milosavljevic, A.; Cekic, B.; Manasijevic, M.; Popovic, N.; Backovic, N.; Djuric, M.; Kunosic, A.; Nemes, K.

1993-12-01

125

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

NASA Astrophysics Data System (ADS)

The atomic volume of an AxByCz ternary intermetallic compound can be calculated starting from volumes of some proper A-B, A-C and B-C binary phases. The three methods by Colinet, Muggianu and Kohler, originally used to estimate thermodynamic quantities, and a new method here proposed, were tested to derive volume data in eight systems containing 91 ternary phases with the known structure. The comparison between experimental and calculated volume values shows the best agreement both for the Kohler method and for the new proposed procedure.

Pani, M.; Merlo, F.

2011-05-01

126

Thermochemical properties of the intermetallic compounds in the lanthanum cadmium system  

NASA Astrophysics Data System (ADS)

Thermochemical properties on the intermetallic compounds in the lanthanum cadmium (La Cd) system were investigated electrochemically. The redox reactions of the La3+/La couple at the Cd-coated W electrodes, which were prepared by the electrodeposition of Cd at the W electrode, were studied by cyclic voltammetry and chronopotentiometry at 673, 723, 773, 823 and 873 K in the LiCl KCl eutectic melts containing 1.2 wt% LaCl3. There were several cathodic and anodic peaks corresponding to the formation and the decomposition of the intermetallic compounds, LaCdx, respectively, in the cyclic voltammograms. Since the amount of Cd adsorbed on the W electrode could be evaluated during the electrochemical measurement, the compositions of all LaCdx could be analyzed exactly from the accumulated coulomb numbers of every anodic peak, which was attributed to the decomposition of each LaCdx. The formation energy of each LaCdx could be also estimated by chronopotentiometry.

Shirai, Osamu; Uehara, Akihiro; Fujii, Toshiyuki; Yamana, Hajimu

2005-09-01

127

N-pentane isomerization with catalysts formed from brominated intermetallic compounds  

SciTech Connect

The intermetallic compounds of aluminum with lanthanum (LaAl/sub 2/), cerium (CeAl/sub 2/), praseodymium (PrAl/sub 2/), erbium (ErAl/sub 2/), samarium (SmAl), and thorium (ThAl/sub 2/) were finely ground and suspended in dichloromethane (1 mmole/8 ml); 2 ml of n-pentane were then injected. Isopentane was the only primary product, but isobutane and C/sub 6/ hydrocarbons formed as secondary products. The conversions and isomerization selectivities after 0.5 hr at 0/sup 0/C were 6.0 and 90% for LaAl/sub 2/, 27.2 and 94.8% for CeAl/sub 2/, 8.9 and 85.3% for PrAl/sub 2/, 16.2 and 92.6% for ErAl/sub 2/, 3.6 and 91.3% for SmAl, and 16.7 and 97Vertical Bar3< for ThAl/sub 2/. With increasing extent of bromination beyond a 1:3 intermetallic compound/bromine ratio, the conversion increased and the isopentane yield decreased.

Imamura, H.; Wallace, W.E.

1980-07-01

128

Magnetic susceptibility and parameters of electronic structure of Al 2 REM (Gd, Dy, and Ho) intermetallic compounds at high temperatures  

Microsoft Academic Search

The magnetic susceptibility of Al2REM (REM?=?Gd, Dy, and Ho) intermetallic compounds is experimentally investigated by the Faraday method in a wide temperature\\u000a interval (2902000 K) in different magnetic fields (0.31.3 T). In the crystalline state, the temperature dependences of the\\u000a susceptibility follow the generalized CurieWeiss law. In the liquid phase, the magnetic susceptibility of these intermetallic\\u000a compounds above the melting

N. S. Uporova; S. A. Uporov; V. E. Sidorov

129

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

NASA Astrophysics Data System (ADS)

The synthesis of solid state materials has traditionally been accomplished using rigorous heating treatments at high temperatures (1,000C) to overcome the slow rate of diffusion between two reactants. Re-grinding and re-heating treatments improve the rate of reaction between two solids; however, the high temperatures required to overcome the diffusion barrier limit the products accessible to the most thermodynamically stable phases. In this work, nano-scale solids such as alloys and intermetallics were synthesized via solution techniques where metal compounds are reduced by NaBH4 or n-butyllithium at temperatures below 300C. To form hollow particles, metal nanoparticles of Co, Ni, Pb were synthesized via reduction by NaBH4 in water and reacted with K2PtCl 6, which resulted in the formation of alloys in the case of Co-Pt and Ni-Pt. PbPt intermetallic hollow particles were synthesized by heating a composite of PbO and hollow Pt nanoparticles in tetraethylene glycol (TEG) at 140C. With n-butyllithium as a reducing agent, Au3M (M = Fe, Co, Ni) nanoparticles could be synthesized as isolatable solids in the L12 structure. PtSn and AuCu3 intermetallics were synthesized using NaBH4 and TEG. The PtSn and AuCu3 nanoparticles were characterized by transmission electron microscopy in attempts to learn about the phase diagrams of nanoscale solids. The purpose of this work was to synthesize nanoparticles via solution-mediated routes at low temperatures in compositions and morphologies not observed in the bulk, and learn about the phase diagrams of nanoparticles to understand why it is possible to access solids at temperatures significantly below those used in traditional solid state chemistry.

Vasquez, Yolanda

130

Electronic properties of HffXY intermetallic compounds (X =Si, Ge; Y =S, Se, Te)  

NASA Astrophysics Data System (ADS)

The electric field gradient (efg) parameters were calculated for the ternary system HfXY (X =Si, Ge; Y =S, Se, Te), using the full-potential linear augmented plane wave (LAPW) method applying the generalized gradient approximation (GGA). The major contribution to the efg value in these compounds comes from the p-p contribution next to the probe nucleus. The intermetallic compounds HfXY (X =Si, Ge; Y =S, Se, Te) show similar electronic properties. This similarity can be attributed to the resemblance of the crystallographic structure and the alike electronic structure of the X and Y ligand atoms, having two and four p-electrons in the external orbital, respectively.

Yaar, I.; Halevy, I.; Kahane, S.; Beck, A.; Berant, Z.

131

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

132

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

NASA Astrophysics Data System (ADS)

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

Tsud, N.; Skla, T.; utara, F.; Veltrusk, K.; Dudr, V.; Fabk, S.; Sedl?ek, L.; Chb, V.; Prince, K. C.; Matoln, V.

2005-12-01

133

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 4f 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.

2012-11-01

134

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

135

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

SciTech Connect

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

Jongik Park

2004-12-19

136

Current problems of the electrochemistry of titanium and boron. Synthesis of titanium diboride and titanium intermetallic compounds in ionic melts  

Microsoft Academic Search

The current state of research into the titanium and boron electrochemistry and high-temperature electrochemical synthesis of titanium diboride and titanium intermetallic compounds with the iron triad metals is analysed. The prospects for the development of these studies are discussed. Primary attention is paid to the electrochemical properties and stability of halide systems containing titanium in various oxidation states together with

Viktor I. Shapoval; I. V. Zarutskii; Viktor V. Malyshev; N. N. Uskova

1999-01-01

137

Effects of inter-metallic compound on high temperature reliability of flip chip interconnects for fine pitch applications  

Microsoft Academic Search

Solder joint is a method widely used to attach electronic chip on substrate. It is a generally knowledge that solder joint contains inter-metallic compound (IMC) at interconnects of solder bump and copper pads. The magnitude of IMC layer thickness impacts reliability of chip level packages. Extensive experimental investigations are conducted, however complementary numerical studies are needed to fully characterise the

E. H. Amalu; N. N. Ekere; G. Aminu

2011-01-01

138

The effects of lamellar structure in the TiAl intermetallic compound on its acoustic emission behavior during tensile deformation  

Microsoft Academic Search

The dynamic behavior of TiAl intermetallic compounds during tensile deformation has been determined by the different appearance of the (?2 + ?) lamellar structure using the acoustic emission (AE) method. The AE events of these materials are obviously different. There is, however, no effectively direct evidence to prove the relationship between the microstructure of these TiAl alloys and the AE

A. Zhu; K. Yoshida; H. Tagaki; K. Sakamaki

1996-01-01

139

Fabrication of NiTi intermetallic compound coating made by laser plasma hybrid spraying of mechanically alloyed powders  

Microsoft Academic Search

NiTi intermetallic compounds not only have shape memory effects but also high erosion resistance. Therefore, applying this material as a coating is an effective method for preventing erosion. In this study, a mixture of Ti and Ni powders was subjected to a mechanical alloying process. Then, the mechanical and structural properties of the coating fabricated by vacuum plasma spraying and

Hitoshi Hiraga; Takashi Inoue; Shigeharu Kamado; Yo Kojima; Akira Matsunawa; Hirofumi Shimura

2001-01-01

140

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

141

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

142

Fundamental study about CO2 laser welding of titanium aluminide intermetallic compound  

NASA Astrophysics Data System (ADS)

Titanium aluminide intermetallic compound is attracting attentions as heat-resistant and high-specific strength material in the next generation, especially, it is promising material in the field of aerospace components. Conventional machining process including welding, however, can be hardly applied due to its very low ductility. The objective of this study, as a first stage, is to find out paying attention to crack and hardness the fundamental good conditions of the bead-on-plate welding of TiAl intermetallic compound using CO2 laser irradiation. In the experiment, we used the casting gamma titanium aluminide contained iron, vanadium and boron with a thickness of 2mm. We carried out bead-on-plate laser welding in the titanium aluminide material in inert gas environment filled with argon. We measured fused depth, Vickers hardness, transverse crack numbers and so on as major parameters of welding speed from 1000 to 4600 mm/min and initial temperature of specimen from R.T. to 873 K with a beam spot size of 0.5 mm and an output power of 1.5 kW. In addition, the specimens were analyzed by Electron Probe X-ray Micro Analyzer, Energy Dispersive X-ray Spectroscopy and X-ray Diffractometry. As a result of experiments, transverse crack-free welding was achieved, when initial temperature was at 873 K. In every condition, the value of Vickers hardness of fused zone increased compared with base. We think the reason of it is an increase of (alpha) 2(Ti3Al) phase, which is caused by rapid cooling, taking in Oxygen, fine structure and so on.

Kuwahara, Gaku; Yamaguchi, Shigeru; Nanri, Kenzo; Ootani, Masanori; Tetsuka, Masato; Seto, Sachio; Arai, Mikiya; Fujioka, Tomoo

2000-11-01

143

Hydrogen occupancy in the RNi{sub 4}Mg (R=Y, La, Ce, and Nd) intermetallic compounds and hydrides  

SciTech Connect

We have investigated the effect of hydrogen on the electronic strtucture of the RNi{sub 4}Mg (R=Y, La, Ce, Pr, and Nd) intermetallics. By means of a two-step approach, the projected plane-wave and linearized plane-waves methods, we studied the hydrogen-insertion energetics on the intermetallic matrix and the H-vacancy formation in the hydride compound. We found that particular interstitial sites in the intermetallics are suitable to allocate hydrogen and form a solid solution. The effect of these interstitials on the electronic structure is discussed. In the other hand, the hydrogen-occupied sites in the hydride are found to be energetically equivalent.

Hahn-Herrera, Otto; Orgaz, Emilio [Departamento de Fisica y Quimica Teorica, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, 04510 Mexico, Distrito Federal (Mexico); Aburto, Andrea [Departamento de Fisica, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, 04510 Mexico, Distrito Federal (Mexico)

2009-10-15

144

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

145

Structural intermetallics  

Microsoft Academic Search

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

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

1993-01-01

146

Multiphase Intermetallics  

Microsoft Academic Search

Ordered intermetallic compounds, notably the aluminides of nickel, titanium, iron and niobium, have been under intensive investigation for the past two decades as prospective load-bearing materials for high temperatures, with special emphasis on aerospace applications. The stronger of these phases are all catastrophically brittle at and near ambient temperature and this difficulty has proved obdurate. A promising solution appears to

R. W. Cahn

1995-01-01

147

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

148

Magnetic susceptibility and parameters of electronic structure of Al2REM (Gd, Dy, and Ho) intermetallic compounds at high temperatures  

NASA Astrophysics Data System (ADS)

The magnetic susceptibility of Al2REM (REM = Gd, Dy, and Ho) intermetallic compounds is experimentally investigated by the Faraday method in a wide temperature interval (290-2000 K) in different magnetic fields (0.3-1.3 T). In the crystalline state, the temperature dependences of the susceptibility follow the generalized Curie-Weiss law. In the liquid phase, the magnetic susceptibility of these intermetallic compounds above the melting point increases for all examined samples. The parameters of the electronic structure of the compounds are calculated based on the experimental data. It is established that the effective magnetic moment per rareearth metal atom is smaller than that characteristic of the free REM+ ion.

Uporova, N. S.; Uporov, S. A.; Sidorov, V. E.

2011-08-01

149

An electronic criterion for the intrinsic embrittlement of structural intermetallic compounds  

Microsoft Academic Search

Development of intermetallics for high-temperature structural applications has long been impeded by their brittleness. To overcome the brittleness, efforts have been devoted to understand the atomic bonding nature of intermetallics. However, there are no simple theoretical or experimental means for investigating the electronic origin of the brittleness. We find a simple experimental method, which employs the Kelvin-probe technique to measure

W. Li; Y. Wang; M. Cai; C. W. Wang

2005-01-01

150

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

151

Magnetic properties and magnetocaloric effects in Gd1-xHoxNiIn intermetallic compounds  

NASA Astrophysics Data System (ADS)

Magnetic properties and magnetocaloric effects (MCEs) of the intermetallic Gd1-xHoxNiIn (x=0-1) compounds have been evaluated by magnetization and heat capacity measurements. The Curie temperature TC can be tuned from near 100 K to 20 K by substituting Ho for Gd atoms. In addition, all the compounds with Ho atoms undergo two successive magnetic transitions with the decrease of temperature: a paramagnetic (PM) to ferromagnetic (FM) transition around TC and a spin-reorientation (SR) transition around 7-9 K. It is found that both transitions contribute to the magnetic entropy change (?SM). For a field change of 5 T, the maximum values of -?SM for Gd0.4Ho0.6NiIn are 6 J/kg K at Tt=9 K and 10 J/kg K at TC=52 K, respectively. These two -?SM peaks overlap partly and result in a wide working temperature range of MCE, and thus leading to the largest RC value of 443 J/kg in the Gd1-xHoxNiIn system.

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

2012-09-01

152

Intermetallic matrix composites  

SciTech Connect

This book presents a symposium on the complex processing-microstructure-property relationships in intermetallic matrix composite materials. It may appear to the reader that some of the work reported in this volume does not bear on this question, but it should be remembered that intermetallic compounds have properties similar to both ceramics (at low temperatures) and metals (at high temperatures). Thus the techniques for toughening brittle matrix composites at ambient temperatures as well as those for strengthening ductile matrix composites at elevated temperatures need to be applied to the intermetallic situation. For this reason, the session on microstructure-based modeling of the behavior of intermetallic matrix composites drew heavily on ceramic and metal matrix experience. The session discussing processing was also a mix of ceramic and metallurgical approaches, while stressing novel methods particular to composite microstructures. Thermodynamic compatibility and conventional microstructure-mechanical property studies make up the bulk of the papers as they address a large deficiency in our understanding in this important area.

Anton, D.L. (United Technologies Research Center, East Hartford, CT (US)); Martin, P.L. (Rockwell International Science Center, Thousand Oaks, CA (US)); Miracle, D.B. (Wright Research and Development Center, Wright-Patterson Air Force Base, OH (US)); McMeeking, R. (Univ. of California, Santa Barbara, CA (US))

1990-01-01

153

Complex intermetallic phase in multicrystalline silicon doped withtransition metals  

SciTech Connect

We report the observation of an alloy phase with fluorite-type structure containing Ni, Fe, Cu, and Si, found as precipitates in multi-crystalline silicon. The analysis of extended x-ray absorption fine-structure microspectroscopy ({micro}-EXAFS) measurements on the K edges of the transition metals of the precipitates and a synthetic reference material with composition of Ni{sub 0.82}Fe{sub 0.21}Cu{sub 0.02}Si{sub 1.94} support a structure model similar to NiSi{sub 2} but with mixed occupancies of Fe on the Ni site and Cu on the Si site. This observation provides evidence that transition metals interact during precipitation within silicon and form complex silicides.

Heuer, Matthias; Buonassisi, Tonio; Marcus, Matthew A.; Istratov,Andrei A.; Pickett, Matthew D.; Shibata, Tomohiro; Weber, Eicke R.

2006-01-01

154

Irradiation behavior of intermetallic uranium compounds used as fuel for research and test reactors  

SciTech Connect

The majority of research and test reactors around the world employ aluminum fuel element designs that contain dispersed powders of uranium compounds as fuel. Specifically, two compounds are used, the uranium oxide U/sub 3/O/sub 8/ and an uranium aluminide mixed phase composed of the intermetallic compounds UAl/sub 2/, UAl/sub 3/, and UAl/sub 4/, all made with highly enriched uranium (HEU), i.e., 93% /sup 235/U. The reduction of /sup 235/U enrichment to below 20%, to so-called low enriched uranium (LEU), required the use of higher density fuels for those applications where simply increased fuel loading was not feasible. Fuel-dispersant loading is in practice limited to approx. 45 vol%. Fuel development in the Reduced Enrichment Research and Test Reactor Program has focused on uranium silicides (U/sub 3/Si and U/sub 3/Si/sub 2/) as the most promising high-density fuels. The compounds U/sub 6/Fe and U/sub 6/Mn as well as U/sub 3/Si containing some aluminum or copper were tested in search of stable high-density fuel. Some properties of the traditional and newly tested fuels are shown. All fuels were tested in the Oak Ridge Research Reactor in the form of miniature fuel plates. The irradiation performance capability of fuel plates is determined by the extent of plate thickness increases caused by fuel/aluminum interaction and irradiation-induced swelling of the fuel. The fuel swelling obtained with immersion density measurements is shown.

Hofman, G.L.

1987-01-01

155

Measurements of charge localization effects in uranium and plutonium intermetallic compounds from LIII X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

At the heart of the complex behavior of 5f-electrons in uranium and plutonium is the variable localization of the 5f orbital. Plutonium, in particular, can behave like a localized lanthanide system or a delocalized transition-metal system, depending on its coordination environment. This behavior gives rise to a variety of novel physical properties in U and Pu compounds: unexpected magnetic susceptibilities, non-Fermi-liquid behavior, superconductivity, etc. To understand the dual nature of U and Pu 5f orbitals, we report measurements of the actinide LIII-edge X-ray absorption spectra, including high-resolution partial fluorescence yield measurements, for a wide variety of intermetallics, including ?-U, UCoGa5, UCd11, ?- and ?-Pu, PuCoGa5, and PuCoIn5. A systematic shift of the LIII-edge energy is observed, and is correlated to the Sommerfeld coefficient from heat capacity measurements. Based on these results, we argue that this type of experiment is a direct measure of the degree of 5f orbital localization for U and Pu.

Jiang, Yu; Booth, C. H.; Bauer, E. D.; Mitchell, J. N.; Tobash, P. H.; Thompson, J. D.; Sarrao, J. L.; Wall, M. A.; Allen, P. G.; Nordlund, D.

2011-03-01

156

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

Microsoft Academic Search

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

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

2005-01-01

157

Electrodeposition of AlNi intermetallic compounds from aluminum chloride- N-( n-butyl)pyridinium chloride room temperature molten salt  

Microsoft Academic Search

Electrodeposition of aluminumnickel intermetallic compounds (particularly Ni3Al) has been carried out onto platinum and mild steel cathodes from a 2:1 (mole ratio) aluminum(III) chloride-N-(n-butyl)pyridinium chloride (BPC) molten bath saturated with nickel(II) chloride at room temperature. A single phase of AlNi alloy is difficult to obtain by controlled-potential and controlled-current methods; however, it can be obtained by pulse current plating. The

Muhammad Rostom Ali; Atshushi Nishikata; Tooru Tsuru

2001-01-01

158

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

Microsoft Academic Search

With the trend of further miniaturization of very-large-scale-integration (VLSI) of circuits, electromigration becomes a reliability concern in solder alloys. The polarity effect of electromigration on intermetallic compound (IMC) formation at the anode and the cathode in solder V-groove samples has been investigated. The V-groove solder line samples, with width of about 100 mum and length of 500--700 mum, were used

Hua Gan

2004-01-01

159

Strain based approach for predicting the solder joint fatigue life with the addition of intermetallic compound using finite element modeling  

Microsoft Academic Search

Finite element analysis is extensively used for simulating the effect of accelerated temperature cycling in electronic packages. There are number of issues that need to be addressed to improve the current FEM models. One of the limitations for the models presently available is excluding the effect of intermetallic compounds (IMC) (Cu6Sn5, Cu3Sn) formation and growth between solder joint and Cu

Mohammad M Hossain; Dereje Agonafer; P. Viswanadham; Tommi Reinikainen

2004-01-01

160

Site preference determination in L1 ternary intermetallic compounds AlTi-X (X = Cr, Mn, Pd)  

Microsoft Academic Search

The intermetallic compound AlTi is one of the most promising candidates of high temperature structural material because of its high melting temperature, low density and superior oxidation resistance. However, since AlTi is brittle at low temperature, coming from a tetragonal D0 structure with a lower symmetry than a cubic one, its application has been limited. One approach to improve a

M. Kogachi; A. Kameyama

1993-01-01

161

Formation of the granular structure in the intermetallic compound Ni 3 Al in high-temperature synthesis under compression  

Microsoft Academic Search

The process of high-temperature synthesis of the Ni3Al intermetallic compound under conditions of a thermal explosion of the 3Ni-Al powder mixture under compression is considered.\\u000a Quantitative estimates of dispersion of the granular structure of the synthesized intermetallide are made within the framework\\u000a of the mathematical model proposed in the present paper.

V. E. Ovcharenko; O. V. Lapshin; I. S. Ramazanov

2006-01-01

162

Effects of reflow profile and thermal conditioning on intermetallic compound thickness for SnAgCu soldered joints  

Microsoft Academic Search

Purpose The purpose of this paper is to investigate the effects of reflow time, reflow peak temperature, thermal shock and thermal aging on the intermetallic compound (IMC) thickness for Sn3.0Ag0.5Cu (SAC305) soldered joints. Design\\/methodology\\/approach A four-factor factorial design with three replications is selected in the experiment. The input variables are the peak temperature, the duration of time above

Jianbiao Pan; Tzu-Chien Chou; Jasbir Bath; Dennis Willie; Brian J. Toleno

2009-01-01

163

High Temperature Materials Based on the Intermetallic Compound NiAl Reinforced by Refractory Metals for Advanced Energy Conversion Technologies  

Microsoft Academic Search

Advanced NiAl-based high temperature materials are developed and characterized for structural applications in energy conversion systems. The intermetallic compound NiAl with B2 superlattice structure exhibits superior physical and high temperature mechanical properties, and excellent oxidation resistance. Disadvantages of polycrystalline pure NiAl are the lack in plasticity and fracture toughness at room temperature and insufficient high temperature strength at temperatures above

Georg Frommeyer; Ralf Rablbauer

164

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

Microsoft Academic Search

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

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

1994-01-01

165

Electron-spin-resonance of some rare-earths ions in cubic intermetallic compounds (AuCu3-structure)  

Microsoft Academic Search

We report on the ESR of Gd3+, Er3+, and Yb3+ in MPd3 (M = Sc, Y, La, Ce, Lu) and CeRh3 intermetallic compounds. X-band (9.3 GHz) measurements were carried out between 0.6 and 40 K. Below T = 1.6 K we used our new continuously working He3 cryostat. The Gd resonance in ScPd3 and YPd3 shows a weak bottleneck behaviour.

T. Gambke; B. Elschner; R. Kremer; M. Schanz

1983-01-01

166

Recovery and accumulation of high-purity hydrogen with the use of hydride-forming intermetallic compounds  

SciTech Connect

The influence of argon, nitrogen, methane, ethylene, oxygen, hydrogen sulfide, and carbon and sulfur oxides on selective hydrogen absorption from its mixtures with these gases at 20-150{degrees}C and 0.1-50 atm by intermetallic compounds of rare-earth and 3d transition metals have been studied by X-ray phase, chemical, chromatographic, and mass-spectral analyses, calorimetry, and X-ray photoelectron spectroscopy.

Tarasov, B.P.; Shilkin, S.P. [Institute of New Chemical Problems, Moscow (Russian Federation)

1995-06-20

167

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

168

An Investigation Into the Fabrication and Electrical Properties of Ni-Al Intermetallic Compound Thin Films  

NASA Astrophysics Data System (ADS)

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 SEM. The preferred (111) orientation in both as-deposited and annealed films are identified using X-ray diffractometer (XRD). The electrical properties of the alloy films were studied, and show good metallic conduction characteristics. From room temperature to 200C, the resistance of the thin films are assumed to be linear as a function of varying temperature. All the thin films show a positive temperature coefficient of resistance (TCR). As 1% O2 was introduced into the vacuum chamber during sputtering, the root mean square roughness of the films increased, grain size turned out to be smaller, and the crystallization process was blocked. The amorphous Al2O3 phase was found in XRD patterns. The results of TCR measurement show a different electric conduction mechanism compared with alloy films.

Zhou, Jicheng; Zhu, Jinbo; Yan, Jianwu

169

Mechanical Strength and Failure Characterization of Sn-Ag-Cu Intermetallic Compound Joints at the Microscale  

NASA Astrophysics Data System (ADS)

Continuous miniaturization of microelectronic devices has led the industry to develop interconnects on the order of a few microns for advanced superhigh-density and three-dimensional integrated circuits (3D ICs). At this scale, interconnects that conventionally consist of solder material will completely transform to intermetallic compounds (IMCs) such as Cu6Sn5. IMCs are brittle, unlike conventional solder materials that are ductile in nature; therefore, IMCs do not experience large amounts of plasticity or creep before failure. IMCs have not been fully characterized, and their mechanical and thermomechanical reliability is questioned. This study presents experimental efforts to characterize such material. Sn-based microbonds are fabricated in a controlled environment to assure complete transformation of the bonds to Cu6Sn5 IMC. Microstructural analysis including scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD) is utilized to determine the IMC material composition and degree of copper diffusion into the bond area. Specimens are fabricated with different bond thicknesses and in different configurations for various tests. Normal strength of the bonds is measured utilizing double cantilever beam and peeling tests. Shear tests are conducted to quantify the shear strength of the material. Four-point bending tests are conducted to measure the fracture toughness and critical energy release rate. Bonds are fabricated in different sizes, and the size effect is investigated. The shear strength, normal strength, critical energy release rate, and effect of bond size on bond strength are reported.

Ladani, Leila; Razmi, Jafar

2012-03-01

170

Effect of Constant and Cyclic Current Stressing on the Evolution of Intermetallic Compound Layers  

NASA Astrophysics Data System (ADS)

In this paper the effects of constant and cyclic power loads on the evolution of interfacial reaction layers in lead-free solder interconnections are presented. Firstly, the differences in the growth behavior of intermetallic compound (IMC) layers at the cathode and anode sides of the interconnections are rationalized. This is done by considering the changes in the intrinsic fluxes of elements owing to electromigration as well as taking into account the fact that the growth of Cu3Sn and Cu6Sn5 are coupled via interfacial reactions. In this way, better understanding of the effect of electron flux on the growth of each individual layer in the Cu-Sn system can be achieved. Secondly, it is shown that there is a distinct difference between steady-state current stressing (constant current, constant temperature) and power cycling with alternating on- and off-cycle periods (accompanied by a change of temperature). The reasons behind the observed differences are subsequently discussed. Finally, special care is taken to ensure that the current densities are chosen in such a way that there is no risk for even partial melting of the solder interconnections.

Laurila, T.; Karppinen, J.; Vuorinen, V.; Paul, A.; Paulasto-Krckel, M.

2011-07-01

171

Synthesis of NiAl Intermetallic Compound Nanosized Powders by Pulsed Wire Discharge  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

172

Electromigration effect on pancake type void propagation near the interface of bulk solder and intermetallic compound  

NASA Astrophysics Data System (ADS)

Due to the reduction in the size of electronic devices and solder interconnects, their current densities are rapidly increasing and the effect of electromigration becomes more critical to interconnect failure. Traditional methods are not sufficient to determine the failure mechanisms of solder interconnects under such high current densities. An approach to predict the electromigration effect upon interconnect failure including void propagation is timely and useful to the electronics industry. The stress gradient in a 95.5Sn-4Ag-0.5Cu eutectic solder with a void defect is analyzed numerically to determine the electromigration and stress migration forces. A kinetic mass diffusion model is developed to predict void width and propagation speed near the interface between the intermetallic compound and bulk solder caused by electromigration. A three-dimensional finite element analysis has been performed to analyze the current crowding effect in the interconnect. The proposed kinetic model gives a reasonable prediction for the void width and propagation velocity as compared with experimental results.

Yao, Yao; Keer, Leon M.; Fine, Morris E.

2009-03-01

173

An electronic criterion for the intrinsic embrittlement of structural intermetallic compounds  

SciTech Connect

Development of intermetallics for high-temperature structural applications has long been impeded by their brittleness. To overcome the brittleness, efforts have been devoted to understand the atomic bonding nature of intermetallics. However, there are no simple theoretical or experimental means for investigating the electronic origin of the brittleness. We find a simple experimental method, which employs the Kelvin-probe technique to measure the electron work function. The typical intermetallics in three alloy systems (Ni-Al, Fe-Al, and Ti-Al) were chosen as examples. An electronic criterion was therefore proposed for judging intrinsic brittleness. This criterion could provide some principles for improving the ductility of intermetallics and is also expected to be extendable to other materials (e.g., quasicrystalline alloys and metallic glasses)

Li, W.; Wang, Y.; Cai, M.; Wang, C.W. [Department of Mechanical Engineering, Changchun University, Changchun, 130022 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150006 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150006 (China); Department of Physics, P.O. Box 642814, Washington State University, Pullman, Washington 99164-2814 (United States); Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Wuhan Institute of Technology, Wuhan, 470074 (China)

2005-10-15

174

Deformation and fracture of ordered intermetallic compounds. Foreign trip report, December 15, 1988-January 14, 1990.  

National Technical Information Service (NTIS)

The research at Tohoku University was primarily on mechanistic interpretation of the available mechanical properties of ordered intermetallic alloys. This included initiation mechanisms of the active slip and twinning, anomalous yield and flow behavior, a...

M. H. Yoo

1990-01-01

175

Gd116Co49Sn118: A Complex Intermetallic Phonon-Glass/Electron-Crystal  

NASA Astrophysics Data System (ADS)

State-of-the art thermoelectric devices today operate at very low efficiencies and are expensive to produce. However, the growing need for alternate energy sources based on novel technologies has brought thermoelectrics to the forefront of applied materials research. Thermoelectrics could have a significant impact in this area, if their performance is significantly enhanced to a figure of merit (ZT) above 1.5. Our research focuses on the growth and structure-property relationships of intermetallics, specifically crystal structures with large lattice parameters that contain heavy atoms. These materials may be good thermoelectric candidates due to their potentially low lattice thermal conductivities and enhanced Seebeck values resulting from polar intermetallic properties. We have recently grown Gd116Co49Sn118 (Fm-3m, a 30.2 ), a compound related to the Dy117Co57Sn112 structure type. Physical property measurements indicate that this is an ambipolar semiconductor with an exceptionally low lattice thermal conductivity (?l 0.5 W/m-K). The observed phonon-glass/electron-crystal properties make Gd116Co49Sn118 and its analogues potential thermoelectric candidates.

Schmitt, Devin; Haldolaarachchige, Neel; Xiong, Yimin; Jin, Rongying; Young, David; Chan, Julia

2011-03-01

176

Structural intermetallics  

SciTech Connect

The intent of the symposium was to provide a detailed and in-depth perspective of the approaches, results and progress toward the structural application of intermetallic compounds and their composites. Longer and insightful presentations which focused on real progress and trends rather than recent results, and extended discussion periods formed the centerpiece of this symposium to achieve these goals. Emphasis was placed on a balance of presentations covering basic research, alloy development and applications. Programs of large magnitudes are being carried out throughout the world to develop intermetallics for structural applications. Programs of large magnitudes are being carried out throughout the world to develop intermetallics for structural applications. The majority of the focus is on the development of microstructure and alloy compositions to solve the poor ductility and toughness of these intermetallics. Considerable progress has been made in understanding as well as solving the ductility and toughness issues. Component and engine tests are being initiated with Ti[sub 3]Al, TiAl, Ni[sub 3]Al and NiAl alloys. Separate abstracts were prepared for 94 papers in this symposium.

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

1993-01-01

177

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

178

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

Microsoft Academic Search

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

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

2001-01-01

179

Experimental studies of the electronic structure of I-II and I-III intermetallic compounds: Progress report, June 15, 1985January 14, 1986  

Microsoft Academic Search

The interest in a detailed study of I-II, I-III intermetallic compounds stems from their potential use as electrode materials in high energy density batteries or as solid blankets for nuclear reactors. There also exists a basic interest in the problem, because only a reduced number of I-II, I-III intermetallics (LiAl, LiGa, LiIn, LiZn, LiCd, and NaTl) crystallize in the unusual

Curelaru

1986-01-01

180

Effect of La 2O 3 on microstructure and high-temperature wear property of hot-press sintering FeAl intermetallic compound  

Microsoft Academic Search

FeAl intermetallic compound with different contents of rare earth oxide La2O3 addition was prepared by hot pressing the mechanically alloyed powders. Effect of La2O3 on microstructure and high-temperature wear property of the sintered FeAl samples was investigated in this paper. The results showed that 1 wt.% La2O3 addition could refine the microstructure and increase the density of the FeAl intermetallic

Xingwei MA; Zhuji JIN; Shi YAN; Jiujun XU

2009-01-01

181

Environmental embrittlement caused by hydrogen for intermetallic compounds: Preliminary model of ductility reduction  

SciTech Connect

The reduction of fracture elongation caused by environmental embrittlement has been dealt with for intermetallic alloys as follows. The fresh surface that is formed by plastic deformation increases with an increase in tensile deformation, and hydrogen permeating through the fresh surface into the specimen increases and embrittles its surface layer. Thus, a microcrack nucleates at the surface layer. The crack propagates unstably through the specimen because of the low fracture toughness of intermetallic alloys, resulting in the fracture of the specimen. Hydrogen permeating into the specimen increases with the increasing fresh surface area and increasing period of exposure to the environment. The dependence of fracture elongation on strain rate and hydrogen pressure has been described by a phenomenological and preliminary model, which has been proposed according to the consideration mentioned previously. The experimental data which were reported for intermetallic alloys have been compared to the phenomenological model.

Nakamura, Morihiko; Kumagai, Tatsuo

1999-12-01

182

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

SciTech Connect

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

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

2012-02-15

183

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

184

Effects of ultrasonic vibration on the iron-containing intermetallic compounds of high silicon aluminum alloy with 2% Fe  

Microsoft Academic Search

The effects of ultrasonic vibration (USV), the combined effects of USV and the addition of Mn on the morphology of iron-containing intermetallic compounds of Al20Si2.0Fe2.0Cu0.4Mg1.0Ni alloy have been studied respectively. The mechanism of shape-transformation of Fe-containing phases is also investigated. A large amount of long needle-like ?-Al5FeSi phases accompanied with a few ?-Al4FeSi2 phases existed in the matrix of high

Gu Zhong; Shusen Wu; Huawen Jiang; Ping An

2010-01-01

185

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

SciTech Connect

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

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

1987-03-10

186

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

Microsoft Academic Search

The intermetallic compounds Mg2Si, MoSi2, WSi2, CrSi2, NbSi2, Ti5Si3, TiSi2, ZrSi2 and Al3Nb were investigated in a pressure range up to 70 kbar and a temperature range up to 1500C in order to determine previously unknown elastic constants and possible phase transformations. The experiments were carried out using the multi-anvil-X-ray apparatus MAX-80 and synchrotron radiation at HASYLAB. A complete phase

T. Peun; J. Lauterjung; E. Hinze

1995-01-01

187

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

Microsoft Academic Search

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

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

1994-01-01

188

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

189

Radiation-induced crystalline-to-amorphous transition in intermetallic compounds of the Cu-Ti alloy system  

SciTech Connect

Recent progress in molecular-dynamics studies of radiation-induced crystalline-to-amorphous transition in the ordered intermetallic compounds of the Cu-Ti system is discussed. The effect of irradiation was simulated by the generation of Frenkel pairs,which resulted in both the formation of stable point defects and chemical disorder upon defect recombination. The thermodynamic, structural and mechanical responses of the compounds during irradiation were determined by monitoring changes in the system potential energy, volume expansion, pair correlation function, diffraction patterns, and elastic constants. It was found that the intermetallics Cu{sub 4}Ti{sub 3}, CuTi, and CuTi{sub 2} could be rendered amorphous by the creation of Frenkel pairs, but Cu{sub 4}Ti could not, consistent with experimental observations during electron irradiation. However, the simulations showed that Cu{sub 4}Ti did become amorphous when clusters of Frenkel pairs were introduced, indicating that this compound may be susceptible to amorphization by heavy-ion bombardment. A generalization of the Lindemann criterion was used to develop a thermodynamic description of solid-state amorphization as a disorder- induced melting process.

Lam, N.Q.; Okamoto, P.R.; Devanathan, R. (Argonne National Lab., IL (United States)); Sabochick, M.J. (Gulf States Utilities Co., Beaumont, TX (United States). Computer Applications Div.)

1992-02-01

190

Atomic Magnetic Moment and Exchange Interaction between Mn Atoms in Intermetallic Compounds in Mn-Ge System  

NASA Astrophysics Data System (ADS)

Magnetic properties of four intermetallic compounds, \\varepsilon, \\varepsilon1, ? and ?, in manganese-germanium system are studied by means of magnetization measurement and neutron diffraction. Exchange coefficients of the interaction between Mn atoms in the compounds are estimated quantitatively using the molecular field approximation, based on the localized moment model. The exchange coefficient between Mn atoms on different sublattices is found to depend largely on the interatomic distance: The exchange coefficient is found to be negative for smaller interatomic distances than rc{=}2.9 and positive for larger distances. The magnitude of atomic magnetic moment in the compounds is consistently discussed using the Pauling valence, after Mri and Mitsui (J. Phys. Soc. Jpn. 25 (1968) 82).

Yamada, Nobuyoshi

1990-01-01

191

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

SciTech Connect

The crystal structure of the ternary intermetallic compound Yb{sub 3}Pd{sub 2}Sn{sub 2} has been determined ab initio from powder X-ray diffraction data. The compound crystallizes as a new structure type in the orthorhombic space group Pbcm and lattice constants a=0.58262(3), b=1.68393(8), c=1.38735(7) nm. Yb{sub 3}Pd{sub 2}Sn{sub 2} is composed of a complex {sub {infinity}}[Pd{sub 2}Sn{sub 2}]{sup {delta}-} polyanionic network in which the Yb ions are embedded. A comparison between this structure and those of Eu{sub 3}Pd{sub 2}Sn{sub 2} and Ca{sub 3}Pd{sub 2}Sn{sub 2}, other novel polar intermetallic compounds, was made. DC susceptibility and {sup 170}Yb Moessbauer spectroscopic measurements indicate a close-to divalent Yb behavior. Moreover, a hybridization between 4f and conduction electrons is suggested by electronic structure calculations and heat capacity measurements. - Graphical Abstract: Polyanionic networks for Yb{sub 3}Pd{sub 2}Sn{sub 2} and Eu{sub 3}Pd{sub 2}Sn{sub 2}. Highlights: > We determined ab initio the crystal structure of the novel ternary Yb{sub 3}Pd{sub 2}Sn{sub 2} stannide. > This structure has been compared with those of other polar 3:2:2 stannides discovered in this work. > Measurements of physical properties on Yb{sub 3}Pd{sub 2}Sn{sub 2} point to a close-to-divalent Yb ion. > Electron structure calculation and heat capacity indicate some hybridization between 4f and conduction electrons.

Solokha, P. [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Curlik, I. [Institute of Experimental Physics, Watsonova 47, SK 043 53 Kosice (Slovakia); Giovannini, M., E-mail: giovam@chimica.unige.it [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Lee-Hone, N.R. [Physics Department and Centre for the Physics of Materials, McGill University, Montreal, Canada H3A 2T8 (Canada); Reiffers, M. [Institute of Experimental Physics, Watsonova 47, SK 043 53 Kosice (Slovakia); Faculty of Sciences, University of Presov, 17. Novembra 1, SK 080 78 Presov (Slovakia); Ryan, D.H. [Physics Department and Centre for the Physics of Materials, McGill University, Montreal, H3A 2T8 (Canada); Saccone, A. [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy)

2011-09-15

192

Effect of Bi Segregation on the Asymmetrical Growth of Cu-Sn Intermetallic Compounds in Cu/Sn-58Bi/Cu Sandwich Solder Joints During Isothermal Aging  

NASA Astrophysics Data System (ADS)

An asymmetrical interfacial microstructure was observed at both top and bottom interfaces of Cu/Sn-58Bi/Cu solder joints after isothermal aging at 120C for different times. The asymmetrical interfacial microstructure resulted from asymmetrical Bi segregation, which was attributed to the density difference between Bi and Sn atoms. Bi atoms were driven to the bottom solder/Cu interface by gravity during the liquid soldering procedure since Bi atoms are more massive than Sn atoms. With increasing aging time, Bi accumulated at the bottom Cu3Sn/Cu interface and the Bi segregation enhanced Cu6Sn5 intermetallic compound growth, blocked Sn transport to the Cu3Sn intermetallic compound, and facilitated growth of the Cu6Sn5, based on the measured thicknesses of intermetallic compounds (including Cu6Sn5 and Cu3Sn) at both bottom and top interfaces for Cu/Sn-58Bi/Cu sandwich joints under the same aging process.

Hu, Xiaowu; Li, Yulong; Li, Ke; Min, Zhixian

2013-09-01

193

The Effect of Sn Orientation on Intermetallic Compound Growth in Idealized Sn-Cu-Ag Interconnects  

NASA Astrophysics Data System (ADS)

The work reported here explores the influence of crystal orientation on the growth of the interfacial intermetallic layer during electromigration in Cu||Sn||Cu solder joints. The samples were thin, planar Sn-Ag-Cu (SAC) solder layers between Cu bars subject to a uniaxial current. Electron backscatter diffraction (EBSD) was used to characterize the microstructure before and after testing. The most useful representation of the EBSD data identifies the Sn grain orientation by the angle between the Sn c-axis and the current direction. The tested samples included single-crystal joints with c-axis nearly parallel to the current ("green" samples) and with c-axis perpendicular to the current ("red" samples). At current density of 104 A/cm2 (steady-state temperature of ~150C), an intermetallic layer grew at an observable rate in the "green" samples, but not in the "red" ones. A current density of 1.15 104 A/cm2 (temperature ~160C) led to measurable intermetallic growth in both samples. The growth fronts were nearly planar and the growth rates constant (after an initial incubation period); the growth rates in the "green" samples were about 10 those in the "red" samples. The Cu concentrations were constant within the joints, showing that the intermetallic growth is dominated by the electromigration flux. The measured growth rates and literature values for the diffusion of Cu in Sn were used to extract values for the effective charge, z *, that governs the electromigration of Cu. The calculated value of z * is significantly larger for current perpendicular to the c-axis than along it.

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

2013-04-01

194

Effect of Crystal Fields on the Magnetic Properties of Samarium Intermetallic Compounds  

Microsoft Academic Search

Neither of the intermetallics SmAl2 (a ferromagnet below TC=120 K) and SmSn3 (an antiferromagnet below TN=11 K) show the sign reversal predicted by White and Van Vleck for the 4f-induced Knight shift in the paramagnetic region. On the other hand, no particular anomaly has been observed in the temperature dependence of the susceptibility. An explanation for this is given in

H. W. de Wijn; A. M. van Diepen; K. H. Buschow

1973-01-01

195

The influence of Sn-Cu-Ni(Au) and Sn-Au intermetallic compounds on the solder joint reliability of flip chips on low temperature co-fired ceramic substrates  

Microsoft Academic Search

The formation of intermetallic compounds in the solder joint of a flip chip or chip scale package depends on the under bump metallurgy (UBM), the substrate top surface metallisation, the solder alloy and the application conditions. To evaluate the influence of intermetallic compounds on the solder joint reliability, a detailed study on the influence of the UBM, the gold finish

N. Duan; J. Scheer; J. Bielen; M. Van Kleef

2003-01-01

196

Chemistry of intermetallic hydrides  

SciTech Connect

Certain intermetallic hydrides are safe, convenient and inexpensive hydrogen storage compounds. A particular advantage of such compounds is the ease with which their properties can be modified by small changes in alloy composition or preparation. This quality can be exploited to optimize their storage properties for particular applications, e.g. as intermetallic hydride electrodes in batteries. We will be concerned herein with the more important aspects of the thermodynamic and structural principles which regulate the behavior of intermetallic hydrogen systems and then illustrate their application using the archetype hydrides of LaNi5, FeTi and Mg alloys. The practical utility of these classes of materials will be briefly noted.

Reilly, J.J.

1991-01-01

197

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

198

Geometric origin of magnetic frustration in the ?-Al?Mn giant-unit-cell complex intermetallic.  

PubMed

The structurally ordered ?-Al(4)Mn complex intermetallic phase with 563 atoms in the giant unit cell shows the typical broken-ergodicity phenomena of a magnetically frustrated spin system. The low-field zero-field-cooled and field-cooled magnetic susceptibilities show splitting below the spin freezing temperature T(f) = 2.7 K. The ac susceptibility exhibits a frequency-dependent cusp, associated with a frequency-dependent freezing temperature T(f)(?). The decay of the thermoremnant magnetization is logarithmically slow in time and shows a dependence on the aging time t(w) and the cooling field H(fc) typical of an ultraslow out-of-equilibrium dynamics of a nonergodic spin system that approaches thermal equilibrium, but can never reach it on the experimentally accessible time scale. The above features classify the ?-Al(4)Mn complex intermettalic among spin glasses. The origin of frustration of magnetic interactions was found to be geometrical due to the distribution of a significant fraction of Mn spins on triangles with antiferromagnetic coupling. The ?-Al(4)Mn phase is a geometrically frustrated spin glass. PMID:21406894

Jazbec, S; Jagli?i?, Z; Vrtnik, S; Wencka, M; Feuerbacher, M; Heggen, M; Roitsch, S; Dolinek, J

2011-01-12

199

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

SciTech Connect

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

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

2011-07-15

200

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

201

Experimental Studies of the Electronic Structure of I-II and I-III Intermetallic Compounds: Progress Report, June 15, 1985-January 14, 1986.  

National Technical Information Service (NTIS)

The interest in a detailed study of I-II, I-III intermetallic compounds stems from their potential use as electrode materials in high energy density batteries or as solid blankets for nuclear reactors. There also exists a basic interest in the problem, be...

I. M. Curelaru

1986-01-01

202

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

203

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

Microsoft Academic Search

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

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

1994-01-01

204

Plasma-melting and plasma-melt-gas-atomization of high temperature intermetallic compounds (Nb3Al)  

NASA Astrophysics Data System (ADS)

There has been much interest in rapidly solidified niobium-aluminides (Nb3Al) as structural materials for ultrahigh temperature applications. Pressurizing melting atmosphere to approximately 0.25 MPa can reduce Al vaporization during plasma melting. A unique plasma-melt-gas-atomization process (PMGA) has been developed for making rapidly-solidified powder of high temperature intermetallic compounds such as Nb3Al. In this technique, we use only water-cooled copper as a tundish for bottom poring, instead of refractories or refractory metals. The crystal structure of PMGA'ed Nb3Al powder consists of an almost Al-saturated solid solution of niobium (bcc). This fact means that the solidification rate of PMGA is sufficiently high.

Kohno, T.; Kohmoto, H.; Murahashi, N.

205

Phase stability and elasticity of C15 transition-metal intermetallic compounds  

SciTech Connect

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

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

1995-03-01

206

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

Microsoft Academic Search

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

W. J. Tomlinson; H. G. Rhodes

1987-01-01

207

Magnetic susceptibility and parameters of electronic structure of Al2R (R = La, Ce, Sm, Gd, Dy, Ho, Yb) intermetallic compounds at high temperatures  

Microsoft Academic Search

Magnetic properties of intermetallic compounds Al2R (R = La, Ce, Sm, Gd, Dy, Ho, Yb) are investigated in a wide temperature (20-1650C) and magnetic fields (0,3-1,3 T) ranges. For all the samples the increase of magnetic susceptibility with temperature growth was found in liquid state. From experimental data several parameters of electronic structure of the compounds were obtained. In particular,

N. Uporova; S. Uporov; V. Sidorov; K. Shunyaev; R. Zakharov; S. Petrova

2011-01-01

208

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

SciTech Connect

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

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

2009-11-15

209

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

SciTech Connect

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

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

2000-02-01

210

Structure and phase stability of binary zintl-phase compounds: lithium-group 13 intermetallics and metal-doped group 14 clathrate compounds.  

PubMed

The structure/bonding relationship in a series of intermetallic phases of Li with Al, Ga, and In was investigated by density functional theory and complemented by a model based on tight-binding theory and the method of moments. The combination of these two approaches provides a simple scheme which allows for both a comprehensive understanding of structural trends and the ability to predict low-energy structures for a given composition. This analysis gives a straightforward picture of phase stability in terms of local geometric features such as triangular, square, and hexagonal arrangements of atoms. The approach was extended to examine the structural properties of metal-doped clathrate compounds of C, Si, Ge, and Sn. Clathrate-type phases based on the frameworks Si172, Ge172, Si40, and Ge40 are not only likely to be energetically favorable but may also exhibit high thermoelectric efficiency. PMID:12391658

Ker, Alyssa; Todorov, Evgeny; Rousseau, Roger; Uehara, Kentaro; Lannuzel, Franois-Xavier; Tse, John S

2002-06-17

211

Melting transition in molecular-dynamics simulations of the Ni0.5Zr0.5 intermetallic compound  

NASA Astrophysics Data System (ADS)

Results are provided from molecular-dynamics (MD) simulations for a Ni0.5Zr0.5 model adapted to Hausleitner-Hafner interatomic potentials, including estimates for the formation energies of vacancies, interstitials, and antisite defects in the orthorhombic structure of the intermetallic compound. The equilibrium melting temperature Tm is estimated from the change in the growth direction of a crystal-liquid layer structure under annealing. From the MD data the isentropic Kauzmann temperature is evaluated and its relation to the simulated glass transition temperature is discussed. With regard to superheating experiments, homogeneous melting of the crystal is studied in the absence of extrinsic defects for temperatures above Tm. For the considered closed system without particle exchange with the environment, the results indicate that some 400 K above Tm a steady-state Ni-Frenkel pair density is already established long before the melting transition occurs. This implies that homogeneous melting takes place in this compound by the combined action of Ni and Zr defects, probably by the formation of antisite defects, in a similar way as proposed in the literature for solid state amorphization in this system.

Teichler, H.

1999-04-01

212

Ab-initio calculation of structural, electronic, and optical characterizations of the intermetallic trialuminides ScAl{sub 3} compound  

SciTech Connect

We present first-principles study of the electronic and the optical properties for the intermetallic trialuminides ScAl{sub 3} compound using the full-potential linear augmented plane wave method within density-functional theory. We have employed the generalized gradient approximation (GGA), which is based on exchange-correlation energy optimization to calculate the total energy. Also we have used the Engel-Vosko GGA formalism, which optimizes the corresponding potential for calculating the electronic band structure and optical properties. The electronic specific heat coefficient ({gamma}), which is a function of density of states, can be calculated from the density of states at Fermi energy N(E{sub F}). The N(E{sub F}) of the phase L1{sub 2} is found to be lower than that of D0{sub 22} structure which confirms the stability of L1{sub 2} structure. We found that the dispersion of the band structure of D0{sub 22} is denser than L1{sub 2} phase. The linear optical properties were calculated. The evaluations are based on calculations of the energy band structure. - Graphical abstract: Crystal structure of L1{sub 2} (a) and D0{sub 22} (b) phases of ScAl{sub 3} compound.

Hussain Reshak, Ali, E-mail: maalidph@yahoo.co.u [Institute of Physical Biology-South Bohemia University - Nove Hrady 37333 (Czech Republic); Charifi, Z., E-mail: charifi_z@yahoo.f [Physics Department, Faculty of Science and Engineering, University of M'sila, 28000 M'sila (Algeria); Baaziz, H. [Physics Department, Faculty of Science and Engineering, University of M'sila, 28000 M'sila (Algeria)

2010-06-15

213

Synthesis and Characterization of Zirconium-Antimony Binary and Interstitial Ternary Intermetallic Compounds.  

National Technical Information Service (NTIS)

A family of Zr sub 5 Sb sub 3 Z compounds (Z = C, O, Al, Si, P, S, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se) have been synthesized in the Mn sub 5 Si sub 3 structure. Structural refinements were carried out for the compounds Zr sub 5 Sb sub 3 Al, Zr sub 5 Sb su...

E. Garcia

1987-01-01

214

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

Microsoft Academic Search

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

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

2010-01-01

215

Mechanism of the Delayed Growth of Intermetallic Compound at the Interface between Sn?4.0Ag?0.5Cu and Cu?Zn Substrate  

Microsoft Academic Search

A Cu?Zn wetting layer was very effective to depress the excessive growth of intermetallic compound (IMC). The effect of Zn\\u000a addition to the Cu layer on the IMC growth and microvoid formation in the solder interface was similar to the effect of Zn\\u000a addition into the Sn-Ag-Cu (SAC) solders. In this study, the mechanism of slow IMC growth at the

Young Min Kim; Kyoung-Moo Harr; Young-Ho Kim

2010-01-01

216

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

Microsoft Academic Search

A study was performed which examined the solid state, intermetallic compound layer growth kinetics between 63Sn-37Pb solder and a 76Au-21Pt-3Pd (wt.%) thick film conductor on 96% alumina substrates. A linear, multivariable regression analysis was used to assess the experimental data according to the following empirical relationship: x-x0=Atn exp(-?H\\/RT). A time exponent of n=0.780.08 was observed, suggesting that a combination of

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

1997-01-01

217

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

Microsoft Academic Search

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

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

2004-01-01

218

Phase transformation and morphology of the intermetallic compounds formed at the Sn9Zn3.5Ag\\/Cu interface in aging  

Microsoft Academic Search

The morphology and phase transformation of the intermetallic compounds (IMCs) formed at the Sn9Zn3.5Ag\\/Cu interface in a solid-state reaction have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The monoclinic ??-Cu6Sn5 transforms to the hexagonal ?-Cu6Sn5 and the orthorhombic Cu5Zn8 transforms to the body-centered cubic (bcc)

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

2008-01-01

219

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

Microsoft Academic Search

The new chemical synthesis process developed in this laboratory for the preparation of the fine powders of intermetallic compounds\\u000a by the vapor-phase reduction of mixtures of constituent metal chlorides by magnesium vapor, described in Part I for titanium\\u000a aluminides, was applied to the synthesis of nickel aluminide particles. NiAl, NiAl3, and Ni2Al3 were formed by reducing mixtures of NiCl2 and

H. Y. Sohn; S. Paldey

1998-01-01

220

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

221

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

Microsoft Academic Search

The presence of an unfilled f-electron shell in rare earth intermetallic compounds under conditions of strong electron correlation between localized and\\u000a delocalized electrons is responsible for the formation of local magnetic moments. According to the data of neutron, synchrotron,\\u000a and other investigations of a number of such systems, the interaction of these moments with the local crystalline environment,\\u000a hybridization with

P. A. Alekseev; N. V. Znamenski?; V. N. Lazukov; V. E. Ke?lin; I. A. Kovalev; S. L. Kruglov; E. V. Nefedova; I. P. Sadikov

2006-01-01

222

Modeling of electromigration on void propagation at the interface between under bump metallization and intermetallic compound in flip-chip ball grid array solder joints  

NASA Astrophysics Data System (ADS)

A void pattern in Sn4Ag0.5Cu solder joints under EM stressing was empirically obtained at the under bump metallization/intermetallic compound (UBM/IMC) interface. The pattern was associated with current crowding and consumption of the UBM layer. A kinetic model was employed and modified to describe the void propagation at UBM/IMC interface. Based on the continuity condition, the void growth velocity was calculated. The analytical results were in good agreement with the experimental data.

Jen, Ming-Hwa R.; Liu, Lee-Cheng; Lai, Yi-Shao

2010-05-01

223

Cathodic deposition of refractory intermetallic compounds from FLINAK melts Part II: Preparative cathodic deposition of TiB 2 and ZrB 2 and coatings thereof  

Microsoft Academic Search

At 700C the production of TiB2 was performed by cathodic deposition of this refractory intermetallic compound on carbon cathodes from FLINAK melts containing Ti(IV) and B(III) in concentration ratios ranging from 1:3 to 1:2 and total concentrations from 2 to 10 mol% at current densities from 0.2 to 3 A cm-2. Current efficiencies were always lower than 100% but the

H. Wendt; K. Reuhl; V. Schwarz

1992-01-01

224

NMR study of magnetic state of Mn in Y-Mn intermetallic compounds: YMn2, Y6Mn23 and YMn12  

Microsoft Academic Search

55Mn spin-echo NMR spectra of the magnetically ordered states of YMn2, Y6Mn23 and YMn12 intermetallic compounds and their field-dependence have been observed at 4.2 K. The analysis of the spectra of YMn2 has suggested that YMn2 is an antiferromagnet with a [111] easy direction of magnetization. This result is consistent with the neutron diffraction study of this material. In the

Kazuyoshi Yoshimura; Yoji Nakamura

1983-01-01

225

Nuclear Quadrupole Coupling and Crystal-Field Effects in the Cubic Intermetallic Compounds ErAl3, TmAl3, and YbAl3  

Microsoft Academic Search

The presence of a large nuclear quadrupole coupling of the Al nucleus, as measured with NMR, in the cubic rare-earth aluminum intermetallic compounds beta-ErAl3, TmAl3, and YbAl3 indicates that the net charges at the rare-earth and aluminum sites differ by as much as 3 to 4 unit charges. Data on the magnetic susceptibility and this result have been used to

H. W. de Wijn; A. M. van Diepen; K. H. Buschow

1970-01-01

226

Effects of microstructure and environment on room-temperature tensile properties of B2-type polycrystalline CoTi intermetallic compound  

Microsoft Academic Search

Room-temperature tensile property and fracture mode of B2-type polycrystalline CoTi intermetallic compound was studied as functions of microstructure and environment. Using a hot-rolled CoTi sheet, various microstructures were prepared by different heat treatments and pre-straining. Tensile elongation as well as ultimate tensile strength (UTS) of specimens deformed in vacuum (i.e. intrinsic tensile elongation and strength) depended on microstructure. The hot-rolled

Yasuyuki Kaneno; Takayuki Takasugi

2003-01-01

227

Au-Cu Ordered Intermetallic Compounds: Structure, Thermodynamics and Mechanical Properties  

NASA Astrophysics Data System (ADS)

Structure, thermodynamics and mechanical properties of ordered bimetalic Au-Cu compounds AuCu_3, AuCu(I), AuCu(II) and Au_3Cu studied at elevated temperatures. For comparison simulations are also carried for pure copper, gold and their random solid solutions at the same concentrations as the ordered compounds. The volumetric and structural properties are studied upto 700 K for ordered compounds and upto melting for pure metals and random solid solutions. But, mechanical properties (elastic constants) are only calculated at room temperature and below the disorder-order transition (600 K)

Cagin, Tahir; Kimura, Yoshitaka; Li, Hao; Goddard, William A.

1997-03-01

228

Possible Mechanism of the Pseudogap Formation in Intermetallic Compound Al3V  

NASA Astrophysics Data System (ADS)

The pseudogaps in compounds give a unique electronic character in the materials such as the ones in the skutterudites. The Al3V compound with DO22 structure has also a deep pseudogap that has been explained by the presence of the covalent Al-V and Al- Al bonds in the compound [1]. We propose another possibility of the formation of the pseudogap in the DO22 compound using a density functional method. We introduce a Peierls distortions along c-axis of the double-stacked ordered unit cell, we calculate the density of states and check the gap formation. We will apply the mechanism to the other systems with pseudogap. [1] M. Krajc'i and J. Hafner, J. Phys.: Condens. Matter, 14, 1865 (2002).

Miyahara, Susumu; Tsumuraya, Kazuo

2007-03-01

229

Heat capacity studies of crystal field effects in rare-earth-iron intermetallic compounds  

Microsoft Academic Search

The heat capacity of the RFe2 compounds (R = Gd, Tb, Dy, Ho, Er, Tm and Lu) and the pseudobinary compound Ho(06)Tb(0.4)Fe2 was studied and throughout the temperature region 4.2 to 300 K. Crystal field intensity parameters and the energy level diagrams for the rare earth ions were determined. In addition, the magnetocrystalline free energies, rare earth ion magnetic moment

D. J. Germano

1980-01-01

230

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

Microsoft Academic Search

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

H. E. N. Stone

1976-01-01

231

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

Microsoft Academic Search

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

H. E. N. Stone

1976-01-01

232

The magnetostriction of the intermetallic compound ErCo2 near the magnetic phase transition paramagnetism-ferrimagnetism  

NASA Astrophysics Data System (ADS)

The purpose of this work was the investigation of magnetostriction near magnetic phase transition paramagnetism-ferrimagnetism in ferrimagnetic intermetallic compound ErCo2. It is known that 3d-electrons are delocalized and form a 3d-zone in it, whereas 4f-electrons localized and create an effective exchange field which acts on the Co sublattice. It leads to magnetic ordering of the last. We have found there is a sharp jump in the curve of thermal expansion near T = 37K, which indicates the presence of first order phase transition. Volume magnetostriction ? reach huge values (3.103 in the field ?0H = 4T near TC). At temperatures T > TC ?|| and ?? have small values in the absence of an external magnetic field. However, in fields H>Hcrit ? || and ?? rapidly increase and get the values that have the same order of magnitude as at TapproxTC. This indicates that the external magnetic field can restore the magnetism of 3d-subsystem at T>TC.

Nikitin, S. A.; Karpenkov, D. Yu; Karpenkov, A. Yu; Nizhankovskii, N. I.; Palewski, T.; Skokov, K. P.

2011-07-01

233

The order of the magnetic phase transitions in RCo2 (R = rare earth) intermetallic compounds  

NASA Astrophysics Data System (ADS)

It has been found experimentally that the order of the magnetic phase transitions in RCo2 compounds (R standing for rare-earth metals) at Tc changes from second order for the light-rare-earth series up to TbCo2 to first order for the heavier-rare-earth compounds DyCo2, HoCo2 and ErCo2. On the basis of results of fixed-spin-moment band-structure calculations for the isostructural compound YCo2 at different lattice constants, we propose an explanation for this behaviour. In contrast to the widely accepted Inoue-Shimizu theory for this class of compounds, our explanation also includes Pr, Nd which were thought to behave differently due to the influence of crystal-field effects. We show that an itinerant-electron metamagnetic transition in these compounds can occur only over a certain range of lattice constants and that the possibility of a first-order phase transition is connected to features of the electronic structure rather than to the magnitude of the transition temperature as conjectured earlier. The influence of the latter is only important if the transition takes place at elevated temperatures, where effects of spin fluctuations can suppress a first-order transition.

Khmelevskyi, S.; Mohn, P.

2000-11-01

234

Complex fragment emission from hot compound nuclei  

SciTech Connect

The experimental evidence for compound nucleus emission of complex fragments at low energies is used to interpret the emission of the same fragments at higher energies. The resulting experimental picture is that of highly excited compound nuclei formed in incomplete fusion processes which decay statistically. In particular, complex fragments appear to be produced mostly through compound nucleus decay. In the appendix a geometric-kinematic theory for incomplete fusion and the associated momentum transfer is outlined. 10 refs., 19 figs.

Moretto, L.G.

1986-03-01

235

Powder metallurgical processing of magnetostrictive materials based on rare earth-iron intermetallic compounds  

SciTech Connect

Procedures are described for fabrication of high density rare earth-iron magnetostrictive compounds by powder metallurgical techniques. The fabrication involves a sequence of steps which includes preparing the pre-alloyed compounds, pulverizing them into a fine powder, compacting in suitable sizes and shapes, and sintering. Samples prepared by these procedures are carefully characterized by scanning electron microscopy, x-ray diffraction, dilatometry, and magnetic measurements. Process steps are found to exert important influences upon densities, microstructure and magnetic properties attained after densification. Investigations on a number of these process steps, including milling time and medium, sintering, and magnetic powder alignment are described.

Malekzadeh, M.

1978-01-01

236

Near-net shape processing of TiAl intermetallic compounds via pseudoHIP-SHS route  

Microsoft Academic Search

?-Titanium aluminide (TiAl) is well known to have excellent potential for high temperature structural applications. The self propagating high-temperature synthesis (SHS) process has been expected to provide new fabrication routes for intermetallic materials. In recent years, considerable research on the reactive sintering process has been carried out for near-net shaping of intermetallics. In this study, we present a new fabrication

K. N. Ishihara; P. H. Shingu

1995-01-01

237

Synthesis and structural characterization of A{sub 3}In{sub 2}Ge{sub 4} and A{sub 5}In{sub 3}Ge{sub 6} (A=Ca, Sr, Eu, Yb)-New intermetallic compounds with complex structures, exhibiting Ge-Ge and In-In bonding  

SciTech Connect

Reported are the synthesis and the structural characterization of four new polar intermetallic phases, which exist only with mixed alkaline-earth and rare-earth metal cations in narrow homogeneity ranges. (Sr{sub 1-x}Ca{sub x}){sub 5}In{sub 3}Ge{sub 6} and (Eu{sub 1-x}Yb{sub x}){sub 5}In{sub 3}Ge{sub 6} (x{approx}0.7) crystallize in the orthorhombic space group Pnma with two formula units per unit cell (own structure type, Pearson symbol oP56). The lattice parameters are as follows: a=13.109(3)-13.266(3) A, b=4.4089(9)-4.4703(12) A, and c=23.316(5)-23.557(6) A. (Sr{sub 1-x}Ca{sub x}){sub 3}In{sub 2}Ge{sub 4} and (Sr{sub 1-x}Yb{sub x}){sub 3}In{sub 2}Ge{sub 4} (x{approx}0.4-0.5) adopt another novel monoclinic structure-type (space group C2/m, Z=4, Pearson symbol mS36) with lattice parameters in the range a=19.978(2)-20.202(2) A, b=4.5287(5)-4.5664(5) A, c=10.3295(12)-10.3447(10) A, and {beta}=98.214(2)-98.470(2){sup o}, depending on the metal cations and their ratio. The polyanionic sub-structures in both cases are based on chains of InGe{sub 4} corner-shared tetrahedra. The A{sub 5}In{sub 3}Ge{sub 6} structure (A=Sr/Ca or Sr/Yb) also features Ge{sub 4} tetramers, and isolated In atoms in nearly square-planar environment, while the A{sub 3}In{sub 2}Ge{sub 4} structure (A=Sr/Ca or Eu/Yb) contains zig-zag chains of In and Ge strings with intricate topology of cis- and trans-bonds. The experimental results have been complemented by tight-binding linear muffin-tin orbital (LMTO) band structure calculations. - Graphical abstract: The anion sub-network of A{sub 5}In{sub 3}Ge{sub 6} is based upon tetrahedral [InGe{sub 4}] chains, Ge{sub 4} tetramers isosteric with 1,3-cis-butadiene, and distorted square-planar [InGe{sub 4}] fragments. The structure of A{sub 3}In{sub 2}Ge{sub 4} is a combination of infinite Ge chains with cis- and trans-bonds in a complex (tttctc){sub n} pattern, tetrahedral [InGe{sub 4}] chains, and In zig-zag chains.

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)

2010-06-15

238

Magnetic Structure of Rare-Earth-Cobalt (RCo2) Intermetallic Compounds  

Microsoft Academic Search

Saturation magnetization and neutron diffraction measurements have been performed on cubic Laves phase compounds RCo2 in which R is Nd, Tb, Ho, and Er. Neutron powder patterns obtained at room temperature and at 15K allowed the determination of the magnetic structures. The low-temperature patterns are of the ferromagnetic or ferrimagnetic type, with large magnetic intensities superimposed on the nuclear peaks.

R. M. Moon; W. C. Koehler; John Farrell

1965-01-01

239

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

Microsoft Academic Search

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

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

1992-01-01

240

Internal asymmetry in complex compounds  

Microsoft Academic Search

This paper deals with the question whether lm:etnal asymmetry may ~rise In those Inorganic complexes of transition metals with coordination number six in which a strong ilgand field exists (low-spin complexes). In s,.ich complexes the maximum internal a~mmetry may be expected for de and d T electron configurations of the central atom {in the valence state}, a smaller asymmetry for

I. B. Bersuker

1962-01-01

241

Tuneable intramolecular intermetallic interactions as a new tool for programming linear heterometallic 4f-4f complexes.  

PubMed

Statistical mechanics predicts that the design of pure organized heteropolymetallic chains of metal ions bound to linear receptors depends on controlled deviations from the mixing rule DeltaE(MiMj) = 1/2 (DeltaE(MiMi) + DeltaE(MjMj)), whereby DeltaE(MiMj) is the intramolecular intermetallic interaction between neighboring metal i and metal j along the receptor. A thorough investigation of linear polymetallic trivalent lanthanide triple-stranded helicates shows that such deviations are amplified by an increase in the nuclearity of the final complexes and are thus easily evidenced in the tetranuclear heterobimetallic helicates [La(4-y)Lu(y)(L6)3](12+) (y = 0-4). The chemical and physical origins of this unprecedented behavior are discussed together with its practical consequences for programming pure heteropolymetallic 4f-4f complexes. PMID:17915861

Dalla-Favera, Natalia; Hamacek, Josef; Borkovec, Michal; Jeannerat, Damien; Ercolani, Gianfranco; Piguet, Claude

2007-10-04

242

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

243

Structural transformations in the deuterium-containing intermetallic compound (Ti3Al)D1.2 induced by high-pressure torsion  

NASA Astrophysics Data System (ADS)

The intermetallic compound Ti3Al (which is a very brittle material) with a high deuterium concentration ( x = 1.2) is fabricated in a monolithic state by high-pressure torsion at room temperature. The structure of the intermetallic samples is studied by X-ray diffraction and transmission electron microscopy after deformation at various degrees. Under certain conditions, the main volume of the material is found to transform into an amorphous state, and areas 1-2 nm in size with an atomic arrangement close to the initial arrangement are also present in the material. The possible causes of the deformation-induced amorphization of the material alloyed with interstitial atoms are discussed.

Eshchenko, R. N.; Elkina, O. A.; Patselov, A. M.; Pilyugin, V. P.

2009-06-01

244

Electronic properties of Hf2X intermetallic compounds (X =Al, Si, Ni, Ga and Ge)  

NASA Astrophysics Data System (ADS)

The electric field gradient (EFG) parameters were calculated for the binary system Hf2X (X =Al, Si, Ni, Ga and Ge), using the full-potential linear augmented plane wave method, applying the generalized gradient approximation. The major contribution to the EFG value in these compounds comes from the p-p contribution next to the probe nucleus. The only other significant contribution is a d-d contribution to the nickel site in Hf2Ni, arises from the broad spatial distribution of the nickel 3d electrons. The similarity in the electronic properties of the Hf2X compounds, with the exception of Hf2Ni, can be attributed to the resemblance of the crystallographic structure and the alike electronic structure of the X-ligand atom, having one or two p-electrons in the external orbital with close shells below.

Yaar, I.; Halevy, I.; Kahane, S.; Beck, A.; Berant, Z.

245

Electronic properties of Hf2X intermetallic compounds (X = Al, Si, Ni, Ga and Ge)  

NASA Astrophysics Data System (ADS)

The electric field gradient (EFG) parameters were calculated for the binary system Hf2X (X = Al, Si, Ni, Ga and Ge), using the full-potential linear augmented plane wave method, applying the generalized gradient approximation. The major contribution to the EFG value in these compounds comes from the p p contribution next to the probe nucleus. The only other significant contribution is a d d contribution to the nickel site in Hf2Ni, arises from the broad spatial distribution of the nickel 3d electrons. The similarity in the electronic properties of the Hf2X compounds, with the exception of Hf2Ni, can be attributed to the resemblance of the crystallographic structure and the alike electronic structure of the X-ligand atom, having one or two p-electrons in the external orbital with close shells below.

Yaar, I.; Halevy, I.; Kahane, S.; Beck, A.; Berant, Z.

2007-04-01

246

Ab initio calculation of atomic level stress in intermetallic compounds and glasses  

NASA Astrophysics Data System (ADS)

The atomic level stress is largely unexplored as a characterization tool that is sensitive to the local atomic environment. Local quantities, such as magnetic moment and volume, are directly related to the local pressure. For example the local Voronoi volume and pressure have the expected inverse relationship and magnetic moments are reduced due to reduced volume associated with pressure. For a simple system with one atom per unit cell at equilibrium the local stresses are zero. An atom in a multicomponent system can find itself under pressure that results from its cage of surrounding atoms. The atomic level stress is calculated with the Locally Self-consistent Multiple scattering (LSMS) method for Al-Au and Cu-Zr compounds and glasses, and trends are compared to the results for simple B2 compounds with atoms of different sizes.

Ojha, Madhusudan; Nicholson, Don M.; Egami, Takeshi

2012-02-01

247

First-principles statistical mechanics of structural stability of intermetallic compounds  

Microsoft Academic Search

While as elemental solids, Al, Ni, Cu, Rh, Pd, Pt, and Au crystallize in the face-centered-cubic (fcc) structure, at low temperatures, their 50%-50% compounds exhibit a range of structural symmetries: CuAu has the fcc-based L10 structure, CuPt has the rhombohedral L11 structure, and CuPd and AlNi have the body-centered-cubic B2 structure, while CuRh does not exist (it phase separates into

Z. W. Lu; S.-H. Wei; Alex Zunger; S. Frota-Pessoa; L. G. Ferreira

1991-01-01

248

First principles study of structural, electronic, mechanical and thermal properties of A15 intermetallic compounds Ti3X (X=Au, Pt, Ir)  

NASA Astrophysics Data System (ADS)

The structural, electronic, elastic, mechanical and thermal properties of Ti3Au, Ti3Pt and Ti3Ir intermetallic compounds crystallizing in A15 structure have been studied using density functional theory within generalized gradient approximation (GGA) for the exchange correlation potential. Elastic properties such as Young's modulus (E), rigidity modulus (G), bulk modulus (B), Poisson's ratio (?) and elastic anisotropic factor (A) have been calculated. From the present study it is noted that Ti3Ir is the hardest compound among the three materials studied due to its larger bulk modulus. Also, it is more ductile in nature.

Rajagopalan, M.; Rajiv Gandhi, R.

2012-12-01

249

Crystal-field interactions and magnetism in rare-earth transition-metal intermetallic compounds  

Microsoft Academic Search

The description of basic experiments of the rare-earth hard magnetic materials, high-field magnetization curves on single-crystalline samples of Ho2Co17 and Nd2Fe14B is reviewed with the aim to derive parameters physically relevant on atomic scale. The anisotropic magnetic properties have been found to be of single-ion origin. The successful description of the rare-earth compounds Ho2Co17, Nd2Fe14B, Pr2Fe14B, ErNi5, PrRu2Si2, ErRu2Si2 in

R. J Radwanski; R. Michalski; Z. Ropka; A. Blaut

2002-01-01

250

Possible ferrimagnetic coupling in light-rare-earth transition-metal intermetallic compounds  

Microsoft Academic Search

The possibility of ferrimagnetic coupling between the magnetic moments of the light-rare-earth (Nd, Pr) ions and of the transition-metal (Fe) ions in Nd6Ga3Fe11- and Pr6Ga3Fe11-based compounds is deduced from the high-field magnetization curves measured at 4.2 K on magnetically aligned and on free-powder samples and from the temperature dependence of the magnetization. The ferrimagnetic coupling is very weak: at 4.2

Z. G. Zhao; F. R. de Boer; V. H. M. Duijn; K. H. J. Buschow; Y. C. Chuang

1994-01-01

251

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

SciTech Connect

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

Leon-Escamilla, E.A.

1996-10-17

252

Nuclear Spin-Lattice Relaxation in the La1-cGdcAl2 Intermetallic Compounds  

Microsoft Academic Search

The contribution of Gd impurities to the spin-lattice relaxation of La139 and Al27 nuclei in the compound La1-cGdcAl2 is studied for values of c from 0.0013 to 0.10, applied magnetic fields between 3.6 and 24.4 kOe, and temperatures from 1.2 to 300 K. The impurity component of the magnetization recovery for Al27 is characterized by an exp[-(ttau1)12] time dependence, indicating

M. R. McHenry; B. G. Silbernagel; J. H. Wernick

1972-01-01

253

GMR in intermetallics  

SciTech Connect

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

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

1996-04-01

254

Magnetic behaviour of Er1-xZrxFe2 intermetallic compounds.  

PubMed

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

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

2013-10-21

255

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

NASA Astrophysics Data System (ADS)

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

Lu, Z. W.; Zunger, Alex

1994-09-01

256

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

257

Synthesis and characterization of zirconium-antimony binary and interstitial ternary intermetallic compounds  

SciTech Connect

A family of Zr/sub 5/Sb/sub 3/Z compounds (Z = C, O, Al, Si, P, S, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se) have been synthesized in the Mn/sub 5/Si/sub 3/ structure. Structural refinements were carried out for the compounds Zr/sub 5/Sb/sub 3/Al, Zr/sub 5/Sb/sub 3/Si, Zr/sub 5/Sb/sub 3/S, Zr/sub 5/Sb/sub 3/Fe, Zr/sub 5/Sb/sub 3/(Fe/sub 2/3/In/sub 1/3/). Extended-Hueckel band calculations were carried out on Zr/sub 5/Sb/sub 3/, Zr/sub 5/Sb/sub 3/S, and Zr/sub 5/Sb/sub 3/Fe. A high density of states at the Fermi energy, low lying and strongly bonding ZrSb states in the Zr/sub 5/Sb/sub 3/ host, and the strong bonding interactions between Zr and the interstitial element, combine to permit the extensive interstitial chemistry observed. The Zr-Sb binary system was reinvestigated. Five new phases were identified: Zr/sub 5/Sb/sub 3/ (Y/sub 5/Bi/sub 3/-type), ZrSb/sub 1-x/ (FeSi-type), ZrSb (ZrSb-type), ZrSb/sub 2/ (PbCl/sub 2/-type), and Zr/sub 2/Sb/sub 3/. The structure type of an additional compound was elucidated, Zr/sub 2/Sb (La/sub 2/Sb-type). The unique structure type for ZrSb was determined by a single crystal x-ray diffraction experiment, and structural refinements were also carried out for Zr/sub 5/Sb/sub 3/ (Y/sub 5/Bi/sub 3/ and Mn/sub 5/Si/sub 3/) and ZrSb/sub 2/ (PbCl/sub 2/). Extended-Hueckel band calculations were carried out on the two ZrSb/sub 2/ structural polymorphs, PbCl/sub 2/ and ZrSb/sub 2/ types.

Garcia, E.

1987-08-01

258

Competing magnetic interactions in the intermetallic compounds Pr5Ge3 and Nd5Ge3  

NASA Astrophysics Data System (ADS)

Magnetic properties of polycrystalline Pr5Ge3 and Nd5Ge3 (hexagonal, Mn5Si3-type) compounds have been studied. Magnetization measurements in 0.5 T field indicate that the Pr5Ge3 orders antiferromagnetically at 18 K (TN). However, in an applied field of 10 mT, the zero-field-cooled and field-cooled magnetization bifurcates below ~65 K. This and the positive paramagnetic Curie temperature, obtained from the Curie-Weiss fit to the paramagnetic susceptibility, suggest the presence of competing ferromagnetic and antiferromagnetic interactions. The magnetization versus field isotherm at 5 K shows an S-shaped curve and a weak tendency to saturation in fields of 9 T with negligible hysteresis. The magnetic moment attains a value of 1.6 ?B/Pr3+ at 5 K in 9 T. The magnetic entropy change near the magnetic transition has been calculated by measuring magnetization versus field isotherms close to TN. The entropy change is found to be considerably large. Neutron diffraction study indicates that below ~43 K the Nd5Ge3 has flat spiral ordering with wave vector K = [0, 0, +/-1/5] (the flat spiral axis coincides with cell parameter, a). Neutron diffraction study of Pr5Ge3 suggests that the magnetic structure of Pr5Ge3 could be similar to that in Nd5Ge3.

Nirmala, R.; Morozkin, A. V.; Nigam, A. K.; Lamsal, Jagat; Yelon, W. B.; Isnard, O.; Granovsky, S. A.; Bharathi, K. Kamala; Quezado, S.; Malik, S. K.

2011-04-01

259

Microstructural modifications induced by swift ions in the NiTi intermetallic compound  

NASA Astrophysics Data System (ADS)

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

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

1998-11-01

260

Magnetic and structural properties of Pd-Mn-Sn intermetallics compounds  

NASA Astrophysics Data System (ADS)

Magnetic and structural properties of Heusler Pd0.5Mn0.5-xSnx with x = 0.05, 0.10, 0.17, 0.20 and 0.25, have been studied by magnetisation and X-ray diffraction measurements at room and low temperatures. The crystal structure at room temperature is L21 cubic phase for x = 0.17, 0.20, 0.25 and B2 cubic phase for x = 0.10. Martensite structure 10M, was observed at room temperature for x = 0.05. X-ray measurements at low temperatures revealed a structural transformation from B2 to 14M for the x = 0.10 case. The lattice parameter of the L21 phase decreases linearly with the concentration, x. A ferromagnetic behaviour has been detected for L21 compounds, but the ferromagnetic exchange characteristic of each composition is of different strength. This gives rise to different Curie temperatures.

Da Rocha, F. S.; Kakuno, E. M.; Kinast, E. J.; Mazzaro, I.; Fraga, G. L. F.

2011-09-01

261

Magnetic properties and structure of nonstoichiometric rare-earth transition-metal intermetallic compounds TbNi 2 Mn x (0 ? x ? 1.5)  

Microsoft Academic Search

Crystal structure, magnetization, coercive force, magnetic susceptibility, and anisotropic magnetostriction of nonstoichiometric\\u000a rare-earth transition-metal intermetallic compounds TbNi2Mn\\u000a x\\u000a (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

N. V. Mushnikov; V. S. Gaviko; E. G. Gerasimov; P. B. Terentev; I. A. Tkach

2010-01-01

262

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

Microsoft Academic Search

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

M. Andrecut; I. Pop; I. Burda

1993-01-01

263

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

264

Texture evolution during hot-rolling and recrystallization in B2-type FeAl, NiAl and CoTi intermetallic compounds  

Microsoft Academic Search

The texture evolution during the hot-rolling and the recrystallization of B2-type Fe48Al, Ni50Al and Co50Ti (expressed\\u000a by at.%) intermetallic compounds were investigated. By hot-rolling at 973K, Fe48Al showed a microstructure with coarse grains\\u000a elongated along rolling direction, while Ni50Al and Co50Ti showed a deformed microstructure featured by the heavily distorted\\u000a (elongated) grains and\\/or the deformation bands. The hot-rolling texture of

Yasuyuki Kaneno; Tetsuo Yamaguchi; Takayuki Takasugi

2006-01-01

265

Hot rolling workability, texture and grain boundary character distribution of B2-type FeAl, NiAl and CoTi intermetallic compounds  

Microsoft Academic Search

Hot-rolling workability, texture and grain boundary character distribution of B2-type FeAl, NiAl and CoTi intermetallic compounds were investigated as a function of alloy stoichiometry. All the FeAl (i.e., Fe-38Al, -43Al and -48Al, denoted by at.%), and stoichiometric NiAl and CoTi were successfully hot-rolled at 1273 K but off-stoichiometric NiAl (Ni-48Al and -52Al) and CoTi (Co-48Ti and -49Ti) failed. After hot-rolling,

Y. Kaneno; T. Yamaguchi; T. Takasugi

2005-01-01

266

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

PubMed

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

Wang, Hongsen; Alden, Laif; Disalvo, F J; Abrua, Hctor D

2008-04-21

267

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

PubMed

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

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

2009-03-30

268

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

PubMed

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

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

2011-04-03

269

Nuclear Magnetic Resonances of Mn55 and N14 in Ferrimagnetic Intermetallic Mn4N---Anisotropic and Transferred Hyperfine Fields in Intermetallic Compound  

Microsoft Academic Search

NMR of Mn55 and N14 in Mn4N were studied in its ferrimagnetic ordered phase, by using both pulsed and steady state methods. Three resonance lines are separately observed from corner site Mn (Mn-I), face-centered site Mn (Mn-II) and N. The resonance line of Mn-II is much broader than those of Mn-I and N, and has a complex structure, which can

Hisashi Abe; Motohiro Matsuura; Akira Hirai; Junsuke Haruna; Mamoru Mekata

1967-01-01

270

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

SciTech Connect

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

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

1996-04-01

271

Spherical particles of intermetallic compounds of a large radius with a core-shell structure in aluminum alloys with scandium  

NASA Astrophysics Data System (ADS)

The structures of two-phase alloys that form upon slow solidification of a dilute Al-Sc melt containing a small amount of titanium additives (0.06 wt %) are studied. Near-spherical scandium trialuminide particles having a considerable linear size (up to 10-20 ?m) are found to grow. The study of the inner structure of the particles (dispersoids) reveals titanium impurities in the intermetallic structure. In addition, the following specific features of the structure are elucidated: a core-shell structure with a variation in the scandium and titanium content over the spheroid volume.

Shubin, A. B.; Popova, E. A.; Shunyaev, K. Yu.; Pastukhov, E. A.

2010-08-01

272

Effect of Tm substitution on the magnetic and magnetocaloric properties in the intermetallic compounds (Tb1-xTmx)Co2  

NASA Astrophysics Data System (ADS)

The magnetic and magnetocaloric properties of the intermetallic compounds Tb1-xTmxCo2 (with x = 0, 0.2 and 0.5) have been studied. It is found that partial replacement of Tb by Tm in TbCo2 leads to a reduction in the ordering temperature, which is attributed to the decrease in the exchange strength due to the lower spin value of Tm3+ as compared with that of Tb3+. The analysis of the zero-field heat capacity data at low temperature shows that the coefficient of electronic heat capacity increases with increase in Tm content and is attributed to the presence of local spin fluctuations. The variation of the magnetocaloric effect (MCE) has been explained on the basis of the magnetic properties. Temperature dependence of the MCE shows that this system may be useful for magnetic refrigeration applications in a sub-room temperature regime.

Singh, Niraj K.; Kumar, Pramod; Suresh, K. G.; Coelho, A. A.; Gama, S.; Nigam, A. K.

2007-03-01

273

Ab Initio Study of Structural Properties of Intermetallic Compounds PtX (X = Si, Ge, Sn and Pb) Under High Pressure  

NASA Astrophysics Data System (ADS)

High pressure effect on the structural evolution properties of intermetallic compounds PtX (X = Si, Ge, Sn AND Pb) was studied based on the first principle density functional theory. The compressibility of PtSi and PtGe under high pressure presents anisotropic behavior. The crystal stacking characteristic of the PtX (X = Si and Ge) along the three axes may be responsible for their anisotropic axial compressibility under high pressure. The sequence of axial compressibility for PtSi is c < a < b, whereas PtGe exhibits the sequence of a < c < b. The pressure derivative of c/a was qualified to be 8.9210-4GPa-1 and 1.3810-3GPa-1 for PtSn and PtPb, respectively. The applied pressure stabilized the crystal structures of PtSn and PtPb.

Li, C. Y.; Yu, Z. H.; L, T. Q.

2012-07-01

274

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

275

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

276

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

277

Structure and uniaxial magnetocrystalline anisotropy of intermetallic compounds La{sub 2}Co{sub 17{minus}x}Ti{sub x}  

SciTech Connect

The crystal structure and magnetic properties of intermetallic compounds La{sub 2}Co{sub 17{minus}x}Ti{sub x} (0.8{le}x{le}1.2) have been investigated by x-ray powder diffraction and magnetic measurement. The lattice parameters of La{sub 2}Co{sub 17{minus}x}Ti{sub x} with the rhombohedral Th{sub 2}Zn{sub 17}-type structure are a=8.518{endash}8.531{Angstrom}, c=12.344{endash}12.379{Angstrom}. Ti atoms show a strong preference for occupying 6c crystallographic positions. The La{sub 2}Co{sub 17{minus}x}Ti{sub x} compounds are ferromagnetic. The Curie temperature decreases from 972 to 872 K, and the saturation magnetic moment decreases from 23.2 to 21.3{mu}{sub B}/f.u. with x=0.8{endash}1.2. The La{sub 2}Co{sub 16}Ti compound exhibits favorable uniaxial anisotropy, and the easy magnetization direction is parallel to the c axis. The anisotropy field is 23 kOe at 1.5 K for this compound. {copyright} {ital 1997 American Institute of Physics.}

Liu, Q. [Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080, Peoples Republic of (China); Liang, J. [Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080, Peoples Republic of (China)]|[International Center for Materials Physics, Academia Sinica, Shenyang 110015, Peoples Republic of (China); Rao, G.; Tang, W.; Sun, J.; Chen, X. [Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080, Peoples Republic of (China); Shen, B. [Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080, Peoples Republic of (China)]|[State Key Laboratory of Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, Peoples Republic of (China)

1997-09-01

278

Complex Polyamines: Unique Prion Disaggregating Compounds  

PubMed Central

Among the candidate anti-prion chemotherapeutic agents identified to date, complex polyamines constitute the only class of compounds that possess the ability to remove pre-existing PrPSc molecules from infected cells. The potency of branched polyamines such as cationic dendrimers increases with the density of positive charges on their surface. Cationic dendrimers appear to accumulate together with PrPSc molecules in lysosomes, where the acidic environment facilitates dendrimer-mediated PrPSc disaggregation. Dendrimers can disaggregate a range of different amyloid proteins by interacting with specific epitopes on each protein. Studies with model peptides suggest that dendrimers may cause fiber breakage and capping of elongating fibers. Potential limitations to the development of dendrimers as therapeutic compounds for neurodegenerative disorders of protein misfolding such as prion diseases include poor bioavailability, limited spectrum of activity, and detrimental neurological side effects. A related group of compounds, lipopolyamines, are smaller molecules containing a lipophilic tail that may assist membrane targeting. Developing strategies to enable the safe delivery of potent complex polyamines to the central nervous system represents a critical avenue for future research.

Supattapone, Surachai; Piro, Justin R.; Rees, Judy R.

2011-01-01

279

Intermetallic Compounds Formed in In-3Ag Solder BGA Packages with ENIG and ImAg Surface Finishes  

NASA Astrophysics Data System (ADS)

During the reflow process of In-3Ag solder ball grid array (BGA) packages with electroless nickel immersion gold (ENIG) and immersion silver (ImAg) surface finishes, continuous (Au0.9Ni0.1)In2 and scallop-shaped (Ag0.9Cu0.1)In2 intermetallic layers form at the interfaces of In-3Ag solder with Au/Ni/Cu and Ag/Cu pads, respectively. The (Au0.9Ni0.1)In2 layer breaks into clusters with increases in the aging time and temperature. Aging at 115 C results in the formation of an additional continuous Ni10In27 layer on the Ni/Cu pads and the migration of (Au0.9Ni0.1)In2 intermetallic clusters into the solder matrix. In contrast, the (Ag0.9Cu0.1)In2 scallops grow into a continuous layer after aging treatment. Accompanying the interfacial reactions, AgIn2 precipitates in the interior of In-3Ag solder balls and coarsens during aging, causing the ball shear strengths of reflown ENIG (1.18 N) and ImAg (1.11 N)-surface-finished solder joints to decrease gradually. However, the migration of (Au0.9Ni0.1)In2 clusters into the solder matrix of ENIG-surface-finished In-3Ag packages leads to an increase in their ball shear strengths after aging at 115 C over 300 h. Both the ENIG- and ImAg-surface-finished In-3Ag solder joints, after ball shear tests, have fractured across the solder balls with ductile characteristics.

Chuang, T. H.; Jain, C. C.; Wang, S. S.

2009-11-01

280

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

SciTech Connect

The hydrogenation properties of the LaNi{sub 5} (CaCu{sub 5} type, hP6, P6/mmm) and Pd substituted derivatives LaNi{sub 5-x}Pd{sub x} compounds have been studied in the whole homogeneity range of the solid solution (0.25{<=}x{<=}1.5). The pressure versus hydrogen content isotherms show several plateaus and an increase of the plateau pressure as a function of palladium concentration. The volume increase of the Pd substituted alloys should have resulted in a lowering, and not an increase, of the plateau pressure, according to the conventional models based on the size effect. In order to elucidate the origin of this anomalous behavior, both an experimental and a theoretical ab initio electronic structure investigation have been carried out. Experimentally, the nature and the structural properties of the hydrides have been studied by both in situ and ex situ neutron diffraction. The crystal structures of the three hydride phases are reported (LaNi{sub 3.5}Pd{sub 1.5}D{sub 1.96}, filled-up CaCu{sub 5} type, P6/mmm; LaNi{sub 4}PdD{sub 2.72}, LaNi{sub 2}(Ni{sub 0.75}Pt{sub 0.25}){sub 3}H{sub 2.61} type, oI128, Ibam; LaNi{sub 4.75}Pd{sub 0.25}D{sub 5.67}, partly ordered CaCu{sub 5} type, P6mm). In addition, the phase diagram of LaNi{sub 5-x}Pd{sub x}-H system has been investigated. The electronic and thermodynamic properties of both intermetallic compounds and the hydrides have been studied by ab initio electronic structure calculations. The theoretical results are in good agreement with our experimental data, and show that electronic interactions play a major role in the hydrogenation behavior of these Pd substituted intermetallic compounds, and that these effects cannot be accounted for by a simplistic model based on the size effect alone. -- Graphical abstract: Phase diagram of the system LaNi{sub 5-x}Pd{sub x}-D{sub 2} (absorption) at 25 {sup o}C and 25 bar. Display Omitted

Prigent, J. [Chimie Metallurgique des Terres Rares, Institut de Chimie et Materiaux Paris-Est, CNRS, Universite Paris-Est, 2-8 rue H. Dunant, 94320 Thiais Cedex (France); Laboratoire de Thermodynamique et Physico-Chimie des Hydrures et Oxydes, Universite Paris-Sud Orsay, Bat. 415, 91405 Orsay (France); Joubert, J.-M., E-mail: jean-marc.joubert@icmpe.cnrs.f [Chimie Metallurgique des Terres Rares, Institut de Chimie et Materiaux Paris-Est, CNRS, Universite Paris-Est, 2-8 rue H. Dunant, 94320 Thiais Cedex (France); Gupta, M. [Laboratoire de Thermodynamique et Physico-Chimie des Hydrures et Oxydes, Universite Paris-Sud Orsay, Bat. 415, 91405 Orsay (France)

2011-01-15

281

Intermetallic-matrix compositesa review  

Microsoft Academic Search

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

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

1996-01-01

282

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

NASA Astrophysics Data System (ADS)

SrZn2Sn2 and Ca2Zn3Sn6, two closely related new polar intermetallic compounds, were obtained by high temperature reactions of the elements. Their crystal structures were determined with single crystal XRD methods, and their electronic structures were analyzed by means of DFT calculations. The Zn-Sn structure part of SrZn2Sn2 comprises (anti-)PbO-like {ZnSn4/4} and {SnZn4/4} layers. Ca2Zn3Sn6 shows similar {ZnSn4/4} layers and {Sn4Zn} slabs constructed of a covalently bonded Sn scaffold capped by Zn atoms. For both phases, the two types of layers are alternatingly stacked and interconnected via Zn-Sn bonds. SrZn2Sn2 adopts the SrPd2Bi2 structure type, and Ca2Zn3Sn6 is isotypic to the R2Zn3Ge6 compounds (R=La, Ce, Pr, Nd). Band structure calculations indicate that both SrZn2Sn2 and Ca2Zn3Sn6 are metallic. Analyses of the chemical bonding with the electron localization function (ELF) show lone pair like basins at Sn atoms and Zn-Sn bonding interactions between the layers for both title phases, and covalent Sn-Sn bonding within the {Sn4Zn} layers of Ca2Zn3Sn6.

Stegmaier, Saskia; Fssler, Thomas F.

2012-08-01

283

Developments in rare earth intermetallics  

SciTech Connect

The magnetic properties of rare earth intermetallics have been the subject of numerous investigations in recent years. However, while the preparation of new intermetallic compounds and the determination of their properties have been the prime concern in former years, more recently the analysis and theoretical explanation of the available data has become most important. Furthermore single crystals have now become available, which permit new experiments. Also many investigations on pseudo-binary systems have permitted the systematic determination of the primary magnetic properties. After a summary of the magnetic properties of intermetallics where the B-moment is zero and nonzero, some examples of pseudobinary systems and especially applications of R-3d multicomponent systems as the basis for advanced permanent magnets are discussed. Finally RE-3d alloys with metalloids and non-metals are discussed with emphasis on the newly developed R-Fe-B permanent magnets.

Kirchmayr, H.R.

1984-09-01

284

DEVELOPMENT OF INTERMETALLIC COMPOUNDS FOR VERY HIGH TEMPERATURE APPLICATIONS. Summary Technical Report, January 1, 1962 through August 31, 1962  

Microsoft Academic Search

Investigations of the intermediate-temperature problems, particularly ; those of oxidation, of the zirconium and niobium beryllides are discussed. The ; primary emphasis of the work was on additives to these compounds to promote ; intermediate-temperature oxidation resistance. Aluminum and NiAl additions to ; ZrBe completely eliminate accelerated oxidation of this compound at ; intermediate temperatures (1100 to 1700 un. Concent

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

1962-01-01

285

Experimental characterization and mechanical behavior analysis on intermetallic compounds of 96.5Sn3.5Ag and 63Sn37Pb solder bump with Ti-Cu-Ni UBM on copper chip  

Microsoft Academic Search

This study investigated the mechanical behavior of flip-chip lead-free solder bumps affected by solder\\/UBM intermetallic compound formation in the duration of isothermal aging. To attain the objective, test vehicles of Sn-Ag (lead-free) and Sn-Pb (lead-containing) solder bump systems were used to experimentally characterize and analyze their mechanical behavior. By way of metallurgical microscopy and SEM observation, the interfacial microstructure of

Chih-Tang Peng; Chia-Tai Kuo; Kuo-Ning Chiang; Terry Ku; Kenny Chang

2004-01-01

286

Experimental characterization and mechanical behavior analysis of intermetallic compounds of Sn3.5Ag lead-free solder bump with Ti\\/Cu\\/Ni UBM on copper chip  

Microsoft Academic Search

Due to todays trend towards green products, the environmentally conscious manufacturers are moving toward lead-free schemes for electronic devices and components. Nowadays the bumping process has become a branch of the infrastructure of flip chip bonding technology. However, the formation of excessively brittle intermetallic compound (IMC) between under bump metallurgy (UBM)\\/solder bump interface influences the strength of solder bumps within

Chih-tang Peng; Chia-tai Kuo; Kuo-ning Chiang; Terry Ku; Kenny Chang

2006-01-01

287

Thermodynamic and kinetic study on intermetallic compounds palladium-indium and tripalladium-indium: Bulk and thin film cases  

Microsoft Academic Search

I have thermodynamically and kinetically studied the compounds PdIn and Pd3In, which including experimental investigation and thermodynamic modeling of the In-Pd binary system, diffusion in the bulk B2 compound PdIn, grain growth in nanoscale PdIn thin films, and phase transformation in Pd 3In of both deformed alloys and sputter deposited thin films. In the modeling of the In-Pd binary system,

Mianliang Huang

2004-01-01

288

Interfacial intermetallic compound growth and shear strength of low-silver SnAgCuBiNi/Cu lead-free solder joints  

NASA Astrophysics Data System (ADS)

The growth rule of the interfacial intermetallic compound (IMC) and the degradation of shear strength of Sn-0.8Ag-0.5Cu-2.0Bi-0.05Ni (SACBN)/Cu solder joints were investigated in comparison with Sn-3.0Ag-0.5Cu (SAC305)/Cu solder joints aging at 373, 403, and 438 K. The results show that (Cu1- x ,Ni x )6Sn5 phase forms between the SACBN solder and Cu substrate during soldering. The interfacial IMC thickens constantly with the aging time increasing, and the higher the aging temperature, the faster the IMC layer grows. Compared with the SAC305/Cu couple, the SACBN/Cu couple exhibits a lower layer growth coefficient. The activation energies of IMC growth for SACBN/Cu and SAC305/Cu couples are 111.70 and 82.35 kJ/mol, respectively. In general, the shear strength of aged solder joints declines continuously. However, SACBN/Cu solder joints exhibit a better shear strength than SAC305/Cu solder joints.

Wei, Guo-qiang; Wang, Lei; Peng, Xin-qiang; Xue, Ming-yang

2013-09-01

289

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 260C and 300C for 10 s, respectively. Aging treatment was carried out at 150C 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 300C, 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 300C was lower than that bonded at 260C 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

290

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

291

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

NASA Astrophysics Data System (ADS)

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

Divi, M.

2012-07-01

292

Electrical and Hall Resistivity in Rare Earth Intermetallic Compounds RAg1-xInx (R: Gd, Tb and Dy)  

NASA Astrophysics Data System (ADS)

The electrical resistivity and the Hall resistivity in polycrystalline specimens of RAg1-xInx have been measured from 4.2 K to room temperature and the paramagnetic region up to room temperature, respectively. The spin disorder resistivity at 0 K, ?m(0), takes a maximum near the boundary of the different magnetic structures in each compound system, and that above the Curie temperature, ?m(?), increases with x in Gd system, while it takes a maximum around x{=}0.3 in Tb and Dy systems. The ordinary Hall coefficient, R0, is positive for all the compounds. On the other hand, the spontaneous Hall coefficient, Rs, is negative for all the compounds except GdAg and TbAg and its magnitude increases with x for x?0.1 in all the systems. The results have been discussed on the basis of the localized spin model.

Yagasaki, Katsuma; Fujii, Hironobu; Fujiwara, Hiroshi; Okamoto, Tetsuhiko

1980-07-01

293

Origin of the anomalous contributions to the ac magnetic susceptibility of rare-earth-iron intermetallic compounds  

NASA Astrophysics Data System (ADS)

A systematic ac magnetic susceptibility, ?ac(T) , study has been performed on several R2Fe14BHx ( R=rare earth) compounds in order to determine the origin of the anomalous behavior of ?ac(T) not related to spin reorientation transitionsthe so-called non-SRT anomalies. All the measurements have been performed on magnetically oriented samples to identify the anomalies due to domain-wall displacements. Different types of non-SRT anomalies have been found. It has been found that the anomalous behavior is mainly due to the existence of mobile defects coupled to the domain walls, which existence has been confirmed by performing magnetic aftereffect measurements. However, this mechanism alone cannot explain the whole phenomenology and other influences on ?ac(T) have to be taken into account to correctly describe the non-SRT anomalies. Specifically, three situations are possible when analyzing the anomalous behavior of ?ac(T) : (1) compounds with no magnetic R anisotropy, in which the non-SRT anomalies are due to the existence of one or more mobile defects coupled to the domain walls, (2) compounds in which a large magnetic R anisotropy can influence the domain-wall mobility at very low temperatures, and (3) compounds in which a large magnetic R anisotropy and the existence of SRTs can influence the response of the domain walls coupled to mobile defects. Different fitting models have been proposed for each case.

Piquer, C.; Bartolom, J.; de Francisco, C.; Muoz, J. M.

2009-05-01

294

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

PubMed

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

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

2013-03-25

295

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

NASA Astrophysics Data System (ADS)

The thermal expansion and magnetostriction of Co-rich HoFe11?xCoxTi compounds were investigated; using the strain gauge method in the temperature range 77560 K, under applied magnetic fields up to 1.5 T. Both linear thermal expansion coefficient and volume magnetostriction of HoFe2Co9Ti exhibit a large anomaly near the spin reorientation transition. In HoCo11Ti sample, this anomaly is only present in the volume curve at the spin reorientation transition. The temperature dependence of anisotropic magnetostriction shows a similar behaviour in both samples. There is no saturation in the isotherm curves of anisotropic magnetostriction in HoCo11Ti compound. In contrast, saturation behaviour starts approximately from T=410 K in HoFe2Co9Ti. The magnetovolume effect in Fe-containing compound at around spin reorientation transition in the maximum available magnetic field is approximately two times larger than that in the other sample. The anisotropic and volume magnetostriction results are discussed in terms of the contribution of magnetostriction attributed to the magnetic sublattices R and T and the local magnetic moment model.

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

2013-10-01

296

The analysis of the magnetic properties in the intermetallic YxGd1-xNi3 compounds  

NASA Astrophysics Data System (ADS)

In the paper an influence of Gd/Y substitution on the magnetic properties and exchange interactions of the YxGd1-xNi3 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) polycrystalline compounds have been studied. The partial replacement of Gd by Y atoms is reflected in decreasing of the Curie temperature (TC) as well as decreasing of effective the magnetic moment (?eff). It has been shown that such a behaviour strongly depends on the magnetic interactions. Exchange coupling parameters of R-R (ARR), T-T (ATT) and R-T (ART) have been evaluated from M(T) magnetization curves (2-300 K, 2 T) based on the mean field theory (MFT) calculation. The magnetocaloric effect (MCE) has been estimated from the family of magnetic isotherms. The magnetic entropy indicates relatively small change with the Gd/Y substitution. The value of ?Sm(T,H) is higher for Gd-rich compounds and, respectively, decreases with Gd/Y substitution.

Bajorek, Anna; Chrobak, Artur; Che?kowska, Gra?yna; Kwiecie?-Grudziecka, Marzena

2012-12-01

297

Effect of Cross-Interaction between Ni and Cu on Growth Kinetics of Intermetallic Compounds in Ni/Sn/Cu Diffusion Couples during Aging  

NASA Astrophysics Data System (ADS)

The solid-state, cross-interaction between the Ni layer on the component side and the Cu pad on the printed circuit board (PCB) side in ball grid array (BGA) solder joints was investigated by employing Ni(15 ?m)/Sn(65 ?m)/Cu ternary diffusion couples. The ternary diffusion couples were prepared by sequentially electroplating Sn and Ni on a Cu foil and were aged isothermally at 150, 180, and 200C. The growth of the intermetallic compound (IMC) layer on the Ni side was coupled with that on the Cu side by the mass flux across the Sn layer that was caused by the difference in the Ni content between the (Cu1- x Ni x )6Sn5 layer on the Ni side and the (Cu1- y Ni y )6Sn5 layer on the Cu side. As the consequence of the coupling, the growth rate of the (Cu1- x Ni x )6 Sn5 layer on the Ni side was rapidly accelerated by decreasing Sn layer thickness and increasing aging temperature. Owing to the cross-interaction with the top Ni layer, the growth rate of the (Cu1- y Ni y )6Sn5 layer on the Cu side was accelerated at 150C and 180C but was retarded at 200C, while the growth rate of the Cu3Sn layer was always retarded. The growth kinetic model proposed in an attempt to interpret the experimental results was able to reproduce qualitatively all of the important experimental observations pertaining to the growth of the IMC layers in the Ni/Sn/Cu diffusion couple.

Hong, K. K.; Ryu, J. B.; Park, C. Y.; Huh, J. Y.

2008-01-01

298

27Al and 63Cu NMR studies on intermetallic Kondo compound CeCu3Al2  

NASA Astrophysics Data System (ADS)

Detailed 27Al and 63Cu nuclear magnetic resonance (NMR) experiments have been performed in between 4.5 and 295 K on a polycrystalline sample of CeCu3Al2 which has a Kondo temperature 11K. The NMR spectral features and Knight shift measurements show that in this compound, Cu occupy both c and g lattice sites, while Al occupy only the g sites. From the temperature dependence of Knight shift (K), the hyperfine fields for 63Cu and 27Al at the g sites have been estimated as 2.02(5) and 1.67(5)kOe/?B, respectively, and that for 63Cu at c sites as -3.83(5)kOe/?B. Nuclear spin-lattice relaxation time (T1) measurements indicate that though the relaxation process is governed by fluctuations of magnetic interaction, nuclear quadrupolar interaction also has a significant contribution, especially towards relaxation of 63Cu in both c and g sites. For 27Al, K and T1 have yielded the effective 4f-spin correlation rate 1/?4f. The behavior of its temperature dependence indicates that at low temperatures in CeCu3Al2, the valence state of cerium might not be stable.

Bandyopadhyay, B.; Majumder, M.; Ghoshray, A.; Ghoshray, K.

2010-11-01

299

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

Microsoft Academic Search

The interfacial reactions between Sn-0.4Co-0.7Cu eutectic alloy and immersion Au\\/electroless Ni(P)\\/Cu substrate were investigated after reflow soldering at 260degC for 2 minutes. Common Sn-4.0Ag-0.5Cu and eutectic Sn-0.7Cu solders were used as reference. Two types of intermetallic compounds (IMC) were found in the solder matrix of the Sn-0.4Co-0.7Cu alloy, namely coarser CoSn2 and finer Cu6 Sn5 particles, while only one ternary

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

2006-01-01

300

INTERMETALLIC COATINGS FOR HIGH TEMPERATURE APPLICATIONS - A REVIEW  

Microsoft Academic Search

Protection of high temperature materials in the aggressive environment is achieved by the use of coatings. Various types of high temperature coatings have been developed over the years to accomplish this protection. One class of coating is based exclusively on the use of intermetallic compounds such as aluminides and silicides of transition and refractory metals. These intermetallic coatings are produced

P. C Patnaik

1989-01-01

301

Treatment of Complex Cyanide Compounds for Reuse or Disposal.  

National Technical Information Service (NTIS)

Complex cyanides (ferro-and ferricyanide) in industrial waste water effluents impose a direct threat upon the environment. Methods to recover or destroy these compounds were evaluated in laboratory studies. The techniques tested include electrolysis, ozon...

T. N. Hendrickson L. G. Daignault

1973-01-01

302

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

303

Orientation distribution, morphology, and size distribution of copper-tin intermetallic compound in reactions between molten solder and copper in flip chip solder joints  

NASA Astrophysics Data System (ADS)

Metallic bonding between copper and solder is achieved through the formation and growth of Cu-Sn intermetallic compound (IMC) at the interface between them. Many reliability issues of solder joints are related to the formation and growth of the IMC since failure tends to occur at solder joint interfaces. Thus understanding on IMC formation and growth can help to improve reliability of solder joints. In this study, a systematic study on formation, growth and morphology of Cu6Sn5 IMC has been conducted. To understand formation mechanism of the Cu6Sn 5, structural relationship between the Cu6Sn5 and substrate Cu was investigated. The orientation distribution of the Cu 6Sn5 scallops and its relationship with the orientation of Cu was studied using synchrotron radiation based micro x-ray diffraction. The orientation of the Cu6Sn5 scallops had a strong dependence on that of Cu. The [-101] direction of Cu6Sn5 is always parallel to [110] of the Cu. The misfit was 0.24%. The strong correlation in orientation suggests that Cu6Sn5 forms prior to the Cu3Sn in solder reaction. The orientation relationship was still valid when pure Sn reacted with Cu, suggesting that Pb-free solders will show same results. A (001) single crystal Cu was used as substrate to simplify experimental conditions because the low misfit directions between Cu 6Sn5 and Cu lie on (001) plane of Cu. The morphology of Cu 6Sn5 showed a dramatic change, indicating that ripening and growth mechanism of Cu6Sn5 may be different from the usual case. Once Cu6Sn5 has formed, both ripening and growth of Cu6Sn5 takes place at the solder/metal interface. It was found that morphology of Cu6Sn5 scallops depends on composition of solder. The Cu6Sn5 scallops showed round scallop-type morphology when the SnPb solder composition was changed from eutectic (63Sn37Pb) to about 40Sn60Pb. In other compositions, the IMCs showed faceted morphology. The 55Sn45Pb solder was chosen to measure the size distribution and growth rate of scallops. Average radius of scallops was proportional to cube root of time, and size distribution was in good agreement with the Flux-Driven-Ripening (FDR) theory, which assumed nonconservative ripening under constant total interfacial area between the scallops and solder.

Suh, Jongook

304

Metal complex catalysis in the synthesis of organomagnesium compounds  

NASA Astrophysics Data System (ADS)

The published data on the synthesis of organomagnesium compounds assisted by metal complex catalysts are generalised and described systematically for the first time. Hydro-, carbo- and cyclomagnesiation reactions of unsaturated compounds with R1MgR2 (R1 = Alk, Ar; R2 = H, Hal; R1 = R2 = Alk) catalysed by Ti, Zr and other transition metal salts and complexes are considered. Selected examples of applications of organomagnesium reagents to organic synthesis are given.

Dzhemilev, Usein M.; Ibragimov, Askhat G.

2005-09-01

305

Recovery of rare metals from scrap of rare earth intermetallic material by chemical vapour transport  

Microsoft Academic Search

A dry process for recovery of rare metals from sludges of Sm2Co17, Nd2Fe14B and LaNi5 intermetallic compounds was investigated using chemical vapour transport along a given temperature gradient. Chlorine and aluminium chloride were used as a chlorinating agent and a transporting agent respectively, and the rare metal chlorides were chemically transported as vapour complexes, e.g. RAlnCl3+3n (R = rare earth),

Kuniaki Murase; Ken-ichi Machida; Gin-ya Adachi

1995-01-01

306

Complex compound polyvinyl alcohol-titanic acid/titanium dioxide  

NASA Astrophysics Data System (ADS)

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

Prosanov, I. Yu.

2013-02-01

307

Emission of complex fragments in compound nucleus decay  

SciTech Connect

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

Moretto, L.G.

1986-04-01

308

FUNDAMENTAL STUDIES IN HIGH TEMPERATURE MATERIALS PHENOMENA. SCOPE I. HIGH TEMPERATURE-PRESSURE PHYSICAL PROPERTY MEASUREMENTS. SCOPE II. ELECTRICAL RESISTIVITY MEASUREMENTS OF MATERIALS IN RELATION TO HIGH TEMPERATURE TRANSFORMATIONS. SCOPE III. TRANSFORMATIONS IN AB INTERMETALLIC COMPOUNDS. Annual Progress Report, March 12, 1963  

Microsoft Academic Search

Progress on high-temperature and high-pressure physical property ; measurements, electrical resistivity measurements of materials in relation to ; high-temperature transformations, and studies of transformations in AB ; intermetallic compounds is reported. Highly sensitive equipment for the ; noncontact rotating field method of measuring dielectric loss was designed and ; constructed. Pyroelectric measurements on high-permittivity relaxation materials ; demonstrated ferroelectric properties

M. E. Bell; W. R. Buessem; R. Roy; C. C. Crowe; G. W. Brindley

1963-01-01

309

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

310

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

311

Complex conductivity of UTX compounds in high magnetic fields  

SciTech Connect

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

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

2008-01-01

312

Weldability of intermetallic alloys  

SciTech Connect

Ordered intermetallic alloys are a unique class of material that have potential for structural applications at elevated temperatures. The paper describes the welding and weldability of these alloys. The alloys studied were nickel aluminide (Ni[sub 3]Al), titanium aluminide (Ti[sub 3]Al), and iron aluminide.

David, S.A. (Oak Ridge National Lab., TN (United States))

1990-01-01

313

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

SciTech Connect

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

Cao, Qing

2012-07-26

314

Synthesis of Ni 3Al intermetallic powder in eutectic molten salts  

Microsoft Academic Search

The powders of Ni3Al intermetallic compounds were simply and economically synthesized by the chemical reaction in the various molten salts systems. In the relatively low temperature ranges, we studied to synthesize Ni3Al intermetallic powders from Al and NiCl2 in five kinds of eutectic molten salts by varying the reaction time and mole ratio of reactants. Ni3Al intermetallic powders could be

Hyun-Suk Choo; Kwan-Young Lee; Yun-Sung Kim; Jung-Ho Wee

2005-01-01

315

Magnetoelastic waves in rare-earth intermetallics  

Microsoft Academic Search

A theory of low frequency magnetoelastic waves is developed for rare-earth intermetallic compounds crystallizing in the Laves-phase (C15) structure. The long-wavelength modes of the lattice are calculated in terms of three sets of force constants. The triply-degenerate set of oscillations in which only the rare earths move is shown to be the only set which can couple to the magnetization

K. B. Hathaway; J. R. Cullen

1978-01-01

316

Complexes of polyvinyl alcohol with insoluble inorganic compounds  

NASA Astrophysics Data System (ADS)

Hybrid materials of polyvinyl alcohol-hydroxides/oxides of Be, Mg, Zn, Cd, B, Al, Cr, and Fe have been obtained. The studies have been carried out by the methods of optical spectroscopy, X-ray diffraction, and synchronous thermal analysis. Interpretation of experimental data is presented, presuming that, in systems with zinc, boron, aluminum, chromium, and iron hydroxides/oxides, interpolymeric complexes of polyvinyl alcohol with corresponding polymeric inorganic compounds are formed. They belong to a new class of materials with unusual structure containing chains of inorganic polymers isolated in the organic matrix.

Prosanov, I. Yu.; Bulina, N. V.; Gerasimov, K. B.

2013-10-01

317

Interdiffusion in Intermetallics  

NASA Astrophysics Data System (ADS)

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

Belova, Irina V.; Murch, Graeme E.

2013-10-01

318

Magnetic characteristics of rare-earth indium RIn (R=Y, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm) intermetallic compounds  

Microsoft Academic Search

Measurements of the magnetic susceptibility of the RIn compounds from 4.2 to 270 K have been made. All compounds except YIn and SmIn exhibit Curie-Weiss behavior at high temperatures with effective magnetic moments agreeing reasonably well with the free-ion 3+ picture modified by RKKY exchange except for GdIn, which gives an unusually high value for the effective moment. With the

H. Gamari-Seale; T. Anagnostopoulos; J. K. Yakinthos

1979-01-01

319

Magnetic characteristics of rare-earth indium R2In (R=Y, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm) intermetallic compounds  

Microsoft Academic Search

Measurements of the magnetic susceptibility of the R2In compounds from 4.2 to 270 K have been made. All compounds except Y2In and Sm2In exhibit Curie-Weiss behavior at high temperatures with effective magnetic moments agreeing reasonably well with the free-ion 3+ picture modified by RKKY exchange except for Gd2In, which gives an unusually high value for the effective moment. With the

Helen Gamari-Seale; T. Anagnostopoulos; J. K. Yakinthos

1979-01-01

320

New icosahedral nanoclusters in crystal structures of intermetallic compounds: Topological types of 50-atom deltahedra D50 in samson phases ?-Mg2Al3 and ?-Mg23Al30  

NASA Astrophysics Data System (ADS)

A database of intermetallic compounds has been compiled using the TOPOS program package. This database includes 514 topological types, containing 12- and 13-atom icosahedral i clusters. An isolated group of 1649 i clusters is described by 14 point groups and their maximum symmetry D 3 d (bar 3 m) and T h ( m bar 3) is established, respectively, in 47 and 25 types of crystal structures. A structural analysis of the outer quasispherical shells showed that local 63-atom i configurations 1@12@50, which contain 50 atoms in the second layer, are implemented in 8 out of 19 cases. Examples of new topologically different types of 50-atom D50 deltahedra in the Samson phases ?-Mg23Al30 and ?-Mg2Al3 are presented. Four topologically different sites with coordination numbers of 5, 6, 6, or 7 are established in the ? shell and seven sites with coordination numbers of 5, 5, 6, 6, 6, 6, or 7 are found in the ? shell. The inner i clusters for the ?-Mg2Al3 structure (with the symmetry bar 3 m) and the ?-Mg23Al30 structure (with the symmetry bar 3) have a similar chemical composition, i.e., Mg7Al6 and Mg6Al7, and their 50-atom shells are chemically identical to 18Mg + 32Al. The configurations found supplement the series of known two-layer icosahedral Bergman and Mackay clusters in the form of deltahedra with 32- and 42-atom shells.

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

2012-12-01

321

Characterization and modeling of intermetallic phases formed during soldering of Sn-Pb-Ag alloy on copper substrates  

Microsoft Academic Search

In solder-copper diffusion couples an intermetallic compound layer forms when tin in the solder alloy reacts with the copper substrate. During reflow soldering, the intermetallic compound may also dissolve from the layer into the molten solder. Experimental studies using 62% tin-36% lead-2% silver solder on copper substrates were done in order to evaluate the growth and dissolution behavior of these

P. Mathew Schaefer

1997-01-01

322

Recent advances in ordered intermetallics  

SciTech Connect

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

Liu, C.T.

1992-12-31

323

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

324

159Tb NMR in Tb(Fe1-xCox)2 and Tb0.8Y0.2Fe2 Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

Spin echo NMR measurements on 159Tb have been done in magnetically ordered state of the cubic Laves phase compounds Tb(Fe1-xCox)2 and Tb0.8Y0.2Fe2. Satellite structures observed in the compounds with x?0.2 are assigned to various Fe, Co configurations in the nearest neighbor shell. The resonance frequency corresponding to the -1/2{?ftrightarrow}1/2 transition decreases from 3798 3 MHz in TbFe2 to 3387 3 MHz in TbCo2 with increasing Co concentration. The frequency differences between the lines corresponding to the -3/2{?ftrightarrow}-1/2 and -1/2{?ftrightarrow}1/2 transitions are 685 6 MHz in TbFe2 and 675 7 MHz in TbCo2.

Shimizu, Kenji; Okeya, So-haku

1986-04-01

325

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

326

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

Microsoft Academic Search

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 direction, the first peak is ascribed to a spontaneous first-order spin reorientation transition (SRT) at T1=63 K, and the second one

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

2010-01-01

327

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

Microsoft Academic Search

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

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

2010-01-01

328

Intermetallics for permanent magnets  

SciTech Connect

Going back as far as 1931, it is shown by the examples MnAl, Fe-Nd, Fe-Nd-B, Fe(-Ti)-Sm how the history of permanent magnet materials might have evolved differently if hints had been heeded that were discernible long before a particular magnet development actually began. This account relates the lessons learned, discusses the directions being taken in the exploration of multicomponent alloy systems, and suggests ways to search for intermetallics that are potential permanent magnet materials.

Stadelmaier, H.H. (North Carolina State Univ., Raleigh, NC (United States). Dept. of Materials Science and Engineering)

1993-11-01

329

Complex Hydride Compounds with Enhanced Hydrogen Storage Capacity  

SciTech Connect

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

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

2008-02-18

330

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

331

Sorption of heterocyclic compounds from a complex mixture of coal-tar compounds on natural clayey till  

Microsoft Academic Search

The sorption and desorption of heterocyclic organic compounds in a complex multisolute system to a natural clayey till was investigated. The composition of the solutes reflect a simplified composition of an aqueous phase in contact with coal tar. Sorption was studied for two ratios (s:l) of clayey till (solid) to aqueous phase (liquid). The effect of the complex mixture of

Mette M. Broholm; Kim Broholm; Erik Arvin

1999-01-01

332

The Generalized Standard Addition Method: Intermetallic Interferences in Anodic Stripping Voltammetry.  

National Technical Information Service (NTIS)

A barrier to routine application of anodic stripping voltammetry is the possible formation of intermetallic compounds which can lead to significant errors in the estimated analyte concentrations. As the well known method of standard additions can correct ...

R. W. Gerlach B. R. Kowalski

1981-01-01

333

Codetermination of crystal structures at high pressure: Combined application of theory and experiment to the intermetallic compound AuGa2  

NASA Astrophysics Data System (ADS)

A combination of x-ray diffraction at high pressures and first-principles calculations reveals the sequence of crystal-structural phase transitions in AuGa2 from cubic (Fm3m) to orthorhombic (Pnma) at 10 (4) GPa and then to monoclinic (P21/n) at 33 (6) GPa. Neither theory nor experiment would have been adequate, on their own, in documenting this sequence of phases, but together they confirm a sequence differing from the Fm3m?Pnma?P63/mmc transitions predicted for CaF2 and Pnma ? P1121/a transition reported for PbCl2 and SnCl2. The combined results from theory and experiment also allow us to constrain the equations of state of the three phases of AuGa2. Calculations on the analog PbCl2 predict a transition to the P21/n phase seen in AuGa2 that could, therefore, be a common high-pressure phase for PbCl2-structured compounds.

Godwal, B. K.; Stackhouse, S.; Yan, J.; Speziale, S.; Militzer, Burkhard; Jeanloz, R.

2013-03-01

334

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

SciTech Connect

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

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

1995-11-01

335

Electrochemical Synthesis of Complex Compounds of Transition Elements with Carboxyl and Carbonyl-containing Ligands  

Microsoft Academic Search

Complex compounds of d- and f-elements with carboxyl- and carbonyl-containing ligands were synthesized by the electrochemical method. The influence exerted by a number of factors on the process course was studied. The dependence of the electrosynthesis parameters on the composition of the forming compounds was established. The composition of these compounds was determined. A new method for anodic synthesis of

V. Yu. Frolov; S. N. Bolotin; V. T. Panyshkin

2005-01-01

336

FE-investigation of the stress\\/strain and fracture mechanics properties of intermetallic phase regions in leadfree solder interconnects  

Microsoft Academic Search

This main objective of this paper is to use a finite element analysis of the state of stress and strain within an intermetallic layer at the interface of a lead-free solder joint for an investigation of the comparatively unknown fracture mechanics properties and critical state of stress of intermetallic compounds. For this purpose we discuss the magnitude and sign of

W. H. Miillera; Taoufiq Hannach; H. J. Albrecht

2006-01-01

337

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

338

Spectroscopic properties of complex compounds of uranyl phosphates  

SciTech Connect

The reflection and luminescence-excitation spectra of tetracoordinated compounds of uranyl orthophosphates, metaphosphates and pyrophosphates have been studied in the 19 000--50 000-cm region. Their weak dependence on the type of ligand and second-sphere cation has been established, and their identity to the spectra of uranyl chlorides and UW impurity centers in LiF has been demonstrated. An interpretation of the observed experimental results is proposed in the framework of existing theoretical concepts of the electronic structure of uranyl compounds.

Sytko, V.V.; Krasilov, Y.I.; Kuznetsov, N.T.; Aleshkevich, N.I.; Pobedina, A.B.

1985-07-01

339

Storage of Hydrogen Isotopes in Intermetallic Compounds.  

National Technical Information Service (NTIS)

High-pressure studies of LaCo sub 5 have produced a hydride with the LaCo sub 5 H sub 9 composition, which is the expected maximum stoichiometry. A comparison of hydrogen solubility in ErCo sub 5 with previous studies in PrCo sub 5 , PrCo sub 3 , and ErCo...

S. A. Steward J. F. Lakner F. Uribe

1976-01-01

340

Fundamentals of Mechanical Behavior in Intermetallic Compounds.  

National Technical Information Service (NTIS)

Research in the first year of this program has examined mechanical behavior and creep of titanium aluminide alloys, both based on Ti3Al and TiAl, with the goal being better understanding of relation ships between microstructure and mechanical properties o...

J. M. Howe A. W. Thompson

1991-01-01

341

Methanation by catalysts formed from intermetallic compounds  

Microsoft Academic Search

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

H. Imamura; W. E. Wallace

1979-01-01

342

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

343

Proceedings of intermetallic matrix composites II  

SciTech Connect

This book contains the proceedings of Intermetallic Matrix Composites II. Topics covered include: intermetallic composites; integration of the Ti aluminide metal matrix composite; limitations of the fiber pushout test; quantitative test techniques; intermetallic eutectics; physical vapor deposition; deformation processing; melt infiltration; solid state displacement, niobium base alloys; and molybdenum alloys.

Miracle, D.B. (Air Force Wright Aeronautical Labs., Wright-Patterson AFB, OH (United States)); Anton, D.L. (United Technologies Research Center, East Hartford, CT (United States)); Graves, J.A. (Rockwell International Corp., Thousand Oaks, CA (United States). Science Center)

1992-01-01

344

Compositions and Methods for Enhanced Delivery of Compounds via Transfection Complexes.  

National Technical Information Service (NTIS)

The present invention relates to compositions and methods for enhanced delivery of compounds (e.g., drugs, nucleic acids, peptides, etc.) via transfection complexes (e.g., liposomes). In particular, the present invention utilizes agents that synergistical...

L. Wing R. C. MacDonald

2005-01-01

345

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

Microsoft Academic Search

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

Sun Kwok

2009-01-01

346

Third Intermetallic Matrix Composites Symposium, volume 350  

SciTech Connect

Partial contents include: issues in potential IMC application for aerospace structures; powder metallurgy processing of intermetallic matrix composites; microstructure and properties of intermetallic matrix composites produced by reaction synthesis; combustion synthesis of niobium aluminide matrix composites; ambient temperature synthesis of bulk intermetallics; wear behavior of SHS intermetallic matrix composites; fracture characteristics of metal-intermetallic laminates produced by SHS reactions; and vapor phase synthesis of Ti aluminides and the interfacial bonding effect on the mechanical property of micro-composites reinforced by pyrolized SiC fibers.

Graves, J.A.; Bowman, R.R.; Lewandowski, J.J.

1994-04-01

347

Thermodynamics of the sorption of cerium complex compounds on anionite  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

348

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, Ti2AlC, Ti3SiC2, ZrAlC2, Zr2Al3C5, to Al4C3 is also discussed.

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

1982-08-01

349

Magnetic properties of rare earth-Lead intermetallics  

Microsoft Academic Search

Magnetic susceptibilities of the series of intermetallics represented by the formula RPb3 (R = Ce, Pr, Nd, Sm, Eu and Gd) are reported for temperatures ranging from 2.8 to 300K. Curie-Weiss behavior is noted for all compounds except SmPb3 with slopes in good agreement with that expected for assemblages of free tripositive ions (dipositive for EuPb3). The behavior of SmPb3

R. D. Hutchens; W. E. Wallace

1971-01-01

350

FORMATION OF TiCu INTERMETALLIC COATINGS ON COPPER SUBSTRATE  

Microsoft Academic Search

In an attempt to modify the surface properties of copper substrate, TiCu intermetallic compounds were produced on oxygen-free high-conductivity (OFHC) copper by physical vapor deposition followed subsequently with diffusion annealing. The structure and phase identification were evaluated by means of X-ray diffraction, electron probe microanalysis (EPMA), metallographic examination (optical and scanning electron microscopy [SEM]), energy-dispersive X-ray analysis (EDS), and microhardness

M. R. Bateni; S. Mirdamadi; F. Ashrafizadeh; J. A. Szpunar; R. A. L. Drew

2001-01-01

351

A Computational Method for Planning Complex Compound Distributions under Container, Liquid Handler, and Assay Constraints.  

PubMed

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

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

2013-04-19

352

Analysis of hypotensive compounds occurring in complex agents.  

PubMed

This is a review of analytical methods, such as spectrophotometry, derivative spectrophotometry and various chromatographic (gas chromatography-GC, high-performance liquid chromatography-HPLC, thin-layer chromatography-TLC, high-performance thin-layer chromatography-HPTLC, liquid chromatography-tandem mass spectrometry-LC-MS, microchip electrophoresis-MCE, capillary electrophoresis-CE) and electroanalytical methods (differential pulse polarography-DPP, cathodic stripping voltammetry-CSV, anodic stripping voltammetry-ASV, differential pulse voltammetry-DPV, cyclic voltammetry-CV, stripping voltammetry-SV, square wave voltammetry-SWV, square wave polarography-SWP) that are used in the analysis of hypotensive complex agents. This review is based on representative publications that were published between 1995 and 2009. PMID:20873410

Stolarczyk, Mariusz; Ma?lanka, Anna; Apola, Anna; Krzek, Jan

353

Mechanisms of reactions of organoaluminium compounds with alkenes and alkynes catalyzed by Zr complexes  

NASA Astrophysics Data System (ADS)

The results of studies dealing with mechanisms of hydro-, carbo- and cycloalumination of alkenes and alkynes catalyzed by zirconium complexes are generalized and systematized for the first time. Data about the structures of intermediates responsible for the formation of the target compounds are presented and the available data on the effect of the structure of organoaluminium compounds and the electronic and steric factors determining the catalytic activity of metal complexes in these reactions are considered in detail. Much attention is paid to studies of the influence of reaction conditions on the chemo-, regio- and stereoselectivity of the Zr-containing complex catalysts. The bibliography includes 217 references.

Parfenova, L. V.; Khalilov, Leonard M.; Dzhemilev, Usein M.

2012-06-01

354

High Temperature Deformation Behavior and Microstructural Evolution of Ti47Al2Cr4Nb Intermetallic Alloys  

Microsoft Academic Search

TiAl-base intermetallic compounds have been investigated for advanced high temperature structural applications due to their attractive properties such as low density, good elevated temperature strength, high resistance to oxidation and excellent creep properties. However, the poor ductility and low fracture toughness of TiAl-base intermetallic compounds at ambient temperature are the major limitations for practical application. A great deal of researches

Hee Y. Kim; Soon H. Hong

1998-01-01

355

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

356

An integral strategy toward the rapid identification of analogous nontarget compounds from complex mixtures.  

PubMed

Identification of nontarget compounds in complex mixtures is of significant importance in various scientific fields. On the basis of the universal property that the compounds in complex mixtures can be classified to various analogous families, this study presents a general strategy for the rapid identification of nontarget compounds from complex matrixes using herbal medicine as an example. The proposed strategy consists of three sequential steps. First, a blank control sample is prepared for the purpose of removing interferences in the complex matrixes via automatic chromatographic and mass spectrometric data comparisons. Second, the diagnostic ions guided bridging network strategy is developed for the rapid classification of analogous compounds and structural characterizations. Finally, a quantitative structure retention relationship (QSRR) is built to validate the identifications and to differentiate isomers. Using this strategy, we have successfully identified a total of 45 organic acids from Mai-Luo-Ning and Flos Lonicerae injection, and 46 ginsenosides from Shen-Mai injection samples. The QSRR approach enabled a successful differentiation of most isomers. The proposed strategy will be expected to be applicable to the identification of nontarget compounds in complex mixtures. PMID:23838303

Wu, Liang; Gong, Ping; Wu, Yuzheng; Liao, Ke; Shen, Hanyuan; Qi, Qu; Liu, Huiying; Wang, Guangji; Hao, Haiping

2013-06-26

357

Pressure tuning of competing magnetic interactions in intermetallic CeFe2  

SciTech Connect

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

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

2012-07-20

358

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: {[PMo12O40][Ni(Phen)2(H2O)]2}K2OH- (1) and [Cd2(Phen)4Cl2][HPW12O40]H2O (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 [HPW12O40]2- and novel metal-chloride-ligand coordination complexes [Cd2(Phen)4Cl2]2+.Graphical abstractTwo 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

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

359

Intermetallic-Based High-Temperature Materials  

SciTech Connect

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

Sikka, V.K.

1999-04-25

360

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

Microsoft Academic Search

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

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

1969-01-01

361

Assessing the Geochemical Reactivity of FeDOM Complexes in Lacustrine Sediments Using Nitroaromatic Probe Compounds  

Microsoft Academic Search

The complexation environment of Fe in anoxic sediment porefluids is important for understanding its role in biogeochemical reactions in these systems. These include the microbial dissolution of iron-bearing sediments and the degradation of hydrophobic pesticides. We studied the effect of naturally occurring Fe-DOM complexes on the reduction of two nitroaromatic compounds (NACs) as a surrogate for probing electron-transfer kinetics, and

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

2007-01-01

362

Coordination chemistry of anticrowns: Complexation of cyclic trimeric perfluoro- o-phenylenemercury with nitro compounds  

Microsoft Academic Search

Cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 (1) is capable of reacting with nitromethane to give complex {[(o-C6F4Hg)3](CH3NO2)} (2) containing one molecule of the nitro compound per one macrocycle molecule. In this complex, the nitromethane ligand is bound to 1 by its both oxygen atoms, one of which is simultaneously coordinated to all three Hg centres of the macrocycle while the other interacts

I. A. Tikhonova; K. I. Tugashov; F. M. Dolgushin; A. A. Yakovenko; P. V. Petrovskii; G. G. Furin; A. P. Zaraisky; V. B. Shur

2007-01-01

363

A comment on the description of the structure of intermetallic phases  

NASA Astrophysics Data System (ADS)

The mean fictive atomic radii beginning with interactive distances, are calculated by means of exponential weighting, and effective coordination numbers are obtained. Assuming that the concept itself is accepted, these are free of arbitrariness in limiting the sphere of coordination, at least in the cases of ionic (salts) and intermetallic compounds without any covalent part in chemical bonding. It is found that in 'classical' cases common values of coordination numbers occur. Finally, the values for elements such as alpha- and beta-Mn, Ga, and In as well as for intermetallic compounds correspond partly to accustomed ones while some are in striking contrast.

Hoppe, R.; Meyer, G.

1980-06-01

364

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

DOEpatents

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

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

2004-01-06

365

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

PubMed Central

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

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

2011-01-01

366

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

Microsoft Academic Search

Air samples were collected between September 2000 and September 2001 in Izmir, Turkey at three sampling sites located around a petrochemical complex and an oil refinery to measure ambient volatile organic compound (VOC) concentrations. VOC concentrations were 420-fold higher than those measured at a suburban site in Izmir, Turkey. Ethylene dichloride, a leaded gasoline additive used in petroleum refining and

Eylem Cetin; Mustafa Odabasi; Remzi Seyfioglu

2003-01-01

367

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

PubMed

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

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

2013-08-18

368

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

EPA Science Inventory

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

369

Complex Organic Compounds in Titan and Their Relevance to Origins of Life  

NASA Astrophysics Data System (ADS)

Titan is the largest satellite of Saturn, and has dense (ca. 1500 hPa) atmosphere mainly composed of nitrogen and methane. In addition to various organic compounds, aerosol is found in the atmosphere. It is suggested that the aerosol was made of complex organic compounds, which was formed from Titan atmosphere by such energies as ultraviolet light, high-energy electrons (discharges) and cosmic rays. Voyager and Cassini missions partly revealed the nature of the aerosol. A wide variety of laboratory simulation experiments have been conducted by using a gas mixture of nitrogen and methane, and the resulting solid products are often referred as "Titan tholins". We performed experiments to simulate actions of cosmic rays in the lower atmosphere of Titan. Mixtures of methane (1-10%) and nitrogen (balance) were irradiated with high-energy protons from accelerators. The major resulting products were complex organic compounds with molecular weights of several hundreds, giving amino acids after acid hydrolysis. Such complex amino acid precursors might be collected on the surface of Titan with rain of methane. The composition of terrestrial atmosphere is unknown, but nitrogen should have been one of the major constituents together with minor compounds like methane or carbon monoxide. In such cases the same kinds of chemical evolution occurred in primitive Earth. If complex organic compounds formed primitive atmosphere by cosmic rays were collected in the primitive Ocean by water rain, they are major sources for the first life on Earth together with extraterrestrial organics. Such chemical evolution scenario via complex organics will be presented.

Kobayashi, Kensei; Taniuchi, Toshinori; Hosogai, Tomohiro; Kaneko, Takeo; Takano, Yoshinori

370

High-temperature ordered intermetallic alloys. 4  

Microsoft Academic Search

This volume is a record of the proceedings of the fourth MRS Symposium on High-Temperature Ordered Intermetallic Alloys. It represents a reasonably complete description of worldwide progress in this area at this time. This series has emerged as the premier forum, for discussion of the behavior of ordered intermetallics. The Fourth Symposium lived up to the reputation generated by its

L. A. Johnson; D. P. Pope; J. O. Stiegler

1991-01-01

371

Process for synthesizing compounds from elemental powders  

DOEpatents

A process for synthesizing intermetallic compounds from elemental powders. The elemental powders are initially combined in ratio a 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, B.H.; Wright, R.N.

1990-01-01

372

Process for synthesizing compounds from elemental powders  

DOEpatents

A process for synthesizing intermetallic compounds from elemental powders. The elemental powders are initially combined in ratio a 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, B.H.; Wright, R.N.

1990-12-31

373

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

SciTech Connect

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

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

1996-03-01

374

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

375

(High-temperature ordered intermetallic alloys)  

SciTech Connect

The traveler was invited to tour through and provide technical guidance for the Japan National Project on High-Temperature Ordered Intermetallic Alloys, which was sponsored by MITI, Japan. The traveler stayed in Japan for three weeks and visited a total of nine research institutes and industrial laboratories active in intermetallic research. During the visit, the traveler learned of the recent research and development of two intermetallic model materials--titanium aluminide (TiAl) and niobium aluminide (Nb{sub 3}Al) selected by MITI. The traveler also gave lectures on recent advances in ordered intermetallic alloys with emphases on brittle fracture and ductility improvement. The MITI's project has provided leadership and stimulated interest in intermetallic research and development among Japan industries.

Liu, C.T.

1991-04-10

376

Separations of olefins and heterocyclic organic compounds based on reversible complexation reactions  

SciTech Connect

Recently, membranes and thin films derived from ion exchange materials have received considerable attention with respect to their structural, physical and chemical properties. The authors report the facilitated transport of 1-hexene and 1,5-hexadiene between two decane phases separated by thin, hydrated membranes (ca. 25 {mu}m). The flux of olefin across the membranes is enhanced by factors of several hundred when silver ions are exchanged for sodium ions. Synthetic fuels derived from coal liquids, tar sands or oil shale contain a wide variety of nonvolatile chemical compounds containing nitrogen and sulfur. Many of these compounds display mutagenic or carcinogenic activity. Therefore, these classes of compounds are undesirable pollutants which must be removed from fuels and other related hydrocarbon products. They authors are exploring a novel process for the selective removal of organic nitrogen and sulfur compounds from hydrocarbon phases. The process is based on electrochemically modulated chemical complexation. The complexing agents are water-soluble derivatives of Fe metalloporphyrins. Results for the removal of isoquinoline and pentamethyene sulfide from iso-octane and the subsequent concentration of these compounds in a second (waste) hydrocarbon phase are presented.

Koval, C.A.; Drew, S.; Spontarelli, T.; Noble, R.D. (Univ. of Colorado, Boulder (USA))

1988-01-01

377

Cyclodextrin inclusion compounds of vanadium complexes: structural characterization and catalytic sulfoxidation.  

PubMed

Reaction of potassium vanadate with the hydrazone ligand derived from Schiff-base condensation of salicylaldehyde and biphenyl-4-carboxylic acid hydrazide (H(2)salhybiph) in the presence of two equivalents alpha-cyclodextrin (alpha-CD) in water yields the 1:2 inclusion compound K[VO(2)(salhybiph)@(alpha-CD)(2)]. Characterization in solution confirmed the integrity of the inclusion compound in the polar solvent water. The inclusion compound crystallizes together with additional water molecules as K[VO(2)(salhybiph)@(alpha-CD)(2)].18H(2)O in the monoclinic space group P2(1). Two alpha-CD rings forming a hydrogen bonded head to head dimer are hosting the hydrophobic biphenyl side chain of the complex K[VO(2)(salhybiph)]. The supramolecular aggregation of the inclusion compound in the solid state is established through hydrogen bonding interactions among adjacent alpha-CD hosts and with vanadate moieties of the guest complexes as well as ionic interactions with the potassium counterions. In contrast the supramolecular structure of the guest complex K[VO(2)(salhybiph)] without the presence of CD host molecules is governed by pi-pi-stacking interactions and additional CH/pi interactions. The new inclusion complex K[VO(2)(salhybiph)@(alpha-CD)(2)] and the analogous 1:1 inclusion compound with beta-CD were tested as catalyst in the oxidation of methyl phenyl sulfide (thioanisol) using hydrogen peroxide as oxidant in a water/ethanol mixture, under neutral as well as acidic conditions. PMID:19201031

Lippold, Ines; Vlay, Kristin; Grls, Helmar; Plass, Winfried

2008-12-29

378

Fracture toughness of Cu-Sn intermetallic thin films  

NASA Astrophysics Data System (ADS)

Intermetallic compounds (IMCs) are formed as a result of interaction between solder and metallization to form joints in electronic packaging. These joints provide mechanical and electrical contacts between components. The knowledge of fracture strength of the IMCs will facilitate predicting the overall joint property, as it is more disposed to failure at the joint compared to the solder because of its brittle characteristics. The salient feature of this paper is the measurement of the fracture toughness and the critical energy-release rate of Cu3Sn and Cu6Sn5 intermetallic thin films, which is the result of the interaction between Sn from the solder and Cu from the metallization. To achieve the objective, a controlled buckling test was used. A buckling test in the current work refers to one that displays large transverse displacement caused by axial compressive loading on a slender beam. The stress and strain along the beam can be easily calculated by the applied displacement. Fracture-toughness values of Cu3Sn and Cu6Sn5 are 2.85 MPa ?m 0.17 MPa ?m and 2.36 MPa ?m 0.15 MPa ?m, respectively. Corresponding critical energy-release rate values are 65.5 J/m2 8.0 J/m2 and 55.9 J/m2 7.3 J/m2, respectively. The values obtained were much higher than the ones measured in bulk intermetallic samples but correlated well with those values obtained from conventional fracture-toughness specimens when fracture was confined within the intermetallic layers. Hence, the controlled buckling test is a promising fast and effective way to elucidate mechanical properties of thin films.

Balakrisnan, B.; Chum, C. C.; Li, M.; Chen, Z.; Cahyadi, T.

2003-03-01

379

Mild and Efficient Nitration of Aromatic Compounds Mediated by Transition-Metal Complexes  

Microsoft Academic Search

Aromatic compounds were efficiently nitrated under facile reaction conditions by employing 69% nitric acid catalyzed by transition-metal complexes such as [Co(NH3)5Cl]Cl2, [Cu(NH3)4]SO4, Mn(acac)3, [Ni(NH3)6]Cl2, [Ni(en)3]S2O3, and Hg[Co(SCN)4]. The reaction was completed smoothly at room temperature and afforded corresponding mono-nitro derivatives in quantitative yield. This new method offers efficient and facile regioselective mononitration of aromatic compounds.

Abdulla; S. Amina; Y. Arun Kumar; M. Arifuddin; K. C. Rajanna

2011-01-01

380

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

381

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

PubMed

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

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

2010-03-01

382

Formation and photochemistry of organic sulfur compound-chlorine atom complexes  

NASA Astrophysics Data System (ADS)

Photochemical reactions of organic sulfur compounds (CH3SCH3, C2H5SCH3 and C2H5SC2H5)-chlorine atom complexes have been studied using a combined pulse radiolysis-laser flash photolysis technique. Excitation of all complexes has resulted in photobleaching with a similar quantum yield (0.370.07), independent of solvent polarities and concentration of solutes. The results were compared with previous studies of the analogous dimethyl sulfoxide (DMSO)-Cl complexes. It is concluded that the significant change of photobleaching quantum yields of the excited DMSO-Cl complex observed in the DMSO-CCl4 mixed solvent is mainly due to the specific solvation effect of DMSO for cations.

Okubo, Yu; Kido, Yuta; Fujiyoshi, Ryoko; Sumiyoshi, Takashi

2009-12-01

383

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

384

Complexation of organic compounds in the presence of Al 3+ during micellar flocculation  

Microsoft Academic Search

Complexes of Al and model pollutants phenol, benzoic acid, 2,4-D (2,4-dichlorophenoxyacetic acid) and 2,4-DB (2,4-dichlorophenoxybutiric acid) play a key role in the removal of organic pollutants by co-adsorption on micelles of anionic surfactants flocculated by means of Al3+. This technique, known as adsorptive micellar flocculation (AMF), is related to removal of organic compounds by coagulationprecipitation with Al and Fe salts.

Federico I. Talens-Alesson; Salvation Anthony; Marion Bryce

2004-01-01

385

Flow injection determination of carboxylate, phosphate, and sulfhydryl compounds using metal exchange complexation.  

PubMed

The determination of carboxylate, phosphorous, and sulfhydryl compounds has been studied using flow injection by measuring the decrease in absorbance of the Fe(III)-salicylate complex due to preferential ligand interaction with ferric ion. Targeted compounds include polycarboxylates such as sodium citrate, sodium oxalate, and EDTA, anionic phosphorous compounds such as sodium monofluoroorthophosphate, sodium trimetaphosphate, and sodium hexametaphosphate, and sulfhydryl compounds such as cysteine, glutathione, and captopril. Initial flow injection optimization has focused on citrate based on its ability to replace salicylate ion in the Fe(III)-salicylate complex causing a decrease in absorbance at 525 nm proportional to the citrate concentration. Two flow injection analysis methods are developed. In the first method, offline reaction flow injection, sodium citrate dissolved in 100 ?mol L(-1) Fe-salicylate is injected in a carrier solution of 100 ?mol L(-1) Fe-salicylate. The decrease in peak area is linear over a range of 1.36-109 ?mol L(-1) using a flow rate of 1 mL min(-1) and an injection volume of 100 ?L. The effect of pH on the Fe-salicylate complex absorbance is studied from 1 to 3.5; pH 3 shows both a high and stable complex absorbance in the visible range which provided important potential selectivity over UV detection. The limit of detection is found to be less than 57 nmol L(-1) depending on the Fe(III)-salicylate concentration used. The second method is reverse flow injection using the sample as a flowing stream in which 3 mmol L(-1) Fe(III)-salicylate is injected and the decrease in the response with increased sample concentration was monitored. The commercially available pharmaceutical product (Citroma)() is used to assess the accuracy and precision of the two proposed methods as compared to a reference method. PMID:22748549

Mansour, Fotouh R; Shafi, Mohammad A; Danielson, Neil D

2012-03-13

386

Magnetic interactions in pseudobinary rare earth-3d intermetallics  

Microsoft Academic Search

Magnetic measurements on pseudobinary intermetallic compounds of the series R(MnxFe1-x)2(R = Y, Gd, Er) R6(MnxFe1-x)23(R = Y, Gd, Tb, Dy, Ho, Er, Tm) R2(FexCo1-x)17(R = Y, Gd, Dy) R2(FexNi1-x)17(R = Y, Gd) are reported. Magnetization and susceptibility measurements have been performed at temperatures from 4 K to 1500 K. The magnetic interactions between Mn and Fe are discussed in terms

HANS R. KIRCHMAYR; GERFRIED HILSCHER; WALTER STEINER; GUNTER WIESINGER

1973-01-01

387

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

388

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

389

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

390

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

391

Bonding, Energetics and Mechanical Properties of Intermetallics.  

National Technical Information Service (NTIS)

To fulfill the great potential of intermetallic alloys for use in high temperature structural applications, it is necessary to understand on the microscopic level the mechanisms controlling their mechanical behavior, including such key phenomena as disloc...

A. J. Freeman Y. N. Gornostyrev O. N. Mryasov O. Y. Kontsevoi N. I. Medvedeva

2001-01-01

392

Second International Symposium on Structural Intermetallics.  

National Technical Information Service (NTIS)

These proceedings represent the written record of the Second International Symposium on Structural Intermetallics which was held at the Seven Spring Mountain Resort, Champion, Pennsylvania, from September 21, through September 25, 1997. The intent of the ...

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

1997-01-01

393

SCB ignition of pyrotechnics, thermites and intermetallics.  

National Technical Information Service (NTIS)

We investigated ignition of pyrotechnics, metal-fuel/metal-oxide compositions (thermites), and exothermic alloy compositions (intermetallics) using a semiconductor bridge (SCB). It was shown that these materials could be ignited at low energy levels with ...

R. W. Bickes M. C. Grubelich

1996-01-01

394

Slater-Pauling behavior within quaternary intermetallic borides of the Ti3Co5B2 structure-type  

NASA Astrophysics Data System (ADS)

First-principles, density-functional studies of several intermetallic borides of the general type M2M?Ru5-nRhnB2 (n=0-5; M=Sc, Ti, Nb; M?=Fe, Co) show that the variation in saturation magnetic moment with valence-electron count follows a Slater-Pauling curve, with a maximum moment occurring typically at 66 valence electrons. The magnetic moments in these compounds occur primarily from the 3d electrons of the magnetically active M? sites, with some contribution from the Ru/Rh sites via magnetic polarization. Electronic DOS curves reveal that a rigid-band approach is a reasonable approximation for the estimation of saturation moments and the analysis of orbital interactions in this family of complex borides. COHP analyses of the M?-M? orbital interactions indicate optimized interactions in the minority spin states for Co-containing phases, but strong bonding interactions remaining in Fe-containing phases.

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

2009-10-01

395

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

SciTech Connect

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

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

2011-12-05

396

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

397

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

PubMed

Air samples were collected between September 2000 and September 2001 in Izmir, Turkey at three sampling sites located around a petrochemical complex and an oil refinery to measure ambient volatile organic compound (VOC) concentrations. VOC concentrations were 4-20-fold higher than those measured at a suburban site in Izmir, Turkey. Ethylene dichloride, a leaded gasoline additive used in petroleum refining and an intermediate product of the vinyl chloride process in the petrochemical complex, was the most abundant volatile organic compound, followed by ethyl alcohol and acetone. Evaluations based on wind direction clearly indicated that ambient VOC concentrations measured were affected by the refinery and petrochemical complex emissions. VOC concentrations showed seasonal variations at all sampling sites. Concentrations were highest in summer, followed by autumn, probably due to increased evaporation of VOCs from fugitive sources as a result of higher temperatures. VOC concentrations generally increased with temperature and wind speed. Temperature and wind speed together explained 1-60% of the variability in VOC concentrations. The variability in ambient VOC concentrations that could not be explained by temperature and wind speed can be attributed to the effect of other factors (i.e. wind direction, other VOC sources). PMID:12873403

Cetin, Eylem; Odabasi, Mustafa; Seyfioglu, Remzi

2003-08-01

398

Probing Complex Free-Radical Reaction Pathways of Fuel Model Compounds  

SciTech Connect

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

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

2012-01-01

399

Magnetocrystalline anisotropy constants, rotational hysteresis energy and magnetic domain structure in UFe 6Al 6, UFe 9AlSi 2 and ScFe 10Si 2 intermetallic compounds  

Microsoft Academic Search

The magnetic torque, T, was applied to determine the anisotropy constants K1 and K2 of the UFe6Al6, UFe9AlSi2 and ScFe10Si2 compounds. The mechanism of magnetization reversal processes in these compounds was investigated on the basis of the analysis of the rotational hysteresis energy, Wr and rotational hysteresis integral, R, calculated from the magnetic torque curves. Applying the powder pattern method,

J. J. Wyslocki; W. Suski; P. Pawlik; K. Wochowski; B. Kotur; O. I. Bodak

1996-01-01

400

In situ examination of moving crack tips in ordered intermetallics.  

SciTech Connect

Recent studies have shown that high stress concentrations at moving crack tips in the intermetallic compound NiTi can induce a crystalline-to-amorphous (C-A) transformation of the crack tip region. This stress-induced C-A transformation has a temperature dependence and crystallization behavior similar to those of ion irradiation-induced C-A transformation of NiTi. The present study examines if these similarities between stress- and irradiation-induced amorphization hold true for two other intermetallic compounds, CuTi and Ni{sub 3}Ti. In situ straining was performed in an intermediate-voltage transmission electron microscope. The presence or absence of an amorphous phase was determined by dark field imaging and selected area diffraction of crack tip regions. Crack tips in both CuTi and Ni{sub 3}Ti were found to remain crystalline upon fracture. The observed absence of stress-induced amorphization in Ni{sub 3}Ti is consistent with its known absence during irradiation, but the absence in CuTi differs from its known irradiation-induced amorphization behavior. Reasons for the similarity and difference are discussed.

Heuer, J.; Lam, N. Q.; Okamoto, P. R.; Stubbins, J. F.

1999-01-25

401

Laser processing issues of nanosized intermetallic Fe-Sn and metallic Sn particles  

NASA Astrophysics Data System (ADS)

Intermetallic Fe-Sn and nanocrystalline metallic Sn nanoparticles have been successfully synthesized from organic precursors using the laser pyrolysis technique with ethylene as sensitizer. Nano-structured Sn (single phase) was prepared by the pyrolysis of Sn(CH3)4 (TMT) vapors. Controlled Fe/Sn atomic ratios, ranging from 0.69 to 1.64 were obtained for the prepared Fe-Sn nanopowders by the control of Fe(CO)5 and TMT flows, respectively. XRD studies evidence three main phases: the tetragonal metallic Sn phase and the intermetallic FeSn2 phase and, to a much lesser extent, the cubic ternary carbide Fe3SnC. Complex core-shell structural characteristics were found by HRTEM analysis. More complete information about the Fe phase distributions in the new intermetallic Fe-Sn nanomaterial is provided by temperature dependent 57Fe Mssbauer spectroscopy.

Alexandrescu, R.; Morjan, I.; Dumitrache, F.; Birjega, R.; Fleaca, C.; Morjan, Iuliana; Scarisoreanu, M.; Luculescu, C. R.; Dutu, E.; Kuncser, V.; Filoti, G.; Vasile, E.; Ciupina, V.

2012-09-01

402

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

PubMed Central

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

Mazurek, Monica A

2002-01-01

403

Synthesis and superconductivity of intermetallic compounds Y{sub 2}Ni{sub {ital x}}B{sub 8{minus}{ital x}}C{sub 2}, YNi{sub {ital x}}Cu{sub 2{minus}{ital x}}B{sub 2}C, and YNi{sub {ital x}}Cu{sub 2{minus}{ital x}}Si{sub 2}C  

SciTech Connect

Borocarbide and silicocarbide intermetallic Y{sub 2}Ni{sub {ital x}}B{sub 8{minus}{ital x}}C{sub 2} ({ital x}=1, 2, 3, 5), YNiCuB{sub 2}C, and YNi{sub {ital x}}Cu{sub 2{minus}{ital x}}Si{sub 2}C ({ital x}=0, 2) were prepared and their superconductivity was studied. The results indicated that with the change of the ratio of Ni to B in Y{sub 2}Ni{sub {ital x}}B{sub 8{minus}{ital x}}C{sub 2}, secondary phases were introduced into YNi{sub 2}B{sub 2}C phase. A {ital T}{sub {ital c}} of 15.0 K was observed for the compounds {ital x}=2, 3, and 5, which originated from the major phase YNi{sub 2}B{sub 2}C in these samples. Partial substitution of Ni by Cu reduced the {ital T}{sub {ital c}} to 11.0 K for YNiCuB{sub 2}C. For Si substitution system, no bulk superconductivity was found in YNi{sub 2}Si{sub 2}C and YCu{sub 2}Si{sub 2}C. But a minor superconducting phase ({ital T}{sub {ital c}}{approximately}4 K) with a volume fraction of the order of near 1{percent} was observed in them. It was noticed that for the temperature-dependent magnetization of superconducting compounds containing Ni, a significant difference between zero-field cooling and field cooling curves before {ital T}{sub {ital c}} was always observed, which was tentatively attributed to Ni-containing impurity. {copyright} {ital 1996 American Institute of Physics.}

Zhao, W.; Tang, J. [Department of Physics, University of New Orleans, New Orleans, Louisiana 70148 (United States); Lee, Y.; OConnor, C.J. [Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148 (United States)

1996-04-01

404

Dislocation sources in ordered intermetallics  

SciTech Connect

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

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

1996-09-01

405

NMR study of trialuminide intermetallics  

NASA Astrophysics Data System (ADS)

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

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

1998-03-01

406

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

PubMed Central

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

2012-01-01

407

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

PubMed

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

Atakan, Zerrin

2012-12-01

408

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

409

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 considerationsmaking 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

410

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

411

Antidiabetic vanadium compound and membrane interfaces: interface-facilitated metal complex hydrolysis.  

PubMed

The interactions of metabolites of the antidiabetic vanadium-containing drug bis(maltolato)oxovanadium(IV) (BMOV) with lipid interface model systems were investigated and the results were used to describe a potentially novel mechanism by which these compounds initiate membrane-receptor-mediated signal transduction. Specifically, spectroscopic studies probed the BMOV oxidation and hydrolysis product interaction with interfaces created from cetyltrimethylammonium bromide (CTAB) which mimics the positively charged head group on phosphatidylcholine. (1)H and (51)V NMR spectroscopies were used to determine the location of the dioxobis(maltolato)oxovanadate(V) and the maltol ligand in micelles and reverse micelles by measuring changes in the chemical shift, signal linewidth, and species distribution. Both micelles and reverse micelles interacted similarly with the complex and the ligand, suggesting that interaction is strong as anticipated by Coulombic attraction between the positively charged lipid head group and the negatively charged complex and deprotonated ligand. The nature of the model system was confirmed using dynamic light scattering studies and conductivity measurements. Interactions of the complex/ligand above and below the critical micelle concentration of micelle formation were different, with much stronger interactions when CTAB was in the form of a micelle. Both the complex and the ligand penetrated the lipid interface and were located near the charged head group. These studies demonstrate that a lipid-like interface affects the stability of the complex and raise the possibility that ligand exchange at the interface may be important for the mode of action for these systems. Combined, these studies support recently reported in vivo observations of BMOV penetration into 3T3-L1 adipocyte membranes and increased translocation of a glucose transporter to the plasma membrane. PMID:21667212

Crans, Debbie C; Schoeberl, Samantha; Gaidamauskas, Ernestas; Baruah, Bharat; Roess, Deborah A

2011-06-11

412

Diffusion of heterocyclic compounds from a complex mixture of coaltar compounds in natural clayey till  

Microsoft Academic Search

The diffusion of coaltar compounds in natural clayey till was studied experimentally. Cores were exposed to a solution with near constant concentration of coaltar compounds in a multi-component mixture for 5 months, the cores were subsequently sub-sampled and analyzed. Diffusion profile data strongly indicates highly non-linear sorption isotherms. For dibenzofuran, dibenzothiophene, 2-methylquinoline, carbazole, phenanthrene, and fluorene, the profiles indicated significantly

Mette M. Broholm; Kim Broholm; Erik Arvin

1999-01-01

413

Intermetallic hydrides: A review with ab initio aspects  

Microsoft Academic Search

The review aims to provide a coverage of different classes of intermetallic systems, which have the ability of absorbing hydrogen in different amounts, like binary and ternary Laves phases and Haucke-type intermetallics. Such intermetallic hydrides are attractive for applied research as potential candidates for on-board vehicular use (engines, batteries, etc.). Focus is made here on the fundamental features regarding the

Samir F. Matar

2010-01-01

414

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

PubMed

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

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

2011-11-08

415

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

SciTech Connect

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

Gomez Del Campo, J.

1996-10-01

416

Concentration and removal of nitrogen and sulfur containing compounds from organic liquids phases using electrochemically reversed chemical complexation  

SciTech Connect

A process is being developed to concentrate and remove sulfur- and nitrogen-containing compounds from organic liquid phases. These phases could include coal liquids, oil from shale or tar sands, as well as conventional crude oil. This process uses reversible complexation and electrolysis. A cyclical contacting scheme is proposed: the compounds are first extracted from a polluted hydrocarbon phase using an aqueous phase containing a complexing agent; the aqueous phase is then contacted with a waste hydrocarbon phase and the complexing agent is oxidized, releasing any complexed pollutants into the waste hydrocarbon phase. This cycle is repeated to extract more pollutants, i.e. sulfur and nitrogen compounds, from the contaminated phase and concentrate them in the waste phase. A description of the process and preliminary results for one system are presented.

Koval, C.A.; Drew, S.M.; Spontarelli, T.; Noble, R.D.

1988-10-01

417

The formation of intermetallics in dissimilar Ti6Al4V\\/copper\\/AISI 316 L electron beam and Nd:YAG laser joints  

Microsoft Academic Search

The welds of titanium alloys with steels suffer from the brittleness of resulting intermetallic compounds. In present study, we report the feasibility of Ti6Al4V to stainless steel AISI 316L welding through pure copper interlayer carried out by electron beam and pulsed Nd:YAG laser. The nature and the localization of intermetallic phases in these welds have been studied by SEM, EDS,

I. Tomashchuk; P. Sallamand; H. Andrzejewski; D. Grevey

2011-01-01

418

Spark plasma sintering of titanium aluminide intermetallics and its composites  

NASA Astrophysics Data System (ADS)

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

Aldoshan, Abdelhakim Ahmed

419

Conjugate reduction of alpha,beta-unsaturated carbonyl compounds catalyzed by a copper carbene complex.  

PubMed

[reaction: see text] An N-heterocyclic carbene copper chloride (NHC-CuCl) complex (2) has been prepared and used to catalyze the conjugate reduction of alpha,beta-unsaturated carbonyl compounds. The combination of catalytic amounts of 2 and NaOt-Bu with poly(methylhydrosiloxane) (PMHS) as the stoichiometric reductant generates an active catalyst for the 1,4-reduction of tri- and tetrasubstituted alpha,beta-unsaturated esters and cyclic enones. The active catalytic species can also be generated in situ from 1,3-bis(2,6-di-isopropylphenyl)-imidazolium chloride (1) CuCl(2).2H(2)O in the presence of NaOt-Bu and PMHS. PMID:12841744

Jurkauskas, Valdas; Sadighi, Joseph P; Buchwald, Stephen L

2003-07-10

420

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

421

Structure-Induced Covalent Bonding in Al-Li Compounds  

NASA Astrophysics Data System (ADS)

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

Nozawa, Kazuki; Ishii, Yasushi

2010-06-01

422

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

423

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

424

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

PubMed

We demonstrate a simple and reproducible technique to synthesize crystalline and superconducting In-Sn intermetallic nanowires sheathed in carbon nanotubes (CNTs). The method is based on the catalytic reaction of C(2)H(2) over a mixture of both SnO(2) and In(2)O(3) particles. Importantly, tetragonal ?-In(3)Sn and hexagonal ?-InSn(4) nanowires with diameters of less than 100nm are selectively synthesized at different SnO(2) to In(2)O(3) weight ratios. CNTs may serve as cylindrical nanocontainers for continuous growth of liquid-phased In(1-x)Sn(x) nanowires during growth process as well as for their solidification into In-Sn intermetallic nanowires during the cooling process. Microscopic and spectroscopic analyses clearly reveal evidence of a core-shell structure of the CNT-sheathed In-Sn intermetallic nanowires. Magnetization measurements show that the superconducting In-Sn nanowires have a critical magnetic field higher than the value of their bulk intermetallic compounds. Our method can be adopted to the nanofabrication of analogous binary and ternary alloys. PMID:22728332

Jeong, Namjo; Yeo, Jeong-gu

2012-06-25

425

MD study of primary damage in L10 TiAl structural intermetallics  

NASA Astrophysics Data System (ADS)

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

Voskoboinikov, Roman E.

2013-05-01

426

Nonstoichiometry of Al-Zr intermetallic phases.  

National Technical Information Service (NTIS)

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

V. Radmilovic G. Thomas

1994-01-01

427

Surfaces of Intermetallics: Quasicrystals and Beyond  

SciTech Connect

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

Yuen, Chad [Ames Laboratory

2012-10-26

428

Synthetic multifunctional metallic-intermetallic laminate composites  

Microsoft Academic Search

The field of material microstructure design targeted for a specific set of structural and functional properties is now a recognized field of focus in materials science and engineering. This paper describes a new class of structural materials called metallic-intermetallic laminate (MIL) composites, which can have their micro-, meso- and macrostructure designed to achieve a wide array of material properties and

Kenneth S. Vecchio

2005-01-01

429

Synthesis and guest exchange reactions of inclusion compounds of cucurbit[8]uril with nickel( II ) and copper( II ) complexes  

Microsoft Academic Search

Inclusion compounds of the macrocyclic cavitand cucurbit[8]uril (CB[8]) with the nickel(II) complex, {trans-[Ni(en)2(H2O)2]@CB[8]}Cl2 23.5H2O, the copper(II) complex, {2[Cu(dien)(bipy)(H2O)]@CB[8]}(ClO4)4 11H2O, and the organic molecules, 2(pyCN)@CB[8]} 16H2O and {2(bpe)@CB[8]} 17H2O, where bipy is 4,4?-bipyridyl, pyCN is 4-cyanopyridine, and bpe is trans-1,2-bis(4-pyridyl)ethylene, were synthesized. The inclusion compounds with organic molecules were synthesized starting from\\u000a inclusion compounds of cucurbit[8]uril with cyclam and ethylenediamine complexes

T. V. Mitkina; D. Yu. Naumov; N. V. Kurateva; O. A. Gerasko; V. P. Fedin

2006-01-01

430

Complexes of Iron with Phenolic Compounds from Soybean Nodules and Other Legume Tissues: Prooxidant and Antioxidant Properties  

Microsoft Academic Search

The low-molecular-mass fraction of the soybean nodule cytosol contains Fe capable of catalyzing free radical production through Fenton chemistry. A large portion of the pool of catalytic Fe, measured as bleomycin-detectable Fe, was characterized as complexes of Fe with phenolic compounds of three classes: phenolic acids, cinnamic acids, and flavonoids. Many of these compounds, along with other phenolics present in

Jose F Moran; Robert V Klucas; Rene J Grayer; Joaquin Abian; Manuel Becana

1997-01-01

431

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

432

The effect of surface preparation on the oxidation behavior of gamma TiAl-base intermetallic alloys  

Microsoft Academic Search

Titanium aluminides, specifically the intermetallic compound gamma TiAl, are being investigated as potential aerospace and automotive materials due to high specific strength and stiffness. The oxidation behavior of gamma TiAl has been studied extensively. Oxygen exposures tend to produce slow growing alumina rich scales at low temperatures. At higher temperatures (approximately 800 C), the alumina breaks down locally and mixed

F. Dettenwanger; E. Schumann; M. Rhle

1996-01-01

433

In situ synthesis of nanocrystalline intermetallic layer during surface plastic deformation of zirconium  

Microsoft Academic Search

By means of a surface plastic deformation method a nanocrystalline (NC) intermetallic compound was in situ synthesized on the surface layer of bulk zirconium (Zr). Hardened steel shots (composition: 1.0C, 1.5Cr, base Fe in wt.%) were used to conduct repetitive and multidirectional peening on the surface layer of Zr. The microstructure evolution of the surface layer was investigated by X-ray

P. Jiang; Q. Wei; Y. S. Hong; J. Lu; X. L. Wu

2007-01-01

434

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

Microsoft Academic Search

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,

T. Grobstein; J. Doychak

1989-01-01

435

Heat resistance of metal-intermetallic compositions based on NiAl  

Microsoft Academic Search

Heat resistance of the intermetallic compound NiAl, its alloys with Hf and Nb, and composition materials with a microhoneycomb\\u000a structure (tungsten honeycombs with a wall thickness of 0.33 ?m and a core of NiAl or the NiAl-4 at% Nb alloy) are investigated.\\u000a The oxidation rate (w\\u000a +) is calculated by the weight increment from oxidation in air at t =

M. Yu. Belomyttsev; M. S. Evseev; D. A. Kozlov; K. K. Kreitser; V. V. Safonov; L. G. Chernukha; M. A. Shtremel

2007-01-01

436

Formation of Liquid and Intermetallics in Al-to-Mg Friction Stir Welding  

NASA Astrophysics Data System (ADS)

In dissimilar-metal friction stir welding (FSW), intermetallic compounds can form in the stir zone and significantly reduce the joint strength. The formation of intermetallic compounds in Al-to-Mg FSW was investigated in lap and butt FSW of the widely used 6061 Al and AZ31B Mg and discussed using the binary Al-Mg phase diagram as an approximation. Temperature measurements during lap FSW indicated a 703 K (430 C) peak temperature, slightly below the eutectic reaction (Mg) + Al12Mg17 ? L at 710 K (437 C), because the thermocouples were pushed downward during welding. The intermetallic compounds in the stir zone were revealed by color etching and identified by X-ray diffraction (XRD), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM) as Al3Mg2 and Al12Mg17. Additional FSW was conducted near the edge of the upper sheet, and the liquid droplets squeezed out during welding solidified along the edge. Optical microscopy of the solidified droplets and EPMA revealed dendrites of Al3Mg2 and Al12Mg17 and interdendritic eutectics, thus indicating eutectic reactions (Mg) + Al12Mg17 ? L (710 K (437 C)) and (Al) + Al3Mg2 ? L (723 K (450 C)). Differential scanning calorimetry (DSC) confirmed that the solidified droplets melted at 709 K (436 C) and 722 K (449 C), nearly identical to the eutectic temperatures. Formation of intermetallic compounds on the order of 1 mm in size suggests they form upon solidification of the liquated material instead of solid-state diffusion.

Firouzdor, Vahid; Kou, Sindo

2010-12-01

437

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

SciTech Connect

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

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

2009-10-15

438

Point defect concentrations and hardening in binary B2 intermetallics  

SciTech Connect

Point defect hardening in binary B2 intermetallic compounds with the anti-structure defect structure (FeCo and AuZn) and the triple defect structure (NiAl, FeAl, and CoAl) was investigated. Thermodynamic modeling combined with experimental measurements of lattice parameters and bulk densities were used to establish point defect concentrations as functions of composition and temperature. Microhardness measurements were made on samples of varying compositions and quenching temperatures. Solution hardening rates of vacancies were found to be significantly larger than those of anti-site defects. It was possible to relate the hardening rates of anti-site defects to the magnitude of the lattice dilation. This suggests that the elastic size effect was the primary hardening mechanism. No such correlation was found for vacancies.

Pike, L.M.; Chang, Y.A. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering; Liu, C.T. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1997-09-01

439

Hydrogen impurity effects. A(5)Tt(3)Z intermetallic compounds between A = Ca, Sr, Ba, Eu, Yb and Tt = Sn, Pb with Cr(5)B(3)-like structures that are stabilized by hydride or fluoride (Z).  

PubMed

The binary systems Ca-Sn, Ba-Sn, Eu-Sn, Yb-Sn, Sr-Pb, Ba-Pb, and Eu-Pb do not contain Cr(5)B(3)-like A(5)Tt(3) phases when care is taken to exclude hydrogen from the reactions (Tt = tetrel, Si-Pb). All form ternary A(5)Tt(3)H(x)() phases (x < or = 1) with "stuffed" Cr(5)B(3)-like structures instead, and all of those tested, Ca-Sn, Ba-Sn, Sr-Pb, and Ba-Pb, also yield the isostructural A(5)Tt(3)F. The structures and compositions of Ca(5)Sn(3)H(x), Ca(5)Sn(3)F(0.89), Eu(5)Sn(3)H(x), and Sr(5)Pb(3)F have been refined from single-crystal X-ray diffraction data and of Ca(5)Sn(3)D from powder neutron data. The interstitial H, F atoms are bound in a tetrahedral (A(2+))(4) cavity in a Cr(5)B(3)-type metal atom structure. Nine previous reports of binary "Ba(5)Sn(3)", "Yb(5)Sn(3)", "Sr(5)Pb(3)", and "Ba(5)Pb(3)" compounds were wrong and presumably concerned the hydrides. The new ternary phases are generally Pauli-paramagnetic, evidently with pi electrons from the characteristic tetrelide dimers in this structure type at least partially delocalized into the conduction band. The Sn-Sn bonds appear correspondingly shortened on oxidation. Other new phases reported are CaSn (CrB type), Yb(5)Sn(4)H(x) (Sm(5)Ge(4)), YbSn ( approximately TlTe), Ba(5)Pb(3) ( approximately W(5)Si(3)), and Yb(31)Pb(20) (Ca(31)Sn(20)). PMID:11300823

Leon-Escamilla, E A; Corbett, J D

2001-03-12

440

Microstructure and Intermetallic Growth at the Sn-Ag-Cu\\/Ni Interface after Thermal-shearing Cycling  

Microsoft Academic Search

In this work, microstructure and intermetallic growth at the Sn-Ag-Cu\\/Ni interface were researched under the thermal-shearing cycling condition varying from 25 degC to 125 degC. The results show that two kinds of intermetallic compounds, identified as (NixCu 1-x)Sn3 and (CuxN1-x)6 Sn5, were found at the interface between Sn-3.5Ag-0.5Cu and Ni after thermal-shearing cycling. The (CuxN1-x)6Sn5 IMC grows up slowly as

Lihua Qi; Jihua Huang; Jiangang Zhang; Ye Wang

2005-01-01

441

Characterization of microstructure and properties of nanostructured FeAl\\/WC intermetallic composite coating deposited by cold spraying  

Microsoft Academic Search

A nanostuctured Fe-Al\\/WC intermetallic compound-based coating was produced by cold spraying of ball-milled powder assisted with post-annealing treatment. The microstructure of the as-milled powder and cold-sprayed coating was investigated. It was found that the as-milled Fe-Al\\/WC composite alloy powder had lamellar structure and the microstructure of the as-sprayed coating depended significantly on the microstructure of as-milled powder. A Fe-Al intermetallic

Hong-Tao Wang; Gang-Chang Ji; Chang-Jiu Li

2010-01-01

442

Mossbauer spectroscopy of actinide intermetallics  

SciTech Connect

Due to their wider radial extend the 5f electrons may form bands of different width and hybridization in metallic compounds of the light actinides. This leads to a broad spectrum of magnetic properties ranging from the localized magnetism of the lanthanides to the itinerant electron magnetism often found in transition metal compounds. Also, the influence of the crystalline electric field tends to be more pronounced than in rare earth compounds, but is usually not as dominant as in the 3d series. Magnetic structures and the question of 5f electron delocalization are reviewed with respet to actinide Moessbauer data and new results are presented. In particular the influence of applying external pressure is discussed. 60 references, 24 figures.

Kalvius, G.M.; Potzel, W.; Moser, J.; Litterst, F.J.; Asch, L.; Zankert, J.; Potzel, U.; Kratzer, A.; Wunsch, M.; Gal, J.

1984-09-01

443

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

NASA Astrophysics Data System (ADS)

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

Kobayashi, Kensei; Kaneko, Takeo; Saito, Takeshi

1999-01-01

444

Characterization of complex organic compounds formed in simulated planetary atmospheres by the action of high energy particles.  

PubMed

A wide variety of organic compounds, which are not simple organics but also complex organics, have been found in planets and comets. We reported that complex organics was formed in simulated planetary atmospheres by the action of high energy particles. Here we characterized the experimental products by using chromatographic and mass spectrometric techniques. A gaseous mixture of CO, N2 and H2O was irradiated with high energy protons (major components of cosmic rays). Water-soluble non-volatile substances, which gave amino acids after acid-hydrolysis, were characterized by HPLC and mass spectrometry. Major part of the products were complex compounds with molecular weight of several hundreds. Amino acid precursors were produced even when no water was incorporated with the starting materials. It was suggested that complex molecules including amino acid precursors were formed not in solution from simple molecules like HCN, but directly in gaseous phase. PMID:11543332

Kobayashi, K; Kaneko, T; Saito, T

1999-01-01

445

Ligand field and hyperfine interaction of the [Fe(H 2 O) 6 ] 2+ complex in different compounds  

Microsoft Academic Search

A series of compounds all containing the ferrous hexaquo complex were investigated by Mssbauer spectroscopy at 4.2K and in magnetic fields up to 5T and far infrared techniques. The results are interpreted in terms of a T2g ligand field model for which normal distortions of the water octahedron are used as parameters. The ferrous hexaquo complex can be described in

R. Doerfler; O. Leupold; D. L. Nagy; G. Ritter; H. Spiering; R. Zimmermann

1983-01-01

446

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

PubMed

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

Stacey, Timothy E; Fredrickson, Daniel C

2012-03-15

447

Capability of Lactobacillus plantarum IFPL935 to catabolize flavan-3-ol compounds and complex phenolic extracts.  

PubMed

Lactobacillus plantarum IFPL935 was incubated with individual monomeric flavan-3-ols and dimeric A- and B-type procyanidins to identify new metabolites and to determine the effect of compound structural features on bacterial growth and catabolism. Complex extracts rich in A-type proanthocyanidins and phenolic acids from cranberry were also tested. The results showed that L. plantarum IFPL935 exhibited higher resistance to nongalloylated monomeric flavan-3-ols, A-type dimeric procyanidins, and cranberry extract than to (-)-epicatechin-3-O-gallate and B-type dimeric procyanidins. Despite these findings, the strain was capable of rapidly degrading (-)-epicatechin-3-O-gallate, but not A- or B-type dimeric procyanidins. However, it was able to produce large changes in the phenolic profile of the cranberry extract mainly due to the catabolism of hydroxycinnamic and hydroxybenzoic acids. Of most relevance was the fact that L. plantarum IFPL935 cleaved the heterocyclic ring of monomeric flavan-3-ols, giving rise to 1-(3',4'-dihydroxyphenyl)-3-(2?,4?,6?-trihydroxyphenyl)propan-2-ol, activity exhibited by only a few human intestinal bacteria. PMID:22646528

Snchez-Patn, Fernando; Tabasco, Raquel; Monagas, Mara; Requena, Teresa; Pelez, Carmen; Moreno-Arribas, M Victoria; Bartolom, Begoa

2012-07-11

448

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

NASA Astrophysics Data System (ADS)

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

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

449

Separations of olefins and heterocyclic organic compounds based on reversible complexation reactions  

SciTech Connect

While numerous biological processes utilize membranes that contain transporting agents (carriers) to separate molecular and ionic permeates, the potential of synthetic membranes for separations in commercial processes has not been fully realized. In principal, the phenomenon of facilitated transport (FT) in membranes, which relies on the reversible formation of a permeate:carrier complex, can provide selective and efficient separations. Recently, membranes and thin films derived from ion exchange materials have received considerable attention with respect to their structural, physical and chemical properties. The authors report the facilitated transport of 1-hexene and 1,5-hexadiene between two decane phases separated by thin, hydrated membranes (ca. 25 ..mu..m). The flux of olefin across the membranes is enhanced by factors of several hundred when silver ions are exchanged for sodium ions. Flux measurements were made using a two compartment cell arranged vertically and separated by the membrane which was held in place with o-rings and a clamp. The reactions described in this paper can be incorporated into a staged electrochemical separation process. Results for the removal of isoquinoline and pentamethyene sulfide from iso-octane and the subsequent concentration of these compounds is a second (waste) hydrocarbon phase are presented.

Koval, C.A.; Drew, S.; Spontarelli, T.; Noble, R.D. (Departments of Chemistry and Biochemistry and of Chemical Engineering, Univ. of Colorado, Boulder, CO (US))

1988-06-01

450

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

PubMed

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

Rosa, Angela; Ricciardi, Giampaolo

2012-09-04

451

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

Microsoft Academic Search

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

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

2009-01-01

452

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

EPA Science Inventory

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

453

The role of compound nuclei and deep-inelastic scattering in complex fragment production at intermediate energies  

SciTech Connect

The dependence of complex fragment production on the asymmetry of the entrance channel has been investigated with the 18 A MeV /sup 139/La + /sup 12/C, /sup 27/Al, /sup 64/Ni reactions. Invariant cross section plots show a very simple pattern for the two lighter targets and a more complex one for the heavier /sup 64/Ni target. The observed complex fragments are shown to result from quasi-elastic/deep-inelastic reactions and from compound nuclei formed in complete/incomplete fusion processes. 9 refs., 10 figs.

Wozniak, G.J.; Colonna, N.; Charity, R.J.; Moretto, L.G.

1989-02-01

454

Surface-driven, one-step chemical vapor deposition of ?-Al4Cu9 complex metallic alloy film  

NASA Astrophysics Data System (ADS)

The present paper is a paradigm for the one-step formation of complex intermetallic coatings by chemical vapor deposition. It genuinely addresses the challenge of depositing an intermetallic coating with comparable contents of Cu and Al. Depending on processing conditions, a pure ?-Al4Cu9 and multi-phase Al-Cu films are grown with wetting properties of the former being similar to its bulk counterpart. The deposition process and its parametric investigation are detailed. Two metalorganic precursors are used taking into account their transport and chemical properties, and deposition temperature ranges. On line and ex situ characterizations enlighten the competition which occurs at the growing surface between molecular fragments, and which limits growth rates. Notably, introducing a partial pressure of hydrogen gas during deposition reduces Al growth rate from dimethylethylamine alane (DMEAA), by displacing the hydrogen desorption equilibrium. This Al partial growth rate decrease is not sufficient to achieve a Cu/Al atomic ratio that is high enough for the formation of intermetallics with close Al and Cu compositions. A fivefold increase of the flux of the gaseous copper(I) cyclopentadienyl triethylphosphine CpCuPEt3, whereas the DMEAA flux remains constant, results in the targeted Al/Cu atomic ratio equal to 44/56. Nevertheless, the global growth rate is rendered extremely low by the deposition inhibition caused by a massive phosphine adsorption (-PEt3). Despite these limitations, the results pave the way towards the conformal coating of complex surface geometries by such intermetallic compounds.

Prudhomme, Nathalie; Duguet, Thomas; Samlor, Diane; Senocq, Franois; Vahlas, Constantin

2013-10-01

455

Advanced intermetallic alloysbeyond gamma titanium aluminides  

Microsoft Academic Search

Recent studies have shown that Nb-base refractory intermetallic materials may be viable for service at temperatures that compete with the nickel-based superalloys in structural applications. While advanced intermetallics in monolithic form have limited prospects for providing the required balance of properties for use at high operating temperatures, two-phase or multiphase intermetallic systems composed of a ductile, Nb-base refractory phase in

P. R Subramanian; M. G Mendiratta; D. M Dimiduk; M. A Stucke

1997-01-01

456

Tribological properties of FeAl intermetallics under dry sliding  

Microsoft Academic Search

The tribological properties of FeAl intermetallics under dry sliding against AISI52100 steel at ambient conditions were studied on an Optimol SRV oscillating friction and wear tester in a ball-on-disc contact configuration. Effects of load and sliding speed on tribological properties of the FeAl intermetallics were investigated. The worn surfaces of the FeAl intermetallics were examined with a scanning electron microscopy

Jun Yang; Peiqing La; Weimin Liu; Qunji Xue

2004-01-01

457

The corrosion of intermetallic alloys in liquid zinc  

Microsoft Academic Search

We studied the static isothermal corrosion of three intermetallic alloys: Fe3Si, Fe3Al and Ni3Al alloy in liquid zinc at 450C compared with 316 stainless steel in this paper. The three intermetallic alloys showed a lower resistance to corrosion than 316 stainless steel in liquid zinc. The intermetallics exhibited one or two regular corrosion layers, and the corrosion process was controlled

W. J. Wang; J. P. Lin; Y. L. Wang; G. L. Chen

2007-01-01

458

Brushing up on the history of intermetallics in dentistry  

NASA Astrophysics Data System (ADS)

Employing a silver-tin-mercury intermetallic to repair cavities may seem a little unusual, but intermetallics are quite common in dentistry, ranging from gold crowns to braces. Although the human mouth can be unfriendly territory for a brittle intermetallic alloy, dental amalgam has been around since 659 A.D., and its technology has been developed to the point where a filling can be expected to last 30 years or more.

Waterstrat, Richard M.

1990-03-01

459

Synthetic multifunctional metallic-intermetallic laminate composites  

Microsoft Academic Search

The field of material microstructure design targeted for a specific set of structural and functional properties is now a recognized\\u000a field of focus in materials science and engineering. This paper describes a new class of structural materials called metallic-intermetallic\\u000a laminate (MIL) composites, which can have their micro-, meso- and macrostructure designed to achieve a wide array of material\\u000a properties and

Kenneth S. Vecchio

2005-01-01

460

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

PubMed

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

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

2010-09-21