One-pot solvothermal synthesis of ordered intermetallic Pt{sub 2}In{sub 3} as stable and efficient electrocatalyst towards direct alcohol fuel cell application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jana, Rajkumar; Peter, Sebastian C., E-mail: sebastiancp@jncasr.ac.in

Ordered intermetallic Pt{sub 2}In{sub 3} nanoparticles have been synthesized by superhydride reduction of K{sub 2}PtCl{sub 4} and InCl{sub 3}.xH{sub 2}O precursors using facile, one-pot solvothermal method. We report surfactant free solvothermal synthesis of a novel ordered Pt{sub 2}In{sub 3} intermetallic nanoparticles for the first time. The structure and morphology of the catalyst has been confirmed by powder X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, energy-dispersive spectrometry and X-ray photoelectron spectroscopy. The electrocatalytic properties of the catalysts have been investigated by cyclic voltammetry and chronoamperometry. The as prepared Pt{sub 2}In{sub 3} catalyst exhibit far superior electrocatalytic activity andmore » stability towards alcohol oxidation over commercial Pt/C. The specific activity of as synthesized catalyst was found to be ~3.2 and ~2.3 times higher than commercial Pt/C for methanol and ethanol oxidation, respectively. This improved activity and durability of the Pt{sub 2}In{sub 3} nanoparticles can make the catalyst an ideal catalyst candidate for direct alcohol fuel cell. - Graphical abstract: The ordered structure of Pt{sub 2}In{sub 3} nanoparticles synthesized by solvothermal method has confirmed through XRD and TEM. Cyclic voltametry and chronoamperometry showed improved catalytic activity and stability compared to commercial Pt/C. - Highlights: • Ordered Pt{sub 2}In{sub 3} nanoparticles were synthesized by solvothermal method. • Electrooxidation of alcohols on Pt{sub 2}In{sub 3} catalyst was investigated in acidic medium. • Pt{sub 2}In{sub 3} catalyst has superior catalytic activity compared to commercial Pt/C. • Pt{sub 2}In{sub 3} catalyst exhibited much higher stability than commercial Pt/C.« less

Structure Defect Property Relationships in Binary Intermetallics

NASA Astrophysics Data System (ADS)

Medasani, Bharat; Ding, Hong; Chen, Wei; Persson, Kristin; Canning, Andrew; Haranczyk, Maciej; Asta, Mark

2015-03-01

Ordered intermetallics are light weight materials with technologically useful high temperature properties such as creep resistance. Knowledge of constitutional and thermal defects is required to understand these properties. Vacancies and antisites are the dominant defects in the intermetallics and their concentrations and formation enthalpies could be computed by using first principles density functional theory and thermodynamic formalisms such as dilute solution method. Previously many properties of the intermetallics such as melting temperatures and formation enthalpies were statistically analyzed for large number of intermetallics using structure maps and data mining approaches. We undertook a similar exercise to establish the dependence of the defect properties in binary intermetallics on the underlying structural and chemical composition. For more than 200 binary intermetallics comprising of AB, AB2 and AB3 structures, we computed the concentrations and formation enthalpies of vacancies and antisites in a small range of stoichiometries deviating from ideal stoichiometry. The calculated defect properties were datamined to gain predictive capabilities of defect properties as well as to classify the intermetallics for their suitability in high-T applications. Supported by the US DOE under Contract No. DEAC02-05CH11231 under the Materials Project Center grant (Award No. EDCBEE).

Microstructure and tribological properties of TiCu2Al intermetallic compound coating

NASA Astrophysics Data System (ADS)

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

2011-04-01

TiCu2Al ternary intermetallic compound coating has been in situ synthesized successfully on pure Ti substrate by laser cladding. Tribological properties of the prepared TiCu2Al 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 TiCu2Al intermetallic compound coating decreased with increasing normal load and sliding speed. The wear rate of the TiCu2Al 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.

Single crystal growth of the Er2PdSi3 intermetallic compound

NASA Astrophysics Data System (ADS)

Mazilu, I.; Frontzek, M.; Löser, W.; Behr, G.; Teresiak, A.; Schultz, L.

2005-02-01

Single crystals of the Er2PdSi3 intermetallic compound melting congruently at 1648 ∘C, were grown by a floating zone method with radiation heating. The control of oxygen content was the key factor to avoid oxide precipitates, which can affect effective grain selection in the crystal growth process. Crystals grown at velocities of 5 mm/h with a preferred direction close to (1 0 0) with inclination angles of about 12 ∘ against the rod axis show very distinct facets at the rod surface. The crystals are Pd-depleted and Si-rich with respect to the nominal Er2PdSi3 stoichiometry, but exhibit inferior element segregation. Measurements on oriented single crystalline samples revealed antiferromagnetic ordering below 7 K, a magnetic easy axis parallel to the (0 0 1) axis of the AlB2-type hexagonal unit cell, and anisotropic electric properties.

Large positive magnetoresistance in intermetallic compound NdCo2Si2

NASA Astrophysics Data System (ADS)

Roy Chowdhury, R.; Dhara, S.; Das, I.; Bandyopadhyay, B.; Rawat, R.

2018-04-01

The magnetic, magneto-transport and magnetocaloric properties of antiferromagnetic intermetallic compound NdCo2Si2 (TN = 32K) have been studied. The compound yields a positive magnetoresistance (MR) of about ∼ 123 % at ∼ 5K in 8 T magnetic field. The MR value is significantly large vis - a - vis earlier reports of large MR in intermetallic compounds, and possibly associated with the changes in magnetic structure of the compound. The large MR value can be explained in terms of field induced pseudo-gaps on Fermi surface.

Development of B2 Shape Memory Intermetallics Beyond NiAl, CoNiAl and CoNiGa

NASA Astrophysics Data System (ADS)

Gerstein, G.; Firstov, G. S.; Kosorukova, T. A.; Koval, Yu. N.; Maier, H. J.

2018-06-01

The present study describes the development of shape memory alloys based on NiAl. Initially, this system was considered a promising but unsuccessful neighbour of NiTi. Later, however, shape memory alloys like CoNiAl or CoNiGa were developed that can be considered as NiAl derivatives and already demonstrated good mechanical properties. Yet, these alloys were still inferior to NiTi in most respects. Lately, using a multi-component approach, a CoNiCuAlGaIn high entropy intermetallic compound was developed from the NiAl prototype. This new alloy featured a B2 phase and a martensitic transformation along with a remarkable strength in the as-cast state. In the long-term, this new approach might led to a breakthrough for shape memory alloys in general.

Electron density determination and bonding in tetragonal binary intermetallics by convergent beam electron diffraction

NASA Astrophysics Data System (ADS)

Sang, Xiahan

Intermetallics offer unique property combinations often superior to those of more conventional solid solution alloys of identical composition. Understanding of bonding in intermetallics would greatly accelerate development of intermetallics for advanced and high performance engineering applications. Tetragonal intermetallics L10 ordered TiAl, FePd and FePt are used as model systems to experimentally measure their electron densities using quantitative convergent beam electron diffraction (QCBED) method and then compare details of the 3d-4d (FePd) and 3d-5d (FePt) electron interactions to elucidate their role on properties of the respective ferromagnetic L10-ordered intermetallics FePd and FePt. A new multi-beam off-zone axis condition QCBED method has been developed to increase sensitivity of CBED patterns to change of structure factors and the anisotropic Debye-Waller (DW) factors. Unprecedented accuracy and precision in structure and DW factor measurements has been achieved by acquiring CBED patterns using beam-sample geometry that ensures strong dynamical interaction between the fast electrons and the periodic potential in the crystalline samples. This experimental method has been successfully applied to diamond cubic Si, and chemically ordered B2 cubic NiAl, tetragonal L10 ordered TiAl and FePd. The accurate and precise experimental DW and structure factors for L10 TiAl and FePd allow direct evaluation of computer calculations using the current state of the art density functional theory (DFT) based electron structure modeling. The experimental electron density difference map of L1 0 TiAl shows that the DFT calculations describe bonding to a sufficient accuracy for s- and p- electrons interaction, e. g., the Al-layer. However, it indicate significant quantitative differences to the experimental measurements for the 3d-3d interactions of the Ti atoms, e.g. in the Ti layers. The DFT calculations for L10 FePd also show that the current DFT approximations

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

PubMed

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

2014-06-16

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

Defect structures in ordered intermetallics; grain boundaries and surfaces in FeAl, NiAl, CoAl and TiAl

NASA Astrophysics Data System (ADS)

Mutasa, Batsirai Manyara

Ordered intermetallics based on transition metal aluminides have been proposed as structural materials for advanced aerospace applications. The development of these materials, which have the advantages of low density and high operating temperatures, have been focused on the aluminides of titanium, nickel and iron. Though these materials exhibit attractive properties at elevated temperatures, their utilization is limited due to their propensity for low temperature fracture and susceptibility to decreased ductility due to environmental effects. A major embrittlement mechanism at ambient temperatures in these aluminides has been by the loss of cohesive strength at the interfaces (intergranular failure). This study focuses on this mechanism of failure, by undertaking a systematic study of the energies and structures of specific grain boundaries in some of these compounds. The relaxed atomistic grain boundary structures in B2 aluminides, FeAl, NiAl and CoAl and L10 gamma-TiAl were investigated using molecular statics and embedded atom potentials in order to explore general trends for a series of B2 compounds as well as TiAl. The potentials used correctly predict the proper mechanism of compositional disorder of these compounds. Using these potentials, point defects, free surface energies and various grain boundary structures of similar energies in three B2 compounds, FeAl, NiAl and CoAl were studied. These B2 alloys exhibited increasing anti-phase boundary energies respectively. The misorientations chosen for detailed study correspond to the Sigma5(310) and Sigma5(210) boundaries. These boundaries were investigated with consideration given to possible variations in the local chemical composition. The effects of both boundary stoichiometry and bulk stoichiometry on grain boundary energetics were also considered. Defect energies were calculated for boundaries contained in both stoichiometric and off-stoichiometric bulk. The surface energies for these aluminides were also

Multi-component intermetallic electrodes for lithium batteries

DOEpatents

Thackeray, Michael M; Trahey, Lynn; Vaughey, John T

2015-03-10

Multi-component intermetallic negative electrodes prepared by electrochemical deposition for non-aqueous lithium cells and batteries are disclosed. More specifically, the invention relates to composite intermetallic electrodes comprising two or more compounds containing metallic or metaloid elements, at least one element of which can react with lithium to form binary, ternary, quaternary or higher order compounds, these compounds being in combination with one or more other metals that are essentially inactive toward lithium and act predominantly, but not necessarily exclusively, to the electronic conductivity of, and as current collection agent for, the electrode. The invention relates more specifically to negative electrode materials that provide an operating potential between 0.05 and 2.0 V vs. metallic lithium.

First-principle calculation on mechanical and thermal properties of B2-NiSc with point defects

NASA Astrophysics Data System (ADS)

Yuan, Zhipeng; Cui, Hongbao; Guo, Xuefeng

2017-01-01

Using the first-principles plane-wave pseudo-potential method based on density functional theory, the effect of vacancy and anti-position defect on the mechanical and thermal properties of B2-NiSc intermetallics were discussed in detail. Several parameters, such as the shear modulus, bulk modulus, modulus of elasticity, C 11-C 11, the Debye temperature and Poisson's ratio, have been calculated to evaluate the effect of vacancy and anti-position defect on the hardness, ductility and thermal properties of B2-NiSc intermetallics. The results show that VNi, ScNi, VSc and NiSc the four point defects all make the crystal hardness decrease and improve plasticity of B2-NiSc intermetallics. The entropy, enthalpy and free energy of VNi, ScNi, VSc and NiSc are monotonously changed as temperature changes. From the perspective of free energy, NiSc is the most stable, while ScNi is the most unstable. Debye temperature of NiSc intermetallics with four different point defects shows VNi, ScNi, VSc and NiSc the four point defects all reduce the stability of B2-NiSc intermetallics. Project supported by the National Natural Science Foundation of China (Nos. 51301063, 51571086) and the Talent Introduction Foundation of Henan Polytechnic University (No. Y-2009).

Quaternary borocarbides: New class of intermetallic superconductors

NASA Technical Reports Server (NTRS)

Nagarajan, R.; Gupta, L. C.; Dhar, S. K.; Mazumdar, Chandan; Hossain, Zakir; Godart, C.; Levy-Clement, C.; Padalia, B. D.; Vijayaraghavan, R.

1995-01-01

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

Hot Corrosion Behavior of Ti-48Al and Ti-48Al-2Cr Intermetallic Alloys Produced by Electric Current Activated Sintering

NASA Astrophysics Data System (ADS)

Garip, Y.; Ozdemir, O.

2018-06-01

In this study, Ti-48Al and Ti-48Al-2Cr (at. pct) intermetallic alloys were produced by electric current activated sintering (ECAS). In order to characterize the phase formation and microstructures of these alloys, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis were used. The XRD result shows that the intermetallic alloys are composed of γ-TiAl and α 2-Ti3Al phases. The microstructure is dense with a low amount of porosity. The hot corrosion behavior of intermetallic alloys was carried out in a salt mixture of 25 wt pct K2SO4 and 75 wt pct Na2SO4 at 700 °C for 180 hours. The morphology of corroded surfaces was observed by SEM-EDS and XRD. Corrosion phases were identified as TiO2 and Al2O3. Well-adhering oxide scale was detected on the corroded sample surface at the end of 180 hours, and no spallation was observed. In addition, a parabolic curve was obtained at the weight change rate vs time.

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

DOEpatents

Paul, Brian Kevin; Wilson, Richard Dean; Alman, David Eli

2004-01-06

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.

Antiferromagnetism, structural instability and frustration in intermetallic AFe4X2 systems

NASA Astrophysics Data System (ADS)

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

2013-03-01

Magnetic systems with reduced dimensionality or frustration attract strong interest because these features lead to an increase of quantum fluctuations and often result in unusual properties. Here, we present a detailed study of the magnetic, thermodynamic, and structural properties of the intermetallic AFe4X2 compounds (A=Sc,Y,Lu,Zr; X=Si,Ge) crystallizing in the ZrFe4Si2 structure type. Our results evidence that these compounds cover the whole regime from frustrated AFM order up to an AFM quantum critical point. Susceptibility χ(T), specific heat, resistivity, and T-dependent XRD measurements were performed on polycrystalline samples. In all compounds we observed a Curie-Weiss behavior in χ(T) at high T indicating a paramagnetic moment of about 3μB/Fe. Magnetic and structural transitions as previously reported for YFe4Ge2 occur in all compounds with trivalent A. However, transition temperatures, nature of the transition as well as the relation between structural and magnetic transitions change significantly with the A element. Low TN's and large θCW /TN ratios confirm the relevance of frustration. The results are analyzed and discussed with respect to electronic, structural and magnetic instabilities applying DFT calculations. Financial support from the DFG (GRK 1621) is acknowledged

Intermetallic structures with atomic precision for selective hydrogenation of nitroarenes

DOE PAGES

Pei, Yuchen; Qi, Zhiyuan; Goh, Tian Wei; ...

2017-11-14

It is essential to bridge the structure-properties relationship of bimetallic catalysts for the rational design of heterogeneous catalysts. Different from random alloys, intermetallic compounds (IMCs) present atomically-ordered structures, which is advantageous for catalytic mechanism studies. Here, we used Pt-based intermetallic nanoparticles (iNPs), individually encapsulated in mesoporous silica shells, as catalysts for the hydrogenation of nitroarenes to functionalized anilines. With the capping-free nature and ordered atomic structure, PtSn iNPs show >99% selectivity to hydrogenate the nitro group of 3-nitrostyrene albeit with a lower activity, in contrast to Pt 3Sn iNPs and Pt NPs. The geometric structure of PtSn iNPs in eliminatingmore » Pt threefold sites hampers the adsorption/dissociation of molecular H 2 and leads to a non-Horiuti-Polanyi hydrogenation pathway, while Pt 3Sn and Pt surfaces are saturated by atomic H. Calculations using density functional theory (DFT) suggest a preferential adsorption of the nitro group on the intermetallic PtSn surface contributing to its high selectivity.« less

A review of rapid solidification studies of intermetallic compounds

NASA Technical Reports Server (NTRS)

Koch, C. C.

1985-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2009-03-01

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.

Method of making sintered ductile intermetallic-bonded ceramic composites

DOEpatents

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

1999-05-18

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.

High-temperature site preference and atomic short-range ordering characteristics of ternary alloying elements in γ'-Ni3Al intermetallics

NASA Astrophysics Data System (ADS)

Eriş, Rasim; Mekhrabov, Amdulla O.; Akdeniz, M. Vedat

2017-10-01

Remarkable high-temperature mechanical properties of nickel-based superalloys are correlated with the arrangement of ternary alloying elements in L12-type-ordered γ‧-Ni3Al intermetallics. In the current study, therefore, high-temperature site occupancy preference and energetic-structural characteristics of atomic short-range ordering (SRO) of ternary alloying X elements (X = Mo, W, Ta, Hf, Re, Ru, Pt or Co) in Ni75Al21.875X3.125 alloy systems have been studied by combining the statistico-thermodynamical theory of ordering and electronic theory of alloys in the pseudopotential approximation. Temperature dependence of site occupancy tendencies of alloying X element atoms has been predicted by calculating partial ordering energies and SRO parameters of Ni-Al, Ni-X and Al-X atomic pairs. It is shown that, all ternary alloying element atoms (except Pt) tend to occupy Al, whereas Pt atoms prefer to substitute for Ni sub-lattice sites of Ni3Al intermetallics. However, in contrast to other X elements, sub-lattice site occupancy characteristics of Re atoms appear to be both temperature- and composition-dependent. Theoretical calculations reveal that site occupancy preference of Re atoms switches from Al to both Ni and Al sites at critical temperatures, Tc, for Re > 2.35 at%. Distribution of Re atoms at both Ni and Al sub-lattice sites above Tc may lead to localised supersaturation of the parent Ni3Al phase and makes possible the formation of topologically close-packed (TCP) phases. The results of the current theoretical and simulation study are consistent with other theoretical and experimental investigations published in the literature.

Microstructure and properties of Ti-Al intermetallic/Al2O3 layers produced on Ti6Al2Mo2Cr titanium alloy by PACVD method

NASA Astrophysics Data System (ADS)

Sitek, R.; Bolek, T.; Mizera, J.

2018-04-01

The paper presents investigation of microstructure and corrosion resistance of the multi-component surface layers built of intermetallic phases of the Ti-Al system and an outer Al2O3 ceramic sub-layer. The layers were produced on a two phase (α + β) Ti6Al2Mo2Cr titanium alloy using the PACVD method with the participation of trimethylaluminum vapors. The layers are characterized by a high surface hardness and good corrosion, better than that of these materials in the starting state. In order to find the correlation between their structure and properties, the layers were subjected to examinations using optical microscopy, X-ray diffraction analysis (XRD), surface analysis by XPS, scanning electron microscopy (SEM), and analyses of the chemical composition (EDS). The properties examined included: the corrosion resistance and the hydrogen absorptiveness. Moreover growth of the Al2O3 ceramic layer and its influence on the residual stress distribution was simulated using finite element method [FEM]. The results showed that the produced layer has amorphous-nano-crystalline structure, improved corrosion resistance and reduces the permeability of hydrogen as compared with the base material of Ti6Al2Mo2Cr -titanium alloy.

Synthesis, Structure and bonding Analysis of the Polar Intermetallic Phase Ca2Pt2Cd

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samal, Saroj L.; Corbett, John D.

The polar intermetallic phase Ca2Pt2Cd was discovered during explorations of the Ca-Pt-Cd system. The compound was synthesized by high temperature reactions, and its structure refined by single-crystal X-ray diffraction as orthorhombic, Immm, a = 4.4514(5), b = 5.8415(6), c = 8.5976(9) Å, Z = 2. The structure formally contains infinite, planar networks of [Pt2Cd]4– along the ab plane, which can be described as tessellation of six and four-member rings of the anions, with cations stuffed between the anion layers. The infinite condensed platinum chains show a substantial long–short distortion of 0.52 Å, an appreciable difference between Ca2Pt2Cd (26 valence electrons)more » and the isotypic but regular Ca2Cu2Ga (29 VE). The relatively large cation proportion diminishes the usual dominance of polar (Pt–Cd) and 5d–5d (Pt–Pt) contributions to the total Hamilton populations.« less

Ag–Pt compositional intermetallics made from alloy nanoparticles

DOE PAGES

Pan, Yung -Tin; Yan, Yuqi; Shao, Yu -Tsun; ...

2016-09-07

Intermetallics are compounds with long-range structural order that often lies in a state of thermodynamic minimum. They are usually considered as favorable structures for catalysis due to their high activity and robust stability. However, formation of intermetallic compounds is often regarded as element specific. For instance, Ag and Pt do not form alloy in bulk phase through the conventional metallurgy approach in almost the entire range of composition. Herein, we demonstrate a bottom-up approach to create a new Ag–Pt compositional intermetallic phase from nanoparticles. By thermally treating the corresponding alloy nanoparticles in inert atmosphere, we obtained an intermetallic material thatmore » has an exceptionally narrow Ag/Pt ratio around 52/48 to 53/47, and a structure of interchangeable closely packed Ag and Pt layers with 85% on tetrahedral and 15% on octahedral sites. This rather unique stacking results in wavy patterns of Ag and Pt planes revealed by scanning transmission electron microscope (STEM). Finally, this Ag–Pt compositional intermetallic phase is highly active for electrochemical oxidation of formic acid at low anodic potentials, 5 times higher than its alloy nanoparticles, and 29 times higher than the reference Pt/C at 0.4 V (vs RHE) in current density.« less

Ag–Pt compositional intermetallics made from alloy nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Yung -Tin; Yan, Yuqi; Shao, Yu -Tsun

Intermetallics are compounds with long-range structural order that often lies in a state of thermodynamic minimum. They are usually considered as favorable structures for catalysis due to their high activity and robust stability. However, formation of intermetallic compounds is often regarded as element specific. For instance, Ag and Pt do not form alloy in bulk phase through the conventional metallurgy approach in almost the entire range of composition. Herein, we demonstrate a bottom-up approach to create a new Ag–Pt compositional intermetallic phase from nanoparticles. By thermally treating the corresponding alloy nanoparticles in inert atmosphere, we obtained an intermetallic material thatmore » has an exceptionally narrow Ag/Pt ratio around 52/48 to 53/47, and a structure of interchangeable closely packed Ag and Pt layers with 85% on tetrahedral and 15% on octahedral sites. This rather unique stacking results in wavy patterns of Ag and Pt planes revealed by scanning transmission electron microscope (STEM). Finally, this Ag–Pt compositional intermetallic phase is highly active for electrochemical oxidation of formic acid at low anodic potentials, 5 times higher than its alloy nanoparticles, and 29 times higher than the reference Pt/C at 0.4 V (vs RHE) in current density.« less

Chemical effect on diffusion in intermetallic compounds

NASA Astrophysics Data System (ADS)

Chen, Yi-Ting

With the trend of big data and the Internet of things, we live in a world full of personal electronic devices and small electronic devices. In order to make the devices more powerful, advanced electronic packaging such as wafer level packaging or 3D IC packaging play an important role. Furthermore, ?-bumps, which connect silicon dies together with dimension less than 10 ?m, are crucial parts in advanced packaging. Owing to the dimension of ?-bumps, they transform into intermetallic compound from tin based solder after the liquid state bonding process. Moreover, many new reliability issues will occur in electronic packaging when the bonding materials change; in this case, we no longer have tin based solder joint, instead, we have intermetallic compound ?-bumps. Most of the potential reliability issues in intermetallic compounds are caused by the chemical reactions driven by atomic diffusion in the material; thus, to know the diffusivities of atoms inside a material is significant and can help us to further analyze the reliability issues. However, we are lacking these kinds of data in intermetallic compound because there are some problems if used traditional Darken's analysis. Therefore, we considered Wagner diffusivity in our system to solve the problems and applied the concept of chemical effect on diffusion by taking the advantage that large amount of energy will release when compounds formed. Moreover, by inventing the holes markers made by Focus ion beam (FIB), we can conduct the diffusion experiment and obtain the tracer diffusivities of atoms inside the intermetallic compound. We applied the technique on Ni3Sn4 and Cu3Sn, which are two of the most common materials in electronic packaging, and the tracer diffusivities are measured under several different temperatures; moreover, microstructure of the intermetallic compounds are investigated to ensure the diffusion environment. Additionally, the detail diffusion mechanism was also discussed in aspect of diffusion

Up-and-coming IMCs. [Intermetallic-Matrix Composites

NASA Technical Reports Server (NTRS)

Bowman, Randy; Noebe, Ronald

1989-01-01

While the good oxidation and environmental resistance, high melting points, and comparatively low densities of such ordered intermetallics as Ti3Al, NiAl, FeAl, and NbAl3 render them good candidates for advanced aerospace structures, their poor toughness at low temperatures and low strength at elevated temperatures have prompted the development of fiber-reinforced intermetallic-matrix composites (IMCs) with more balanced characteristics. Fabrication methods for continuous-fiber IMCs under development include the P/M 'powder cloth' method, the foil/fiber method, and thermal spraying. The ultimate success of IMCs depends on fibers truly compatible with the matrix materials.

First principles electronic and thermal properties of some AlRE intermetallics

NASA Astrophysics Data System (ADS)

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

2008-10-01

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

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

PubMed

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

2015-02-05

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

Magnetic ordering in TmGa.

PubMed

Cadogan, J M; Stewart, G A; Muñoz Pérez, S; Cobas, R; Hansen, B R; Avdeev, M; Hutchison, W D

2014-03-19

We have determined the magnetic structure of the intermetallic compound TmGa by high-resolution neutron powder diffraction and (169)Tm Mössbauer spectroscopy. This compound crystallizes in the orthorhombic (Cmcm) CrB-type structure and its magnetic structure is characterized by magnetic order of the Tm sublattice along the a-axis. The initial magnetic ordering occurs at 15(1) K and yields an incommensurate antiferromagnetic structure described by the propagation vector k1 = [0 0.275(2) 0]. At 12 K the dominant ferromagnetic ordering of the Tm sublattice along the a-axis develops in what appears to be a first-order transition. At 3 K the magnetic structure of TmGa is predominantly ferromagnetic but a weakened incommensurate component remains. The ferromagnetic Tm moment reaches 6.7(2) μB at 3 K and the amplitude of the remaining incommensurate component is 2.7(4) μB. The (169)Tm hyperfine magnetic field at 5 K is 631(1) T.

Longitudinal recording on FePt and FePtX (X = B, Ni) intermetallic compounds

NASA Astrophysics Data System (ADS)

Li, Ning

1999-11-01

Near field recording on high coercivity FePt intermetallic compound media using a high Bsat write element was investigated. Untextured FePt media were prepared by magnetron sputtering on ZrO2 disks at a substrate temperature of 450°C, with post annealing at 450°C for 8 hrs. Both multilayer and cosputtered precursors produced the ordered tetragonal L10 phase with high coercivity between 5kOe and 12kOe. To improve readback noise decrease magnetic domain size, FePtB media were subsequently prepared by cosputtering. Over-write, roll-off, signal to noise ratio and non-linear transition shift (NLTS) ere measured by both metal in gap (MIG) and merged MR heads. FePtB media showed similar NLTS to commercial CoCrPtTa longitudinal media, but 5dB lower signal to noise ratio. By operating recording transducers in near contact, reasonable values of (>30dB) could be obtained. VSM Rotational Transverse Magnetization has been used for measuring the anisotropy field of magnetic thin films. Magnetization reversal during rotation of a 2D isotropic an applied field is discussed. The relationship between the transverse magnetization My and the applied field H was numerically solved. An excellent approximation for the transverse magnetization is found to be: My/Ms=A(1- H/Hk) 2.5, where A = 1.1434, and Hk is the anisotropy field. For curve fitting to experimental data, both A and Hk were used as fitting parameters. Comparison between a constructed torque hysteresis method and this VSM RTM method have been made theoretically and experimentally. Both results showed that VSM RTM will give better extrapolation of the anisotropy field. The torque measurement will slightly overestimate the anisotropy field. The anisotropy fields of FePt and FePtX (X = B, Ni) films were characterized using this VSM RTM technique with comparison to a CoCrTaPt disk. Anisotropy energy was derived. Hc/Hk was used as an indicator for coherent rotation of a single domain. Interactions between magnetic domains were

Polar Intermetallics Pr 5Co 2Ge 3 and Pr 7Co 2Ge 4 With Planar Hydrocarbon-Like Metal Clusters

DOE PAGES

Lin, Qisheng; Aguirre, Kaiser; Saunders, Scott M.; ...

2017-06-19

Planar hydrocarbon-like metal clusters may foster new insights linking organic molecules with conjugated π-π bonding interactions and inorganic structures in terms of their bonding characteristics. However, such clusters are uncommon in polar intermetallics. Herein, we report two polar intermetallic phases, Pr 5Co 2Ge 3 and Pr 7Co 2Ge 4, both of which feature such planar metal clusters, viz., ethylene-like [Co 2Ge 4] clusters plus the concatenated forms and polyacene-like [Co 2Ge 2] n ribbons in Pr 5Co 2Ge 3, and 1,2,4,5-tetramethylbenzene-like [Co4Ge6] cluster in Pr 7Co 2Ge 4. Just as in the related planar organic structures, these metal-metalloid species aremore » dominated by covalent bonding interactions. Both compounds magnetically order at low temperature with net ferromagnetic components: Pr 5Co 2Ge 3 via a series of transitions below 150 K; and Pr 7Co 2Ge 4 via a single ferromagnetic transition at 19 K. Spin-polarized electronic structure calculations for Pr 7Co 2Ge 4 reveal strong spin-orbit coupling within Pr and considerable magnetic contributions from Co atoms. This work suggests that similar structural chemistry can emerge for other rare earth-late transition metal-main group systems.« less

First-principles study of the structural, elastic, vibrational, thermodynamic and electronic properties of the Mo2B intermetallic under pressure

NASA Astrophysics Data System (ADS)

Escamilla, R.; Carvajal, E.; Cruz-Irisson, M.; Romero, M.; Gómez, R.; Marquina, V.; Galván, D. H.; Durán, A.

2016-12-01

The structural, elastic, vibrational, thermodynamic and electronic properties of the Mo2B intermetallic under pressure are assessed using first-principles calculations based on the generalized gradient approximation (GGA) proposed by Perdew-Wang (PW91). Our results show that the calculated structural parameters at a pressure of zero GPa are in good agreement with the available experimental data. The effect of high pressures on the lattice constants shows that the compression along the c-axis and along the a-axis are similar. The elastic constants were calculated using the static finite strain technique, and the bulk shear moduli are derived from the ideal polycrystalline aggregate. We find that the elastic constants, elastic modulus and hardness monotonically increase as a function of pressure; consequently, the structure is dynamically stable and tends from brittle to ductile behavior under pressure. The Debye temperature θD increases and the so-called Gru¨ neisen constant γ decreases due to stiffening of the crystal structure. The phonon dispersion curves were obtained using the direct method. Additionally, the internal energy (ΔE), the Helmholtz free energy (ΔF), the entropy (S) and the lattice contribution to the heat capacity Cv were calculated and analyzed with the help of the phonon dispersion curves. The N(EF) and the electron transfer between the B and Mo atoms increase as a function of pressure.

Magnetic order of intermetallic FeGa3 -yGey studied by μ SR and 57Fe Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Munevar, J.; Cabrera-Baez, M.; Alzamora, M.; Larrea, J.; Bittar, E. M.; Baggio-Saitovitch, E.; Litterst, F. J.; Ribeiro, R. A.; Avila, M. A.; Morenzoni, E.

2017-03-01

Temperature-dependent magnetization, muon spin rotation, and 57Fe Mössbauer spectroscopy experiments performed on crystals of intermetallic FeGa3 -yGey (y =0.11 ,0.14 ,0.17 ,0.22 ,0.27 ,0.29 ,0.32 ) are reported. Whereas at y =0.11 even a sensitive magnetic microprobe such as μ SR does not detect magnetism, all other samples display weak ferromagnetism with a magnetic moment of up to 0.22 μB per Fe atom. As a function of doping and of temperature, a crossover from short-range to long-range magnetic order is observed, characterized by a broadly distributed spontaneous internal field. However, y =0.14 and 0.17 remain in the short-range-ordered state down to the lowest investigated temperature. The transition from short-range to long-range order appears to be accompanied by a change of the character of the spin fluctuations, which exhibit a spin-wave excitation signature in the long-range-order part of the phase diagram. Mössbauer spectroscopy for y =0.27 and 0.32 indicates that the internal field lies in the plane perpendicular to the crystallographic c axis. The field distribution and its evolution with doping suggest that the details of the Fe magnetic moment formation and the consequent magnetic state are determined not only by the dopant concentration, but also by the way the replacement of the Ga atoms surrounding the Fe is accomplished.

Phase transition of intermetallic TbPt at high temperature and high pressure

NASA Astrophysics Data System (ADS)

Qin, Fei; Wu, Xiang; Yang, Ke; Qin, Shan

2018-04-01

Here we present synchrotron-based x-ray diffraction experiments combined with diamond anvil cell and laser heating techniques on the intermetallic rare earth compound TbPt (Pnma and Z  =  4) up to 32.5 GPa and ~1800 K. The lattice parameters of TbPt exhibit continuous compression behavior up to 18.2 GPa without any evidence of phase transformation. Pressure-volume data were fitted to a third-order Birch-Murnaghan equation of state with V 0  =  175.5(2) Å3, {{K}{{T0}}}   =  110(5) GPa and K{{T0}}\\prime   =  3.8(7). TbPt exhibits anisotropic compression with β a   >  β b   >  β c and the ratio of axial compressibility is 2.50:1.26:1.00. A new monoclinic phase of TbPt assigned to the Pc or P2/c space group was observed at 32.5 GPa after laser heating at ~1800 K. This new phase is stable at high pressure and presented a quenchable property on decompression to ambient conditions. The pressure-volume relationship is well described by the second-order Birch-Murnaghan equation of state, which yields V 0  =  672(4) Å3, {{K}{{T0}}}   =  123(6) GPa, which is about ~14% more compressible than the orthorhombic TbPt. Our results provide more information on the structure and elastic property view, and thus a better understanding of the physical properties related to magnetic structure in some intermetallic rare earth alloys.

RETRACTED ARTICLE: Precipitation behavior of B2-ordered aluminide

NASA Astrophysics Data System (ADS)

Han, Chang-Suk

2006-12-01

Fine dispersion of disordered phases is obtained in Ni-Al-Cr and Fe-Al-Co temary systems. A transmission electron microscope investigation has been performed on the precipitation of α-Cr in B2-ordered β-NiAl with different stoichiometry and α-Fe in B2-FeAl(Co) compound. Precipitation behavior and hardening were investigated by measuring the hardness variation. The hardness of NiAl and FeAl increases appreciably with the fine precipitation of α-Cr and α-Fe, and over-age softening occurs after prolonged aging. In the case of B2-NiAl(Cr), perfect lattice coherency is maintained at the interfaces between the α-Cr particles and the matrix during the initial stage of aging. After prolonged aging, a loss of coherency occurs by the attraction of matrix dislocations to the particle/matrix interface, followed by climbing around the particles. On the other hand, in the case of B2-FeAl(Co), the disordered α-Fe phase is present as a precipitate in the B2-FeAl(Co) matrix and has a cubic-cubic orientation with the matrix. At the early aging periods, prismatic dislocation loops formed in the B2-FeAl(Co) matrix. B2-FeAl(Co) matrix is typically hardened by the precipitation of α-Fe.

Deformation twinning in metals and ordered intermetallics-Ti and Ti-aluminides

NASA Astrophysics Data System (ADS)

Yoo, M. H.; Fu, C. L.; Lee, J. K.

1991-06-01

The role of deformation twinning in the strength and ductility of metals and ordered intermetallic alloys is examined on the basis of crystallography, energetics and kinetics of deformation twinning. A systematic analysis is made by taking Ti, Ti3AI, TiAl, and A13Ti as four model systems. In comparison with profuse twinning in Ti, the intrinsic difficulty of twinning in Ti3A1 is rationalized in terms of the interchange shuffling mechanism. A fault (SISF) dragging mechanism based on the interaction torque explains the physical source for the low mobility of screw superdislocations in TiAl, which may lead to (111) [ 11bar{2}] twin nucleation. In TiAl and A13Ti alloys, the twin-slip (ordinary) conjugate relationship makes an important contribution to the strain compatibility for high-temperature plasticity. Potentially beneficial alloying additions to promote twinning are discussed. Les conséquences de la déformation par maclage sur la fracture et la ductilité des métaux et alliages intermétalliques ordonnés sont étudiées en fonction de la cristallographie, de l'énergie et de la cinétique des déformations par maclage. Une analyse systématique a été faite en considérant Ti, Ti3AI, TiAl et A13Ti comme quatre systèmes modèles. En comparaison avec le nombre important de maclages observés dans Ti, la difficulté intrinsèque des maclages dans Ti3AI est rationalisée en terme de mécanisme d'“interchange shuffling”. Un mécanisme de “dragging fault” basé sur l'interaction “torque” explique l'origine physique de la faible mobilité des superdislocations vissées dans TiAl qui peuvent conduire à la nucléation des macles (111) 112. Dans les alliages tels TiAl et A13Ti, la relation conjuguée entre la macle et le glissement (ordinaire) contribue de façon importante à la compatibilité des contraintes lors de la déformation plastique à haute température. Des effets bénéfiques potentiels liés à des éléments d'addition sur le processus

FP-LAPW study of structural, electronic, elastic, mechanical and thermal properties of AlFe intermetallic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jain, Ekta, E-mail: jainekta05@gmail.com; Pagare, Gitanjali, E-mail: gita-pagare@yahoo.co.in; Sanyal, S. P., E-mail: sps.physicsbu@gmail.com

2016-05-06

The structural, electronic, elastic, mechanical and thermal properties of AlFe intermetallic compound in B{sub 2}-type (CsCl) structure have been investigated using first-principles calculations. The exchange-correlation term was treated within generalized gradient approximation. Ground state properties i.e. lattice constants (a{sub 0}), bulk modulus (B) and first-order pressure derivative of bulk modulus (B’) are presented. The density of states are derived which show the metallic character of present compound. Our results for C{sub 11}, C{sub 12} and C{sub 44} agree well with previous theoretical data. Using Pugh’s criteria (B/G{sub H} < 1.75), brittle character of AlFe is satisfied. In addition shear modulusmore » (G{sub H}), Young’s modulus (E), sound wave velocities and Debye temperature (θ{sub D}) have also been estimated.« less

Synthesis of Au-induced structurally ordered AuPdCo intermetallic core-shell nanoparticles and their use as oxygen reduction catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuttiyiel, Kurian A.; Sasaki, Kotaro; Adzic, Radoslav R.

Embodiments of the disclosure relate to intermetallic nanoparticles. Embodiments include nanoparticles having an intermetallic core including a first metal and a second metal. The first metal may be palladium and the second metal may be at least one of cobalt, iron, nickel, or a combination thereof. The nanoparticles may further have a shell that includes palladium and gold.

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

NASA Technical Reports Server (NTRS)

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

1989-01-01

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

Magnetic Ordering of Antiferromagnetic Trimer System 2b·3CuCl2·2H2O

NASA Astrophysics Data System (ADS)

Sanda, M.; Kubo, K.; Asano, T.; Morodomi, H.; Inagaki, Y.; Kawae, T.; Wang, J.; Matsuo, A.; Kindo, K.; Sato, T. J.

2012-12-01

In this paper, we present the magnetic properties of 2b·3CuCl2·2H2O (b = betaine, C5H11NO2). 2b·3CuCl2·2H2O is the first model substance for a two-dimensional S = 1/2 orthogonal antiferromagnetic trimer system. We have performed magnetic susceptibility, magnetization curve, and specific heat under extreme conditions: low temperatures and high magnetic fields in this system. The experimental results indicate that this substance is a magnetically S = 1/2 antiferromagnetic trimer system. The magnetization also shows one-third of the saturation value (MS ~ 3.2μB/f.u.) between 5 and 14T The specific heat in a zero field shows a sharp peak at 1.38K corresponding to a long-range magnetic ordering, TN. As the magnetic field increases, the TN shifts remarkably to a lower temperature and is suppressed. Above 5T, the specific heat has no anomaly down to 150mK In the plateau region with an energy gap, the magnetic ordering seems to be disappeared.

Magnetic properties of Gd intermetallics

DOE PAGES

Petit, Leon; Szotek, Zdzislawa; Jackson, Jerome; ...

2017-04-06

Here, using first-principles calculations, based on disordered local moment theory, combined with the self-interaction corrected local spin density approximation, we study magnetic interactions in GdX intermetallics for X = Cu, Zn, Ga, Cd, and Mg. Our predicted magnetic orders and ordering temperatures both at zero and other pressures agree well with experiments including the large increase in the Curie temperature of GdCd under pressure that is shown by our own experimental measurements. From our results it emerges that the Ruderman-Kittel-Kasuya-Yosida interaction on its own can not explain the observed behaviour under pressure, and that the magnetic ordering mechanism is stronglymore » influenced by the occupations of both Gd and anion d-bands.« less

Method of making sintered ductile intermetallic-bonded ceramic composites

DOEpatents

Plucknett, Kevin; Tiegs, Terry N.; Becher, Paul F.

1999-01-01

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.

Ni.sub.3 Al-based intermetallic alloys having improved strength above 850.degree. C.

DOEpatents

Liu, Chain T.

2000-01-01

Intermetallic alloys composed essentially of: 15.5% to 17.0% Al, 3.5% to 5.5% Mo, 4% to 8% Cr, 0.04% to 0.2% Zr, 0.04% to 1.5% B, balance Ni, are characterized by melting points above 1200.degree. C. and superior strengths at temperatures above 1000.degree. C.

Thermomechanical processing of plasma sprayed intermetallic sheets

DOEpatents

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2001-01-01

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

Intermetallics as innovative CRM-free materials

NASA Astrophysics Data System (ADS)

Novák, Pavel; Jaworska, Lucyna; Cabibbo, Marcello

2018-03-01

Many of currently used technical materials cannot be imagined without the use of critical raw materials. They require chromium (e.g. in stainless and tool steels), tungsten and cobalt (tool materials, heat resistant alloys), niobium (steels and modern biomaterials). Therefore there is a need to find substitutes to help the European economy. A promising solution can be the application of intermetallics. These materials offer wide variety of interesting properties, such as high hardness and wear resistance or high chemical resistance. In this paper, the overview of possible substitute materials among intermetallics is presented. Intermetallics based on aluminides and silicides are shown as corrosion resistant materials, composites composed of ceramics in intermetallic matrix as possible tool materials. The manufacturing processes are being developed to minimize the disadvantages of these materials, mainly the room-temperature brittleness.

B2+L2{sub 1} ordering in Co{sub 2}MnAl Heusler alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vinesh, A., E-mail: attatappa85@gmail.com; Sudheesh, V. D.; Lakshmi, N.

Magnetic and structural properties of B2 ordered Co{sub 2}MnAl Heusler alloy have been studied by X-ray diffraction and DC magnetization techniques. X-ray diffractogram shows the structure is of B2 type with preferential site disorder between Mn and Al atoms and presence of a small L2{sub 1} phase. DC magnetization studies at low temperature establish that the antiferromagnetic nature arises mainly due to the antiparallel coupling of spin moments of 3d electrons of Co with Mn atoms. Curie temperature (T{sub c}) is 733 K which is close to T{sub c} of the L2{sub 1} phase.

Facet-Dependent Deposition of Highly Strained Alloyed Shells on Intermetallic Nanoparticles for Enhanced Electrocatalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chenyu; Sang, Xiahan; Gamler, Jocelyn T. L.

Compressive surface strains can enhance the performance of platinum-based core@shell electrocatalysts for the oxygen reduction reaction (ORR). Bimetallic core@shell nanoparticles (NPs) are widely studied nanocatalysts but often have limited lattice mismatch and surface compositions; investigations of core@shell NPs with greater compositional complexity and lattice misfit are in their infancy. Here, a new class of multimetallic NPs composed of intermetallic cores and random alloy shells is reported. Specifically, face-centered cubic (fcc) Pt- Cu random alloy shells were deposited non-epitaxially on PdCu B2 intermetallic seeds, giving rise to faceted core@shell NPs with highly strained surfaces. In fact, high resolution transmission electron microscopymore » (HRTEM) revealed orientation-dependent surface strains, where the compressive strains were minimal on Pt-Cu {111} facets but greater on {200} facets. These core@shell NPs provide higher specific and mass activities for the ORR when compared to conventional Pt-Cu NPs. Moreover, these intermetallic@random alloy NPs displayed high endurance, undergoing 10,000 cycles with only a slight decay in activity and no apparent structural changes.« less

Facet-Dependent Deposition of Highly Strained Alloyed Shells on Intermetallic Nanoparticles for Enhanced Electrocatalysis

DOE PAGES

Wang, Chenyu; Sang, Xiahan; Gamler, Jocelyn T. L.; ...

2017-08-25

Compressive surface strains can enhance the performance of platinum-based core@shell electrocatalysts for the oxygen reduction reaction (ORR). Bimetallic core@shell nanoparticles (NPs) are widely studied nanocatalysts but often have limited lattice mismatch and surface compositions; investigations of core@shell NPs with greater compositional complexity and lattice misfit are in their infancy. Here, a new class of multimetallic NPs composed of intermetallic cores and random alloy shells is reported. Specifically, face-centered cubic (fcc) Pt- Cu random alloy shells were deposited non-epitaxially on PdCu B2 intermetallic seeds, giving rise to faceted core@shell NPs with highly strained surfaces. In fact, high resolution transmission electron microscopymore » (HRTEM) revealed orientation-dependent surface strains, where the compressive strains were minimal on Pt-Cu {111} facets but greater on {200} facets. These core@shell NPs provide higher specific and mass activities for the ORR when compared to conventional Pt-Cu NPs. Moreover, these intermetallic@random alloy NPs displayed high endurance, undergoing 10,000 cycles with only a slight decay in activity and no apparent structural changes.« less

Effect of Mg2Sn Intermetallic on the Grain Refinement in As-cast AM Series Alloy

NASA Astrophysics Data System (ADS)

She, J.; Pan, F. S.; Hu, H. H.; Tang, A. T.; Yu, Z. W.; Song, K.

2015-08-01

In the present work, in order to investigate the grain refinement mechanism of AM containing Sn alloys, the as-cast AM60, AM90 alloys, and the alloys with addition of 1 wt.% Sn were fabricated by traditional casting, respectively. During the solidification of AM + Sn alloys, the morphology of divorced eutectic Mg17Al12 was refined by Mg2Sn intermetallic that served as the heterogeneous nucleation cores. The modified Mg17Al12 effectively restricted the grain growth and resulted in a grain refinement. As a result, the yield strength of as-cast AM alloys was significantly enhanced by addition of Sn, while the ductility also improved. Moreover, the edge-to-edge model was employed to predict the orientation relationship between Mg17Al12 and Mg2Sn.

Experimental and theoretical investigations of the polar intermetallics SrPt{sub 3}Al{sub 2} and Sr{sub 2}Pd{sub 2}Al

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stegemann, Frank; Benndorf, Christopher; Touzani, Rachid St.

SrPt{sub 3}Al{sub 2}, a CaCu{sub 5} relative (P6/mmm; a = 566.29(3), c = 389.39(3) pm; wR{sub 2} = 0.0202, 121 F{sup 2} values, 9 parameters), and Sr{sub 2}Pd{sub 2}Al, isostructural to Ca{sub 2}Pt{sub 2}Ge (Fdd2; a = 1041.45(5), b = 1558.24(7), c = 604.37(3) pm; wR{sub 2} = 0.0291, 844 F{sup 2} values, 25 parameters) have been prepared from the elements. The crystal structures have been investigated by single crystal X-ray diffraction. Structural relaxation confirmed the electronic stability of SrPt{sub 3}Al{sub 2}, while orthorhombic Sr{sub 2}Pd{sub 2}Al might be a metastable polymorph as it is energetically competitive to its monoclinicmore » variant. Both compounds are predicted to be metallic conductors as their density-of-states (DOS) are non-zero at the Fermi level. COHP bonding analysis coupled with Bader effective charge analysis suggest that the title compounds are polar intermetallic phases in which strong Pt–Al and Pd–Al covalent bonds are present, while a significant electron transfer from Sr atoms to the [Pt{sub 3}Al{sub 2}]{sup δ–} or [Pd{sub 2}Al]{sup δ–} network is found. - Graphical abstract: Chains of Pd atoms in the crystal structure of Sr{sub 2}Pd{sub 2}Al get connected by Al atoms in the shape of a distorted tetrahedra. The band structure calculations confirm weak Pd–Pd interactions. - Highlights: • SrPt{sub 3}Al{sub 2} and Sr{sub 2}Pd{sub 2}Al discovered and crystallographically investigated. • DFT predicts the here reported orthorhombic Sr{sub 2}Pd{sub 2}Al to be competitive in energy to the presently unknown monoclinic Sr{sub 2}Pd{sub 2}Al. • Bader charge analysis indicates SrPt{sub 3}Al{sub 2} and Sr{sub 2}Pd{sub 2}Al are polar intermetallics.« less

Characterization of Impact Initiation of Aluminum-Based Intermetallic-Forming Reactive Materials

DTIC Science & Technology

2011-12-01

compressed intermetallic-forming aluminum-based reactive materials upon impact initiation, consisting of equi-volumetric tantalum-aluminum, tungsten-aluminum...18 2.3.4 Dynamic Energy Release Characterization using Pig Test . . . . . . 21 2.3.5 Shock Compression of Reactive Powder Mixtures...is to evaluate the reaction initiation characteristics of quasi-statically compressed intermetallic-forming aluminum-based reactive materials upon

A-site ordered quadruple perovskite oxides

NASA Astrophysics Data System (ADS)

Youwen, Long

2016-07-01

The A-site ordered perovskite oxides with chemical formula display many intriguing physical properties due to the introduction of transition metals at both A‧ and B sites. Here, research on the recently discovered intermetallic charge transfer occurring between A‧-site Cu and B-site Fe ions in LaCu3Fe4O12 and its analogues is reviewed, along with work on the magnetoelectric multiferroicity observed in LaMn3Cr4O12 with cubic perovskite structure. The Cu-Fe intermetallic charge transfer leads to a first-order isostructural phase transition accompanied by drastic variations in magnetism and electrical transport properties. The LaMn3Cr4O12 is a novel spin-driven multiferroic system with strong magnetoelectric coupling effects. The compound is the first example of cubic perovskite multiferroics to be found. It opens up a new arena for studying unexpected multiferroic mechanisms. Project supported by the National Basic Research Program of China (Grant No. 2014CB921500), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB07030300), and the National Natural Science Foundation of China (Grant No. 11574378).

Metal- and intermetallic-matrix composites for aerospace propulsion and power systems

NASA Technical Reports Server (NTRS)

Doychak, J.

1992-01-01

The requirements for high specific strength refractory materials of prospective military, civil, and space propulsion systems are presently addressed in the context of emerging capabilities in metal- and intermetallic-matrix composites. The candidate systems encompass composite matrix compositions of superalloy, Nb-Zr refractory alloy, Cu-base, and Ti-base alloy types, as well as such intermetallics as TiAl, Ti3Al, NiAl, and MoSi2. The brittleness of intermetallic matrices remains a major consideration, as does their general difficulty of fabrication.

Investigation on thixojoining to produce hybrid components with intermetallic phase

NASA Astrophysics Data System (ADS)

Seyboldt, Christoph; Liewald, Mathias

2018-05-01

Current research activities at the Institute for Metal Forming Technology of the University of Stuttgart are focusing on the manufacturing of hybrid components using semi-solid forming strategies. One process investigated is the joining of different materials in the semi-solid state and is so called "thixojoining". In this process, metallic inlays are inserted into the semi-solid forming die before the actual forming process and are then joined with a material which was heated up to its semi-solid state. Earlier investigations have shown that using this process a very well-shaped form closure can be produced. Furthermore, it was found that sometimes intermetallic phases are built between the different materials, which decisively influence the part properties of such hybrid components for its future application. Within the framework presented in this paper, inlays made of aluminum, brass and steel were joined with aluminum in the semi-solid state. The aim of the investigations was to create an intermetallic bond between the different materials. For this investigations the liquid phase fraction of the aluminum and the temperature of the inlay were varied in order to determine the influence on the formation of the intermetallic phase. Forming trials were performed using a semi-solid forming die with a disk shaped design. Furthermore, the intermetallic phase built was investigated using microsections.

RAPID COMMUNICATION: Formation of MgB2 at ambient temperature with an electrochemical process: a plausible mechanism

NASA Astrophysics Data System (ADS)

Jadhav, A. B.; Subhedar, K. M.; Hyam, R. S.; Talaptra, A.; Sen, Pintu; Bandyopadhyay, S. K.; Pawar, S. H.

2005-06-01

The binary intermetallic MgB2 superconductor has been synthesized by many research groups. However, the mechanism of its formation is not clearly understood. In this communication, a comprehensive mechanism of the formation of MgB2 from Le Chatelier's principle of equilibrium reaction has been explained both for solid-state reaction and electrodeposition methods.

X-ray structural study of intermetallic alloys RT{sub 2}Si and RTSi{sub 2} (R=rare earth, T=noble metal)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gribanov, Alexander, E-mail: avgri@mail.r; Chemistry Department of the Moscow State University, Leninskie Gory, GSP-1, 119991 Moscow; Grytsiv, Andriy

Two series of intermetallic alloys, RT{sub 2}Si and RTSi{sub 2}, have been synthesized from stoichiometric compositions. The crystal structures of EuPt{sub 1+x}Si{sub 2-x} (CeNiSi{sub 2}-type), CeIr{sub 2}Si (new structure type), YbPd{sub 2}Si and YbPt{sub 2}Si (both YPd{sub 2}Si-type) have been elucidated from X-ray single crystal CCD data, which were confirmed by XPD experiments. The crystal structures of LaRh{sub 2}Si and LaIr{sub 2}Si (CeIr{sub 2}Si-type), {l_brace}La,Ce,Pr,Nd{r_brace}AgSi{sub 2} (all TbFeSi{sub 2}-type), and EuPt{sub 2}Si (inverse CeNiSi{sub 2}-type) were characterized by XPD data. RT{sub 2}Si/RTSi{sub 2} compounds were neither detected in as-cast alloys Sc{sub 25}Pt{sub 50}Si{sub 25}, Eu{sub 25}Os{sub 25}Si{sub 50} and Eu{submore » 25}Rh{sub 25}Si{sub 50} nor after annealing at 900 {sup o}C. Instead, X-ray single crystal data prompted Eu{sub 2}Os{sub 3}Si{sub 5} (Sc{sub 2}Fe{sub 3}Si{sub 5}-type) and EuRh{sub 2+x}Si{sub 2-x} (x=0.04, ThCr{sub 2}Si{sub 2}-type) as well as a new structure type for Sc{sub 2}Pt{sub 3}Si{sub 2} (own type). - Graphical abstract: Two series of the intermetallic compounds, RT{sub 2}Si and RTSi{sub 2}, have been investigated by X-ray diffraction methods. The new tetragonal CeIr{sub 2}Si-type of the crystal structure was described and the interrelation between orthorhombic CeNiSi{sub 2} and tetragonal CeIr{sub 2}Si had been discussed as a similar packing of the BaAl{sub 4} and AlB{sub 2} slabs.« less

Microstructure and wear properties of laser clad Ti2Ni3Si/Ni3Ti multiphase intermetallic coatings

NASA Astrophysics Data System (ADS)

Wang, H. M.; Tang, H. B.; Cai, L. X.; Cao, F.; Zhang, L. Y.; Yu, R. L.

2005-05-01

Wear resistant Ti2Ni3Si/Ni3Ti multiphase intermetallic coatings with a microstructure consisting of Ti2Ni3Si primary dendrites and interdendritic Ti2Ni3Si/Ni3Ti eutectic were fabricated on a substrate of 0.2% C plain carbon steel by a laser cladding process with Ti-Ni-Si alloy powders. The Ti2Ni3Si/Ni3Ti coatings have excellent wear resistance and a low coefficient of friction under metallic dry sliding wear test conditions with hardened 0.45% C carbon steel as the silide-mating counterpart. The excellent tribological properties of the coating are attributed to the high hardness, strong covalent-dominant atomic bonds of the ternary metal silicide Ti2Ni3Si and to the high yield strength and strong yield anomaly of the intermetallic compound Ni3Ti.

Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity

DOEpatents

Wright, Randy B.

1992-01-01

Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation).

Copper/solder intermetallic growth studies.

PubMed

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

1993-08-01

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

Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity

DOEpatents

Wright, R.B.

1992-01-14

Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation). 23 figs.

Electromigration in Sn-Cu intermetallic compounds

NASA Astrophysics Data System (ADS)

Wei, C. C.; Chen, C. F.; Liu, P. C.; Chen, Chih

2009-01-01

As the shrinking in bump size continues, the effect of intermetallic compounds (IMCs) on electromigration becomes more pronounced. Electromigration in Sn-Cu intermetallic compounds was examined using edge displacement method. It was found that Cu6Sn5 compounds are more susceptible to electromigration than Cu3Sn compounds. The lower solidus temperature and higher resistivity of the Cu6Sn5 IMCs are responsible for its higher electromigration rate. Length-dependent electromigration behavior was found in the stripes of various lengths and the critical length was determined to be between 5 and 10 μm at 225 °C, which corresponded to a critical product between 2.5 and 5 A/cm. Furthermore, the Sn-Cu compounds were proven to have better electromigration resistance than eutectic SnAgCu solder.

Intermetallic negative electrodes for non-aqueous lithium cells and batteries

DOEpatents

Thackeray, Michael M.; Vaughey, John T.; Johnson, Christopher S.; Fransson, Linda M.; Edstrom, Ester Kristina; Henriksen, Gary

2004-05-04

A method of operating an electrochemical cell is disclosed. The cell has an intermetallic negative electrode of Cu.sub.6-x M.sub.x Sn.sub.5, wherein x is .ltoreq.3 and M is one or more metals including Si and a positive electrode containing Li in which Li is shuttled between the positive electrode and the negative electrode during charge and discharge to form a lithiated intermetallic negative electrode during charge. The voltage of the electrochemical cell is controlled during the charge portion of the charge-discharge cycles so that the potential of the lithiated intermetallic negative electrode in the fully charged electrochemical cell is less than 0.2 V but greater than 0 V versus metallic lithium.

TEM study of the martensitic phases in the ductile DyCu and YCu intermetallic compounds [The martensitic phase transformation in ductile DyCu and YCu intermetallic compounds

DOE PAGES

Cao, G. H.; Oertel, C. -G.; Schaarschuch, R.; ...

2017-05-03

DyCu and YCu are representatives of the family of CsCl-type B2 rare earth intermetallic compounds that exhibit high room temperature ductility. Structure, orientation relationship, and morphology of the martensites in the equiatomic compounds DyCu and YCu are examined using transmission electron microscopy (TEM). TEM studies show that the martensite structures in DyCu and YCu alloys are virtually identical. The martensite is of orthorhombic CrB-type B33 structure with lattice parameters a = 0.38 nm, b = 1.22 nm, and c = 0.40 nm. (021¯) twins were observed in the B33 DyCu and YCu martensites. The orientation relationship of B33 and B2more » phases is (111¯)[112]B33 || (110)[001]B2. The simulated electron diffraction patterns of the B33 phase are consistent with those of experimental observations. TEM investigations also reveal that a dominant orthorhombic FeB-type B27 martensite with lattice parameters a = 0.71 nm, b = 0.45 nm, and c = 0.54 nm exists in YCu alloy. (11¯ 1) twins were observed in the B27 YCu martensite. As a result, the formation mechanism of B2 to B33 and B2 to B27 phase transformation is discussed.« less

Codeformation processing of mechanically-dissimilar metal/intermetallic composites

NASA Astrophysics Data System (ADS)

Marte, Judson Sloan

A systematic and scientific approach has been applied to the study of codeformation processing. A series of composites having mechanically-dissimilar phases were developed in which the high temperature flow behavior of the reinforcement material could be varied independent of the matrix. This was accomplished through the use of a series of intermetallic matrix composites (IMCs) as discontinuous reinforcements in an otherwise conventional metal matrix composite. The IMCs are produced using an in-situ reaction synthesis technique, called the XD(TM) process. The temperature of the exothermic synthesis reaction, called the adiabatic temperature, has been calculated and shown to increase with increasing volume percentage of TiB2 reinforcement. Further, this temperature has been shown to effect the size and spacing of the TiB2, microstructural features which are often used in discontinuous composite strength models. Study of the high temperature flow behavior of the components of the metal/IMC composite is critical to the development of an understanding of codeformation. A series of compression tests performed at 1000° to 1200°C and strain-rates of 10-3 and 10-4 sec-1. Peak flow stresses were used to evaluate the influence of material properties and process conditions. These data were incorporated into phenomenologically-based constitutive equations that have been used to predict the flow behavior. It has been determined that plastic deformation of the IMCs occurs readily, and is largely TiB2 independent, at temperatures approaching the melting point of the intermetallic matrices. Ti-6Al-4V/IMC powder blends were extruded at high temperatures to achieve commensurately deformed microstructures. The results of codeformation processing were analyzed in terms of the plastic strain of the IMC particulates. IMC particle deformation was shown to increase with increasing IMC particle size, volume percentage of IMC, extrusion temperature, homologous temperature, extrusion

Intermetallic compounds in heterogeneous catalysis—a quickly developing field

PubMed Central

Armbrüster, Marc; Schlögl, Robert; Grin, Yuri

2014-01-01

The application of intermetallic compounds for understanding in heterogeneous catalysis developed in an excellent way during the last decade. This review provides an overview of concepts and developments revealing the potential of intermetallic compounds in fundamental as well as applied catalysis research. Intermetallic compounds may be considered as platform materials to address current and future catalytic challenges, e.g. in respect to the energy transition. PMID:27877674

On the transferability of electron density in binary vanadium borides VB, V3B4 and VB2.

PubMed

Terlan, Bürgehan; Akselrud, Lev; Baranov, Alexey I; Borrmann, Horst; Grin, Yuri

2015-12-01

Binary vanadium borides are suitable model systems for a systematic analysis of the transferability concept in intermetallic compounds due to chemical intergrowth in their crystal structures. In order to underline this structural relationship, topological properties of the electron density in VB, V3B4 and VB2 reconstructed from high-resolution single-crystal X-ray diffraction data as well as derived from quantum chemical calculations, are analysed in terms of Bader's Quantum Theory of Atoms in Molecules [Bader (1990). Atoms in Molecules: A Quantum Theory, 1st ed. Oxford: Clarendon Press]. The compounds VB, V3B4 and VB2 are characterized by a charge transfer from the metal to boron together with two predominant atomic interactions, the shared covalent B-B interactions and the polar covalent B-M interactions. The resembling features of the crystal structures are well reflected by the respective B-B interatomic distances as well as by ρ(r) values at the B-B bond critical points. The latter decrease with an increase in the corresponding interatomic distances. The B-B bonds show transferable electron density properties at bond critical points depending on the respective bond distances.

Brushing up on the history of intermetallics in dentistry

NASA Astrophysics Data System (ADS)

Waterstrat, Richard M.

1990-03-01

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.

Containerless automated processing of intermetallic compounds and composites

NASA Technical Reports Server (NTRS)

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

1993-01-01

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

Intermetallic Growth and Interfacial Properties of the Grain Refiners in Al Alloys.

PubMed

Li, Chunmei; Cheng, Nanpu; Chen, Zhiqian; Xie, Zhongjing; Hui, Liangliang

2018-04-20

Al₃TM(TM = Ti, Zr, Hf, Sc) particles acting as effective grain refiners for Al alloys have been receiving extensive attention these days. In order to judge their nucleation behaviors, first-principles calculations are used to investigate their intermetallic and interfacial properties. Based on energy analysis, Al₃Zr and Al₃Sc are more suitable for use as grain refiners than the other two intermetallic compounds. Interfacial properties show that Al/Al₃TM(TM = Ti, Zr, Hf, Sc) interfaces in I-ter interfacial mode exhibit better interface wetting effects due to larger Griffith rupture work and a smaller interface energy. Among these, Al/Al₃Sc achieves the lowest interfacial energy, which shows that Sc atoms should get priority for occupying interfacial sites. Additionally, Sc-doped Al/Al₃(Zr, Sc) interfacial properties show that Sc can effectively improve the Al/Al₃(Zr, Sc) binding strength with the Al matrix. By combining the characteristics of interfaces with the properties of intermetallics, the core-shell structure with Al₃Zr-core or Al₃Zr(Sc1-1)-core encircled with an Sc-rich shell forms.

Measurements of microhardness during transient horizontal directional solidification of Al-Rich Al-Cu alloys: Effect of thermal parameters, primary dendrite arm spacing and Al2Cu intermetallic phase

NASA Astrophysics Data System (ADS)

Barros, André Santos; Magno, Igor Alexsander; Souza, Fabrício Andrade; Mota, Carlos Alberto; Moreira, Antonio Luciano; Silva, Maria Adrina; Rocha, Otávio Lima

2015-05-01

In this work, the effect of the growth rate (VL) and cooling rate (TR), primary dendritic arm spacing (λ1) and Al2Cu intermetallic phase on the microhardness was investigated during transient horizontal directional solidification of Al-3wt%Cu and Al-8wt%Cu alloys. Microstructural characterization of the investigated alloys was performed using traditional techniques of metallography, optical and SEM microscopy and X-Ray diffraction. The microhardness evolution as a function of the thermal and microstructural parameters (VL, TR, and λ1) was evaluated using power and Hall-Petch type experimental laws, which were compared with other laws in the literature. In order to examine the effect of the Al2Cu intermetallic phase, microhardness measurements were performed in interdendritic regions. Finally, a comparative analysis was performed between the experimental data of this work and theoretical models from the literature that have been proposed to predict primary dendrite arm spacing, which have been tested in numerous works considering upward directional solidification.

Slow plastic deformation of extruded NiAl-10TiB2 particulate composites at 1200 and 1300 K

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.; Kumar, S.; Mannan, S. K.; Viswanadham, R. K.

1990-01-01

A dispersion of 1-micron TiB2 particles in the B2 crystal structure NiAl intermetallic can effectively increase its elevated temperature strength, in association with increasing deformation resistance with TiB2 volume fraction. Attention is presently given to alternative densification methods, which may increase the initial as-fabricated dislocation density and lead to enhanced elevated-temperature strength. The 'XD' extrusion method was used to produce NiAl with 10 vol pct TiB2. Although apparent extrusion defects were occasionally found, neither grain-boundary cracking nor particle-matrix separation occurred.

Smart Solution Chemistry to Sn-Containing Intermetallic Compounds through a Self-Disproportionation Process.

PubMed

Zhang, Yuelan; Li, Liping; Li, Qi; Fan, Jianming; Zheng, Jing; Li, Guangshe

2016-09-26

Developing new methods to synthesize intermetallics is one of the most critical issues for the discovery and application of multifunctional metal materials; however, the synthesis of Sn-containing intermetallics is challenging. In this work, we demonstrated for the first time that a self-disproportionation-induced in situ process produces cavernous Sn-Cu intermetallics (Cu3 Sn and Cu6 Sn5 ). The successful synthesis is realized by introducing inorganic metal salts (SnCl2 ⋅2 H2 O) to NaOH aqueous solution to form an intermediate product of reductant (Na2 SnO2 ) and by employing steam pressures that enhance the reduction ability. Distinct from the traditional in situ reduction, the current reduction process avoided the uncontrolled phase composition and excessive use of organic regents. An insight into the mechanism was revealed for the Sn-Cu case. Moreover, this method could be extended to other Sn-containing materials (Sn-Co, Sn-Ni). All these intermetallics were attempted in the catalytic effect on thermal decompositions of ammonium perchlorate. It is demonstrated that Cu3 Sn showed an outstanding catalytic performance. The superior property might be primarily originated from the intrinsic chemical compositions and cavernous morphology as well. We supposed that this smart solution reduction methodology reported here would provide a new recognition for the reduction reaction, and its modified strategy may be applied to the synthesis of other metals, intermetallics as well as some unknown materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Titanium aluminide intermetallic alloys with improved wear resistance

DOEpatents

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

2014-07-08

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

Anisotropic magnetocaloric response in AlFe 2B 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barua, R.; Lejeune, B. T.; Ke, L.

Experimental investigations of the magnetocaloric response of the intermetallic layered AlFe 2B 2 compound along the principle axes of the orthorhombic cell were carried out using aligned plate-like crystallites with an anisotropic [101] growth habit. Results were confirmed to be consistent with density functional theory calculations. Field-dependent magnetization data confirm that the a-axis is the easy direction of magnetization within the (ac) plane. The magnetocrystalline anisotropy energy required to rotate the spin quantization vector from the c-to the a-axis direction is determined as K~0.9 MJ/m 3 at 50 K. Magnetic entropy change curves measured near the Curie transition temperature ofmore » 285 K reveal a large rotating magnetic entropy change of 1.3 J kg -1K -1 at μ 0H app = 2 T, consistent with large differences in magnetic entropy change ΔS mag measured along the a- and c-axes. Overall, this study provides insight of both fundamental and applied relevance concerning pathways for maximizing the magnetocaloric potential of AlFe 2B 2 for thermal management applications.« less

Anisotropic magnetocaloric response in AlFe 2B 2

DOE PAGES

Barua, R.; Lejeune, B. T.; Ke, L.; ...

2018-02-19

Experimental investigations of the magnetocaloric response of the intermetallic layered AlFe 2B 2 compound along the principle axes of the orthorhombic cell were carried out using aligned plate-like crystallites with an anisotropic [101] growth habit. Results were confirmed to be consistent with density functional theory calculations. Field-dependent magnetization data confirm that the a-axis is the easy direction of magnetization within the (ac) plane. The magnetocrystalline anisotropy energy required to rotate the spin quantization vector from the c-to the a-axis direction is determined as K~0.9 MJ/m 3 at 50 K. Magnetic entropy change curves measured near the Curie transition temperature ofmore » 285 K reveal a large rotating magnetic entropy change of 1.3 J kg -1K -1 at μ 0H app = 2 T, consistent with large differences in magnetic entropy change ΔS mag measured along the a- and c-axes. Overall, this study provides insight of both fundamental and applied relevance concerning pathways for maximizing the magnetocaloric potential of AlFe 2B 2 for thermal management applications.« less

A review on the synthesis, crystal growth, structure and physical properties of rare earth based quaternary intermetallic compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mumbaraddi, Dundappa; Sarkar, Sumanta; Peter, Sebastian C., E-mail: sebastiancp@jncasr.ac.in

2016-04-15

This review highlights the synthesis and crystal growth of quaternary intermetallic compounds based on rare earth metals. In the first part of this review, we highlight briefly about intermetallics and their versatile properties in comparison to the constituent elements. In the next part, we have discussed about various synthesis techniques with more focus on the metal flux technique towards the well shaped crystal growth of novel compounds. In the subsequent parts, several disordered quaternary compounds have been reviewed and then outlined most known ordered quaternary compounds with their complex structure. A special attention has been given to the ordered compoundsmore » with structural description and relation to the parent binary and ternary compounds. The importance of electronic and structural feature is highlighted as the key roles in designing these materials for emerging applications. - Graphical abstract: Rare earth based quaternary intermetallic compounds crystallize in complex novel crystal structures. The diversity in the crystal structure may induce unique properties and can be considered them as future materials. - Highlights: • Crystal growth and crystal structure of quaternary rare earth based intermetallics. • Structural complexity of quaternary compounds in comparison to the parent compounds. • Novel quaternary compounds display unique crystal structure.« less

Computer simulations of disordering kinetics in irradiated intermetallic compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spaczer, M.; Caro, A.; Victoria, M.

1994-11-01

Molecular-dynamics computer simulations of collision cascades in intermetallic Cu[sub 3]Au, Ni[sub 3]Al, 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 Ni[sub 3]Al andmore » Cu[sub 3]Au [T. Diaz de la Rubia, A. Caro, and M. Spaczer, 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.« less

AA6082 to DX56-Steel Laser Brazing: Process Parameter-Intermetallic Formation Correlation

NASA Astrophysics Data System (ADS)

Narsimhachary, D.; Pal, S.; Shariff, S. M.; Padmanabham, G.; Basu, A.

2017-09-01

In the present study, laser-brazed AA6082 to DX56-galvanized steel joints were investigated to understand the influence of process parameters on joint strength in terms of intermetallic layer formation. 1.5-mm-thick sheet of aluminum alloy (AA6082-T6) and galvanized steel (DX56) sheet of 0.7 mm thickness were laser-brazed with 1.5-mm-diameter Al-12% Si solid filler wire. During laser brazing, laser power (4.6 kW) and wire feed rate (3.4 m/min) were kept constant with a varying laser scan speed of 3.5, 3, 2.5, 2, 1.5, and 1 m/min. Microstructure of brazed joint reveals epitaxial growth at the aluminum side and intermetallic layer formation at steel interface. Intermetallic layer formation was confirmed by EDS analysis and XRD study. Hardness profile showed hardness drop in filler region, and failure during tensile testing was initiated through the filler region near the steel interface. As per both experimental study and numerical analysis, it was observed that intermetallic layer thickness decreases with increasing brazing speed. Zn vaporization from galvanized steel interface also affected the joint strength. It was found that high laser scan speed or faster cooling rate can be chosen for suppressing intermetallic layer formation or at least decreasing the layer thickness which results in improved mechanical properties.

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

PubMed

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

2010-03-01

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.

Intermetallic Growth and Interfacial Properties of the Grain Refiners in Al Alloys

PubMed Central

Li, Chunmei; Cheng, Nanpu; Chen, Zhiqian; Xie, Zhongjing; Hui, Liangliang

2018-01-01

Al3TM(TM = Ti, Zr, Hf, Sc) particles acting as effective grain refiners for Al alloys have been receiving extensive attention these days. In order to judge their nucleation behaviors, first-principles calculations are used to investigate their intermetallic and interfacial properties. Based on energy analysis, Al3Zr and Al3Sc are more suitable for use as grain refiners than the other two intermetallic compounds. Interfacial properties show that Al/Al3TM(TM = Ti, Zr, Hf, Sc) interfaces in I-ter interfacial mode exhibit better interface wetting effects due to larger Griffith rupture work and a smaller interface energy. Among these, Al/Al3Sc achieves the lowest interfacial energy, which shows that Sc atoms should get priority for occupying interfacial sites. Additionally, Sc-doped Al/Al3(Zr, Sc) interfacial properties show that Sc can effectively improve the Al/Al3(Zr, Sc) binding strength with the Al matrix. By combining the characteristics of interfaces with the properties of intermetallics, the core-shell structure with Al3Zr-core or Al3Zr(Sc1-1)-core encircled with an Sc-rich shell forms. PMID:29677155

Microstructure and tribological properties of TiAg intermetallic compound coating

NASA Astrophysics Data System (ADS)

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

2011-10-01

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.

Intermetallics for Thermal Protection Systems

NASA Astrophysics Data System (ADS)

Marcos, J.

2009-01-01

Future Reusable Launch Vehicles (RLV's) will require improved Thermal Protection Systems (TPS) to achieve the ambitious goal of reducing the cost of delivering a payload to orbit by, at least, an order of magnitude. In this context, metallic materials are good candidates for their use in TPS and hot structures. Up to date, only two major type of materials have been considered and developed in Europe for such type of applications: Oxide Dispersion Strengthened (ODS) and intermetallics (ϒ-TiAl). INASMET, during last years, has been working with the orthorhombic titanium aluminides, whose specific properties are comparable, to those of ODS and ϒ-TiAl materials. The EXPERT mission represents a unique opportunity to test under re-entry conditions this material.

The order-to-disorder transition behavior of PS-b-P2VP thin film system

NASA Astrophysics Data System (ADS)

Ahn, Hyungju; Ryu, Du

2013-03-01

We investigated the transition behavior such as the order-to-disorder transition (ODT) for symmetric poly(styrene)-block-poly(2-vinly pridine) (PS-b-P2VP) using SAXS and GISAXS for block copolymer bulks and films. The bulk transition temperature of PS-b-P2VP was significantly influenced by the interfacial interactions in thin films, leading to the different transition temperature. From these results, we will discuss about the interfacial interaction effects on the phase behaviors in bulks and thin films system of PS-b-P2VP.

Formation of intermetallics at the interface of explosively welded Ni-Al multilayered composites during annealing

NASA Astrophysics Data System (ADS)

Ogneva, T. S.; Lazurenko, D. V.; Bataev, I. A.; Mali, V. I.; Esikov, M. A.; Bataev, A. A.

2016-04-01

The Ni-Al multilayer composite was fabricated using explosive welding. The zones of mixing of Ni and Al are observed at the composite interfaces after the welding. The composition of these zones is inhomogeneous. Continuous homogeneous intermetallic layers are formed at the interface after heat treatment at 620 °C during 5 h These intermetallic layers consist of NiAl3 and Ni2Al3 phases. The presence of mixed zones significantly accelerates the growth rate of intermetallic phases at the initial stages of heating.

Alloy Design Data Generated for B2-Ordered Compounds

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.; Bozzolo, Guillermo; Abel, Phillip B.

2003-01-01

Developing alloys based on ordered compounds is significantly more complicated than developing designs based on disordered materials. In ordered compounds, the major constituent elements reside on particular sublattices. Therefore, the addition of a ternary element to a binary-ordered compound is complicated by the manner in which the ternary addition is made (at the expense of which binary component). When ternary additions are substituted for the wrong constituent, the physical and mechanical properties usually degrade. In some cases the resulting degradation in properties can be quite severe. For example, adding alloying additions to NiAl in the wrong combination (i.e., alloying additions that prefer the Al sublattice but are added at the expense of Ni) will severely embrittle the alloy to the point that it can literally fall apart during processing on cooling from the molten state. Consequently, alloying additions that strongly prefer one sublattice over another should always be added at the expense of that component during alloy development. Elements that have a very weak preference for a sublattice can usually be safely added at the expense of either element and will accommodate any deviation from stoichiometry by filling in for the deficient component. Unfortunately, this type of information is not known beforehand for most ordered systems. Therefore, a computational survey study, using a recently developed quantum approximate method, was undertaken at the NASA Glenn Research Center to determine the preferred site occupancy of ternary alloying additions to 12 different B2-ordered compounds including NiAl, FeAl, CoAl, CoFe, CoHf, CoTi, FeTi, RuAl, RuSi, RuHf, RuTi, and RuZr. Some of these compounds are potential high temperature structural alloys; others are used in thin-film magnetic and other electronic applications. The results are summarized. The italicized elements represent the previous sum total alloying information known and verify the computational

Atomic interaction of the MEAM type for the study of intermetallics in the Al-U alloy

NASA Astrophysics Data System (ADS)

Pascuet, M. I.; Fernández, J. R.

2015-12-01

Interaction for both pure Al and Al-U alloys of the MEAM type are developed. The obtained Al interatomic potential assures its compatibility with the details of the framework presently adopted. The Al-U interaction fits various properties of the Al2U, Al3U and Al4U intermetallics. The potential verifies the stability of the intermetallic structures in a temperature range compatible with that observed in the phase diagram, and also takes into account the greater stability of these structures relative to others that are competitive in energy. The intermetallics are characterized by calculating elastic and thermal properties and point defect parameters. Molecular dynamics simulations show a growth of the Al3U intermetallic in the Al/U interface in agreement with experimental evidence.

Microstructure and high-temperature oxidation resistance of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding

NASA Astrophysics Data System (ADS)

Zhang, Xiaowei; Liu, Hongxi; Wang, Chuanqi; Zeng, Weihua; Jiang, Yehua

2010-11-01

A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600°C and 800°C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface modification technique for Ti6Al4V alloy.

Pb(B{sup {prime}}{sub 1/2}B{sup {prime}{prime}}{sub 1/2})O{sub 3}-type perovskites: Part II. Short-range order parameter as a criterion of the distinction between relaxor and normal ferroelectrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, S.; Jang, H.M.

1997-08-01

A classification scheme of Pb(B{sup {prime}}{sub 1/2}B{sup {prime}{prime}}{sub 1/2})O{sub 3}-type perovskites with respect to the B-site order parameters was proposed based on the theoretical calculation of the short-range order parameter ({sigma}) using the pair-correlation model. The calculated order parameters predict that a Pb(B{sup {prime}}{sub 1/2}B{sup {prime}{prime}}{sub 1/2})O{sub 3}-type perovskite without any charge difference between B{sup {prime}} and B{sup {prime}{prime}} cations [e.g., Pb(Zr{sub 1/2}Ti{sub 1/2})O{sub 3} (PZT)] is represented by a completely disordered state with the absence of a finite coherence length. On the other hand, a Pb(B{sup {prime}}{sub 1/2}B{sup {prime}{prime}}{sub 1/2})O{sub 3} type perovskite system having different ionic charges ismore » characterized either by the short-range ordering with a nanoscale coherence length or by the macroscopic long-range ordering, depending on the magnitude of ionic charge difference between B{sup {prime}} and B{sup {prime}{prime}} ions. The normal ferroelectricity in Pb(B{sup {prime}}{sub 1/2}B{sup {prime}{prime}}{sub 1/2})O{sub 3}-type complex perovskites was then correlated either with a completely disordered state ({sigma}=0) or with a perfectly ordered state ({sigma}=1), whereas the relaxor behavior was attributed to the nanoscale short-range ordering (0{lt}{sigma}{lt}1) in the configuration of the B-site cations. {copyright} {ital 1997 Materials Research Society.}« less

Magnetic susceptibilities of actinide 3d-metal intermetallic compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muniz, R.B.; d'Albuquerque e Castro, J.; Troper, A.

1988-04-15

We have numerically calculated the magnetic susceptibilities which appear in the Hartree--Fock instability criterion for actinide 3d transition-metal intermetallic compounds. This calculation is based on a previous tight-binding description of these actinide-based compounds (A. Troper and A. A. Gomes, Phys. Rev. B 34, 6487 (1986)). The parameters of the calculation, which starts from simple tight-binding d and f bands are (i) occupation numbers, (ii) ratio of d-f hybridization to d bandwidth, and (iii) electron-electron Coulomb-type interactions.

Electron-Poor Polar Intermetallics: Complex Structures, Novel Clusters, and Intriguing Bonding with Pronounced Electron Delocalization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Qisheng; Miller, Gordon J.

Intermetallic compounds represent an extensive pool of candidates for energy related applications stemming from magnetic, electric, optic, caloric, and catalytic properties. The discovery of novel intermetallic compounds can enhance understanding of the chemical principles that govern structural stability and chemical bonding as well as finding new applications. Valence electron-poor polar intermetallics with valence electron concentrations (VECs) between 2.0 and 3.0 e –/atom show a plethora of unprecedented and fascinating structural motifs and bonding features. Furthermore, establishing simple structure-bonding-property relationships is especially challenging for this compound class because commonly accepted valence electron counting rules are inappropriate.

Electron-Poor Polar Intermetallics: Complex Structures, Novel Clusters, and Intriguing Bonding with Pronounced Electron Delocalization

DOE PAGES

Lin, Qisheng; Miller, Gordon J.

2017-12-18

Intermetallic compounds represent an extensive pool of candidates for energy related applications stemming from magnetic, electric, optic, caloric, and catalytic properties. The discovery of novel intermetallic compounds can enhance understanding of the chemical principles that govern structural stability and chemical bonding as well as finding new applications. Valence electron-poor polar intermetallics with valence electron concentrations (VECs) between 2.0 and 3.0 e –/atom show a plethora of unprecedented and fascinating structural motifs and bonding features. Furthermore, establishing simple structure-bonding-property relationships is especially challenging for this compound class because commonly accepted valence electron counting rules are inappropriate.

A ship-in-a-bottle strategy to synthesize encapsulated intermetallic nanoparticle catalysts: Exemplified for furfural hydrogenation

DOE PAGES

Maligal-Ganesh, Raghu V.; Xiao, Chaoxian; Goh, Tian Wei; ...

2016-01-28

In this paper, intermetallic compounds are garnering increasing attention as efficient catalysts for improved selectivity in chemical processes. Here, using a ship-in-a-bottle strategy, we synthesize single-phase platinum-based intermetallic nanoparticles (NPs) protected by a mesoporous silica (mSiO 2) shell by heterogeneous reduction and nucleation of Sn, Pb, or Zn in mSiO 2-encapsulated Pt NPs. For selective hydrogenation of furfural to furfuryl alcohol, a dramatic increase in activity and selectivity is observed when intermetallic NPs catalysts are used in comparison to Pt@mSiO 2. Among the intermetallic NPs, PtSn@mSiO 2 exhibits the best performance, requiring only one-tenth of the quantity of Pt usedmore » in Pt@mSiO 2 for similar activity and near 100% selectivity to furfuryl alcohol. A high-temperature oxidation–reduction treatment easily reverses any carbon deposition-induced catalyst deactivation. X-ray photoelectron spectroscopy shows the importance of surface composition to the activity, whereas density functional theory calculations reveal that the enhanced selectivity on PtSn compared to Pt is due to the different furfural adsorption configurations on the two surfaces.« less

Predicting the stability of ternary intermetallics with density functional theory and machine learning

NASA Astrophysics Data System (ADS)

Schmidt, Jonathan; Chen, Liming; Botti, Silvana; Marques, Miguel A. L.

2018-06-01

We use a combination of machine learning techniques and high-throughput density-functional theory calculations to explore ternary compounds with the AB2C2 composition. We chose the two most common intermetallic prototypes for this composition, namely, the tI10-CeAl2Ga2 and the tP10-FeMo2B2 structures. Our results suggest that there may be ˜10 times more stable compounds in these phases than previously known. These are mostly metallic and non-magnetic. While the use of machine learning reduces the overall calculation cost by around 75%, some limitations of its predictive power still exist, in particular, for compounds involving the second-row of the periodic table or magnetic elements.

Strong, ductile, and thermally stable Cu-based metal-intermetallic nanostructured composites.

PubMed

Dusoe, Keith J; Vijayan, Sriram; Bissell, Thomas R; Chen, Jie; Morley, Jack E; Valencia, Leopolodo; Dongare, Avinash M; Aindow, Mark; Lee, Seok-Woo

2017-01-09

Bulk metallic glasses (BMGs) and nanocrystalline metals (NMs) have been extensively investigated due to their superior strengths and elastic limits. Despite these excellent mechanical properties, low ductility at room temperature and poor microstructural stability at elevated temperatures often limit their practical applications. Thus, there is a need for a metallic material system that can overcome these performance limits of BMGs and NMs. Here, we present novel Cu-based metal-intermetallic nanostructured composites (MINCs), which exhibit high ultimate compressive strengths (over 2 GPa), high compressive failure strain (over 20%), and superior microstructural stability even at temperatures above the glass transition temperature of Cu-based BMGs. Rapid solidification produces a unique ultra-fine microstructure that contains a large volume fraction of Cu 5 Zr superlattice intermetallic compound; this contributes to the high strength and superior thermal stability. Mechanical and microstructural characterizations reveal that substantial accumulation of phase boundary sliding at metal/intermetallic interfaces accounts for the extensive ductility observed.

Epitaxial growth of Al9Ir2 intermetallic compound on Al(100): Mechanism and interface structure

NASA Astrophysics Data System (ADS)

Kadok, J.; Pussi, K.; Šturm, S.; Ambrožič, B.; Gaudry, É.; de Weerd, M.-C.; Fournée, V.; Ledieu, J.

2018-04-01

The adsorption of Ir adatoms on Al(100) has been investigated under various exposures and temperature conditions. The experimental and theoretical results reveal a diffusion of Ir adatoms within the Al(100) surface selvedge already at 300 K. Above 593 K, two domains of a (√{5 }×√{5 }) R 26 .6∘ phase are identified by low energy electron diffraction (LEED) and scanning tunneling microscopy measurements. This phase corresponds to the initial growth of an Al9Ir2 compound at the Al(100) surface. The Al9Ir2 intermetallic domains are terminated by bulklike pure Al layers. The structural stability of Al9Ir2 (001) grown on Al(100) has been analyzed by density functional theory based calculations. Dynamical LEED analysis is consistent with an Ir adsorption leading to the growth of an Al9Ir2 intermetallic compound. We propose that the epitaxial relationship Al9Ir2(001 ) ∥Al (100) and Al9Ir2[100 ] ∥Al [031 ]/[013 ] originates from a matching of Al atomic arrangements present both on Al(100) and on pure Al(001) layers present in the Al9Ir2 compound. Finally, the interface between Al9Ir2 precipitates and the Al matrix has been characterized by transmission electron microscopy measurements. The cross-sectional observations are consistent with the formation of Al9Ir2 (001) compounds. These measurements indicate an important Ir diffusion within Al(100) near the surface region. The coherent interface between Al9Ir2 and the Al matrix is sharp.

The structure, stability, and infrared spectrum of B 2N, B 2N +, B 2N -, BO, B 2O and B 2N 2.

NASA Astrophysics Data System (ADS)

Martin, J. M. L.; François, J. P.; Gijbels, R.

1992-05-01

The structure, infrared spectrum, and heat of formation of B 2N, B 2N -, BO, and B 2O have been studied ab initio. B 2N is very stable; B 2O even more so. B 2N, B 2N -, B 2O, and probably B 2N + have symmetric linear ground-state structures; for B 2O, an asymmetric linear structure lies about 12 kcal/mol above the ground state. B 2N +, B 2N - and B 2O have intense asymmetric stretching frequencies, predicted near 870, 1590 and 1400 cm -1, respectively. Our predicted harmonic frequencies and isotopic shifts for B 2O confirm the recent experimental identification by Andrews and Burkholder. Absorptions at 1889.5 and 1998.5 cm -1 in noble-gas trapped boron nitride vapor belong the BNB and BNBN ( 3Π), respectively; a tentative assignment of 882.5 cm -1 to BNB + is proposed. Total atomization energies Σ De (Σ D0) are computed (accuracy ±2 kcal/mol) as: BO 193.1 (190.4), B 2O 292.5 (288.7), B 2N 225.0 (250.3) kcal/mol. The ionization potential and electron affinity of B 2N are predicted to be 8.62±0.1 and 3.34±0.1 eV. The MP4-level additivity approximations involved in G1 theory results in errors on the order of 1 kcal/mol in the Σ De values.

Magnetocaloric effect and other low-temperature properties of Pr2Pt2 In

NASA Astrophysics Data System (ADS)

Mboukam, J. J.; Sondezi, B. M.; Tchokonté, M. B. Tchoula; Bashir, A. K. H.; Strydom, A. M.; Britz, D.; Kaczorowski, D.

2018-05-01

We report on X-ray diffraction, electrical transport, heat capacity and magnetocaloric effect measurements of a polycrystalline sample of Pr2Pt2 In . The compound forms in the tetragonal Mo2FeB2 type structure and orders ferromagnetically at TC=9 K. In the ordered state, its thermodynamic and electrical transport properties are dominated by magnon contributions with an energy gap of about 8 K in the spin-wave spectrum. The magnitude of magnetocaloric effect is similar to the values reported for most rare-earth based intermetallics. Characteristic behavior of the isothermal magnetic entropy change maximum points to a second-order character of the ferromagnetic phase transition in the compound studied.

Effect of Mn and Fe on the Formation of Fe- and Mn-Rich Intermetallics in Al–5Mg–Mn Alloys Solidified Under Near-Rapid Cooling

PubMed Central

Liu, Yulin; Huang, Gaoren; Sun, Yimeng; Zhang, Li; Huang, Zhenwei; Wang, Jijie; Liu, Chunzhong

2016-01-01

Mn was an important alloying element used in Al–Mg–Mn alloys. However, it had to be limited to a low level (<1.0 wt %) to avoid the formation of coarse intermetallics. In order to take full advantage of the benefits of Mn, research was carried out to investigate the possibility of increasing the content of Mn by studying the effect of cooling rate on the formation of Fe- and Mn-rich intermetallics at different content levels of Mn and Fe. The results indicated that in Al–5Mg–Mn alloy with low Fe content (<0.1 wt %), intermetallic Al6(Fe,Mn) was small in size and amount. With increasing Mn content, intermetallic Al6(Fe,Mn) increased, but in limited amount. In high-Fe-containing Al–5Mg–Mn alloys (0.5 wt % Fe), intermetallic Al6(Fe,Mn) became the dominant phase, even in the alloy with low Mn content (0.39 wt %). Cooling rate played a critical role in the refinement of the intermetallics. Under near-rapid cooling, intermetallic Al6(Fe,Mn) was extremely refined. Even in the high Mn and/or high-Fe-containing alloys, it still demonstrated fine Chinese script structures. However, once the alloy composition passed beyond the eutectic point, the primary intermetallic Al6(Fe,Mn) phase displayed extremely coarse platelet-like morphology. Increasing the content of Fe caused intermetallic Al6(Fe,Mn) to become the primary phase at a lower Mn content. PMID:28787888

Effect of Mn and Fe on the Formation of Fe- and Mn-Rich Intermetallics in Al-5Mg-Mn Alloys Solidified Under Near-Rapid Cooling.

PubMed

Liu, Yulin; Huang, Gaoren; Sun, Yimeng; Zhang, Li; Huang, Zhenwei; Wang, Jijie; Liu, Chunzhong

2016-01-29

Mn was an important alloying element used in Al-Mg-Mn alloys. However, it had to be limited to a low level (<1.0 wt %) to avoid the formation of coarse intermetallics. In order to take full advantage of the benefits of Mn, research was carried out to investigate the possibility of increasing the content of Mn by studying the effect of cooling rate on the formation of Fe- and Mn-rich intermetallics at different content levels of Mn and Fe. The results indicated that in Al-5Mg-Mn alloy with low Fe content (<0.1 wt %), intermetallic Al₆(Fe,Mn) was small in size and amount. With increasing Mn content, intermetallic Al₆(Fe,Mn) increased, but in limited amount. In high-Fe-containing Al-5Mg-Mn alloys (0.5 wt % Fe), intermetallic Al₆(Fe,Mn) became the dominant phase, even in the alloy with low Mn content (0.39 wt %). Cooling rate played a critical role in the refinement of the intermetallics. Under near-rapid cooling, intermetallic Al₆(Fe,Mn) was extremely refined. Even in the high Mn and/or high-Fe-containing alloys, it still demonstrated fine Chinese script structures. However, once the alloy composition passed beyond the eutectic point, the primary intermetallic Al₆(Fe,Mn) phase displayed extremely coarse platelet-like morphology. Increasing the content of Fe caused intermetallic Al₆(Fe,Mn) to become the primary phase at a lower Mn content.

Thermal Shock and Oxidation Behavior of HiPIMS TiAlN Coatings Grown on Ti-48Al-2Cr-2Nb Intermetallic Alloy

PubMed Central

Badini, Claudio; Deambrosis, Silvia M.; Padovano, Elisa; Fabrizio, Monica; Ostrovskaya, Oxana; Miorin, Enrico; D’Amico, Giuseppe C.; Montagner, Francesco; Biamino, Sara; Zin, Valentina

2016-01-01

A High Power Impulse Magnetron Sputtering (HiPIMS) method for depositing TiAlN environmental barrier coatings on the surface of Ti-48Al-2Cr-2Nb alloy was developed in view of their exploitation in turbine engines. Three differently engineered TiAlN films were processed and their performance compared. Bare intermetallic alloy coupons and coated specimens were submitted to thermal cycling under oxidizing atmosphere up to 850 °C or 950 °C, at high heating and cooling rates. For this purpose, a burner rig able to simulate the operating conditions of the different stages of turbine engines was used. Microstructures of the samples were compared before and after each test using several techniques (microscopy, XRD, and XPS). Coating-intermetallic substrate adhesion and tribological properties were investigated too. All the TiAlN films provided a remarkable increase in oxidation resistance. Good adhesion properties were observed even after repeated thermal shocks. HiPIMS pretreatments of the substrate surfaces performed before the coating deposition significantly affected the oxidation rate, the oxide layer composition and the coating/substrate adhesion. PMID:28774082

Atom probe tomography of intermetallic phases and interfaces formed in dissimilar joining between Al alloys and steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemmens, B.

While Si additions to Al are widely used to reduce the thickness of the brittle intermetallic seam formed at the interface during joining of Al alloys to steel, the underlying mechanisms are not clarified yet. The developed approach for the site specific atom probe tomography analysis revealed Si enrichments at grain and phase boundaries between the θ (Fe{sub 4}Al{sub 13}) and η (Fe{sub 2}Al{sub 5}) phase, up to about ten times that of the concentration in Al. The increase in Si concentration could play an important role for the growth kinetics of the intermetallic phases formed for example in hot-dipmore » aluminizing of steel. - Highlights: •Si additions to Al reduce thickness of intermetallic seam in joining with steel. •Approach developed for the site specific APT analysis of the intermetallic seam •Si enrichment at grain and phase boundaries possibly affects growth of intermetallics.« less

In situ XPS study of methanol reforming on PdGa near-surface intermetallic phases

PubMed Central

Rameshan, Christoph; Stadlmayr, Werner; Penner, Simon; Lorenz, Harald; Mayr, Lukas; Hävecker, Michael; Blume, Raoul; Rocha, Tulio; Teschner, Detre; Knop-Gericke, Axel; Schlögl, Robert; Zemlyanov, Dmitry; Memmel, Norbert; Klötzer, Bernhard

2012-01-01

In situ X-ray photoelectron spectroscopy and low-energy ion scattering were used to study the preparation, (thermo)chemical and catalytic properties of 1:1 PdGa intermetallic near-surface phases. Deposition of several multilayers of Ga metal and subsequent annealing to 503–523 K led to the formation of a multi-layered 1:1 PdGa near-surface state without desorption of excess Ga to the gas phase. In general, the composition of the PdGa model system is much more variable than that of its PdZn counterpart, which results in gradual changes of the near-surface composition with increasing annealing or reaction temperature. In contrast to near-surface PdZn, in methanol steam reforming, no temperature region with pronounced CO2 selectivity was observed, which is due to the inability of purely intermetallic PdGa to efficiently activate water. This allows to pinpoint the water-activating role of the intermetallic/support interface and/or of the oxide support in the related supported PdxGa/Ga2O3 systems, which exhibit high CO2 selectivity in a broad temperature range. In contrast, corresponding experiments starting on the purely bimetallic model surface in oxidative methanol reforming yielded high CO2 selectivity already at low temperatures (∼460 K), which is due to efficient O2 activation on PdGa. In situ detected partial and reversible oxidative Ga segregation on intermetallic PdGa is associated with total oxidation of intermediate C1 oxygenates to CO2. PMID:22875996

Formation of the Fe-Containing Intermetallic Compounds during Solidification of Al-5Mg-2Si-0.7Mn-1.1Fe Alloy

NASA Astrophysics Data System (ADS)

Que, Zhongping; Wang, Yun; Fan, Zhongyun

2018-06-01

Iron (Fe) is the most common and the most detrimental impurity element in Al alloys due to the formation of Fe-containing intermetallic compounds (IMCs), which are harmful to mechanical performance of the Al-alloy components. In this paper we investigate the formation of Fe-containing IMCs during solidification of an Al-5Mg-2Si-0.7Mn-1.1Fe alloy under varied solidification conditions. We found that the primary Fe-containing intermetallic compound (P-IMC) in the alloy is the BCC α-Al15(Fe,Mn)3Si2 phase and has a polyhedral morphology with {1 1 0} surface termination. The formation of the P-IMCs can be easily suppressed by increasing the melt superheat and/or cooling rate, suggesting that the nucleation of the α-Al15(Fe,Mn)3Si2 phase is difficult. In addition, we found that the IMCs with a Chinese script morphology is initiated on the {1 0 0} surfaces of the P-IMCs during the binary eutectic reaction with the α-Al phase. Both the binary and ternary eutectic IMCs are also identified as the BCC α-Al15(Fe,Mn)3Si2 phase. Furthermore, we found that the Fe content increases and the Mn content decreases in the Fe-containing intermetallic compounds with the decrease of the formation temperature, although the sum of the Fe and Mn contents in all of the IMCs is constant.

Modification of tribology and high-temperature behavior of Ti 48Al 2Cr 2Nb intermetallic alloy by laser cladding

NASA Astrophysics Data System (ADS)

Liu, Xiu-Bo; Wang, Hua-Ming

2006-06-01

In order to improve the tribology and high-temperature oxidation properties of the Ti-48Al-2Cr-2Nb intermetallic alloy simultaneously, mixed NiCr-Cr 3C 2 precursor powders had been investigated for laser cladding treatment to modify wear and high-temperature oxidation resistance of the material. The alloy samples were pre-placed with NiCr-80, 50 and 20%Cr 3C 2 (wt.%), respectively, and laser treated at the same parameters, i.e., laser output power 2.8 kW, beam scanning speed 2.0 mm/s, beam dimension 1 mm × 18 mm. The treated samples underwent tests of microhardness, wear and high-temperature oxidation. The results showed that laser cladding with different constitution of mixed precursor NiCr-Cr 3C 2 powders improved surface hardness in all cases. Laser cladding with NiCr-50%Cr 3C 2 resulted in the best modification of tribology and high-temperature oxidation behavior. X-ray diffraction (XRD), optical microscope (OM), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS) analyses indicated that the formation of reinforced Cr 7C 3, TiC and both continuous and dense Al 2O 3, Cr 2O 3 oxide scales were supposed to be responsible for the modification of the relevant properties. As a result, the present work had laid beneficial surface engineering foundation for TiAl alloy applied as future light weight and high-temperature structural candidate materials.

Discontinuously reinforced intermetallic matrix composites via XD synthesis. [exothermal dispersion

NASA Technical Reports Server (NTRS)

Kumar, K. S.; Whittenberger, J. D.

1992-01-01

A review is given of recent results obtained for discontinuously reinforced intermetallic matrix composites produced using the XD process. Intermetallic matrices investigated include NiAl, multiphase NiAl + Ni2AlTi, CoAl, near-gamma titanium aluminides, and Ll2 trialuminides containing minor amounts of second phase. Such mechanical properties as low and high temperature strength, compressive and tensile creep, elastic modulus, ambient ductility, and fracture toughness are discussed as functions of reinforcement size, shape, and volume fraction. Microstructures before and after deformation are examined and correlated with measured properties. An observation of interest in many of the systems examined is 'dispersion weakening' at high temperatures and high strain rates. This behavior is not specific to the XD process; rather similar observations have been reported in other discontinuous composites. Proposed mechanisms for this behavior are presented.

MgB2-Based Bolometer Array for Far Infra-Red Thermal Imaging and Fourier Transform Spectroscopy Applications

NASA Technical Reports Server (NTRS)

Lakew, B.; Aslam, S.; Brasunas, J.

2012-01-01

The mid-superconducting critical temperature (T(sub c) approximately 39 K) of the simple binary, intermetallic MgB, [1] makes it a very good candidate for the development of the next generation of electrooptical devices (e.g. [2]). In particular, recent advances in thin film deposition teclmiques to attain higb quality polycrystalline thin film MgB, deposited on SiN-Si substrates, with T(sub c) approximately 38K [3] coupled with the low voltage noise performance of the film [4] makes it higbly desirable for the development of moderately cooled bolometer arrays for integration into future space-bourne far infra-red (FIR) spectrometers and thermal mappers for studying the outer planets, their icy moons and other moons of interest in the 17-250 micrometer spectral wavelength range. Presently, commercially available pyroelectric detectors operating at 300 K have specific detectivity, D(*), around 7 x 10(exp 8) to 2 x 10(exp 9) centimeters square root of Hz/W. However, a MgB2 thin film based bolometer using a low-stress (less than 140 MPa) SiN membrane isolated from the substrate by a small thermal conductive link, operating at 38 K, promises to have two orders of magnitude higher specific detectivity [5][6].

3D study of intermetallics and their effect on the corrosion morphology of rheocast aluminium alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mingo, B.; Arrabal, R., E-mail: rarrabal@ucm.es; Pardo, A.

In the present study, the effect of heat treatment T6.1 on the microstructure and corrosion behaviour of rheocast aluminium alloy A356 is investigated on the basis of 2D/3D characterization techniques and electrochemical and SKPFM measurements. Heat treatment strengthens the α-Al matrix, modifies the intermetallic particles and spheroidizes eutectic Si. These changes do not modify significantly the corrosion behaviour of the alloy. 3D SEM-Tomography clearly shows that the corrosion advances in the shape of narrow paths between closely spaced intermetallics without a major influence of eutectic Si. - Highlights: • T6.1 spheroidizes Si, strengthens the matrix and modifies the intermetallics. •more » Electrochemical behaviour of untreated and heat-treated alloys is similar. • 3D SEM-Tomography provides additional information on the corrosion morphology. • Corrosion advances as paths between intermetallics with little influence of Si.« less

High temperature behavior of B2-based ruthenium aluminide systems

NASA Astrophysics Data System (ADS)

Cao, Fang

Ru-modified NiAl-based bond coats have the potential to improve the durability of Superalloy-Thermal Barrier Coating systems (TBCs) for advanced gas turbine engines. A fundamental understanding of the high temperature mechanical behavior across the Ni-Al-Ru B2 phase field can provide direction for the development of these new bond coats for TBCs. The purpose of this study has been to describe the fundamental processes of creep deformation in single phase B2 Ru-Al-Ni ternary alloys which would form the basis for the bond coats. To accomplish this, five ternary alloys with compositions located within the B2 field across the NiAl-RuAl phase region were fabricated and investigated. Special emphasis was placed on characterizing creep deformation and describing the operative creep mechanisms in these alloys. At room temperature, brittle failure was observed in the Ni-rich alloys in compression, while improved strength and ductility were displayed in two Ru-rich ternary alloys at temperatures up to 700°C. Exceptional creep strength was observed in these alloys, as compared to other high melting temperature B2 intermetallics. A continuous increase of the melting temperature and creep resistance with the increasing of the Ru/Ni ratio in these alloys was observed. Post-creep dislocation analyses identified the presence of <100> and <110> edge dislocations in the Ni-rich alloys, while uniformly distributed jogged <100> screw dislocations predominated in the Ru-rich ternary alloys. A transition of the creep mechanism from viscous glide controlled to jogged screw motion in these Ru-Al-Ni ternary B2 alloys with increasing Ru/Ni ratio is demonstrated by the characteristics of the creep deformation process, stress change creep tests, post-creep dislocation analyses, and numerical modeling. Additionally, the knowledge of the cyclic oxidation behavior of ruthenium aluminide-based alloy is essential, as many high-temperature applications for which this intermetallic might be

Magnetic damping in sputter-deposited C o2MnGe Heusler compounds with A 2 ,B 2 , and L 21 orders: Experiment and theory

NASA Astrophysics Data System (ADS)

Shaw, Justin M.; Delczeg-Czirjak, Erna K.; Edwards, Eric R. J.; Kvashnin, Yaroslav; Thonig, Danny; Schoen, Martin A. W.; Pufall, Matt; Schneider, Michael L.; Silva, Thomas J.; Karis, Olof; Rice, Katherine P.; Eriksson, Olle; Nembach, Hans T.

2018-03-01

We show that very low values of the magnetic damping parameter can be achieved in sputter deposited polycrystalline films of C o2MnGe annealed at relatively low temperatures ranging from 240 °C to 400 °C. Damping values as low as 0.0014 are obtained with an intrinsic value of 0.0010 after spin-pumping contributions are considered. Of importance to most applications is the low value of inhomogeneous linewidth that yields measured linewidths of 1.8 and 5.1 mT at 10 and 40 GHz, respectively. The damping parameter monotonically decreases as the B 2 order of the films increases. This trend is reproduced and explained by ab initio calculations of the electronic structure and damping parameter. Here, the damping parameter is calculated as the structure evolves from A 2 to B 2 to L 21 orders. The largest decrease in the damping parameter occurs during the A 2 to B 2 transition as the half-metallic phase becomes established.

Intermetallic Strengthened Alumina-Forming Austenitic Steels for Energy Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Bin; Baker, Ian

2016-03-31

In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, the materials required must be strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and L1 2 precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe 2Nb + L1 2-Ni 3Al precipitates) without harmful effects on oxidation resistance. Microstructural and microchemical analyses of the recently developed alumina-forming austenitic (AFA) steels (Fe-14Cr-32Ni-3Nb-3Al-2Ti-based) indicated they are strengthened by Nimore » 3Al(Ti) L1 2, NiAl B 2, Fe 2Nb Laves phase and MC carbide precipitates. Different thermomechanical treatments (TMTs) were performed on these stainless steels in an attempt to further improve their mechanical properties. The thermo-mechanical processing produced nanocrystalline grains in AFA alloys and dramatically increased their yield strength at room temperature. Unfortunately, the TMTs didn’t increase the yield strengths of AFA alloys at ≥700ºC. At these temperatures, dislocation climb is the dominant mechanism for deformation of TMT alloys according to strain rate jump tests. After the characterization of aged AFA alloys, we found that the largest strengthening effect from L1 2 precipitates can be obtained by aging for less than 24 h. The coarsening behavior of the L1 2 precipitates was not influenced by carbon and boron additions. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these AFA steels after creep tests. Though the Laves and B2-NiAl phase precipitated along the boundaries can improve the creep properties, cracks were still initiated and propagated along the boundaries, which suggests that the boundaries are

Formation of intermetallic compound coating on magnesium AZ91 cast alloy

NASA Astrophysics Data System (ADS)

Zhu, Tianping; Gao, Wei

2009-08-01

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

Homogeneous (Cu, Ni)6Sn5 intermetallic compound joints rapidly formed in asymmetrical Ni/Sn/Cu system using ultrasound-induced transient liquid phase soldering process.

PubMed

Li, Z L; Dong, H J; Song, X G; Zhao, H Y; Tian, H; Liu, J H; Feng, J C; Yan, J C

2018-04-01

Homogeneous (Cu, Ni) 6 Sn 5 intermetallic compound (IMC) joints were rapidly formed in asymmetrical Ni/Sn/Cu system by an ultrasound-induced transient liquid phase (TLP) soldering process. In the traditional TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system consisted of major (Cu, Ni) 6 Sn 5 and minor Cu 3 Sn IMCs, and the grain morphology of (Cu, Ni) 6 Sn 5 IMCs subsequently exhibited fine rounded, needlelike and coarse rounded shapes from the Ni side to the Cu side, which was highly in accordance with the Ni concentration gradient across the joints. However, in the ultrasound-induced TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system only consisted of the (Cu, Ni) 6 Sn 5 IMCs which exhibited an uniform grain morphology of rounded shape with a remarkably narrowed Ni concentration gradient. The ultrasound-induced homogeneous intermetallic joints exhibited higher shear strength (61.6 MPa) than the traditional heterogeneous intermetallic joints (49.8 MPa). Copyright © 2017 Elsevier B.V. All rights reserved.

Electron-Poor Polar Intermetallics: Complex Structures, Novel Clusters, and Intriguing Bonding with Pronounced Electron Delocalization.

PubMed

Lin, Qisheng; Miller, Gordon J

2018-01-16

Intermetallic compounds represent an extensive pool of candidates for energy related applications stemming from magnetic, electric, optic, caloric, and catalytic properties. The discovery of novel intermetallic compounds can enhance understanding of the chemical principles that govern structural stability and chemical bonding as well as finding new applications. Valence electron-poor polar intermetallics with valence electron concentrations (VECs) between 2.0 and 3.0 e - /atom show a plethora of unprecedented and fascinating structural motifs and bonding features. Therefore, establishing simple structure-bonding-property relationships is especially challenging for this compound class because commonly accepted valence electron counting rules are inappropriate. During our efforts to find quasicrystals and crystalline approximants by valence electron tuning near 2.0 e - /atom, we observed that compositions close to those of quasicrystals are exceptional sources for unprecedented valence electron-poor polar intermetallics, e.g., Ca 4 Au 10 In 3 containing (Au 10 In 3 ) wavy layers, Li 14.7 Mg 36.8 Cu 21.5 Ga 66 adopting a type IV clathrate framework, and Sc 4 Mg x Cu 15-x Ga 7.5 that is incommensurately modulated. In particular, exploratory syntheses of AAu 3 T (A = Ca, Sr, Ba and T = Ge, Sn) phases led to interesting bonding features for Au, such as columns, layers, and lonsdaleite-type tetrahedral frameworks. Overall, the breadth of Au-rich polar intermetallics originates, in part, from significant relativistics effect on the valence electrons of Au, effects which result in greater 6s/5d orbital mixing, a small effective metallic radius, and an enhanced Mulliken electronegativity, all leading to ultimate enhanced binding with nearly all metals including itself. Two other successful strategies to mine electron-poor polar intermetallics include lithiation and "cation-rich" phases. Along these lines, we have studied lithiated Zn-rich compounds in which structural

Comparison of the Thermal Expansion Behavior of Several Intermetallic Silicide Alloys Between 293 and 1523 K

NASA Technical Reports Server (NTRS)

Raj, Sai V.

2014-01-01

Thermal expansion measurements were conducted on hot-pressed CrSi(sub 2), TiSi(sub 2), W Si(sub 2) and a two-phase Cr-Mo-Si intermetallic alloy between 293 and 1523 K during three heat-cool cycles. The corrected thermal expansion, (L/L(sub 0)(sub thermal), varied with the absolute temperature, T, as (deltaL/L(sub 0)(sub thermal) = A(T-293)(sup 3) + B(T-293)(sup 2) + C(T-293) + D, where A, B, C and D are regression constants. Excellent reproducibility was observed for most of the materials after the first heat-up cycle. In some cases, the data from the first heatup cycle deviated from those determined in the subsequent cycles. This deviation was attributed to the presence of residual stresses developed during processing, which are relieved after the first heat-up cycle.

Electronic Structure of GdCuGe Intermetallic Compound

NASA Astrophysics Data System (ADS)

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

2018-04-01

The electronic structure of GdCuGe intermetallic compound has been studied. Spin-polarized energy spectrum calculations have been performed by the band method with allowance for strong electron correlations in the 4 f-shell of gadolinium ions. Antiferromagnetic ordering of GdCuGe at low temperatures has been obtained in a theoretical calculation, with the value of the effective magnetic moment of gadolinium ions reproduced in fair agreement with experimental data. The electronic density of states has been analyzed. An optical conductivity spectrum has been calculated for GdCuGe; it reveals specific features that are analogous to the ones discovered previously in the GdCuSi compound with a similar hexagonal structure.

The Effects of Grain Refinement and Rare Earth Intermetallics on Mechanical Properties of As-Cast and Wrought Magnesium Alloys

NASA Astrophysics Data System (ADS)

Pourbahari, Bita; Mirzadeh, Hamed; Emamy, Massoud

2018-03-01

The effects of rare earth intermetallics and grain refinement by alloying and hot extrusion on the mechanical properties of Mg-Gd-Al-Zn alloys have been studied to elucidate some useful ways to enhance the mechanical properties of magnesium alloys. It was revealed that aluminum as an alloying element is a much better grain refining agent compared with gadolinium, but the simultaneous presence of Al and Gd can refine the as-cast grain size more efficiently. The presence of fine and widely dispersed rare earth intermetallics was found to be favorable to achieve finer recrystallized grains during hot deformation by extrusion. The presence of coarse dendritic structure in the GZ61 alloy, grain boundary eutectic containing Mg17Al12 phase in the AZ61 alloy, and rare earth intermetallics with unfavorable morphology in the Mg-4Gd-2Al-1Zn alloy was found to be detrimental to mechanical properties of the alloy in the as-cast condition. As a result, the microstructural refinement induced by hot extrusion process resulted in a significant enhancement in strength and ductility of the alloys. The presence of intermetallic compounds in the extruded Mg-4Gd-2Al-1Zn and Mg-2Gd-4Al-1Zn alloys deteriorated tensile properties, which was related to the fact that such intermetallic compounds act as stress risers and microvoid initiation sites.

Intermetallic alloy welding wires and method for fabricating the same

DOEpatents

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

1996-06-11

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

Intermetallic alloy welding wires and method for fabricating the same

DOEpatents

Santella, Michael L.; Sikka, Vinod K.

1996-01-01

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

Hastatic Order in URu2Si2

NASA Astrophysics Data System (ADS)

Chandra, Premala; Coleman, Piers; Flint, Rebecca

2012-02-01

The hidden order that develops below 17.5K in URu2Si2 has eluded identification for twenty-five years. Here we show that the recent observation of Ising quasiparticles in URu2Si2 suggests a novel ``hastatic order'' (Latin:spear),with a two-component order parameter describing hybridization between electrons and the Ising 5f^2 states of the uranium atoms. Hastatic order breaks time-reversal symmetry by mixing states of different Kramers parity; this accounts for the magnetic anomalies observed in torque magnetometry and the pseudo-Goldstone mode observed in neutron scattering. Hastatic order is predicted to induce a basal-plane magnetic moment of order 0.01μB, a gap to longitudinal spin fluctuations that vanishes continuously at the first-order antiferromagnetic transition and a narrow resonant nematic feature in the scanning tunneling spectra.

Impact resistance and energies of intermetallic bonded diamond composites and polycrystalline diamond compacts and their comparison

NASA Astrophysics Data System (ADS)

Gorla, Sai Prasanth

Chemistry of intermetallic bonded diamond is studied. The impact resistance and energies of intermetallic bonded diamond is compared to current poly crystalline diamond compacts. IBD's are found to have high standards of hardness and have more impact energies absorbed. Intermetallic bonded diamond composite comprises of diamond particles dispersed in Tungsten carbide using Nickel aluminide (Ni3Al) as binder. In previous research conducted on IBD's, diamonds are successfully dispersed in intermetallic alloy of nickel aluminide and processed at 1350°C such that diamond particles remain intact without forming graphite. Composites are formed by milling, pressing the intermetallic binder and diamond particles and sintering at high temperature conditions.

Preparation of Ti3Al intermetallic compound by spark plasma sintering

NASA Astrophysics Data System (ADS)

Ito, Tsutomu; Fukui, Takahiro

2018-04-01

Sintered compacts of single phase Ti3Al intermetallic compound, which have excellent potential as refractory materials, were prepared by spark plasma sintering (SPS). A raw powder of Ti3Al intermetallic compound with an average powder diameter of 176 ± 56 μm was used in this study; this large powder diameter is disadvantageous for sintering because of the small surface area. The samples were prepared at sintering temperatures (Ts) of 1088, 1203, and 1323 K, sintering stresses (σs) of 16, 32, and 48 MPa, and a sintering time (ts) of 10 min. The calculated relative densities based on the apparent density of Ti3Al provided by the supplier were approximately 100% under all sintering conditions. From the experimental results, it was evident that SPS is an effective technique for dense sintering of Ti3Al intermetallic compounds in a short time interval. In this report, the sintering characteristics of Ti3Al intermetallic compacts are briefly discussed and compared with those of pure titanium compacts.

Strength anomaly in B2 FeAl single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshimi, K.; Hanada, S.; Yoo, M.H.

1994-12-31

Strength and deformation microstructure of B2 Fe-39 and 48%Al single crystals (composition given in atomic percent), which were fully annealed to remove frozen-in vacancies, have been investigated at temperatures between room temperature and 1073K. The hardness of as-homogenized Fe-48Al is higher than that of as-homogenized Fe-39Al while after additional annealing at 698K the hardness of Fe-48Al becomes lower than that of Fe-39Al. Fe-39Al single crystals slowly cooled after homogenizing at a high temperature were deformed in compression as a function of temperature and crystal orientation. A peak of yield strength appears around 0.5T{sub m} (T{sub m} = melting temperature). Themore » orientation dependence of the critical resolved shear stress does not obey Schmid`s law even at room temperature and is quite different from that of b.c.c. metals and B2 intermetallics at low temperatures. At the peak temperature slip transition from <111>-type to <001>-type is found to occur macroscopically and microscopically, while it is observed in TEM that some of the [111] dislocations decompose into [101] and [010] on the (1096I) plane below the peak temperature. The physical sources for the positive temperature dependence of yield stress of B2 FeAl are discussed based on the obtained results.« less

Production of an ordered (B2) CuPd nanoalloy by low-temperature annealing under hydrogen atmosphere.

PubMed

Yamauchi, Miho; Tsukuda, Tatsuya

2011-05-14

CuPd (1/1) nanoalloys composed of disordered body-centered-cubic crystals (crystal size = 1.6 nm) were prepared by synchronous reduction of Cu and Pd precursor ions with NaBH(4). In situ XRD measurement revealed that Cu and Pd atoms in the CuPd nanoalloys are arranged into an ordered B2 structure under exposure to H(2) (5 kPa) at 373 K. Ordering of Cu and Pd atoms over a longer distance (up to 3.6 nm) was achieved by annealing the nanoalloys for a longer time under a H(2) atmosphere.

Intermetallic M--Sn.sub.5 (M=Fe, Cu, Co, Ni) compound and a method of synthesis thereof

DOEpatents

Wang, Xiao-Liang; Han, Weiqiang

2017-09-05

Novel intermetallic materials are provided that are composed of tin and one or more additional metal(s) having a formula M.sub.(1-x)-Sn.sub.5, where -0.1.ltoreq.x.ltoreq.0.5, with 0.01.ltoreq.x.ltoreq.0.4 being more preferred and the second metallic element (M) is selected from iron (Fe), copper (Cu), cobalt (Co), nickel (Ni), and a combination of two or more of those metals. Due to low concentration of the second metallic element, the intermetallic compound affords an enhanced capacity applicable for electrochemical cells and may serve as an intermediate phase between Sn and MSn.sub.2. A method of synthesizing these intermetallic materials is also disclosed.

Complex magnetic behaviour and evidence of a superspin glass state in the binary intermetallic compound Er5Pd2

NASA Astrophysics Data System (ADS)

Sharma, Mohit K.; Yadav, Kavita; Mukherjee, K.

2018-05-01

The binary intermetallic compound Er5Pd2 has been investigated using dc and ac magnetic susceptibilities, magnetic memory effect, isothermal magnetization, non-linear dc susceptibility, heat capacity and magnetocaloric effect studies. Interestingly, even though the compound does not show geometrical frustration it undergoes glassy magnetic phase transition below 17.2 K. Investigation of dc magnetization and heat capacity data divulged absence of long-ranged magnetic ordering. Through the magnetic memory effect, time dependent magnetization and ac susceptibility studies it was revealed that the compound undergoes glass-like freezing below 17.2 K. Analysis of frequency dependence of this transition temperature through scaling and Arrhenius law; along with the Mydosh parameter indicate, that the dynamics in Er5Pd2 are due to the presence of strongly interacting superspins rather than individual spins. This phase transition was further investigated by non-linear dc susceptibility and was characterized by static critical exponents γ and δ. Our results indicate that this compound shows the signature of superspin glass at low temperature. Additionally, both conventional and inverse magnetocaloric effect was observed with a large value of magnetic entropy change and relative cooling power. Our results suggest that Er5Pd2 can be classified as a superspin glass system with large magnetocaloric effect.

Hf 3 Fe 4 Sn 4 and Hf 9 Fe 4-x Sn 10+x : Two stannide intermetallics with low-dimensional iron sublattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calta, Nicholas P.; Kanatzidis, Mercouri G.

2016-04-01

This article reports two new Hf-rich intermetallics synthesized using Sn flux: Hf 3Fe 4Sn 4 and Hf 9Fe 4-xSn 10+x. Hf 3Fe 4Sn 4 adopts an ordered variant the Hf 3Cu 8 structure type in orthorhombic space group Pnma with unit cell edges of a=8.1143(5) Å, b=8.8466(5) Å, and c=10.6069(6) Å. Hf 9Fe 4-xSn 10+x, on the other hand, adopts a new structure type in Cmc21 with unit cell edges of a=5.6458(3) Å, b=35.796(2) Å, and c=8.88725(9) Å for x=0. It exhibits a small amount of phase width in which Sn substitutes on one of the Fe sites. Both structuresmore » are fully three-dimensional and are characterized by pseudo one- and two-dimensional networks of Fe–Fe homoatomic bonding. Hf 9Fe 4-xSn 10+x exhibits antiferromagnetic order at TN=46(2) K and its electrical transport behavior indicates that it is a normal metal with phonon-dictated resistivity. Hf 3Fe 4Sn 4 is also an antiferromagnet with a rather high ordering temperature of TN=373(5) K. Single crystal resistivity measurements indicate that Hf 3Fe 4Sn 4 behaves as a Fermi liquid at low temperatures, indicating strong electron correlation.« less

Polarized neutron scattering study of the multiple order parameter system NdB 4 [Polarized neutron scattering study on multiple order parameter system NdB 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metoki, Naoto; Yamauchi, Hiroki; Matsuda, Masaaki

Neutron polarization analysis has been carried out in order to clarify the magnetic structures of multiple order parameter f-electron system NdB 4. We confirmed the noncollinear “all-in all-out” structure (Γ 4) of the in-plane moment, which is in good agreement with our previous neutron powder diffraction study. We found that the magnetic moment along the c-axis m c showed diagonally antiferromagnetic structure (Γ 10), inconsistent with previously reported “vortex” structure (Γ 2). The microscopic mixture of these two structures with →q 0=(0,0,0) appears in phase II and remains stable in phases III and IV, where an incommensurate modulation coexists. Themore » unusual magnetic ordering is phenomenologically understood via Landau theory with the primary order parameter Γ 4 coupled with higher-order secondary order parameter Γ 10. The magnetic moments were estimated to be 1.8 ± 0.2 and 0.2 ± 0.05μ B at T = 7.5K for Γ 4 and Γ 10, respectively. We also found a long-period incommensurate modulation of the →q 1=(0,0,1/2) antiferromagnetic structure of mc with the propagation →q s1=(0.14,0.14,0.1) and →q s2=(0.2,0,0.1) in phase III and IV, respectively. The amplitude of sinusoidal modulation was about m c=1.0 ± 0.2μ B at T=1.5 K. The local (0,0,1/2) structure consists of in-plane ferromagnetic and out-of-plane antiferromagnetic coupling of m c, opposite to the coexisting Γ 10. The mc of Γ 10 is significantly enhanced up to 0.6μ B at T=1.5 K, which is accompanied by the incommensurate modulations. As a result, the Landau phenomenological approach indicates that the higher-order magnetic and/or multipole interactions based on the pseudoquartet f-electron state play important roles.« less

Polarized neutron scattering study of the multiple order parameter system NdB 4 [Polarized neutron scattering study on multiple order parameter system NdB 4

DOE PAGES

Metoki, Naoto; Yamauchi, Hiroki; Matsuda, Masaaki; ...

2018-05-17

Neutron polarization analysis has been carried out in order to clarify the magnetic structures of multiple order parameter f-electron system NdB 4. We confirmed the noncollinear “all-in all-out” structure (Γ 4) of the in-plane moment, which is in good agreement with our previous neutron powder diffraction study. We found that the magnetic moment along the c-axis m c showed diagonally antiferromagnetic structure (Γ 10), inconsistent with previously reported “vortex” structure (Γ 2). The microscopic mixture of these two structures with →q 0=(0,0,0) appears in phase II and remains stable in phases III and IV, where an incommensurate modulation coexists. Themore » unusual magnetic ordering is phenomenologically understood via Landau theory with the primary order parameter Γ 4 coupled with higher-order secondary order parameter Γ 10. The magnetic moments were estimated to be 1.8 ± 0.2 and 0.2 ± 0.05μ B at T = 7.5K for Γ 4 and Γ 10, respectively. We also found a long-period incommensurate modulation of the →q 1=(0,0,1/2) antiferromagnetic structure of mc with the propagation →q s1=(0.14,0.14,0.1) and →q s2=(0.2,0,0.1) in phase III and IV, respectively. The amplitude of sinusoidal modulation was about m c=1.0 ± 0.2μ B at T=1.5 K. The local (0,0,1/2) structure consists of in-plane ferromagnetic and out-of-plane antiferromagnetic coupling of m c, opposite to the coexisting Γ 10. The mc of Γ 10 is significantly enhanced up to 0.6μ B at T=1.5 K, which is accompanied by the incommensurate modulations. As a result, the Landau phenomenological approach indicates that the higher-order magnetic and/or multipole interactions based on the pseudoquartet f-electron state play important roles.« less

Femtosecond laser ablation and nanoparticle formation in intermetallic NiAl

NASA Astrophysics Data System (ADS)

Jorgensen, David J.; Titus, Michael S.; Pollock, Tresa M.

2015-10-01

The ablation behavior of a stoichiometric intermetallic compound β-NiAl subjected to femtosecond laser pulsing in air has been investigated. The single-pulse ablation threshold for NiAl was determined to be 83 ± 4 mJ/cm2 and the transition to the high-fluence ablation regime occurred at 2.8 ± 0.3 J/cm2. Two sizes of nanoparticles consisting of Al, NiAl, Ni3Al and NiO were formed and ejected from the target during high-fluence ablation. Chemical analysis revealed that smaller nanoparticles (1-30 nm) tended to be rich in Al while larger nanoparticles (>100 nm) were lean in Al. Ablation in the low-fluence regime maintained this trend. Redeposited material and nanoparticles remaining on the surface after a single 3.7 J/cm2 pulse, one hundred 1.7 J/cm2 pulses, or one thousand 250 mJ/cm2 pulses were enriched in Al relative to the bulk target composition. Further, the surface of the irradiated high-fluence region was depleted in Al indicating that the fs laser ablation removal rate of the intermetallic constituents in this regime does not scale with the individual pure element ablation thresholds.

The decays B → Ψ(2S)π(K),ηc(2S)π(K) in the pQCD approach beyond the leading-order

NASA Astrophysics Data System (ADS)

Zhang, Zhi-Qing

2017-09-01

Two body B meson decays involving the radially excited meson ψ (2 S) /ηc (2 S) in the final states are studied by using the perturbative QCD (pQCD) approach. We find that: (a) The branching ratios for the decays involving a K meson are predicted as Br (B+ → ψ (2 S)K+) = (5.37-2.22+1.85) ×10-4, Br (B0 → ψ (2 S)K0) = (4.98-2.06+1.71) ×10-4, Br (B+ →ηc (2 S)K+) = (3.54-3.09+3.18) ×10-4, which are consistent with the present data when the next-to-leading-order (NLO) effects are included. Here the NLO effects are from the vertex corrections and the NLO Wilson coefficients. The large errors in the decay B+ →ηc (2 S)K+ are mainly induced by using the decay constant f ηc (2 S) =0.243-0.111+0.079 GeV with large uncertainties. (b) While there seems to be some room left for other higher order corrections or the non-perturbative long distance contributions in the decays involving a π meson, Br (B+ → ψ (2 S)π+) = (1.17-0.50+0.42) ×10-5, Br (B0 → ψ (2 S)π0) =0.54-0.23+0.20 ×10-5, which are smaller than the present data. The results for other decays can be tested via running LHCb and forthcoming Super-B experiments. (c) There is no obvious evidence of the direct CP violation being seen in the decays B → ψ (2 S) π (K) ,ηc (2 S) π (K) in the present experiments, which is supported by our calculations. If a few percent value is confirmed in the future, this would definitely indicate the existence of new physics.

Microstructure and corrosion resistance of TC2 Ti alloy by laser cladding with Ti/TiC/TiB2 powders

NASA Astrophysics Data System (ADS)

Diao, Yunhua; Zhang, Kemin

2015-10-01

In the present work, a TiC/TiB2 composite coating was produced onto a TC2 Ti alloy by laser cladding with Ti/TiC/TiB2 powders. The surface microstructure, phase components and compositions were characterized with methods of optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffractometry (XRD), and energy dispersive spectrometry (EDS). The cladding layer is consisted of Ti, TiC and TiB2. And the surface microhardness was measured. After laser cladding, a maximum hardness of 1100 HV is achieved in the laser cladding surface layer, which is more three times higher than that of the TC2 substrate (∼300 HV). Due to the formation of TiC and TiB2 intermetallic compounds in the alloyed region and grain refinement, the microhardness of coating is higher than TC2 Ti alloy. In this paper, the corrosion property of matrix material and treated samples were both measured in NaCl (3.5 wt%) aqueous solution. From the result we can see that the laser cladding specimens' corrosion property is clearly becoming better than that of the substrate.

Correlation between valence electronic structure and magnetic properties in RCo5 (R = rare earth) intermetallic compound

NASA Astrophysics Data System (ADS)

Zhi-Qin, Xue; Yong-Quan, Guo

2016-06-01

The magnetisms of RCo5 (R = rare earth) intermetallics are systematically studied with the empirical electron theory of solids and molecules (EET). The theoretical moments and Curie temperatures agree well with experimental ones. The calculated results show strong correlations between the valence electronic structure and the magnetic properties in RCo5 intermetallic compounds. The moments of RCo5 intermetallics originate mainly from the 3d electrons of Co atoms and 4f electrons of rare earth, and the s electrons also affect the magnetic moments by the hybridization of d and s electrons. It is found that moment of Co atom at 2c site is higher than that at 3g site due to the fact that the bonding effect between R and Co is associated with an electron transformation from 3d electrons into covalence electrons. In the heavy rare-earth-based RCo5 intermetallics, the contribution to magnetic moment originates from the 3d and 4f electrons. The covalence electrons and lattice electrons also affect the Curie temperature, which is proportional to the average moment along the various bonds. Project supported by the National Natural Science Foundation of China (Grant No. 11274110).

CARDIO-i2b2: integrating arrhythmogenic disease data in i2b2.

PubMed

Segagni, Daniele; Tibollo, Valentina; Dagliati, Arianna; Napolitano, Carlo; G Priori, Silvia; Bellazzi, Riccardo

2012-01-01

The CARDIO-i2b2 project is an initiative to customize the i2b2 bioinformatics tool with the aim to integrate clinical and research data in order to support translational research in cardiology. In this work we describe the implementation and the customization of i2b2 to manage the data of arrhytmogenic disease patients collected at the Fondazione Salvatore Maugeri of Pavia in a joint project with the NYU Langone Medical Center (New York, USA). The i2b2 clinical research chart data warehouse is populated with the data obtained by the research database called TRIAD. The research infrastructure is extended by the development of new plug-ins for the i2b2 web client application able to properly select and export phenotypic data and to perform data analysis.

Microstructure Characterization and Wear-Resistant Properties Evaluation of an Intermetallic Composite in Ni-Mo-Si System.

PubMed

Huang, Boyuan; Song, Chunyan; Liu, Yang; Gui, Yongliang

2017-02-04

Intermetallic compounds have been studied for their potential application as structural wear materials or coatings on engineering steels. In the present work, a newly designed intermetallic composite in a Ni-Mo-Si system was fabricated by arc-melting process with commercially pure metal powders as starting materials. The chemical composition of this intermetallic composite is 45Ni-40Mo-15Si (at %), selected according to the ternary alloy diagram. The microstructure was characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS), and the wear-resistant properties at room temperature were evaluated under different wear test conditions. Microstructure characterization showed that the composite has a dense and uniform microstructure. XRD results showed that the intermetallic composite is constituted by a binary intermetallic compound NiMo and a ternary Mo₂Ni₃Si metal silicide phase. Wear test results indicated that the intermetallic composite has an excellent wear-resistance at room-temperature, which is attributed to the high hardness and strong atomic bonding of constituent phases NiMo and Mo₂Ni₃Si.

Intermetallic layers in temperature controlled Friction Stir Welding of dissimilar Al-Cu-joints

NASA Astrophysics Data System (ADS)

Marstatt, R.; Krutzlinger, M.; Luderschmid, J.; Constanzi, G.; Mueller, J. F. J.; Haider, F.; Zaeh, M. F.

2018-06-01

Friction Stir Welding (FSW) can be performed to join dissimilar metal combinations like aluminium and copper, which is of high interest in modern production of electrical applications. The amount of intermetallic phases in the weld seam is significantly reduced compared to traditional fusion welding technologies. Because the solidus temperature is typically not reached during FSW, the growth of intermetallic phases is impeded and the intermetallic layer thicknesses typically remains on the scale of a few hundred nanometres. These layers provide a substance-to-substance bond, which is the main joining mechanism. Latest research confirms that the layer formation is most likely driven by the heat input during processing. Hence, the welding temperature is the key to achieve high quality joints. In this study, aluminium and copper sheets were welded in lap joint configuration using temperature-controlled FSW. An advanced in-tool measurement set-up was used to determine precise temperature data. Scanning electron microscopy (SEM) was used to analyse metallurgical aspects (e.g. structure and composition of the intermetallic phases) of the joints. The results show a correlation between the welding temperature and the thickness of the intermetallic layer and its structure. The temperature control significantly improved the correlation compared to previous studies. This leads to an enhanced understanding of the dominating joining mechanisms.

Hf{sub 3}Fe{sub 4}Sn{sub 4} and Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x}: Two stannide intermetallics with low-dimensional iron sublattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calta, Nicholas P.; Kanatzidis, Mercouri G., E-mail: m-kanatzidis@northwestern.edu; Materials Science Division, Argonne National Laboratory

This article reports two new Hf-rich intermetallics synthesized using Sn flux: Hf{sub 3}Fe{sub 4}Sn{sub 4} and Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x}. Hf{sub 3}Fe{sub 4}Sn{sub 4} adopts an ordered variant the Hf{sub 3}Cu{sub 8} structure type in orthorhombic space group Pnma with unit cell edges of a=8.1143(5) Å, b=8.8466(5) Å, and c=10.6069(6) Å. Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x}, on the other hand, adopts a new structure type in Cmc2{sub 1} with unit cell edges of a=5.6458(3) Å, b=35.796(2) Å, and c=8.88725(9) Å for x=0. It exhibits a small amount of phase width in which Sn substitutes on one of the Fe sites. Bothmore » structures are fully three-dimensional and are characterized by pseudo one- and two-dimensional networks of Fe–Fe homoatomic bonding. Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x} exhibits antiferromagnetic order at T{sub N}=46(2) K and its electrical transport behavior indicates that it is a normal metal with phonon-dictated resistivity. Hf{sub 3}Fe{sub 4}Sn{sub 4} is also an antiferromagnet with a rather high ordering temperature of T{sub N}=373(5) K. Single crystal resistivity measurements indicate that Hf{sub 3}Fe{sub 4}Sn{sub 4} behaves as a Fermi liquid at low temperatures, indicating strong electron correlation. - Graphical abstract: Slightly different growth conditions in Sn flux produce two new intermetallic compounds: Hf{sub 3}Fe{sub 4}Sn{sub 4} and Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x}. - Highlights: • Single crystals of both Hf{sub 3}Fe{sub 4}Sn{sub 4} and Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x} were grown using Sn flux. • The crystal structures were determined using single crystal X-ray diffraction. • The Fe moments in Hf{sub 3}Fe{sub 4}Sn{sub 4} display AFM order below T{sub N}=373 K. • The Fe moments in Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x} display AFM order below T{sub N}=46 K.« less

Properties of TiNi intermetallic compound industrially produced by combustion synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaieda, Yoshinari

Most TiNi shape memory intermetallic compounds are conventionally produced by the process including high frequency induction vacuum melting and casting. A gravity segregation occurs in a cast TiNi ingot because of the big difference in the specific gravity between Ti and Ni. It is difficult to control accurately the phase transformation temperature of TiNi shape memory intermetallic compound produced by the conventional process, because the martensitic transformation temperature shifts by 10K due to the change in 0.1 % of Ni content. Homogeneous TiNi intermetallic compound is produced by the industrial process including combustion synthesis method, which is a newly developedmore » manufacturing process. In the new process, phase transformation temperatures of TiNi can be controlled accurately by controlling the ratio of Ti and Ni elemental starting powders. The chemical component, the impurities and the phase transformation temperatures of the TiNi products industrially produced by the process are revealed. These properties are vitally important when combustion synthesis method is applied to an industrial mass production process for producing TiNi shape memory intermetallic compounds. TiNi shape memory products are industrially and commercially produced today the industrial process including combustion synthesis. The total production weight in a year is 30 tins in 1994.« less

An intermetallic forming steel under radiation for nuclear applications

NASA Astrophysics Data System (ADS)

Hofer, C.; Stergar, E.; Maloy, S. A.; Wang, Y. Q.; Hosemann, P.

2015-03-01

In this work we investigated the formation and stability of intermetallics formed in a maraging steel PH 13-8 Mo under proton radiation up to 2 dpa utilizing nanoindentation, microcompression testing and atom probe tomography. A comprehensive discussion analyzing the findings utilizing rate theory is introduced, comparing the aging process to radiation induced diffusion. New findings of radiation induced segregation of undersize solute atoms (Si) towards the precipitates are considered.

Factors determining the average atomic volumes in intermetallic compounds.

PubMed

Pauling, L

1987-07-01

In formation of an intermetallic compound from the elementary metals there is usually a contraction in volume. Electron transfer leading to the charge states M(+) and M(-) with increase in valence and decrease in volume explains the more than 2-fold range in contraction for different compounds in the same binary system. In a more thorough analysis, the better packing of atoms of different sizes also needs to be considered.

New twisted intermetallic compound superconductor: A concept

NASA Technical Reports Server (NTRS)

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

1972-01-01

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

Ultrafast and Highly Reversible Sodium Storage in Zinc-Antimony Intermetallic Nanomaterials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nie, Anmin; Gan, Li-yong; Cheng, Yingchun

2015-12-17

The progress on sodium-ion battery technology faces many grand challenges, one of which is the considerably lower rate of sodium insertion/deinsertion in electrode materials due to the larger size of sodium (Na) ions and complicated redox reactions compared to the lithium-ion systems. Here, it is demonstrated that sodium ions can be reversibly stored in Zn-Sb intermetallic nanowires at speeds that can exceed 295 nm s -1. Remarkably, these values are one to three orders of magnitude higher than the sodiation rate of other nanowires electrochemically tested with in situ transmission electron micro­scopy. It is found that the nanowires display aboutmore » 161% volume expansion after the first sodiation and then cycle with an 83% reversible volume expansion. Despite their massive expansion, the nanowires can be cycled without any cracking or facture during the ultrafast sodiation/desodiation process. Additionally, most of the phases involved in the sodiation/desodiation process possess high electrical conductivity. More specifically, the NaZnSb exhibits a layered structure, which provides channels for fast Na + diffusion. This observation indicates that Zn-Sb intermetallic nanomaterials offer great promise as high rate and good cycling stability anodic materials for the next generation of sodium-ion batteries.« less

Mechanical properties of Mo-Si-B alloys fabricated by using core-shell powder with dispersion of yttria nanoparticles

NASA Astrophysics Data System (ADS)

Byun, Jong Min; Bang, Su-Ryong; Choi, Won June; Kim, Min Sang; Noh, Goo Won; Kim, Young Do

2017-01-01

In recent years, refractory materials with excellent high-temperature properties have been in the spotlight as a next generation's high-temperature materials. Among these, Mo-Si-B alloys composed of two intermetallic compound phases (Mo5SiB2 and Mo3Si) and a ductile α-Mo phase have shown an outstanding thermal properties. However, due to the brittleness of the intermetallic compound phases, Mo-Si-B alloys were restricted to apply for the structural materials. So, to enhance the mechanical properties of Mo-Si-B alloys, many efforts to add rare-earth oxide particles in the Mo-Si-B alloy were performed to induce the improvement of strength and fracture toughness. In this study, to investigate the effect of adding nano-sized Y2O3 particles in Mo-Si-B alloy, a core-shell powder consisting of intermetallic compound phases as the core and nano-sized α-Mo and Y2O3 particles surrounding the core was fabricated. Then pressureless sintering was carried out at 1400 °C for 3 h, and the mechanical properties of sintered bodies with different amounts of Y2O3 particles were evaluated by Vickers hardness and 3-point bending test. Vickers hardness was improved by dispersed Y2O3 particles in the Mo-Si-B alloy. Especially, Mo-3Si-1B-1.5Y2O3 alloy had the highest value, 589 Hv. The fracture toughness was measured using Mo-3Si-1B-1.5Y2O3 alloy and the value indicated as 13.5 MPa·√m.

Crystal structure and low-energy Einstein mode in ErV{sub 2}Al{sub 20} intermetallic cage compound

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winiarski, Michał J., E-mail: mwiniarski@mif.pg.gda.pl; Klimczuk, Tomasz

Single crystals of a new ternary aluminide ErV{sub 2}Al{sub 20} were grown using a self-flux method. The crystal structure was determined by powder X-ray diffraction measurements and Rietveld refinement, and physical properties were studied by means of electrical resistivity, magnetic susceptibility and specific heat measurements. These measurements reveal that ErV{sub 2}Al{sub 20} is a Curie-Weiss paramagnet down to 1.95 K with an effective magnetic moment μ{sub eff} =9.27(1) μ{sub B} and Curie-Weiss temperature Θ{sub CW} =−0.55(4) K. The heat capacity measurements show a broad anomaly at low temperatures that is attributed to the presence of a low-energy Einstein mode withmore » characteristic temperature Θ{sub E} =44 K, approximately twice as high as in the isostructural ‘Einstein solid’ VAl{sub 10.1}. - Graphical abstract: A low-energy Einstein mode is observed in a novel intermetallic cage compound ErV{sub 2}Al{sub 20} by specific heat and resistivity measurements. - Highlights: • Single crystals of a new compound ErV{sub 2}Al{sub 20} were grown by self-flux method. • Crystal structure is reported, based on powder x-ray diffraction. • ErV{sub 2}Al{sub 20} is a Curie-Weiss paramagnet. • Low-energy ‘rattling’ phonon mode (Θ{sub E}=44 K) is found in specific heat measurements.« less

Factors determining the average atomic volumes in intermetallic compounds

PubMed Central

Pauling, Linus

1987-01-01

In formation of an intermetallic compound from the elementary metals there is usually a contraction in volume. Electron transfer leading to the charge states M+ and M- with increase in valence and decrease in volume explains the more than 2-fold range in contraction for different compounds in the same binary system. In a more thorough analysis, the better packing of atoms of different sizes also needs to be considered. PMID:16578809

Highly stable carbon coated Mg2Si intermetallic nanoparticles for lithium-ion battery anode

NASA Astrophysics Data System (ADS)

Tamirat, Andebet Gedamu; Hou, Mengyan; Liu, Yao; Bin, Duan; Sun, Yunhe; Fan, Long; Wang, Yonggang; Xia, Yongyao

2018-04-01

Silicon is an ideal candidate anode material for Li-ion batteries (LIBs). However, it suffers from rapid capacity fading due to large volume expansion upon lithium insertion. Herein, we design and fabricate highly stable carbon coated porous Mg2Si intermetallic anode material using facile mechano-thermal technique followed by carbon coating using thermal vapour deposition (TVD), toluene as carbon source. The electrode exhibits an excellent first reversible capacity of 726 mAh g-1 at a rate of 100 mA g-1. More importantly, the electrode demonstrates high rate capability (380 mAh g-1 at high rate of 2 A g-1) as well as high cycle stability, with capacity retentions of 65% over 500 cycles. These improvements are attributable to both Mg supporting medium and the uniform carbon coating, which can effectively increase the conductivity and electronic contact of the active material and protects large volume alterations during the electrochemical cycling process.

Electronic structure, elasticity, bonding features and mechanical behaviour of zinc intermetallics: A DFT study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fatima, Bushra, E-mail: bushrafatima25@gmail.com; Acharya, Nikita; Sanyal, Sankar P.

2016-05-06

The structural stability, electronic structure, elastic and mechanical properties of TiZn and ZrZn intermetallics have been studied using ab-initio full potential linearized augmented plane wave (FP-LAPW) method within generalized gradient approximation for exchange and correlation potentials. The various structural parameters, such as lattice constant (a{sub 0}), bulk modulus (B), and its pressure derivative (B’) are analysed and compared. The investigation of elastic constants affirm that both TiZn and ZrZn are elastically stable in CsCl (B{sub 2} phase) structure. The electronic structures have been analysed quantitatively from the band structure which reveals the metallic nature of these compounds. To better illustratemore » the nature of bonding and charge transfer, we have also studied the Fermi surfaces. The three well known criterion of ductility namely Pugh’s rule, Cauchy’s pressure and Frantsevich rule elucidate the ductile nature of these compounds.« less

Controlling Magnetism via Transition Metal Exchange in the Series of Intermetallics Eu( T1, T2)5In ( T = Cu, Ag, Au)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mudring, Anja -Verena; Smetana, Volodymyr; Pecharsky, Vitalij K.

Three series of intermetallic compounds Eu( T1, T2) 5In (T = Cu, Ag, Au) have been investigated in full compositional ranges. Single crystals of all compounds have been obtained by self-flux and were analyzed by single X-ray diffraction revealing the representatives to fall into two structure types: CeCu 6 ( oP28, Pnma, a = 8.832(3)–9.121(2) Å, b = 5.306(2)–5.645(1) Å, c = 11.059(4)–11.437(3) Å, V = 518.3(3)–588.9(2) Å 3) and YbMo2Al4 ( t I14, I4/ mmm, a = 5.417(3)–5.508(1) Å, c = 7.139(2)– 7.199(2) Å, V = 276.1(2)–285.8(1) Å 3). The structural preference was found to depend on the cation/anionmore » size ratio, while the positional preference within the CeCu 6 type structure shows an apparent correlation with the anion size. Chemical compression, hence, a change in cell volume, which occurs upon anion substitution appears to be the main driving force for the change of magnetic ordering. While EuAg 5In shows antiferromagnetic behavior at low temperatures, mixing Cu and Au within the same type of structure results in considerable changes in the magnetism. The Eu(Cu,Au) 5In alloys with CeCu 6 structure show complex magnetic behaviors and strong magnetic field-induced spin-reorientation transition with the critical field of the transition being dependent on Cu/Au ratio. The alloys adopting the YbMo 2Al 4 type structure are ferromagnets exhibiting unusually high magnetic moments. The heat capacity of EuAu 2.66Cu 2.34In reveals a double-peak structure evolving with the magnetic field. Furthermore, low-temperature X-ray powder diffraction does not show a structural transition.« less

Controlling Magnetism via Transition Metal Exchange in the Series of Intermetallics Eu( T1, T2)5In ( T = Cu, Ag, Au)

DOE PAGES

Mudring, Anja -Verena; Smetana, Volodymyr; Pecharsky, Vitalij K.; ...

2017-11-24

Three series of intermetallic compounds Eu( T1, T2) 5In (T = Cu, Ag, Au) have been investigated in full compositional ranges. Single crystals of all compounds have been obtained by self-flux and were analyzed by single X-ray diffraction revealing the representatives to fall into two structure types: CeCu 6 ( oP28, Pnma, a = 8.832(3)–9.121(2) Å, b = 5.306(2)–5.645(1) Å, c = 11.059(4)–11.437(3) Å, V = 518.3(3)–588.9(2) Å 3) and YbMo2Al4 ( t I14, I4/ mmm, a = 5.417(3)–5.508(1) Å, c = 7.139(2)– 7.199(2) Å, V = 276.1(2)–285.8(1) Å 3). The structural preference was found to depend on the cation/anionmore » size ratio, while the positional preference within the CeCu 6 type structure shows an apparent correlation with the anion size. Chemical compression, hence, a change in cell volume, which occurs upon anion substitution appears to be the main driving force for the change of magnetic ordering. While EuAg 5In shows antiferromagnetic behavior at low temperatures, mixing Cu and Au within the same type of structure results in considerable changes in the magnetism. The Eu(Cu,Au) 5In alloys with CeCu 6 structure show complex magnetic behaviors and strong magnetic field-induced spin-reorientation transition with the critical field of the transition being dependent on Cu/Au ratio. The alloys adopting the YbMo 2Al 4 type structure are ferromagnets exhibiting unusually high magnetic moments. The heat capacity of EuAu 2.66Cu 2.34In reveals a double-peak structure evolving with the magnetic field. Furthermore, low-temperature X-ray powder diffraction does not show a structural transition.« less

Synthesis of Pt 3Y and Other Early–Late Intermetallic Nanoparticles by Way of a Molten Reducing Agent

DOE PAGES

Kanady, Jacob S.; Leidinger, Peter; Haas, Andreas; ...

2017-03-29

Early–late intermetallic phases have garnered increased attention recently for their catalytic properties. To achieve the high surface areas needed for industrially relevant applications, these phases must be synthesized as nanoparticles in a scalable fashion. Herein, Pt 3Y—targeted as a prototypical example of an early–late intermetallic—has been synthesized as nanoparticles approximately 5–20 nm in diameter via a solution process and characterized by XRD, TEM, EDS, and XPS. The key development is the use of a molten borohydride (MEt 3BH, M = Na, K) as both the reducing agent and reaction medium. Readily available halide precursors of the two metals are used.more » Accordingly, no organic ligands are necessary, as the resulting halide salt byproduct prevents sintering, which further permits dispersion of the nanoscale intermetallic onto a support. The versatility of this approach was validated by the synthesis of other intermetallic phases such as Pt 3Sc, Pt 3Lu, Pt 2Na, and Au 2Y.« less

Synthesis of Pt 3Y and Other Early–Late Intermetallic Nanoparticles by Way of a Molten Reducing Agent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanady, Jacob S.; Leidinger, Peter; Haas, Andreas

Early–late intermetallic phases have garnered increased attention recently for their catalytic properties. To achieve the high surface areas needed for industrially relevant applications, these phases must be synthesized as nanoparticles in a scalable fashion. Herein, Pt 3Y—targeted as a prototypical example of an early–late intermetallic—has been synthesized as nanoparticles approximately 5–20 nm in diameter via a solution process and characterized by XRD, TEM, EDS, and XPS. The key development is the use of a molten borohydride (MEt 3BH, M = Na, K) as both the reducing agent and reaction medium. Readily available halide precursors of the two metals are used.more » Accordingly, no organic ligands are necessary, as the resulting halide salt byproduct prevents sintering, which further permits dispersion of the nanoscale intermetallic onto a support. The versatility of this approach was validated by the synthesis of other intermetallic phases such as Pt 3Sc, Pt 3Lu, Pt 2Na, and Au 2Y.« less

B-site cation order/disorder and their valence states in Ba3MnNb2O9 perovskite oxide

NASA Astrophysics Data System (ADS)

Xin, Yan; Huang, Qing; Shafieizadeh, Zahra; Zhou, Haidong

2018-06-01

Polycrystalline samples Ba3MnNb2O9 synthesized by solid state reaction and single crystal samples grown by optical floating zone have been characterized using scanning transmission electron microscopy and electron energy loss spectroscopy. Three types of B-site Mn and Nb ordering phase are observed: fully ordered 1Mn:2Nb; fully disordered; nano-sized 1Mn:1Nb ordered. No electronic structure change for crystals with different ordering/disordering. The Mn valence is determined to be 2+, and Nb valence is 5+. Oxygen 2p orbitals hybridize with Mn 3d and Nb 4d orbitals. Factors that affect the electron energy loss near edge structures of transition metal white-lines in electron energy loss spectroscopy are explicitly illustrated and discussed.

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

NASA Astrophysics Data System (ADS)

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

2013-04-01

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 ~150°C), 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 ~160°C) 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.

Elevated temperature slow plastic deformation of NiAl-TiB2 particulate composites at 1200 and 1300 K

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Viswanadham, R. K.; Mannan, S. K.; Sprissler, B.

1990-01-01

Elevated temperature compression testing has been conducted in air at 1200 and 1300 K with strain rates varying from about 10 to the -4th to about 10 to the -7th/sec on NiAl-TiB2 particulate composites. These materials, which consisted of a B2 crystal structure intermetallic Ni-50 at. pct Al matrix and from 0 to 30 vol pct of approximately 1- micron diameter TiB2 particles, were fabricated by XD synthesis and hot pressed to full density. Flow strength of the composites increased with volume fraction of the strengthening phase with NiAl-30TiB2 being approximately three times stronger than NiAl. Comparison of the light optical and TEM microstructures of as-received and tested samples revealed that reactions did not occur between the two phases, and NiAl-TiB2 interfaces were not cracked during deformation. Additional TEM indicated that the particles stabilize a vastly different microstructure in the NiAl matrix of the composites than that formed in unreinforced NiAl.

Ultrafast synthesis of flower-like ordered Pd3Pb nanocrystals with superior electrocatalytic activities towards oxidation of formic acid and ethanol

NASA Astrophysics Data System (ADS)

Jana, Rajkumar; Subbarao, Udumula; Peter, Sebastian C.

2016-01-01

Ordered intermetallic nanocrystals with high surface area are highly promising as efficient catalysts for fuel cell applications because of their unique electrocatalytic properties. The present work discusses about the controlled synthesis of ordered intermetallic Pd3Pb nanocrystals in different morphologies at relatively low temperature for the first time by polyol and hydrothermal methods both in presence and absence of surfactant. Here for the first time we report surfactant free synthesis of ordered flower-like intermetallic Pd3Pb nanocrystals in 10 s. The structural characteristics of the nanocrystals are confirmed by powder X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. The as synthesized ordered Pd3Pb nanocrystals exhibit far superior electrocatalytic activity and durability towards formic acid and ethanol oxidation over commercially available Pd black (Pd/C). The morphological variation of nanocrystals plays a crucial role in the electrocatalytic oxidation of formic acid and ethanol. Among the catalysts, the flower-like Pd3Pb shows enhanced activity and stability in electrocatalytic formic acid and ethanol oxidation. The current density and mass activity of flower-like Pd3Pb catalyst are higher by 2.5 and 2.4 times than that of Pd/C for the formic acid oxidation and 1.5 times each for ethanol oxidation.

Effect of different thickness crystalline SiC buffer layers on the ordering of MgB{sub 2} films probed by extended x-ray absorption fine structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putri, W. B. K.; Tran, D. H.; Kang, B., E-mail: bwkang@chungbuk.ac.kr

2014-03-07

Extended X-ray absorption fine structure (EXAFS) spectroscopy is a powerful method to investigate the local structure of thin films. Here, we have studied EXAFS of MgB{sub 2} films grown on SiC buffer layers. Crystalline SiC buffer layers with different thickness of 70, 100, and 130 nm were deposited on the Al{sub 2}O{sub 3} (0001) substrates by using a pulsed laser deposition method, and then MgB{sub 2} films were grown on the SiC buffer layer by using a hybrid physical-chemical vapor deposition technique. Transition temperature of MgB{sub 2} film decreased with increasing thickness of SiC buffer layer. However, the T{sub c} droppingmore » went no farther than 100 nm-thick-SiC. This uncommon behavior of transition temperature is likely to be created from electron-phonon interaction in MgB{sub 2} films, which is believed to be related to the ordering of MgB{sub 2} atomic bonds, especially in the ordering of Mg–Mg bonds. Analysis from Mg K-edge EXAFS measurements showed interesting ordering behavior of MgB{sub 2} films. It is noticeable that the ordering of Mg–B bonds is found to decrease monotonically with the increase in SiC thickness of the MgB{sub 2} films, while the opposite happens with the ordering in Mg–Mg bonds. Based on these results, crystalline SiC buffer layers in MgB{sub 2} films seemingly have evident effects on the alteration of the local structure of the MgB{sub 2} film.« less

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

NASA Astrophysics Data System (ADS)

Yang, S. C.; Ho, C. E.; Chang, C. W.; Kao, C. R.

2007-04-01

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, S. C.; Ho, C. E.; Chang, C. W.

2007-04-15

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 themore » 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.« less

Unique intermetallic compounds prepared by shock wave synthesis

NASA Technical Reports Server (NTRS)

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

1971-01-01

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

Hydrogen absorption and its effect on magnetic properties of Nd2Fe14B

NASA Astrophysics Data System (ADS)

Bezdushnyi, R.; Damianova, R.; Tereshina, I. S.; Pankratov, N. Yu.; Nikitin, S. A.

2018-05-01

Magnetic properties of hydrides of the intermetallic compound Nd2Fe14BHx are investigated in the temperature range covering the Curie temperatures (TC) of the compounds (up to 670 K). The temperature dependencies of magnetization are measured under continuous control of hydrogen content in the investigated samples. The dependencies of Curie and spin-reorientation transition (TSR) temperatures on the hydrogen concentration are studied in detail. The dependence of hydrogen concentration on pressure at a constant temperature (near TC) and on the temperature at various pressures are obtained. We attempted to estimate the contributions of the unit cell volume increase upon hydrogenation and the electronic structure change in the variation of TC of the hydrogenated Nd2Fe14 B .

Polarized neutron scattering study of the multiple order parameter system NdB4

NASA Astrophysics Data System (ADS)

Metoki, N.; Yamauchi, H.; Matsuda, M.; Fernandez-Baca, J. A.; Watanuki, R.; Hagihala, M.

2018-05-01

Neutron polarization analysis has been carried out in order to clarify the magnetic structures of multiple order parameter f -electron system NdB4. We confirmed the noncollinear "all-in all-out" structure (Γ4) of the in-plane moment, which is in good agreement with our previous neutron powder diffraction study. We found that the magnetic moment along the c -axis mc showed diagonally antiferromagnetic structure (Γ10), inconsistent with previously reported "vortex" structure (Γ2). The microscopic mixture of these two structures with q⃗0=(0 ,0 ,0 ) appears in phase II and remains stable in phases III and IV, where an incommensurate modulation coexists. The unusual magnetic ordering is phenomenologically understood via Landau theory with the primary order parameter Γ4 coupled with higher-order secondary order parameter Γ10. The magnetic moments were estimated to be 1.8 ±0.2 and 0.2 ±0.05 μB at T =7.5 K for Γ4 and Γ10, respectively. We also found a long-period incommensurate modulation of the q⃗1=(0 ,0 ,1 /2 ) antiferromagnetic structure of mc with the propagation q⃗s 1=(0.14 ,0.14 ,0.1 ) and q⃗s 2=(0.2 ,0 ,0.1 ) in phase III and IV, respectively. The amplitude of sinusoidal modulation was about mc=1.0 ±0.2 μB at T =1.5 K. The local (0 ,0 ,1 /2 ) structure consists of in-plane ferromagnetic and out-of-plane antiferromagnetic coupling of mc, opposite to the coexisting Γ10. The mc of Γ10 is significantly enhanced up to 0.6 μB at T =1.5 K, which is accompanied by the incommensurate modulations. The Landau phenomenological approach indicates that the higher-order magnetic and/or multipole interactions based on the pseudoquartet f -electron state play important roles.

Core–shell PdPb@Pd aerogels with multiply-twinned intermetallic nanostructures: facile synthesis with accelerated gelation kinetics and their enhanced electrocatalytic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Chengzhou; Shi, Qiurong; Fu, Shaofang

Delicately engineering the well-defined noble metal aerogels with favorable structural and compositional features is of vital importance for wide applications. Here, we reported one-pot and facile method for synthesizing core-shell PdPb@Pd hydrogels/aerogels with multiply-twinned grains and ordered intermetallic phase using sodium hypophosphite as a multifunctional reducing agent. Due to the accelerated gelation kinetics induced by increased reaction temperature and specific function of sodium hypophosphite, the formation of hydrogels can be completed within 4 hrs, far faster than the previous reports. Owe to their unique porous structure and favorable geometric and electronic effects, the optimized PdPb@Pd aerogels exhibit enhanced electrochemical performancemore » towards ethylene glycol oxidation with a mass activity of 5.8 times higher than Pd black.Core–shell PdPb@Pd aerogels with multiply-twinned grains and an ordered intermetallic phase was synthesized, which exhibited good electrocatalytic activity towards ethanol oxidation.« less

Joining thick section aluminum to steel with suppressed FeAl intermetallic formation via friction stir dovetailing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reza-E-Rabby, Md.; Ross, Kenneth; Overman, Nicole R.

A new solid-phase technique called friction stir dovetailing (FSD) has been developed for joining thick section aluminum to steel. In FSD, mechanical interlocks are formed at the aluminum-steel interface and are reinforced by metallurgical bonds where intermetallic growth has been uniquely suppressed. Lap shear testing shows superior strength and extension at failure compared to popular friction stir approaches where metallurgical bonding is the only joining mechanism. High resolution microscopy revealed the presence of a 40-70 nm interlayer having a composition of 76.4 at% Al, 18.4 at% Fe, and 5.2 at% Si, suggestive of limited FeAl3 intermetallic formation.

Discovery of Intermetallic Compounds from Traditional to Machine-Learning Approaches.

PubMed

Oliynyk, Anton O; Mar, Arthur

2018-01-16

Intermetallic compounds are bestowed by diverse compositions, complex structures, and useful properties for many materials applications. How metallic elements react to form these compounds and what structures they adopt remain challenging questions that defy predictability. Traditional approaches offer some rational strategies to prepare specific classes of intermetallics, such as targeting members within a modular homologous series, manipulating building blocks to assemble new structures, and filling interstitial sites to create stuffed variants. Because these strategies rely on precedent, they cannot foresee surprising results, by definition. Exploratory synthesis, whether through systematic phase diagram investigations or serendipity, is still essential for expanding our knowledge base. Eventually, the relationships may become too complex for the pattern recognition skills to be reliably or practically performed by humans. Complementing these traditional approaches, new machine-learning approaches may be a viable alternative for materials discovery, not only among intermetallics but also more generally to other chemical compounds. In this Account, we survey our own efforts to discover new intermetallic compounds, encompassing gallides, germanides, phosphides, arsenides, and others. We apply various machine-learning methods (such as support vector machine and random forest algorithms) to confront two significant questions in solid state chemistry. First, what crystal structures are adopted by a compound given an arbitrary composition? Initial efforts have focused on binary equiatomic phases AB, ternary equiatomic phases ABC, and full Heusler phases AB 2 C. Our analysis emphasizes the use of real experimental data and places special value on confirming predictions through experiment. Chemical descriptors are carefully chosen through a rigorous procedure called cluster resolution feature selection. Predictions for crystal structures are quantified by evaluating

In situ Pulsed Laser Deposition of C-Axis Oriented MgB2 Films and Their Characterization

NASA Technical Reports Server (NTRS)

Shinde, Sanjay; Lakew, Brook; Ogale, S. B.; Kulkarni, V. N.; Kale, S. N.; Venkatesan, T.

2004-01-01

The recent discovery of an intermetallic superconductor MgB2 has renewed interest in the area of superconductivity not only because of fundamental understanding of superconductivity but also due to its potential applicability in devices such as thermal detectors. Considerable amount of research has been devoted to obtain MgB2 films by an all in situ growth technique. We have grown MgB2 thin films by an all in situ pulsed laser deposition process from pure B and Mg targets. Ultrathin layers of B and Mg were deposited in a multilayer configuration. Hundreds of such Mg-B bilayers with a capping Mg layer on the top were deposited on sapphire substrate. These depositions were done in high vacuum (approx. 10(exp -7) Torr) and at room temperature. After deposition, such a configuration was annealed at high temperature for a short time in a forming gas (4% H2 in Ar). The best films, obtained by this procedure, showed superconducting transition temperature approx. 30 K. These films have been characterized by x-ray diffraction, Rutherford Backscattering Spectrometry, AC susceptibility-, resistivity- (with and without magnetic field) and 1/f noise-measurements. The physical properties of these films will be presented and discussed.

Investigation of electronic structure and chemical bonding of intermetallic Pd2HfIn: An ab-initio study

NASA Astrophysics Data System (ADS)

Bano, Amreen; Gaur, N. K.

2018-05-01

Ab-initio calculations are carried out to study the electronic and chemical bonding properties of Intermetallic full Heusler compound Pd2HfIn which crystallizes in F-43m structure. All calculations are performed by using density functional theory (DFT) based code Quantum Espresso. Generalized gradient approximations (GGA) of Perdew- Burke- Ernzerhof (PBE) have been adopted for exchange-correlation potential. Calculated electronic band structure reveals the metallic character of the compound. From partial density of states (PDoS), we found the presence of relatively high intensity electronic states of 4d-Pd atom at Fermi level. We have found a pseudo-gap just abouve the Fermi level and N(E) at Fermi level is observed to be 0.8 states/eV, these finding indicates the existence of superconducting character in Pd2HfIn.

Classical ferroelectriclike behavior of highly ordered Pb (S c1 /2N b1 /2)O3 studied by dielectric and Brillouin scattering spectroscopy

NASA Astrophysics Data System (ADS)

Sivasubramanian, V.; Subramanian, V.; Kojima, S.

2016-02-01

The ferroelectric phase transition behavior in the highly ordered Pb (S c1 /2N b1 /2) O3 has been investigated by the dielectric and Brillouin spectroscopy. The dielectric permittivity ɛr exhibits a sharp maximum without any frequency dispersion at its Curie temperature Tc. In the temperature range far above Tc, it was noted that the dielectric permittivity exhibits a noticeable deviation from the Curie-Weiss law below the characteristic intermediate temperature T*=500 K , which is common to most of the Pb-based oxide perovskite relaxors. Upon cooling, the frequency of the longitudinal acoustic phonon mode exhibits a remarkable softening towards Tc. The relaxation time of the order parameter calculated using the Landau-Khalatnikov approach was determined to be more than one order of magnitude lower than that of the disordered Pb (S c1 /2N b1 /2)O3 and is very close to that observed in the paraelectric phase of the classical ferroelectric, BaTi O3 . The observed dielectric and relaxation features are qualitatively discussed in terms of the difference in the strength of the random electric fields.

First-principles screening of structural properties of intermetallic compounds on martensitic transformation

NASA Astrophysics Data System (ADS)

Lee, Joohwi; Ikeda, Yuji; Tanaka, Isao

2017-11-01

Martensitic transformation with good structural compatibility between parent and martensitic phases are required for shape memory alloys (SMAs) in terms of functional stability. In this study, first-principles-based materials screening is systematically performed to investigate the intermetallic compounds with the martensitic phases by focusing on energetic and dynamical stabilities as well as structural compatibility with the parent phase. The B2, D03, and L21 crystal structures are considered as the parent phases, and the 2H and 6M structures are considered as the martensitic phases. In total, 3384 binary and 3243 ternary alloys with stoichiometric composition ratios are investigated. It is found that 187 alloys survive after the screening. Some of the surviving alloys are constituted by the chemical elements already widely used in SMAs, but other various metallic elements are also found in the surviving alloys. The energetic stability of the surviving alloys is further analyzed by comparison with the data in Materials Project Database (MPD) to examine the alloys whose martensitic structures may cause further phase separation or transition to the other structures.

Metal- and intermetallic-matrix composites for aerospace propulsion and power systems

NASA Astrophysics Data System (ADS)

Doychak, J.

1992-06-01

Successful development and deployment of metal-matrix composites and intermetallic- matrix composites are critical to reaching the goals of many advanced aerospace propulsion and power development programs. The material requirements are based on the aerospace propulsion and power system requirements, economics, and other factors. Advanced military and civilian aircraft engines will require higher specific strength materials that operate at higher temperatures, and the civilian engines will also require long lifetimes. The specific space propulsion and power applications require hightemperature, high-thermal-conductivity, and high-strength materials. Metal-matrix composites and intermetallic-matrix composites either fulfill or have the potential of fulfilling these requirements.

Frustration relieved ferrimagnetism in novel A- and B-site-ordered quadruple perovskite.

PubMed

Chen, Wei-tin; Mizumaki, Masaichiro; Saito, Takashi; Shimakawa, Yuichi

2013-07-28

A novel A- and B-site-ordered quadruple perovskite CaCu3Fe2Sb2O12 was obtained and it shows ferrimagnetism below about 170 K. The B-site Fe spin sublattice adapts a tetrahedral framework in a cubic structure and the Fe(3+)-Fe(3+) antiferromagnetic interaction can result in a geometrical spin frustration as seen in a simple perovskite Ca2FeSbO6. With the introduction of Cu(2+) into the A' site, the antiferromagnetic spin frustration is relieved by the strong Cu(2+)-Fe(3+) interaction, and a ferrimagnetic ordering appears at a much higher temperature than the spin-glass transition temperature.

High-Pressure Synthesis: A New Frontier in the Search for Next-Generation Intermetallic Compounds.

PubMed

Walsh, James P S; Freedman, Danna E

2018-06-19

on the cutting-edge methods that made these experiments possible. We review the use of in situ laser heating at high pressure, which led to the discovery of FeBi 2 , the first binary intermetallic compound in the Fe-Bi system. Our work in the Cu-Bi system is described in the context of in situ experiments carried out in the DAC to map its high-pressure phase space, which revealed two intermetallic phases (Cu 11 Bi 7 and CuBi). Finally, we review the discovery of β-NiBi, a novel high-pressure phase in the Ni-Bi system. We hope that this Account will inspire the next generation of solid-state chemists to boldly explore high-pressure phase space.

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

DOEpatents

Rawers, James C.; Alman, David E.; Petty, Jr., Arthur V.

1996-01-01

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

Magnetic Force Microscopy Investigation of Magnetic Domains in Nd2Fe14B

NASA Astrophysics Data System (ADS)

Talari, Mahesh Kumar; Markandeyulu, G.; Rao, K. Prasad

2010-07-01

Remenance and coercivity in Nd2Fe14B materials are strongly dependent on the microstructural aspects like phases morphology and grain size. The coercivity (Hc) of a magnetic material varies inversely with the grain size (D) and there is a critical size below which Hc∝D6. Domain wall pinning by grain boundaries and foreign phases is the important mechanism in explaining the improvement in coercivity and remenance. Nd2Fe14B intermetallic compound with stochiometric composition was prepared from pure elements (Nd -99.5%, Fe—99.95%, B -99.99%) by arc melting in argon atmosphere. Magnetic Force Microscope (MFM) gives high-resolution magnetic domain structural information of ferromagnetic samples. DI-3100 Scanning Probe Microscope with MESP probes was used For MFM characterization of the samples. Magnetic domains observed in cast ingots were very long (up to 40 μm were observed) and approximately 1-5 μm wide due to high anisotropy of the compounds. Magnetic domains have displayed different image contrast and morphologies at different locations of the samples. The domain morphologies and image contrast obtained in this analysis were explained in this paper.

An Investigation of the Microstructure of an Intermetallic Layer in Welding Aluminum Alloys to Steel by MIG Process

PubMed Central

Nguyen, Quoc Manh; Huang, Shyh-Chour

2015-01-01

Butt joints of A5052 aluminum alloy and SS400 steel, with a new type of chamfered edge, are welded by means of metal inert gas welding and ER4043 Al-Si filler metal. The microhardness and microstructure of the joint are investigated. An intermetallic layer is found on the surface of the welding seam and SS400 steel sheet. The hardness of the intermetallic layer is examined using the Vickers hardness test. The average hardness values at the Intermetallic (IMC) layer zone and without the IMC layer zone were higher than that of the welding wire ER4043. The tensile strength test showed a fracture at the intermetallic layer when the tensile strength is 225.9 MPa. The tensile value test indicated the average of welds was equivalent to the 85% tensile strength of the A5052 aluminum alloy. The thickness of the intermetallic layers is non-uniform at different positions with the ranges from 1.95 to 5 μm. The quality of the butt joint is better if the intermetallic layer is minimized. The Si crystals which appeared at the welding seam, indicating that this element participated actively during the welding process, also contributed to the IMC layer’s formation. PMID:28793708

An Investigation of the Microstructure of an Intermetallic Layer in Welding Aluminum Alloys to Steel by MIG Process.

PubMed

Nguyen, Quoc Manh; Huang, Shyh-Chour

2015-12-02

Butt joints of A5052 aluminum alloy and SS400 steel, with a new type of chamfered edge, are welded by means of metal inert gas welding and ER4043 Al-Si filler metal. The microhardness and microstructure of the joint are investigated. An intermetallic layer is found on the surface of the welding seam and SS400 steel sheet. The hardness of the intermetallic layer is examined using the Vickers hardness test. The average hardness values at the Intermetallic (IMC) layer zone and without the IMC layer zone were higher than that of the welding wire ER4043. The tensile strength test showed a fracture at the intermetallic layer when the tensile strength is 225.9 MPa. The tensile value test indicated the average of welds was equivalent to the 85% tensile strength of the A5052 aluminum alloy. The thickness of the intermetallic layers is non-uniform at different positions with the ranges from 1.95 to 5 μm. The quality of the butt joint is better if the intermetallic layer is minimized. The Si crystals which appeared at the welding seam, indicating that this element participated actively during the welding process, also contributed to the IMC layer's formation.

Synthesis of ferromagnetic nanoparticles, formic acid oxidation catalyst nanocomposites, and late-transition metal-boride intermetallics by unique synthetic methods and single-source precursors

NASA Astrophysics Data System (ADS)

Wellons, Matthew S.

The design, synthesis, and characterization of magnetic alloy nanoparticles, supported formic acid oxidation catalysts, and superhard intermetallic composites are presented. Ferromagnetic equatomic alloy nanoparticles of FePt, FePd, and CoPt were synthesized utilizing single-source heteronuclear organometallic precursors supported on an inert water-soluble matrix. Direct conversion of the precursor-support composite to supported ferromagnetic nanoparticles occurs under elevated temperatures and reducing conditions with metal-ion reduction and minimal nanoparticle coalescence. Nanoparticles were easily extracted from the support by addition of water and characterized in structure and magnetic properties. Palladium and platinum based nanoparticles were synthesized with microwave-based and chemical metal-ion reduction strategies, respectively, and tested for catalytic performance in a direct formic acid fuel cell (DFAFC). A study of palladium carbide nanocomposites with various carbonaceous supports was conducted and demonstrated strong activity comparable to commercially available palladium black, but poor catalytic longevity. Platinum-lead alloy nanocomposites synthesized with chemical reduction and supported on Vulcan carbon demonstrated strong activity, excellent catalytic longevity, and were subsequently incorporated into a prototype DFAFC. A new method for the synthesis of superhard ceramics on polymer substrates called Confined Plasma Chemical Deposition (CPCD) was developed. The CPCD method utilizes a tuned Free Electron Laser to selectively decompose the single-source precursor, Re(CO)4(B3H8), in a plasma-like state resulting in the superhard intermetallic ReB2 deposited on polymer substrates. Extension of this method to the synthesis of other hard of superhard ceramics; WB4, RuB2, and B4C was demonstrated. These three areas of research show new synthetic methods and novel materials of technological importance, resulting in a substantial advance in their

Observation of short range order driven large refrigerant capacity in chemically disordered single phase compound Dy2Ni0.87Si2.95.

PubMed

Pakhira, Santanu; Mazumdar, Chandan; Choudhury, Dibyasree; Ranganathan, R; Giri, S

2018-05-16

In this work, we report the successful synthesis of a new intermetallic compound Dy2Ni0.87Si2.95 forming in single phase only with a chemically disordered structure. The random distribution of Ni/Si and crystal defects create a variation in the local electronic environment between the magnetic Dy ions. In the presence of both disorder and competing exchange interactions driven magnetic frustration, originating due to c/a ∼ 1, the compound undergoes spin freezing behaviour below 5.6 K. In the non-equilibrium state below the spin freezing behaviour, the compound exhibits aging phenomena and magnetic memory effects. In the magnetically short-range ordered region, much above the freezing temperature, an unusual occurrence of considerable magnetic entropy change, -ΔSmaxM ∼ 21 J kg-1 K-1 with large cooling power RCP ∼ 531 J kg-1 and adiabatic temperature change, ΔTad ∼ 10 K for a field change of 70 kOe, is observed for this short range ordered cluster-glass compound without any magnetic hysteresis loss.

Synthesis of magnetic CoFe2O4/ordered mesoporous carbon nanocomposites and application in Fenton-like oxidation of rhodamine B.

PubMed

Deng, Jing; Chen, Yi-Jing; Lu, Yu-An; Ma, Xiao-Yan; Feng, Shan-Fang; Gao, Naiyun; Li, Jun

2017-06-01

CoFe 2 O 4 /ordered mesoporous carbon (OMC) nanocomposites were synthesized and tested as heterogeneous peroxymonosulfate (PMS) activator for the removal of rhodamine B. Characterization confirmed that CoFe 2 O 4 nanoparticles were tightly bonded to OMC, and the hybrid catalyst possessed high surface area, pore volume, and superparamagnetism. Oxidation experiments demonstrated that CoFe 2 O 4 /OMC nanocomposites displayed favorable catalytic activity in PMS solution and rhodamine B degradation could be well described by pseudo-first-order kinetic model. Sulfate radicals (SO 4 - ·) were verified as the primary reactive species which was responsible for the decomposition of rhodamine B. The optimum loading ratio of CoFe 2 O 4 and OMC was determined to be 5:1. Under optimum operational condition (catalyst dosage 0.05 g/L, PMS concentration 1.5 mM, pH 7.0, and 25 °C), CoFe 2 O 4 /OMC-activated peroxymonosulfate system could achieve almost complete decolorization of 100 mg/L rhodamine B within 60 min. The enhanced catalytic activity of CoFe 2 O 4 /OMC nanocomposites compared to that of CoFe 2 O 4 nanoparticles could be attributable to the increased adsorption capacity and accelerated redox cycles between Co(III)/Co(II) and Fe(III)/Fe(II).

Cerium-based, intermetallic-strengthened aluminum casting alloy: High-volume co-product development

DOE PAGES

Sims, Zachary C.; Weiss, David; McCall, S. K.; ...

2016-05-23

Here, several rare earth elements are considered by-products to rare earth mining efforts. By using one of these by-product elements in a high-volume application such as aluminum casting alloys, the supply of more valuable rare earths can be globally stabilized. Stabilizing the global rare earth market will decrease the long-term criticality of other rare earth elements. The low demand for Ce, the most abundant rare earth, contributes to the instability of rare earth extraction. In this article, we discuss a series of intermetallic-strengthened Al alloys that exhibit the potential for new high-volume use of Ce. The castability, structure, and mechanicalmore » properties of binary, ternary, and quaternary Al-Ce based alloys are discussed. We have determined Al-Ce based alloys to be highly castable across a broad range of compositions. Nanoscale intermetallics dominate the microstructure and are the theorized source of the high ductility. In addition, room-temperature physical properties appear to be competitive with existing aluminum alloys with extended high-temperature stability of the nanostructured intermetallic.« less

Microstructure and Tribological Properties of Mo–40Ni–13Si Multiphase Intermetallic Alloy

PubMed Central

Song, Chunyan; Wang, Shuhuan; Gui, Yongliang; Cheng, Zihao; Ni, Guolong

2016-01-01

Intermetallic compounds are increasingly being expected to be utilized in tribological environments, but to date their implementation is hindered by insufficient ductility at low and medium temperatures. This paper presents a novel multiphase intermetallic alloy with the chemical composition of Mo–40Ni–13Si (at %). Microstructure characterization reveals that a certain amount of ductile Mo phases formed during the solidification process of a ternary Mo–Ni–Si molten alloy, which is beneficial to the improvement of ductility of intermetallic alloys. Tribological properties of the designed alloy—including wear resistance, friction coefficient, and metallic tribological compatibility—were evaluated under dry sliding wear test conditions at room temperature. Results suggest that the multiphase alloy possesses an excellent tribological property, which is attributed to unique microstructural features and thereby a good combination in hardness and ductility. The corresponding wear mechanism is explained by observing the worn surface, subsurface, and wear debris of the alloy, which was found to be soft abrasive wear. PMID:28774106

Microstructure and Tribological Properties of Mo-40Ni-13Si Multiphase Intermetallic Alloy.

PubMed

Song, Chunyan; Wang, Shuhuan; Gui, Yongliang; Cheng, Zihao; Ni, Guolong

2016-12-06

Intermetallic compounds are increasingly being expected to be utilized in tribological environments, but to date their implementation is hindered by insufficient ductility at low and medium temperatures. This paper presents a novel multiphase intermetallic alloy with the chemical composition of Mo-40Ni-13Si (at %). Microstructure characterization reveals that a certain amount of ductile Mo phases formed during the solidification process of a ternary Mo-Ni-Si molten alloy, which is beneficial to the improvement of ductility of intermetallic alloys. Tribological properties of the designed alloy-including wear resistance, friction coefficient, and metallic tribological compatibility-were evaluated under dry sliding wear test conditions at room temperature. Results suggest that the multiphase alloy possesses an excellent tribological property, which is attributed to unique microstructural features and thereby a good combination in hardness and ductility. The corresponding wear mechanism is explained by observing the worn surface, subsurface, and wear debris of the alloy, which was found to be soft abrasive wear.

Structurally ordered Pt–Zn/C series nanoparticles as efficient anode catalysts for formic acid electrooxidation

DOE PAGES

Zhu, Jing; Zheng, Xin; Wang, Jie; ...

2015-09-15

Controlling the size, composition, and structure of bimetallic nanoparticles is of particular interest in the field of electrocatalysts for fuel cells. In the present work, structurally ordered nanoparticles with intermetallic phases of Pt 3Zn and PtZn have been successfully synthesized via an impregnation reduction method, followed by post heat-treatment. The Pt 3Zn and PtZn ordered intermetallic nanoparticles are well dispersed on a carbon support with ultrasmall mean particle sizes of ~5 nm and ~3 nm in diameter, respectively, which are credited to the evaporation of the zinc element at high temperature. These catalysts are less susceptible to CO poisoning relativemore » to Pt/C and exhibited enhanced catalytic activity and stability toward formic acid electrooxidation. The mass activities of the as-prepared catalysts were approximately 2 to 3 times that of commercial Pt at 0.5 V (vs. RHE). As a result, this facile synthetic strategy is scalable for mass production of catalytic materials.« less

Ordered iron aluminide alloys having an improved room-temperature ductility and method thereof

DOEpatents

Sikka, Vinod K.

1992-01-01

A process is disclosed for improving the room temperature ductility and strength of iron aluminide intermetallic alloys. The process involves thermomechanically working an iron aluminide alloy by means which produce an elongated grain structure. The worked alloy is then heated at a temperature in the range of about 650.degree. C. to about 800.degree. C. to produce a B2-type crystal structure. The alloy is rapidly cooled in a moisture free atmosphere to retain the B2-type crystal structure at room temperature, thus providing an alloy having improved room temperature ductility and strength.

Dendrite segregation in Ni3Al-based intermetallic single crystals alloyed with Cr, Mo, W, Ti, Co, and Re

NASA Astrophysics Data System (ADS)

Drozdov, A. A.; Povarova, K. B.; Morozov, A. E.; Antonova, A. V.; Bulakhtina, M. A.; Alad'ev, N. A.

2015-07-01

The character of dendrite segregation in Ni3Al-based intermetallic VKNA-type alloy single crystals with a dendritic-cellular structure is studied. Distribution coefficient k d of an alloying element (AE) in the alloy during solidification k d = c d.a.I/ c 0 ( c 0 is the AE content in the alloy (liquid phase composition), c d.a.I is the AE content in primary dendrite arms of the alloy (in the solid phase)) and segregation coefficient k s = c d.a.I/ c i.d ( c i.d is the AE content in the interdendritic space) have been found. A comparative study of the dendrite segregation parameters in VKNA-nype Ni3Al-based intermetallic alloys and the well-known ZhS36-type nickel superalloy shows that the intermetallic alloys satisfy to the rule deduced for two- and three-component nickel-based superalloys: if an introduced AE increases the melting temperature of the basic metal, we have k d > 1 (Co, W, Re); if it decreases the melting temperature, we have k d < 1 (Al, Ti, Cr, Mo). Dendrite segregation coefficients k s are dependent on the proportion of the AE contents in the alloys. In nickel superalloys, the dendrite segregation of aluminum, tungsten, and rhenium is higher than that in the intermetallic alloys. The dendrite segregation coefficients of tungsten and rhenium is higher by a factor of 1.5-2 than that in the VKNA-type intermetallic alloys with a low content of refractory metals. This can be due to the retardation of diffusion of refractory metals in the solid phase of a nickel superalloy highly alloyed with these elements.

Self-irradiation damage to the local structure of plutonium and plutonium intermetallics

NASA Astrophysics Data System (ADS)

Booth, C. H.; Jiang, Yu; Medling, S. A.; Wang, D. L.; Costello, A. L.; Schwartz, D. S.; Mitchell, J. N.; Tobash, P. H.; Bauer, E. D.; McCall, S. K.; Wall, M. A.; Allen, P. G.

2013-03-01

The effect of self-irradiation damage on the local structure of δ-Pu, PuAl2, PuGa3, and other Pu intermetallics has been determined for samples stored at room temperature using the extended x-ray absorption fine-structure (EXAFS) technique. These measurements indicate that the intermetallic samples damage at a similar rate as indicated in previous studies of PuCoGa5. In contrast, δ-Pu data indicate a much slower damage accumulation rate. To explore the effect of storage temperature and possible room temperature annealing effects, we also collected EXAFS data on a δ-Pu sample that was held at less than 32 K for a two month period. This sample damaged much more quickly. In addition, the measurable damage was annealed out at above only 135 K. Data from samples of δ-Pu with different Ga concentrations and results on all samples collected from different absorption edges are also reported. These results are discussed in terms of the vibrational properties of the materials and the role of Ga in δ-Pu as a network former.

First-principles study of Al2Sm intermetallic compound on structural, mechanical properties and electronic structure

NASA Astrophysics Data System (ADS)

Lin, Jingwu; Wang, Lei; Hu, Zhi; Li, Xiao; Yan, Hong

2017-02-01

The structural, thermodynamic, mechanical and electronic properties of cubic Al2Sm intermetallic compound are investigated by the first-principles method on the basis of density functional theory. In light of the strong on-site Coulomb repulsion between the highly localized 4f electrons of Sm atoms, the local spin density approximation approach paired with additional Hubbard terms is employed to achieve appropriate results. Moreover, to examine the reliability of this study, the experimental value of lattice parameter is procured from the analysis of the TEM image and diffraction pattern of Al2Sm phase in the AZ31 alloy to verify the authenticity of the results originated from the computational method. The value of cohesive energy reveals Al2Sm to be a stable in absolute zero Kelvin. According to the stability criteria, the subject of this work is mechanically stable. Afterward, elastic moduli are deduced by performing Voigt-Reuss-Hill approximation. Furthermore, elastic anisotropy and anisotropy of sound velocity are discussed. Finally, the calculation of electronic density of states is implemented to explore the underlying mechanism of structural stability.

Influence of Filler Alloy Composition and Process Parameters on the Intermetallic Layer Thickness in Single-Sided Cold Metal Transfer Welding of Aluminum-Steel Blanks

NASA Astrophysics Data System (ADS)

Silvayeh, Zahra; Vallant, Rudolf; Sommitsch, Christof; Götzinger, Bruno; Karner, Werner; Hartmann, Matthias

2017-11-01

Hybrid components made of aluminum alloys and high-strength steels are typically used in automotive lightweight applications. Dissimilar joining of these materials is quite challenging; however, it is mandatory in order to produce multimaterial car body structures. Since especially welding of tailored blanks is of utmost interest, single-sided Cold Metal Transfer butt welding of thin sheets of aluminum alloy EN AW 6014 T4 and galvanized dual-phase steel HCT 450 X + ZE 75/75 was experimentally investigated in this study. The influence of different filler alloy compositions and welding process parameters on the thickness of the intermetallic layer, which forms between the weld seam and the steel sheet, was studied. The microstructures of the weld seam and of the intermetallic layer were characterized using conventional optical light microscopy and scanning electron microscopy. The results reveal that increasing the heat input and decreasing the cooling intensity tend to increase the layer thickness. The silicon content of the filler alloy has the strongest influence on the thickness of the intermetallic layer, whereas the magnesium and scandium contents of the filler alloy influence the cracking tendency. The layer thickness is not uniform and shows spatial variations along the bonding interface. The thinnest intermetallic layer (mean thickness < 4 µm) is obtained using the silicon-rich filler Al-3Si-1Mn, but the layer is more than twice as thick when different low-silicon fillers are used.

Self-Supported Mesostructured Pt-Based Bimetallic Nanospheres Containing an Intermetallic Phase as Ultrastable Oxygen Reduction Electrocatalysts.

PubMed

Kim, Ho Young; Cho, Seonghun; Sa, Young Jin; Hwang, Sun-Mi; Park, Gu-Gon; Shin, Tae Joo; Jeong, Hu Young; Yim, Sung-Dae; Joo, Sang Hoon

2016-10-01

Developing highly active and stable cathode catalysts is of pivotal importance for proton exchange membrane fuel cells (PEMFCs). While carbon-supported nanostructured Pt-based catalysts have so far been the most active cathode catalysts, their durability and single-cell performance are yet to be improved. Herein, self-supported mesostructured Pt-based bimetallic (Meso-PtM; M = Ni, Fe, Co, Cu) nanospheres containing an intermetallic phase are reported, which can combine the beneficial effects of transition metals (M), an intermetallic phase, a 3D interconnected framework, and a mesoporous structure. Meso-PtM nanospheres show enhanced oxygen reduction reaction (ORR) activity, compared to Pt black and Pt/C catalysts. Notably, Meso-PtNi containing an intermetallic phase exhibits ultrahigh stability, showing enhanced ORR activity even after 50 000 potential cycles, whereas Pt black and Pt/C undergo dramatic degradation. Importantly, Meso-PtNi with an intermetallic phase also demonstrated superior activity and durability when used in a PEMFC single-cell, with record-high initial mass and specific activities. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of iron-intermetallics and porosity on tensile and impact properties of aluminum-silicon-copper and aluminum-silicon-magnesium cast alloys

NASA Astrophysics Data System (ADS)

Ma, Zheyuan

Aluminum-silicon (Al-Si) alloys are an important class of materials that constitute the majority of aluminum cast parts produced, due to their superior properties and excellent casting characteristics. Within this family of alloys, Al-Si-Cu and Al-Si-Mg cast alloys are frequently employed in automotive applications. The commercially popular 319 and 356 alloys, representing these two alloy systems, were selected for study in the present work, with the aim of investigating the effect of iron intermetallics and porosity on the alloy performance. This was carried out through a study of the tensile and impact properties, these being two of the important mechanical properties used in design calculations. Iron, through the precipitation of second phase intermetallic constituents, in particular the platelike beta-Al5FeSi phase, is harmful to the alloy properties. Likewise, gas- or shrinkage porosity in castings is also detrimental to the mechanical properties. By determining the optimum alloying, melt processing and solidification parameters (viz., Fe content, Sr modification and cooling rate) required to minimize the harmful effects of porosity and iron intermetallics, and studying their role on the fracture behavior, the fracture mechanism in the alloys could be determined. Castings were prepared from both industrial and experimental 319.2, B319.2 and A356.2 alloy melts, containing Fe levels of 0.2--1.0 wt%. Sr-modified (˜200 ppm) melts were also prepared for each alloy Fe level. The end-chilled refractory mold used provided directional solidification and a range of cooling rates (or dendrite arm spacings, DAS) within the same casting. Tensile and impact test samples machined from specimen blanks sectioned from the castings at various heights above the chill end provided DASs of 23--85mum. All samples were T6-heat-treated before testing. Tests were carried out employing Instron Universal and Instrumented Charpy testing machines. Optical microscopy, image analysis, SEM

Control Al/Mg intermetallic compound formation during ultrasonic-assisted soldering Mg to Al.

PubMed

Xu, Zhiwu; Li, Zhengwei; Li, Jiaqi; Ma, Zhipeng; Yan, Jiuchun

2018-09-01

To prevent the formation of Al/Mg intermetallic compounds (IMCs) of Al 3 Mg 2 and Al 12 Mg 17 , dissimilar Al/Mg were ultrasonic-assisted soldered using Sn-based filler metals. A new IMC of Mg 2 Sn formed in the soldered joints during this process and it was prone to crack at large thickness. The thickness of Mg 2 Sn was reduced to 22 μm at 285 °C when using Sn-3Cu as the filler metal. Cracks were still observed inside the blocky Mg 2 Sn. The thickness of Mg 2 Sn was significantly reduced when using Sn-9Zn as the filler metal. A 17 μm Mg 2 Sn layer without crack was obtained at a temperature of 200 °C, ultrasonic power of Mode I, and ultrasonic time of 2 s. The shear strengths of the joints using Sn-9Zn was much higher than those using Sn-3Cu because of the thinner Mg 2 Sn layer in the former joints. Sn whiskers were prevented by using Sn-9Zn. A cavitation model during ultrasonic assisted soldering was proposed. Copyright © 2018 Elsevier B.V. All rights reserved.

The μ3 model of acids and bases: extending the Lewis theory to intermetallics.

PubMed

Stacey, Timothy E; Fredrickson, Daniel C

2012-04-02

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 Hückel calculations. We begin by illustrating that the third and fourth moments (μ(3) and μ(4)) of the electronic density of states (DOS) distribution tune the properties of a pseudogap. μ(3) controls the balance of states above and below the DOS minimum, with μ(4) then determining the minimum's depth. In this way, μ(3) predicts an ideal occupancy for the DOS distribution. The μ(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 μ(3)-ideal as μ(3)-acidic, and those that are electron-rich as μ(3)-basic. The reaction of μ(3) acids and bases, whether in the formation of a Lewis acid/base adduct or an intermetallic phase, tends to neutralize the μ(3) acidity or basicity of the reactants. This μ(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 μ(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.

Synthesis, Structure, and Complex Magnetism of MIr 2In 8 (M = Eu, Sr)

DOE PAGES

Calta, Nicholas P.; L. Bud’ko, Sergey; Rodriguez, Alexandra P.; ...

2016-03-07

In this paper, we report the synthesis, crystal structure, and physical properties of two new polar intermetallic compounds, EuIr 2In 8 and SrIr 2In 8. Both were synthesized in good yield using In metal as a reactive flux medium, enabling the growth of large crystals for physical property measurements. They crystallize in the orthorhombic space group Pbam with the CeFe 2Al 8 structure type, which is sometimes also referred to as the CaCo 2Al 8 structure type. The two analogues have unit cell parameters of a = 13.847(3) Å, b = 16.118(3) Å, and c = 4.3885(9) Å for Mmore » = Eu and a = 13.847(3) Å, b = 16.113(3) Å, and c = 4.3962(9) Å for M = Sr at room temperature. SrIr 2In 8 is a diamagnetic metal with no local magnetic moments on either the Sr or Ir sites, and the diamagnetic contribution from core electrons overwhelms the expected Pauli paramagnetism normally seen in intermetallic compounds. Magnetism in EuIr 2In 8 is dominated by the local Eu moments, which order antiferromagnetically at 5 K in low applied fields. Increasing the field strength depresses the magnetic ordering temperature and also induces a spin reorientation at lower temperature, indicating complex competing magnetic interactions. Finally, low-temperature heat capacity measurements show a significant enhancement of the Sommerfeld coefficient in EuIr 2In 8 relative to that in SrIr 2In 8, with estimated values of γ = 118(3) and 18.0(2) mJ mol –1 K –2, respectively.« less

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

PubMed

Berns, Veronica M; Fredrickson, Daniel C

2014-10-06

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

Intermetallic Precipitation in Low-Density Steel

NASA Astrophysics Data System (ADS)

Chatterjee, S.; Chatterjee, A.; Chakrabarti, D.

2018-06-01

Low-density steels (LDS) represent a relatively new class of material that contains a large concentration of aluminum. In the present work, we studied the effect of copper addition to these steels. Microanalysis and electron diffraction study were used to demonstrate that on the contrary to the theoretical expectation, copper formed a variety of intermetallic, instead of metallic, precipitates on reaction with aluminum. The precipitation led to a significant age-hardening response that imparted a special characteristic to this material, which had never been reported previously.

Surface improvement and biocompatibility of TiAl 24Nb 10 intermetallic alloy using rf plasma nitriding

NASA Astrophysics Data System (ADS)

Abd El-Rahman, A. M.; Maitz, M. F.; Kassem, M. A.; El-Hossary, F. M.; Prokert, F.; Reuther, H.; Pham, M. T.; Richter, E.

2007-09-01

The present work describes the surface improvement and biocompatibility of TiAl 24Nb 10 intermetallic alloy using rf plasma nitriding. The nitriding process was carried out at different plasma power from 400 W to 650 W where the other plasma conditions were fixed. Grazing incidence X-ray diffractometry (GIXRD), Auger electron spectroscopy (AES), tribometer and a nanohardness tester were employed to characterize the nitrided layer. Further potentiodynamic polarization method was used to describe the corrosion behavior of the un-nitrided and nitrided alloy. It has been found that the Vickers hardness (HV) and corrosion resistance values of the nitrided layers increase with increasing plasma power while the wear rates of the nitrided layers reduce by two orders of magnitude as compared to those of the un-nitrided layer. This improvement in surface properties of the intermetallic alloy is due to formation of a thin modified layer which is composed of titanium nitride in the alloy surface. Moreover, all modified layers were tested for their sustainability as a biocompatible material. Concerning the application area of biocompatibility, the present treated alloy show good surface properties especially for the nitrided alloy at low plasma power of 400 W.

Magnetic ground states in the three O s6 + (5 d2 ) double perovskites B a2M Os O6 (M =Mg ,Zn,and Cd) from Néel order to its suppression

NASA Astrophysics Data System (ADS)

Marjerrison, C. A.; Thompson, C. M.; Sharma, A. Z.; Hallas, A. M.; Wilson, M. N.; Munsie, T. J. S.; Flacau, R.; Wiebe, C. R.; Gaulin, B. D.; Luke, G. M.; Greedan, J. E.

2016-10-01

Three closely related double perovskites (DP) based on the 5 d2 ion, O s6 +,B a2M Os O6 , with M =Mg , Zn, and Cd have been prepared and characterized using x-ray (XRD) and neutron diffraction (ND), dc magnetization, heat capacity, and muon spin relaxation (μ SR ) techniques. All three are cubic, Fm-3 m , at ambient temperature from XRD with Δ d /d ˜5 ×10-4 resolution. For both M =Mg and Zn, ND data at 3.5 K and lower, Δ d /d =2 ×10-3 , resolution show no signs of a distortion. The results are compared with the known DP material, B a2CaOs O6 , which shows antiferromagnetic (AF) order below TN=49 K and a moderate frustration index, f ˜4 , (f =| θCW|/ TN ), where θCW is the Curie-Weiss temperature. B a2MgOs O6 with a unit cell constant a0=8.0757 (1 ) Å , 3% smaller than for B a2CaOs O6 , also shows Néel order below TN=51 K with f ˜2 . However, B a2ZnOs O6,a0=8.0975 (1 ) Å , 0.27% larger than B a2MgOs O6 , does not show Néel order from either heat capacity or μ SR data. A zero field cooled/field cooled (ZFC/FC) irreversibility occurs near 30 K and a broad heat capacity anomaly is detected at a similar temperature. The μ SR data are consistent with a weak spin ordering with an onset below 28 K but with a coexisting dynamic component. B a2CdOs O6 with a0=8.3190 (1 ) Å , 0.5% smaller than B a2CaOs O6 , shows no evidence for any type of order/spin freezing to 0.47 K from any of the measurement techniques applied. The results for M =Zn and Cd appear to lie outside of the mean field theory of Chen and Balents [Phys. Rev. B 84, 094420 (2011), 10.1103/PhysRevB.84.094420] for cubic d2 DP with strong spin orbit coupling, but B a2MgOs O6 , along with B a2CaOs O6 , is likely one of the three predicted AF phases. The remarkable contrast between the doppelgänger pairs M =Mg /Zn and M =Ca /Cd may be traceable to differences in electronic structure of the diamagnetic M ions. All of the super-super exchange pathways in these DP materials involve Os-O-M -O-Os linkages.

High-Temperature Oxidation of Fe3Al Intermetallic Alloy Prepared by Additive Manufacturing LENS

PubMed Central

Łyszkowski, Radosław

2015-01-01

The isothermal oxidation of Fe-28Al-5Cr (at%) intermetallic alloy microalloyed with Zr and B (<0.08 at%) in air atmosphere, in the temperature range of 1000 to 1200 °C, was studied. The investigation was carried out on the thin-walled (<1 mm) elements prepared by Laser Engineered Net Shaping (LENS) from alloy powder of a given composition. Characterization of the specimens, after the oxidation, was conducted using X-ray diffraction (XRD) and scanning electron microscopy (SEM, with back-scatter detector (BSE) and energy-dispersive X-ray spectroscopy (EDS) attachments). The investigation has shown, that the oxidized samples were covered with a thin, homogeneous α-Al2O3 oxide layers. The intensity of their growth indicates that the material lost its resistance to oxidation at 1200 °C. Structural analysis of the thin-walled components’ has not shown intensification of the oxidation process at the joints of additive layers. PMID:28788014

Grain refinement of 7075Al alloy microstructures by inoculation with Al-Ti-B master alloy

NASA Astrophysics Data System (ADS)

Hotea, V.; Juhasz, J.; Cadar, F.

2017-05-01

This paper aims to bring some clarification on grain refinement and modification of high strength alloys used in aerospace technique. In this work it was taken into account 7075 Al alloy, and the melt treatment was carried out by placing in the form of master alloy wire ternary AlTiB the casting trough at 730°C. The morphology of the resulting microstructures was characterized by optical microscopy. Micrographs unfinished and finished with pre-alloy containing ternary Al5Ti1B evidence fine crystals, crystal containing no columnar structure and highlights the size of the dendrites, and intermetallic phases occurring at grain boundaries in Al-Zn-Mg-Cu alloy. It has been found that these intermetallic compounds are MgZn2 type. AlTiB master alloys finishing ensures a fine eutectic structure, which determines the properties of hardware and improving the mechanical properties of aluminum alloys used in aeronautical engineering.

Relaxor-like ferroelectric behaviour favoured by short-range B-site ordering in 10% Ba{sup 2+} substituted MgFe{sub 2}O{sub 4}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chithra Lekha, P.; Ramesh, G.; Revathi, V.

2014-05-01

Graphical abstract: - Highlights: • Mechanism driving polarization in MgFe{sub 2}O{sub 4} is the Maxwell–Wagner polarization. • But Raman studies confirm the existence of local P4{sub 1}22/P4{sub 3}22 symmetry in MgFe{sub 2}O{sub 4}. • Ba{sup 2+} substitution increases ferroelectric ordering, ΔT{sub m} span, and masks electronic contribution. - Abstract: Using the molten salt method, pristine and Ba{sup 2+} substituted MgFe{sub 2}O{sub 4} are prepared. The relaxor-like behaviour observed in the dielectric dispersion indicates the existence of B-site short-range ordering with the local P4{sub 1}22/P4{sub 3}22 symmetry which is confirmed by the Raman spectroscopy. The paper further analyses the origin ofmore » polarization using Maxwell–Wagner fit and Nyquist plot. This work suggests a possible way to increase the relaxor-like ferroelectric ordering, larger span of relaxation temperature (ΔT{sub m}) and the effective masking of electronic contribution by the substitution of Ba{sup 2+} ion.« less

Thermodynamic, electronic and magnetic properties of intermetallic compounds through statistical models

NASA Astrophysics Data System (ADS)

Cadeville, M. C.; Pierron-Bohnes, V.; Bouzidi, L.; Sanchez, J. M.

1993-01-01

Local and average electronic and magnetic properties of transition metal alloys are strongly correlated to the distribution of atoms on the lattice sites. The ability of some systems to form long range ordered structures at low temperature allows to discuss their properties in term of well identified occupation operators as those related to long range order (LRO) parameters. We show that using theoretical determinations of these LRO parameters through statistical models like the cluster variation method (CVM) developed to simulate the experimental phase diagrams, we are able to reproduce a lot of physical properties. In this paper we focus on two points: (i) a comparison between CVM results and an experimental determination of the LRO parameter by NMR at 59Co in a CoPt3 compound, and (ii) the modelling of the resistivity of ferromagnetic and paramagnetic intermetallic compounds belonging to Co-Pt, Ni-Pt and Fe-Al systems. All experiments were performed on samples in identified thermodynamic states, implying that kinetic effects are thoroughly taken into account.

Electrochemical Hydrogen Evolution at Ordered Mo 7 Ni 7

DOE Office of Scientific and Technical Information (OSTI.GOV)

Csernica, Peter M.; McKone, James R.; Mulzer, Catherine R.

2017-04-11

Ni–Mo alloys containing up to ~15 mol % Mo are excellent non-noble electrocatalysts for the hydrogen evolution reaction (HER) in alkaline aqueous electrolytes. To date, studies have not addressed the details of HER activity of ordered Ni–Mo intermetallic compounds, which can contain a significantly larger fraction of Mo (up to 50 mol %) than can be accessed through high-temperature alloying. Here, we present a straightforward and facile synthesis of three phase-pure electrocatalyst powders using a precipitation–reduction approach: ordered Mo7Ni7, disordered Ni0.92Mo0.08, and pure Ni. The Ni0.92Mo0.08 alloy exhibited a nearly 10-fold higher mass-specific HER activity than either pure Ni ormore » Mo7Ni7, where much of the difference could be attributed to relative surface area. Therefore, we attempted to quantify and account for differences in surface areas using electron microscopy, impedance spectroscopy, and gas adsorption measurements. These data suggest that Ni–Mo alloys and intermetallic compounds exhibit substantial pseudocapacitance at potentials near the onset of hydrogen evolution, which can cause impedance spectroscopy to overestimate the interfacial capacitance, and thus the electrochemically active surface area, of these materials. From these observations, we postulate Mo redox activity as the chemical basis for the observed pseudocapacitance of Ni–Mo composites. Furthermore, using gas adsorption measurements, rather than capacitance, to estimate active surface area, we find that ordered Mo7Ni7 is more intrinsically active than the Ni0.92Mo0.08 alloy, implying that Mo7Ni7 intermetallics with high surface area will also give higher mass-specific activities than alloys with comparable roughness.« less

Unexpected Magnetic Ordering on the Cr Substructure in UCr2Si2C and Structural Relationships in Quaternary U-Cr-Si-C Compounds.

PubMed

Lemoine, Pierric; Vernière, Anne; Pasturel, Mathieu; Venturini, Gérard; Malaman, Bernard

2018-03-05

Previous experimental and theoretical studies revealed that carbon insertion into the RCr 2 Si 2 compounds drastically affects the magnetic behavior, since chromium does not carry any magnetic moment in RCr 2 Si 2 C (R = Y, La-Sm, Gd-Er) compounds in contrast to RCr 2 Si 2 (R = Y, Sm, Gd-Lu, Th) compounds. In this study, we report on the unexpected magnetic ordering of chromium atoms in the isotype quaternary UCr 2 Si 2 C compound. While specific heat and magnetic measurements suggest a Pauli paramagnetic behavior, neutron powder diffraction reveals an antiferromagnetic ordering of the chromium substructure at high temperature ( T N > 300 K), while that of uranium remains nonmagnetically ordered down to 2 K. Its magnetic behavior, inverse in comparison to the RCr 2 Si 2 C carbides involving a magnetic lanthanide, is discussed in relation with the singularity of its crystal structure among the series. Moreover, the crystallographic structures and the structural stability of UCr 2 Si 2 C and of two other quaternary U-Cr-Si-C compounds (i.e., UCr 3 Si 2 C and U 2 Cr 3 Si 2 C 3 ), based on the full occupancy of interstitial sites by carbon atoms, are discussed and compared to those of the related ternary intermetallics. Finally, the low-temperature form of UCr 2 Si 2 , corresponding to a displacive transformation around 210 K of the ThCr 2 Si 2 -type structure, is reinvestigated by considering a higher symmetry monoclinic unit cell ( C2/ m) instead of the previously reported triclinic cell ( P1̅). The antiferromagnetic ordering at low temperature ( T N = 30(2) K) of the uranium substructure is confirmed, and its magnetic structure is reanalyzed and discussed considering the monoclinic crystal structure.

Examination of Multiphase (Zr,Ti)(V,Cr,Mn,Ni)2 Ni-MH Electrode Alloys: Part II. Solid-State Transformation of the Interdendritic B2 Phase

NASA Astrophysics Data System (ADS)

Bendersky, L. A.; Wang, K.; Boettinger, W. J.; Newbury, D. E.; Young, K.; Chao, B.

2010-08-01

Solidification microstructure of multicomponent (Zr,Ti)-Ni-(V,Cr,Mn,Co) alloys intended for use as negative electrodes in Ni-metal hydride (Ni-MH) batteries was studied in Part I of this series of articles. Part II of the series examines the complex internal structure of the interdendritic grains formed by solid-state transformation and believed to play an important role in the electrochemical charge/discharge characteristics of the overall alloy composition. By studying one alloy, Zr21Ti12.5V10Cr5.5Mn5.1Co5.0Ni40.2Al0.5Sn0.3, it is shown that the interdendritic grains solidify as a B2 (Ti,Zr)44(Ni,TM)56 phase, and then undergo transformation to Zr7Ni10-type, Zr9Ni11-type, and martensitic phases. The transformations obey orientation relationships between the high-temperature B2 phase and the low-temperature Zr-Ni-type intermetallics, and consequently lead to a multivariant structure. The major orientation relationship for the orthorhombic Zr7Ni10 type is [011]Zr7Ni10//[001]B2; (100)Zr7Ni10//(100)B2. The orientation relationship for the tetragonal Zr9Ni11 type is [001]Zr9Ni11//[001]B2; (130)Zr9Ni11//(100)B2. Binary Ni-Zr and ternary Ti-Ni-Zr phase diagrams were used to rationalize the formation of the observed domain structure.

Sub-4 nm PtZn Intermetallic Nanoparticles for Enhanced Mass and Specific Activities in Catalytic Electrooxidation Reaction

DOE PAGES

Qi, Zhiyuan; Xiao, Chaoxian; Liu, Cong; ...

2017-03-08

Atomically ordered intermetallic nanoparticles (iNPs) have sparked considerable interest in fuel cell applications by virtue of their exceptional electronic and structural properties. However, the synthesis of small iNPs in a controllable manner remains a formidable challenge because of the high temperature generally required in the formation of intermetallic phases. Here in this paper we report a general method for the synthesis of PtZn iNPs (3.2 ± 0.4 nm) on multiwalled carbon nanotubes (MWNT) via a facile and capping agent free strategy using a sacrificial mesoporous silica (mSiO 2) shell. The as-prepared PtZn iNPs exhibited ca. 10 times higher mass activitymore » in both acidic and basic solution toward the methanol oxidation reaction (MOR) compared to larger PtZn iNPs synthesized on MWNT without the mSiO 2 shell. Density functional theory (DFT) calculations predict that PtZn systems go through a “non-CO” pathway for MOR because of the stabilization of the OH* intermediate by Zn atoms, while a pure Pt system forms highly stable COH* and CO* intermediates, leading to catalyst deactivation. Experimental studies on the origin of the backward oxidation peak of MOR coincide well with DFT predictions. Moreover, the calculations demonstrate that MOR on smaller PtZn iNPs is energetically more favorable than larger iNPs, due to their high density of corner sites and lower-lying energetic pathway. Therefore, smaller PtZn iNPs not only increase the number but also enhance the activity of the active sites in MOR compared with larger ones. This work opens a new avenue for the synthesis of small iNPs with more undercoordinated and enhanced active sites for fuel cell applications.« less

Sub-4 nm PtZn Intermetallic Nanoparticles for Enhanced Mass and Specific Activities in Catalytic Electrooxidation Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qi, Zhiyuan; Xiao, Chaoxian; Liu, Cong

2017-03-22

Atomically ordered intermetallic nanoparticles (iNPs) have sparked considerable interest in fuel cell applications by virtue of their exceptional electronic and structural properties. However, the synthesis of small iNPs in a controllable manner remains a formidable challenge because of the high temperature generally required in the formation of intermetallic phases. Here we report a general method for the synthesis of PtZn. iNPs (3.2 +/- 0.4 nm) on multiwalled carbon nanotubes (MWNT) via a facile and capping agent free strategy using a sacrificial mesoporous silica (mSiO(2)) shell. The as-prepared PtZn iNPs exhibited ca. 10 times higher mass activity in both acidic andmore » basic solution toward the methanol oxidation reaction (MOR) compared to larger PtZn iNPs synthesized on MWNT without the mSiO2 shell. Density functional theory (DFT) calculations predict that PtZn systems go through a "non-CO" pathway for MOR because of the stabilization of the OH* intermediate by Zn atoms, while a pure Pt system forms highly stable COH* and CO* intermediates, leading to catalyst deactivation. Experimental studies on the origin of the backward oxidation peak of MOR coincide well with DFT predictions. Moreover, the calculations demonstrate that MOR on smaller PtZn iNPs is energetically more favorable than larger iNPs, due to their high density of corner sites and lower-lying energetic pathway. Therefore, smaller PtZn iNPs not only increase the number but also enhance the activity of the active sites in MOR compared with larger ones. This work opens a new avenue for the synthesis of small iNPs with more undercoordinated and enhanced active sites for fuel cell applications.« less

Section 2: Phase transformation studies in mechanically alloyed Fe-Nz and Fe-Zn-Si intermetallics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, A.; Uwakweh, O.N.C.; Maziasz, P.J.

1997-04-01

The initial stage of this study, which was completed in FY 1995, entailed an extensive analysis characterizing the structural evolution of the Fe-Zn intermetallic system. The primary interest in these Fe-Zn phases stems from the fact that they form an excellent coating for the corrosion protection of steel (i.e., automobile body panels). The Fe-Zn coating generally forms up to four intermetallic phases depending on the particular industrial application used, (i.e., galvanization, galvannealing, etc.). Since the different coating applications are non-equilibrium in nature, it becomes necessary to employ a non-equilibrium method for producing homogeneous alloys in the solid-state to reflect themore » structural changes occurring in a true coating. This was accomplished through the use of a high energy/non-equilibrium technique known as ball-milling which allowed the authors to monitor the evolution process of the alloys as they transformed from a metastable to stable equilibrium state. In FY 1996, this study was expanded to evaluate the presence of Si in the Fe-Zn system and its influence in the overall coating. The addition of silicon in steel gives rise to an increased coating. However, the mechanisms leading to the coating anomaly are still not fully understood. For this reason, mechanical alloying through ball-milling of pure elemental powders was used to study the structural changes occurring in the sandelin region (i.e., 0.12 wt % Si). Through the identification of invariant reactions (i.e., eutectic, etc.) the authors were able to explore the sandelin phenomenon and also determine the various fields or boundaries associated with the Fe-Zn-Si ternary system.« less

Plasma sprayed ceramic thermal barrier coating for NiAl-based intermetallic alloys

NASA Technical Reports Server (NTRS)

Miller, Robert A. (Inventor); Doychak, Joseph (Inventor)

1994-01-01

A thermal barrier coating system consists of two layers of a zirconia-yttria ceramic. The first layer is applied by low pressure plasma spraying. The second layer is applied by conventional atmospheric pressure plasma spraying. This facilitates the attachment of a durable thermally insulating ceramic coating directly to the surface of a highly oxidation resistant NiAl-based intermetallic alloy after the alloy has been preoxidized to promote the formation of a desirable Al2O3 scale.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chenyu; Chen, Dennis P.; Unocic, Raymond R.

The high performance of Pd-based intermetallic nanocatalysts has the potential to replace Pt-containing catalysts for fuel-cell reactions. Conventionally, intermetallic particles are obtained through the annealing of nanoparticles of a random alloy distribution. However, this method inevitably leads to sintering of the nanoparticles and generates polydisperse samples. Here, monodisperse PdCu nanoparticles with the ordered B2 phase were synthesized by seed-mediated co-reduction using PdCu nanoparticle seeds with a random alloy distribution (A1 phase). A time-evolution study suggests that the particles must overcome a size-dependent activation barrier for the ordering process to occur. Characterization of the as-prepared PdCu B2 nanoparticles by electron microscopymore » techniques revealed surface segregation of Pd as a thin shell over the PdCu core. The ordered nanoparticles exhibit superior activity and durability for the oxygen reduction reaction in comparison with PdCu A1 nanoparticles. This seed-mediated co-reduction strategy produced monodisperse nanoparticles ideally suited for structure–activity studies. Furthermore, the study of their growth mechanism provides insights into the size dependence of disorder–order transformations of bimetallic alloys at the nanoscale, which should enable the design of synthetic strategies toward other intermetallic systems.« less

Fabrication of an r-Al2Ti intermetallic matrix composite reinforced with α-Al2O3 ceramic by discontinuous mechanical milling for thermite reaction

NASA Astrophysics Data System (ADS)

Mosleh, A.; Ehteshamzadeh, M.; Taherzadeh Mousavian, R.

2014-10-01

In this study, a powder mixture with an Al/TiO2 molar ratio of 10/3 was used to form an r-Al2Ti intermetallic matrix composite (IMC) reinforced with α-Al2O3 ceramic by a novel milling technique, called discontinuous mechanical milling (DMM) instead of milling and ignition of the produced thermite. The results of energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) of samples with varying milling time indicate that this fabrication process requires considerable mechanical energy. It is shown that Al2Ti-Al2O3 IMC with small grain size was produced by DMM after 15 h of ball milling. Peaks for γ-TiAl as well as Al2Ti and Al2O3 are observed in XRD patterns after DMM followed by heat treatment. The microhardness of the DMM-treated composite produced after heat treatment was higher than Hv 700.

Suppressors made from intermetallic materials

DOEpatents

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

2014-11-04

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

Grain Refinement of Al-Si-Fe-Cu-Zn-Mn Based Alloy by Al-Ti-B Alloy and Its Effect on Mechanical Properties.

PubMed

Yoo, Hyo-Sang; Kim, Yong-Ho; Jung, Chang-Gi; Lee, Sang-Chan; Lee, Seong-Hee; Son, Hyeon-Taek

2018-03-01

We investigated the effects of Al-5.0wt%Ti-1.0wt%B addition on the microstructure and mechanical properties of the as-extruded Al-0.15wt%Si-0.2wt%Fe-0.3wt%Cu-0.15wt%Zn-0.9wt%Mn based alloys. The Aluminum alloy melt was held at 800 °C and then poured into a mould at 200 °C. Aluminum alloys were hot-extruded into a rod that was 12 mm in thickness with a reduction ratio of 38:1. AlTiB addition to Al-0.15Si-0.2Fe-0.3Cu-0.15Zn-0.9Mn based alloys resulted in the formation of Al3Ti and TiB2 intermetallic compounds and grain refinement. With increasing of addition AlTiB, ultimate tensile strength increased from 93.38 to 99.02 to 100.01 MPa. The tensile strength of the as-extruded alloys was improved due to the formation of intermetallic compounds and grain refinement.

A highly active PtCu3 intermetallic core-shell, multilayered Pt-skin, carbon embedded electrocatalyst produced by a scale-up sol-gel synthesis.

PubMed

Bele, M; Jovanovič, P; Pavlišič, A; Jozinović, B; Zorko, M; Rečnik, A; Chernyshova, E; Hočevar, S; Hodnik, N; Gaberšček, M

2014-11-07

We present a novel, scaled-up sol-gel synthesis which enables one to produce 20 g batches of highly active and stable carbon supported PtCu3 nanoparticles as cathode materials for low temperature fuel cell application. We confirm the presence of an ordered intermetallic phase underneath a multilayered Pt-skin together with firm embedment of nanoparticles in the carbon matrix.

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

PubMed

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

2011-09-01

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. Copyright © 2011 Elsevier B.V. All rights reserved.

The growth of protective ultra-thin alumina layers on γ-TiAl(1 1 1) intermetallic single-crystal surfaces

NASA Astrophysics Data System (ADS)

Maurice, V.; Despert, G.; Zanna, S.; Josso, P.; Bacos, M.-P.; Marcus, P.

2005-12-01

An XPS and AES study of the early stages of oxidation of γ-TiAl(1 1 1) surfaces at 650 °C under 1.0 × 10 -7-1.0 × 10 -6 mbar O 2 is reported. The data evidence a first regime of oxidation characterized by the growth of a pure alumina layer followed by a second regime of simultaneous oxidation of both alloying elements. In the first regime, continuous alumina layers from ˜0.4 to ˜1.5 nm thick have been observed by angle-resolved XPS. The composition of the metallic phase underneath the growing oxide is modified by a depletion of Al and the injection of Al vacancies in the metal during the growth of the transient alumina formed at 650 °C. The onset of Ti oxidation was repeatedly observed for a critical concentration in the modified region of the alloy underneath the alumina layer: Ti 75±2Al 25±2 (Ti 50Al 17±2V(Al) 33±2), showing that decreasing the number of Ti-Al bonds in the modified intermetallic region increases the activity of Ti up to a critical point where its oxidation at the oxide/metal interface becomes competitive with that of Al. The growth of Ti 3+ and Ti 4+ oxide particles observed above the alumina layer by angle-resolved XPS indicates the transport of titanium cations trough the alumina layer and their subsequent reaction with oxygen at the outer gas/oxide interface. Improving structural ordering in the intermetallic phase slows down the growth kinetics of the alumina layer and the related Al-depletion of the substrate, and increases the resistance of the alloy to the subsequent oxidation of Ti. This is assigned to two combined effects: a slower diffusion of Al in the better ordered metallic phase and the growth of less defective alumina layers allowing to slow down the ionic transport through the oxide. Highly stable and corrosion resistant alloy surfaces covered by a 0.4 nm thick alumina layer have been obtained by slowly oxidizing the alloy at lower partial pressure (<5.0 × 10 -10 mbar O 2).

Corrosive sliding wear behavior of laser clad Mo 2Ni 3Si/NiSi intermetallic coating

NASA Astrophysics Data System (ADS)

Lu, X. D.; Wang, H. M.

2005-05-01

Many ternary metal silicides such as W 2Ni 3Si, Ti 2Ni 3Si and Mo 2Ni 3Si with the topologically closed-packed (TCP) hP12 MgZn 2 type Laves phase crystal structure are expected to have outstanding wear and corrosion resistance due to their inherent high hardness and sluggish temperature dependence and strong atomic bonds. In this paper, Mo 2Ni 3Si/NiSi intermetallic coating was fabricated on substrate of an austenitic stainless steel AISI321 by laser cladding using Ni-Mo-Si elemental alloy powders. Microstructure of the coating was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). Wear resistance of the coating is evaluated under corrosive sliding wear test condition. Influence of corrosion solutions on the wear resistance of the coating was studied and the wear mechanism was discussed based on observations of worn surface morphology. Results showed that the laser clad Mo 2Ni 3Si/NiSi composite coating have a fine microstructure of Mo 2Ni 3Si primary dendrites and the interdendritic Mo 2Ni 3Si/NiSi eutectics. The coating has excellent corrosive wear resistance compared with austenitic stainless steel AISI321 under acid, alkaline and saline corrosive environments.

Magnetic behavior of R 2Co 14B hydrides (R = La, Pr, Sm, Gd, Tb and Y)

NASA Astrophysics Data System (ADS)

Zhang, L. Y.; Pourarian, F.; Wallace, W. E.

1988-08-01

The structure and magnetic properties of R 2Co 14B sysstems(R = La, Pr, Nd, Sm, Gd, Tb and Y) and their hydrides were studied by means of bulk magnetometry. All R 2Co 14B hydrides presently studied occur in the tetragonal Nd 2Fe 14B-type crystal structure. The composition-temperature isotherms measured fro selected Gd- and Nd- containing systems exhibit some indication of a platuau pressure at higher hydrogen concentrations. Hydrogenation expands the unit volume, Vc, by 1.5 to 3.0%, depending on the nature of R and the content of hydrogen. It was found that introduction of hydrogen into the lattice decreases Ms of the Co sublittice. This is attributed to the effect of electron charge transfer from Hto Co-3d sublittice. Hydrogennation significantly decreases the anistropy fields, HA, and the spin-reorientation transition temperatur, TSR, for Prand Tb-based intermetallics. The results indicates that the hydrogen makes the compounds magnetically softer, which is attributed to the influence of hydrogen on both the 3d and R sublittices. Two types of spin-reorientation transition for the Nd 2Co 14B system were observed. Hydrogenaration reduces both the low transition temperature, TSR 1, and the high transition temperature, TSR 2, which is explained using the Boltich-Wallace mechanism.

Estimation of the composition of intermetallic compounds in LiCl-KCl molten salt by cyclic voltammetry.

PubMed

Liu, Ya L; Liu, Kui; Yuan, Li Y; Chai, Zhi F; Shi, Wei Q

2016-08-15

In this work, the compositions of Ce-Al, Er-Al and La-Bi intermetallic compounds were estimated by the cyclic voltammetry (CV) technique. At first, CV measurements were carried out at different reverse potentials to study the co-reduction processes of Ce-Al, Er-Al and La-Bi systems. The CV curves obtained were then re-plotted with the current as a function of time, and the coulomb number of each peak was calculated. By comparing the coulomb number of the related peaks, the compositions of the Ce-Al, Er-Al and La-Bi intermetallic compounds formed in the co-reduction process could be estimated. The results showed that Al11Ce3, Al3Ce, Al2Ce and AlCe could be formed by the co-reduction of Ce(iii) and Al(iii). For the co-reduction of Er(iii) and Al(iii), Al3Er2, Al2Er and AlEr were formed. In a La(iii) and Bi(iii) co-existing system in LiCl-KCl melts, LaBi2, LaBi and Li3Bi were the major products as a result of co-reduction.

Metal-Intermetallic Laminate Ti-Al3Ti Composites Produced by Spark Plasma Sintering of Titanium and Aluminum Foils Enclosed in Titanium Shells

NASA Astrophysics Data System (ADS)

Lazurenko, Daria V.; Mali, Vyacheslav I.; Bataev, Ivan A.; Thoemmes, Alexander; Bataev, Anatoly A.; Popelukh, Albert I.; Anisimov, Alexander G.; Belousova, Natalia S.

2015-09-01

Metal-intermetallic laminate composites are considered as promising materials for application in the aerospace industry. In this study, Ti-Al3Ti composites enclosed in titanium cases were produced by reactive spark plasma sintering. Sintering was carried out at 1103 K and 1323 K (830 °C and 1050 °C) for 10 minutes. In both cases, high-quality Ti-Al3Ti composites containing thin transition layers at the interfaces were obtained. Al2Ti, AlTi, and AlTi3 intermetallic phases and a solid solution of aluminum in titanium were observed in the transition layers by scanning and transmission electron microscopy. The material sintered at 1323 K (1050 °C) had higher strength in comparison with the composite obtained at 1103 K (830 °C). However, the hardness of the intermetallic component in the sample sintered at higher temperature decreased due to the grain growth. The impact toughness values of both materials were approximately identical.

Interface-related deformation phenomena in intermetallic γ-titanium aluminides

NASA Astrophysics Data System (ADS)

Appel, F.; Wagner, R.

1993-01-01

The development of titanium aluminides towards higher ductility concentrates on Ti-rich alloys which are composed of the intermetallic phases γ(TiAl) and α2(Ti3Al). The two phases form a lamellar microstructure with various types of interfaces. The deformation behaviour of these materials was investigated by compression tests, which were performed for different orientations of the interfacial boundaries with respect to the sample axis. With regard to the mechanical properties the structure of the interfaces and the micromechanisms of deformation were studied by conventional and high resolution electron microscopy. Accordingly, the interfacial boundaries impede the propagation of slip across the lamellae, leading to an athermal contribution to the flow stress.

A Self-Propagating Foaming Process of Porous Al-Ni Intermetallics Assisted by Combustion Reactions

PubMed Central

Kobashi, Makoto; Kanetake, Naoyuki

2009-01-01

The self-propagating foaming process of porous Al-Ni intermetallics was investigated. Aluminum and nickel powders were blended, and titanium and boron carbide powders were added as reactive exothermic agents. The blended powder was extruded to make a rod-shape precursor. Only one end of the rod precursor was heated to ignite the reaction. The reaction propagated spontaneously throughout the precursor. Pore formation took place at the same time as the reaction occurred. Adding the exothermic agent was effective to increase the porosity. Preheating the precursor before the ignition was also very effective to produce porous Al-Ni intermetallics with high porosity.

From Structural Complexity to Structure-Property Relationships in Intermetallics: Development of Density Functional Theory-Chemical Pressure Analysis

NASA Astrophysics Data System (ADS)

Engelkemier, Joshua

The unparalleled structural diversity of intermetallic compounds provides nearly unlimited potential for the discovery and optimization of materials with useful properties, such as thermoelectricity, superconductivity, magnetism, hydrogen storage, superelasticity, and catalysis. This same diversity, however, creates challenges for understanding and controlling the unpredictable structure of intermetallic phases. Moreover, the fundamental design principles that have proven so powerful in molecular chemistry do not have simple analogues for metallic, solid state materials. One of these basic principles is the concept of atomic size effects. Especially in densely packed crystal structures where the need to fill space is in competition with the atoms' preferences for ideal interatomic distances, substitution of one element in a compound for another with similar chemical properties yet different atomic size can have dramatic effects on the ordering of the atoms (which in turn affects the electronic structure, vibrational properties, and materials properties). But because the forces that hold metallic phases together are less easily understood from a local perspective than covalent or ionic interactions in other kinds of materials, it is usually unclear whether the atoms are organized to optimize stabilizing, bonding interactions or rather forced to be close together despite repulsive, steric interactions. This dissertation details the development of a theoretical method, called Density Functional Theory-Chemical Pressure (DFT-CP) analysis, to address this issue. It works by converting the distribution of total energy density from a DFT calculation into a map of chemical pressure through a numerical approximation of the first derivative of energy with respect to voxel volume. The CP distribution is then carefully divided into contact volumes between neighboring atoms, from which it is possible to determine whether atoms are too close together (positive CP) or too far

Laser Cladding of TiAl Intermetallic Alloy on Ti6Al4V -Process Optimization and Properties

NASA Astrophysics Data System (ADS)

Cárcel, B.; Serrano, A.; Zambrano, J.; Amigó, V.; Cárcel, A. C.

In order to improve Ti6Al4V high-temperature resistance and its tribological properties, the deposition of TiAl intermetallic (Ti-48Al-2Cr-2Nb) coating on a Ti6Al4V substrate by coaxial laser cladding has been investigated. Laser cladding by powder injection is an emerging laser material processing technique that allows the deposition of thick protective coatings on substrates,using a high power laser beam as heat source. Laser cladding is a multiple-parameter-dependent process. The main process parameters involved (laser power, powder feeding rate, scanning speed and preheating temperature) has been optimized. The microstructure and geometrical quantities (clad area and dilution) of the coating was characterized by optical microscopy and scanning electron microscopy (SEM). In addition the cooling rate of the clad during the process was measured by a dual-color pyrometer. This result has been related to defectology and mechanical coating properties.

Absence of B1-B2 structural transition in lithium halides under hydrostatic pressure

NASA Astrophysics Data System (ADS)

de Coss, Romeo; Murrieta, Gabriel

2005-03-01

We have investigated the B1-B2 structural transition in LiF, LiCl, LiBr, and LiI under hydrostatic pressure by means of first-principles total-energy calculations using the Full- Potential LAPW method. In order to analyze the gradient effects, we have performed calculations using the local density approximation (LDA) and the generalized gradient approximation (GGA), for the exchange and correlation potential. In agreement with the experimental observations, we find that even for pressures higher than 100 GPa, the Li halides do not present the B1-B2 structural transition. In order to understand this behavior, we have calculated the distribution of the electron densities. From the analysis of the distribution of electron densities for the Li halides in the B1 and B2 phases, we find that for this group of ionic compounds the B1 phase have a distribution of electron densities more homogeneous than in the B2 phase, preventing the B1-B2 structural transition. This work was partially supported by Consejo Nacional de Ciencia y Tecnolog'ia (CONACYT, M'exico) under Grant No. 43830-F.

A phase width for CaGaSn. Crystal structure of mixed intermetallic Ca{sub 4}Ga{sub 4+x}Sn{sub 4−x} and SmGa{sub x}Sn{sub 3−x}, stability, geometry and electronic structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tillard, Monique, E-mail: mtillard@univ-montp2.fr

X-ray single-crystal structure has been established for new compositions in intermetallic systems of tin and gallium. Crystals were successfully obtained in alloys prepared from elements. The structure of SmGaSn{sub 2} (cubic Pm3̄m, a=4.5778(8) Å, Z=1, R1=0.012) is described with atomic disorder at all Sn/Ga positions and the structure of Ca{sub 4}Ga{sub 4.9}Sn{sub 3.1} (hexagonal, P6{sub 3}/mmc, a=4.2233(9), c=17.601(7) Å, Z=1, R1=0.062) raises an interesting question about existence of a composition domain for CaGaSn. Finally, Ca{sub 4}Ga{sub 4.9}Sn{sub 3.1} should be considered as a particular composition of Ca{sub 4}Ga{sub 4+x}Sn{sub 4−x}, a compound assumed to exist in the range x ~more » 0−1. Partial atomic ordering characterizes the Sn/Ga puckered layers of hexagons whose geometries are analyzed and discussed comparatively with analogous arrangements in AlB{sub 2} related hexagonal compounds. The study is supported by rigid band model and DFT calculations performed for different experimental and hypothetic arrangements. - Graphical abstract: A phase width for Ca{sub 4}Ga{sub 4+x}Sn{sub 4−x} belonging to the hexagonal YPtAs structure-type. - Highlights: • Single crystals of mixed tin gallium ternary intermetallics were obtained. • Partial ordering at metal sites and phase width are evidenced for Ca{sub 4}Ga{sub 4+x}Sn{sub 4−x}. • Layer deviation to flatness is studied comparatively with related structures. • Geometry and stability analyses based on DFT calculations are provided.« less

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

PubMed Central

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

2014-01-01

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

High-pressure behavior of A 2 B 2 O 7 pyrochlore (A=Eu, Dy; B=Ti, Zr)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rittman, Dylan R.; Turner, Katlyn M.; Park, Sulgiye

2017-01-28

In situ high-pressure X-ray diffraction and Raman spectroscopy were used to determine the influence of composition on the high-pressure behavior of A 2B 2O 7 pyrochlore (A=Eu, Dy; B=Ti, Zr) up to ~50GPa. Based on X-ray diffraction results, all compositions transformed to the high-pressure cotunnite structure. The B-site cation species had a larger effect on the transition pressure than the A-site cation species, with the onset of the phase transformation occurring at ~41 GPa for B=Ti and ~16 GPa B=Zr. However, the A-site cation affected the kinetics of the phase transformation, with the transformation for compositions with the smaller ionicmore » radii, i.e., A=Dy, proceeding faster than those with a larger ionic radii, i.e., A=Eu. These results were consistent with previous work in which the radius-ratio of the A- and B-site cations determined the energetics of disordering, and compositions with more similarly sized A- and B-site cations had a lower defect formation energy. Raman spectra revealed differences in the degree of short-range order of the different compositions. Due to the large phase fraction of cotunnite at high pressure for B=Zr compositions, Raman modes for cotunnite could be observed, with more modes recorded for A=Eu than A=Dy. These additional modes are attributed to increased short-to-medium range ordering in the initially pyrochlore structured Eu 2Zr 2O 7 as compared with the initially defect-fluorite structured Dy 2Zr 2O 7.« less

Reliable and cost effective design of intermetallic Ni2Si nanowires and direct characterization of its mechanical properties

NASA Astrophysics Data System (ADS)

Han, Seung Zeon; Kang, Joonhee; Kim, Sung-Dae; Choi, Si-Young; Kim, Hyung Giun; Lee, Jehyun; Kim, Kwangho; Lim, Sung Hwan; Han, Byungchan

2015-10-01

We report that a single crystal Ni2Si nanowire (NW) of intermetallic compound can be reliably designed using simple three-step processes: casting a ternary Cu-Ni-Si alloy, nucleate and growth of Ni2Si NWs as embedded in the alloy matrix via designing discontinuous precipitation (DP) of Ni2Si nanoparticles and thermal aging, and finally chemical etching to decouple the Ni2Si NWs from the alloy matrix. By direct application of uniaxial tensile tests to the Ni2Si NW we characterize its mechanical properties, which were rarely reported in previous literatures. Using integrated studies of first principles density functional theory (DFT) calculations, high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDX) we accurately validate the experimental measurements. Our results indicate that our simple three-step method enables to design brittle Ni2Si NW with high tensile strength of 3.0 GPa and elastic modulus of 60.6 GPa. We propose that the systematic methodology pursued in this paper significantly contributes to opening innovative processes to design various kinds of low dimensional nanomaterials leading to advancement of frontiers in nanotechnology and related industry sectors.

Reliable and cost effective design of intermetallic Ni2Si nanowires and direct characterization of its mechanical properties.

PubMed

Han, Seung Zeon; Kang, Joonhee; Kim, Sung-Dae; Choi, Si-Young; Kim, Hyung Giun; Lee, Jehyun; Kim, Kwangho; Lim, Sung Hwan; Han, Byungchan

2015-10-12

We report that a single crystal Ni2Si nanowire (NW) of intermetallic compound can be reliably designed using simple three-step processes: casting a ternary Cu-Ni-Si alloy, nucleate and growth of Ni2Si NWs as embedded in the alloy matrix via designing discontinuous precipitation (DP) of Ni2Si nanoparticles and thermal aging, and finally chemical etching to decouple the Ni2Si NWs from the alloy matrix. By direct application of uniaxial tensile tests to the Ni2Si NW we characterize its mechanical properties, which were rarely reported in previous literatures. Using integrated studies of first principles density functional theory (DFT) calculations, high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDX) we accurately validate the experimental measurements. Our results indicate that our simple three-step method enables to design brittle Ni2Si NW with high tensile strength of 3.0 GPa and elastic modulus of 60.6 GPa. We propose that the systematic methodology pursued in this paper significantly contributes to opening innovative processes to design various kinds of low dimensional nanomaterials leading to advancement of frontiers in nanotechnology and related industry sectors.

Reliable and cost effective design of intermetallic Ni2Si nanowires and direct characterization of its mechanical properties

PubMed Central

Han, Seung Zeon; Kang, Joonhee; Kim, Sung-Dae; Choi, Si-Young; Kim, Hyung Giun; Lee, Jehyun; Kim, Kwangho; Lim, Sung Hwan; Han, Byungchan

2015-01-01

We report that a single crystal Ni2Si nanowire (NW) of intermetallic compound can be reliably designed using simple three-step processes: casting a ternary Cu-Ni-Si alloy, nucleate and growth of Ni2Si NWs as embedded in the alloy matrix via designing discontinuous precipitation (DP) of Ni2Si nanoparticles and thermal aging, and finally chemical etching to decouple the Ni2Si NWs from the alloy matrix. By direct application of uniaxial tensile tests to the Ni2Si NW we characterize its mechanical properties, which were rarely reported in previous literatures. Using integrated studies of first principles density functional theory (DFT) calculations, high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDX) we accurately validate the experimental measurements. Our results indicate that our simple three-step method enables to design brittle Ni2Si NW with high tensile strength of 3.0 GPa and elastic modulus of 60.6 GPa. We propose that the systematic methodology pursued in this paper significantly contributes to opening innovative processes to design various kinds of low dimensional nanomaterials leading to advancement of frontiers in nanotechnology and related industry sectors. PMID:26456769

Electrically reversible cracks in an intermetallic film controlled by an electric field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Z. Q.; Liu, J. H.; Biegalski, M. D.

Cracks in solid-state materials are typically irreversible. We report electrically reversible opening and closing of nanoscale cracks in an intermetallic thin film grown on a ferroelectric substrate driven by a small electric field (~0.83 kV/cm). Accordingly, a nonvolatile colossal electroresistance on-off ratio of more than 10 8 is measured across the cracks in the intermetallic film at room temperature. Cracks are easily formed with low-frequency voltage cycling and remain stable when the device is operated at high frequency, which offers intriguing potential for next-generation high-frequency memory applications. Moreover, endurance testing demonstrates that the opening and closing of such cracks canmore » reach over 10 7 cycles under 10-μs pulses, without catastrophic failure of the film.« less

Electrically reversible cracks in an intermetallic film controlled by an electric field

DOE PAGES

Liu, Z. Q.; Liu, J. H.; Biegalski, M. D.; ...

2018-01-03

Cracks in solid-state materials are typically irreversible. We report electrically reversible opening and closing of nanoscale cracks in an intermetallic thin film grown on a ferroelectric substrate driven by a small electric field (~0.83 kV/cm). Accordingly, a nonvolatile colossal electroresistance on-off ratio of more than 10 8 is measured across the cracks in the intermetallic film at room temperature. Cracks are easily formed with low-frequency voltage cycling and remain stable when the device is operated at high frequency, which offers intriguing potential for next-generation high-frequency memory applications. Moreover, endurance testing demonstrates that the opening and closing of such cracks canmore » reach over 10 7 cycles under 10-μs pulses, without catastrophic failure of the film.« less

Discovery of a Superconducting Cu-Bi Intermetallic Compound by High-Pressure Synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clarke, Samantha M.; Walsh, James P. S.; Amsler, Maximilian

A new intermetallic compound, the first to be structurally identified in the Cu-Bi binary system, is reported. This compound is accessed by high-pressure reaction of the elements. Its detailed characterization, physical property measurements, and ab initio calculations are described. The commensurate crystal structure of Cu 11Bi 7 is a unique variation of the NiAs structure type. Temperature-dependent electrical resistivity and heat capacity measurements reveal a bulk superconducting transition at T c=1.36 K. Density functional theory calculations further demonstrate that Cu 11Bi 7 can be stabilized (relative to decomposition into the elements) at high pressure and temperature. These results highlight themore » ability of high-pressure syntheses to allow for inroads into heretofore-undiscovered intermetallic systems for which no thermodynamically stable binaries are known.« less

Quantum many-body intermetallics: Phase stability of Fe3Al and small-gap formation in Fe2VAl

NASA Astrophysics Data System (ADS)

Kristanovski, Oleg; Richter, Raphael; Krivenko, Igor; Lichtenstein, Alexander I.; Lechermann, Frank

2017-01-01

Various intermetallic compounds harbor subtle electronic correlation effects. To elucidate this fact for the Fe-Al system, we perform a realistic many-body investigation based on a combination of density functional theory with dynamical mean-field theory in a charge self-consistent manner. A better characterization and understanding of the phase stability of bcc-based D 03-Fe3Al through an improved description of the correlated charge density and the magnetic energy is achieved. Upon replacement of one Fe sublattice with V, the Heusler compound Fe2VAl is realized, known to display bad-metal behavior and increased specific heat. Here we document a charge-gap opening at low temperatures in line with previous experimental work. The gap structure does not match conventional band theory and is reminiscent of (pseudo)gap characteristics in correlated oxides.

Exploring phase stability, electronic and mechanical properties of Ce–Pb intermetallic compounds using first-principles calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, Xiaoma; Computational Alloy Design Group, IMDEA Materials Institute, Getafe, Madrid 28906; Wang, Ziru

2016-05-15

The phase stability, electronic and mechanical properties of Ce–Pb intermetallics have been investigated by using first-principles calculations. Five stable and four metastable phases of Ce–Pb intermetallics were verified. Among them, CePb{sub 2} has been confirmed as HfGa{sub 2}-type structure. For Ce{sub 5}Pb{sub 3}, the high pressure phase transformation from D8{sub m} to D8{sub 8} with trivalent Ce has been predicted to occur at P=1.2 GPa and a high temperature phase transformation has been predicted from D8{sub m} to D8{sub 8} with tetravalent Ce at 531.5 K. The calculated lattice constants of the five stable phases are in good agreement withmore » experimental values. The electronic density of states, charge density and electron localization function of Ce{sub 3}Pb have been calculated, which indicated that the Ce and Pb show ionic behavior. The polycrystalline bulk modulus, shear modulus, Young's modulus, and Poisson's ratio are also estimated from the calculated single crystalline elastic constants. All of the calculated elastic constants satisfy mechanical stability criteria. The microhardness and mechanical anisotropy are predicted. The anisotropic nature of the Ce–Pb intermetallic compounds are demonstrated by the three-dimensional orientation dependent surfaces of Young's moduli and linear compressibility are also demonstrated. The longitudinal, transverse and average sound velocities and the Debye temperatures are also obtained in this work. The Ce{sub 3}Pb has the largest Debye temperature of 192.6 K, which means the Ce{sub 3}Pb has a highest melting point and high thermal conductivity than other compounds. - Graphical abstract: The convex hull plots of the enthalpies of formation for Ce–Pb binary systems calculated at 0 K. - Highlights: • The five stable and four metastable phases in the Ce–Pb binary system were predicted. • The crystal structure of CePb{sub 2} has been confirmed as HfGa{sub 2}-type.« less

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

NASA Technical Reports Server (NTRS)

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

1989-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2015-02-01

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

High-pressure behavior of A 2 B 2 O 7 pyrochlore (A=Eu, Dy; B=Ti, Zr)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rittman, Dylan R.; Turner, Katlyn M.; Park, Sulgiye

2017-01-24

In situ high-pressure X-ray diffraction and Raman spectroscopy were used to determine the influence of composition on the high-pressure behavior of A 2B 2O 7 pyrochlore (A = Eu, Dy; B = Ti, Zr) up to ~50 GPa. Based on X-ray diffraction results, all compositions transformed to the high-pressure cotunnite structure. The B-site cation species had a larger effect on the transition pressure than the A-site cation species, with the onset of the phase transformation occurring at ~41 GPa for B = Ti and ~16 GPa B = Zr. But, the A-site cation affected the kinetics of the phase transformation,more » with the transformation for compositions with the smaller ionic radii, i.e., A = Dy, proceeding faster than those with a larger ionic radii, i.e., A = Eu. Our results were consistent with previous work in which the radius-ratio of the A- and B-site cations determined the energetics of disordering, and compositions with more similarly sized A- and B-site cations had a lower defect formation energy. Raman spectra revealed differences in the degree of short-range order of the different compositions. Due to the large phase fraction of cotunnite at high pressure for B = Zr compositions, Raman modes for cotunnite could be observed, with more modes recorded for A = Eu than A = Dy. These additional modes are attributed to increased short-to-medium range ordering in the initially pyrochlore structured Eu 2Zr 2O 7 as compared with the initially defect-fluorite structured Dy 2Zr 2O 7.« less

B-spline algebraic diagrammatic construction: Application to photoionization cross-sections and high-order harmonic generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruberti, M.; Averbukh, V.; Decleva, P.

2014-10-28

We present the first implementation of the ab initio many-body Green's function method, algebraic diagrammatic construction (ADC), in the B-spline single-electron basis. B-spline versions of the first order [ADC(1)] and second order [ADC(2)] schemes for the polarization propagator are developed and applied to the ab initio calculation of static (photoionization cross-sections) and dynamic (high-order harmonic generation spectra) quantities. We show that the cross-section features that pose a challenge for the Gaussian basis calculations, such as Cooper minima and high-energy tails, are found to be reproduced by the B-spline ADC in a very good agreement with the experiment. We also presentmore » the first dynamic B-spline ADC results, showing that the effect of the Cooper minimum on the high-order harmonic generation spectrum of Ar is correctly predicted by the time-dependent ADC calculation in the B-spline basis. The present development paves the way for the application of the B-spline ADC to both energy- and time-resolved theoretical studies of many-electron phenomena in atoms, molecules, and clusters.« less

Adhesive and Cohesive Strength in FeB/Fe2B Systems

NASA Astrophysics Data System (ADS)

Meneses-Amador, A.; Blancas-Pérez, D.; Corpus-Mejía, R.; Rodríguez-Castro, G. A.; Martínez-Trinidad, J.; Jiménez-Tinoco, L. F.

2018-05-01

In this work, FeB/Fe2B systems were evaluated by the scratch test. The powder-pack boriding process was performed on the surface of AISI M2 steel. The mechanical parameters, such as yield stress and Young's modulus of the boride layer, were obtained by the instrumented indentation technique. Residual stresses produced on the boride layer were estimated by using the x-ray diffraction (XRD) technique. The scratch test was performed in order to evaluate the cohesive/adhesive strength of the FeB/Fe2B coating. In addition, a numerical evaluation of the scratch test on boride layers was performed by the finite element method. Maximum principal stresses were related to the failure mechanisms observed by the experimental scratch test. Shear stresses at the interfaces of the FeB/Fe2B/substrate system were also evaluated. Finally, the results obtained provide essential information about the effect of the layer thickness, the residual stresses, and the resilience modulus on the cohesive/adhesive strength in FeB/Fe2B systems.

The oxidation of Ni-rich Ni-Al intermetallics

NASA Technical Reports Server (NTRS)

Doychak, Joseph; Smialek, James L.; Barrett, Charles A.

1988-01-01

The oxidation of Ni-Al intermetallic alloys in the beta-NiAl phase field and in the two phase beta-NiAl/gamma'-Ni3Al phase field has been studied between 1000 and 1400 C. The stoichiometric beta-NiAl alloy doped with Zr was superior to other alloy compositions under cyclic and isothermal oxidation. The isothermal growth rates did not increase monotonically as the alloy Al content was decreased. The characteristically ridged alpha-Al2O3 scale morphology, consisting of cells of thin, textured oxide with thick growth ridges at cell boundaries, forms on oxidized beta-NiAl alloys. The correlation of scale features with isothermal growth rates indicates a predominant grain boundary diffusion growth mechanism. The 1200 C cyclic oxidation resistance decreases near the lower end of the beta-NiAl phase field.

M{sub 2}X intermetallics: Nonmetal insertion in a h.c.-like metallic distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pivan, J.Y.; Guerin, R.

A simple structural model is proposed on the basis of an ideal hexagonal close-packing (AB){sup {infinity}} of the metal atoms M. The metalloid atoms X, located in an ordered manner in the metallic planes with the stacking sequence ..(A){sup {infinity}}.. or ..(B){sup {infinity}}.., generate two types of elementary units called units U{sub I} and U{sub II}. These units are hexagonal prisms with the fundamental vectors a{sub 0}, b{sub 0}, c{sub 0} and the elementary volume V{sub 0}. When the exclusive occurrence of U{sub I} (or U{sub II}) only yields 6-prismatic and triangular sites of metalloid atoms X, additional tetrahedral andmore » pyramidal sites of X atoms are present when units U{sub I} and U{sub II} exist simultaneously. The structures of compounds with the general formula M{sub 2}X (M = 3d, 4d, 5d and (or) 4f, 5f elements, X = B, P, As, Sb, Si, Ge, {hor_ellipsis}) are described in terms of intergrowth mechanisms. Binary, ternary, or even quaternary structures of compounds, with M/X ratios equal or close to two, appear as superstructures of the elementary units. Insofar as no ordering is considered along the stacking direction, the vectorial combinations of the fundamental vectors in the form A = h.a{sub 0}+s.b{sub 0}, B = k.a{sub 0}+t.b{sub 0}, C = c{sub 0} result in supercells with the volume V = (h.t {minus} k.s).V{sub 0}. The attainable symmetry (hexagonal, tetragonal, orthorhombic, monoclinic, {hor_ellipsis}) strongly depends on the particular values of the integers h, s, k, t. The criteria of occurrence of various series of compounds are presented together with their crystallographic features and structural relationships are emphasized. Moreover, the model demonstrates that numerous compounds with the predicted unit cell parameters should be obtained in each crystal system.« less

Principles of Structure and Phase Composition Formation in Composite Master Alloys of the Al-Ti-B/B4c Systems Used for Aluminum Alloy Modification

NASA Astrophysics Data System (ADS)

Zhukov, I. A.; Promakhov, V. V.; Matveev, A. E.; Platov, V. V.; Khrustalev, A. P.; Dubkova, Ya. A.; Vorozhtsov, S. A.; Potekaev, A. I.

2018-03-01

The principles of formation of structure and properties of materials produced by self-propagating hightemperature synthesis (SHS) from the Al-Ti-B/B4C powder systems are identified. It is shown that the SHSmaterials produced from the Al-Ti-B powder systems consist of a TiAl intermetallic matrix with inclusions of titanium diboride particles. It is found out that an introduction of 1 wt.% of TiB2 particles into the melt of the AD35 aluminum alloy allows reducing the grain size from 620 to 220 μm and gives rise to an increase in the ultimate tensile strength of as-cast specimens from 100 to 145 MPa and in the plasticity from 7 to 9%.

Effects of filling material and laser power on the formation of intermetallic compounds during laser-assisted friction stir butt welding of steel and aluminum alloys

NASA Astrophysics Data System (ADS)

Fei, Xinjiang; Jin, Xiangzhong; Peng, Nanxiang; Ye, Ying; Wu, Sigen; Dai, Houfu

2016-11-01

In this paper, two kinds of materials, Ni and Zn, are selected as filling material during laser-assisted friction stir butt welding of Q235 steel and 6061-T6 aluminum alloy, and their influences on the formation of intermetallic compounds on the steel/aluminum interface of the joints were first studied. SEM was used to analyze the profile of the intermetallic compound layer and the fractography of tensile fracture surfaces. In addition, EDS was applied to investigate the types of the intermetallic compounds. The results indicate that a thin iron-abundant intermetallic compound layer forms and ductile fracture mode occurs when Ni is added, but a thick aluminum-abundant intermetallic compound layer generates and brittle fracture mode occurs when Zn is added. So the tensile strength of the welds with Ni as filling material is greater than that with Zn as filling material. Besides, the effect of laser power on the formation of intermetallic compound layer when Ni is added was investigated. The preheated temperature field produced by laser beam in the cross section of workpiece was calculated, and the tensile strength of the joints at different laser powers was tested. Results show that only when suitable laser power is adopted, can suitable preheating temperature of the steel reach, then can thin intermetallic compound layer form and high tensile strength of the joints reach. Either excessive or insufficient laser power will reduce the tensile strength of the joints.

Magnetic properties and large reversible magnetocaloric effect in Er3Pd2

NASA Astrophysics Data System (ADS)

Maji, Bibekananda; Ray, Mayukh K.; Modak, M.; Mondal, S.; Suresh, K. G.; Banerjee, S.

2018-06-01

The magnetic properties and magnetocaloric effect (MCE) of binary intermetallic compound Er3Pd2 were studied. It exhibits a paramagnetic (PM) to antiferromagnetic (AFM) transition at Néel temperature (TN) = 10 K. A large reversible MCE was observed which is related to a second order magnetic transition from PM to AFM state. The values of maximum magnetic entropy change (- Δ SMmax) and adiabatic temperature change (Δ Tadmax) reach 8.9 J/kg-K and 2.9 K respectively for the field change of 50 kOe with no obvious hysteresis loss. The effective magnetic moment was determined to be 10.16 μB/Er3+, which is notably higher than that of free ion value of Er3+ (9.59 μB), suggests that Pd ions also have considerable amount of magnetic moments in this compound.

New Intermetallic Ternary Phosphide Chalcogenide AP2-xXx (A = Zr, Hf; X = S, Se) Superconductors with PbFCl-Type Crystal Structure

NASA Astrophysics Data System (ADS)

Kitô, Hijiri; Yanagi, Yousuke; Ishida, Shigeyuki; Oka, Kunihiko; Gotoh, Yoshito; Fujihisa, Hiroshi; Yoshida, Yoshiyuki; Iyo, Akira; Eisaki, Hiroshi

2014-07-01

We have synthesized a series of intermetallic ternary phosphide chalcogenide superconductors, AP2-xXx (A = Zr, Hf; X = S, Se), using the high-pressure synthesis technique. These materials have a PbFCl-type crystal structure (space group P4/nmm) when x is greater than 0.3. The superconducting transition temperature Tc changes systematically with x, yielding dome-like phase diagrams. The maximum Tc is achieved at approximately x = 0.7, at which point the Tc is 6.3 K for ZrP2-xSex (x = 0.75), 5.5 K for HfP2-xSex (x = 0.7), 5.0 K for ZrP2-xSx (x = 0.675), and 4.6 K for Hfp2-xSx (x = 0.5). They are typical type-II superconductors and the upper and lower critical fields are estimated to be 2.92 T at 0 K and 0.021 T at 2 K for ZrP2-xSex (x = 0.75), respectively.

Dislocations and deformation microstructure in a B2-ordered Al28Co20Cr11Fe15Ni26 high-entropy alloy

NASA Astrophysics Data System (ADS)

Feuerbacher, Michael

2016-07-01

High-entropy alloys are multicomponent metallic materials currently attracting high research interest. They display a unique combination of chemical disorder and crystalline long-range order, and due to their attractive properties are promising candidates for technological application. Many high-entropy alloys possess surprisingly high strength, occasionally in combination with high ductility and low density. The mechanisms effecting these attractive mechanical properties are not understood. This study addresses the deformation mechanism of a Al28Co20Cr11Fe15Ni26 high-entropy alloy, which is a two-phase material, consisting of a B2-ordered matrix and disordered body-centred inclusions. We quantitatively analyse the microstructure and dislocations in deformed samples by transmission-electron-microscopic methods including weak-beam imaging and convergent-beam electron diffraction. We find that the deformation process in the B2 phase is dominated by heterogeneous slip of screw dislocations gliding on planes. The dislocations are perfect superdislocations of the B2 lattice and show no dissociation. This indicates that the antiphase-boundary energy in the structure is very high, inhibiting spread of the dislocation core. Along with the observation of a widely extending strain field associated to the dislocations, our results provide a possible explanation for the high strength of this high-entropy alloy as a direct consequence of its dislocation structure.

Melt Spinning of Intermetallic Alloys: Heat Transfer and Microstructure

DTIC Science & Technology

1992-04-21

newly emerging mdLerials such as titanium aluminides and other intermetallic alloys[4,5]. These materials must possess good mechanical and corrosion...alloys such as titanium aluminides with the surrounding atmosphere, it utilizes a tilting water-cooled copper hearth and the apparatus is in a 5 psi Argon... titanium aluminide in the form of filament or ribbon break olf into short segments. The solidified ribbons have lengths of 5 - 15 mm, widths of 0.5

Structure-Property Relationships in Novel Materials Part I: Frustrated Magnetism and Deintercalation of Honeycomb Oxides Part II: Electron-Precise Gold Intermetallics

NASA Astrophysics Data System (ADS)

Seibel, Elizabeth M.

This thesis is a study of the structure-property relationships of novel materials, broken into two major parts. The first part, "Part I: Frustrated Magnetism and Deintercalation of Honeycomb Oxides" explores new, layered nickel oxides and their properties, specifically the synthesis, structure, magnetism, and applications of the Na3Ni 2BiO6-NaNi2BiO6-NaNi2BiO 6•1.7H2O system. These phases are of interest to the solid-state and physics communities because they display frustrated magnetism on a hexagonal lattice. Chapter 3 explores the chemistry and physics of Na 3Ni2BiO6; Chapter 4 then discusses its chemical deintercalation and subsequent hydration to form the NaNi2BiO 6-NaNi2BiO6•1.7H2O system. These phases are examples of sought-after spin-1/2 systems on a hexagonal lattice. The second part of this thesis, "Part II: Electron-Precise Gold Intermetallics" explores novel, electron-precise intermetallics in the Lanthanide-gold-pnictide ternary system. The chemistry of gold-containing solids has not been well-studied despite gold's unusual physics, motivating the study. There are three new families discussed herein. The first, found in Chapter 7, is of the type LnAuSb (Ln = Lanthanide) which are new Dirac semimetals. The work illustrates a chemical design principle that can be used to predict new Dirac Semimetals, which is important given that the field of topological materials is rapidly growing. Chapter 8 discusses materials of the type LnAuBi2, which are layered intermetallics with a high degree of magnetic anisotropy. Finally, Chapter 9 explores new phases of the form Ln 3Au3Bi4. These materials are semiconductors with high Seebeck coefficients at room temperature, indicating their potential for use as thermoelectric materials.

Strain-induced changes of the electronic properties of B -site ordered double-perovskite Sr2CoIrO6 thin films

NASA Astrophysics Data System (ADS)

Esser, S.; Chang, C. F.; Kuo, C.-Y.; Merten, S.; Roddatis, V.; Ha, T. D.; Jesche, A.; Moshnyaga, V.; Lin, H.-J.; Tanaka, A.; Chen, C. T.; Tjeng, L. H.; Gegenwart, P.

2018-05-01

B -site ordered thin films of double perovskite Sr2CoIrO6 were epitaxially grown by a metalorganic aerosol deposition technique on various substrates, actuating different strain states. X-ray diffraction, transmission electron microscopy, and polarized far-field Raman spectroscopy confirm the strained epitaxial growth on all used substrates. Polarization-dependent Co L2 ,3 x-ray absorption spectroscopy reveals a change of the magnetic easy axis of the antiferromagnetically ordered (high-spin) Co3 + sublattice within the strain series. By reversing the applied strain direction from tensile to compressive, the easy axis changes abruptly from in-plane to out-of-plane orientation. The low-temperature magnetoresistance changes its sign respectively and is described by a combination of weak antilocalization and anisotropic magnetoresistance effects.

FP-LAPW based investigation of structural, electronic and mechanical properties of CePb{sub 3} intermetallic compound

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pagare, Gitanjali, E-mail: gita-pagare@yahoo.co.in; Jain, Ekta, E-mail: jainekta05@gmail.com; Abraham, Jisha Annie, E-mail: disisjisha@yahoo.com

A theoretical study of structural, electronic, elastic and mechanical properties of CePb{sub 3} intermetallic compound has been investigated systematically using first principles density functional theory. The calculations are carried out within the three different forms of generalized gradient approximation (GGA) and LSDA for the exchange correlation potential. The ground state properties such as lattice parameter (a{sub 0}), bulk modulus (B) and its pressure derivative (B′) are calculated and obtained lattice parameter of this compound shows well agreement with the experimental results. We have calculated three independent second order elastic constants (C{sub 11}, C{sub 12} and C{sub 44}), which has notmore » been calculated and measured yet. From energy dispersion curves, it is found that the studied compound is metallic in nature. Ductility of this compound is analyzed using Pugh’s criteria and Cauchy's pressure (C{sub 11}-C{sub 12}). The mechanical properties such as Young's modulus, shear modulus, anisotropic ratio, Poison's ratio have been calculated for the first time using the Voigt–Reuss–Hill (VRH) averaging scheme. The average sound velocities (v{sub m}), density (ρ) and Debye temperature (θ{sub D}) of this compound are also estimated from the elastic constants.« less

The physical and chemical structure of Sagittarius B2. II. Continuum millimeter emission of Sgr B2(M) and Sgr B2(N) with ALMA

NASA Astrophysics Data System (ADS)

Sánchez-Monge, Á.; Schilke, P.; Schmiedeke, A.; Ginsburg, A.; Cesaroni, R.; Lis, D. C.; Qin, S.-L.; Müller, H. S. P.; Bergin, E.; Comito, C.; Möller, Th.

2017-07-01

Context. The two hot molecular cores Sgr B2(M) and Sgr B2(N), which are located at the center of the giant molecular cloud complex Sagittarius B2, have been the targets of numerous spectral line surveys, revealing a rich and complex chemistry. Aims: We seek to characterize the physical and chemical structure of the two high-mass star-forming sites Sgr B2(M) and Sgr B2(N) using high-angular resolution observations at millimeter wavelengths, reaching spatial scales of about 4000 au. Methods: We used the Atacama Large Millimeter/submillimeter Array (ALMA) to perform an unbiased spectral line survey of both regions in the ALMA band 6 with a frequency coverage from 211 GHz to 275 GHz. The achieved angular resolution is 0.̋4, which probes spatial scales of about 4000 au, I.e., able to resolve different cores and fragments. In order to determine the continuum emission in these line-rich sources, we used a new statistical method, STATCONT, which has been applied successfully to this and other ALMA datasets and to synthetic observations. Results: We detect 27 continuum sources in Sgr B2(M) and 20 sources in Sgr B2(N). We study the continuum emission variation across the ALMA band 6 (I.e., spectral index) and compare the ALMA 1.3 mm continuum emission with previous SMA 345 GHz and VLA 40 GHz observations to study the nature of the sources detected. The brightest sources are dominated by (partially optically thick) dust emission, while there is an important degree of contamination from ionized gas free-free emission in weaker sources. While the total mass in Sgr B2(M) is distributed in many fragments, most of the mass in Sgr B2(N) arises from a single object, with filamentary-like structures converging toward the center. There seems to be a lack of low-mass dense cores in both regions. We determine H2 volume densities for the cores of about 107-109 cm-3 (or 105-107 M⊙ pc-3), I.e., one to two orders of magnitude higher than the stellar densities of super star clusters. We

Hierarchical and chemical space partitioning in new intermetallic borides MNi21B20 (M = In, Sn).

PubMed

Wagner, Frank R; Zheng, Qiang; Gumeniuk, Roman; Bende, David; Prots, Yurii; Bobnar, Matej; Hu, Dong-Li; Burkhardt, Ulrich; Grin, Yuri; Leithe-Jasper, Andreas

2017-10-10

The compounds MNi 21 B 20 (M = In, Sn) have been synthesized and their cubic crystal structure determined (space group Pm3[combining macron]m, lattice parameters a = 7.1730(1) Å and a = 7.1834(1) Å, respectively). The structure can be described as a hierarchical partitioning of space based on a reo-e net formed by Ni3 species with large cubical, cuboctahedral and rhombicuboctahedral voids being filled according to [Ni1@Ni3 8 ], [M@Ni3 12 ], and [Ni2 6 @B 20 @Ni3 24 ], respectively. The [Ni 6 @B 20 ] motif inside the rhombicuboctahedral voids features an empty [Ni 6 ] octahedron surrounded by a [B 20 ] cage recently described in E 2 Ni 21 B 20 (E = Zn, Ga). Position-space bonding analysis using ELI-D and QTAIM space partitioning as well as 2- and 3-center delocalization indices gives strong support to an alternative chemical description of space partitioning based on face-condensed [B@Ni 6 ] trigonal prisms as basic building blocks. The shortest B-B contacts display locally nested 3-center B-B-Ni bonding inside each trigonal prism. This clearly rules out the notion of [Ni 6 @B 20 ] clusters and leads to the arrangement of 20 face-condensed [B@Ni2 3 Ni3 3 ] trigonal prisms resulting in a triple-shell like situation Ni2 6 @B 20 @Ni3 24 (reo-e), where the shells display comparable intra- and inter-shell bonding. Both compounds are Pauli paramagnets displaying metallic conductivity.

Ultra-high vacuum compatible preparation chain for intermetallic compounds

NASA Astrophysics Data System (ADS)

Bauer, A.; Benka, G.; Regnat, A.; Franz, C.; Pfleiderer, C.

2016-11-01

We report the development of a versatile material preparation chain for intermetallic compounds, which focuses on the realization of a high-purity growth environment. The preparation chain comprises an argon glovebox, an inductively heated horizontal cold boat furnace, an arc melting furnace, an inductively heated rod casting furnace, an optically heated floating-zone furnace, a resistively heated annealing furnace, and an inductively heated annealing furnace. The cold boat furnace and the arc melting furnace may be loaded from the glovebox by means of a load-lock permitting to synthesize compounds starting with air-sensitive elements while handling the constituents exclusively in an inert gas atmosphere. All furnaces are all-metal sealed, bakeable, and may be pumped to ultra-high vacuum. We find that the latter represents an important prerequisite for handling compounds with high vapor pressure under high-purity argon atmosphere. We illustrate the operational aspects of the preparation chain in terms of the single-crystal growth of the heavy-fermion compound CeNi2Ge2.

Microstructures and mechanical properties of nanocrystalline NiTi intermetallics formed by mechanosynthesis

NASA Astrophysics Data System (ADS)

Arunkumar, S.; Kumaravel, P.; Velmurugan, C.; Senthilkumar, V.

2018-01-01

The formulation of nanocrystalline NiTi shape memory alloys has potential effects in mechanical stimulation and medical implantology. The present work elucidates the effect of milling time on the product's structural characteristics, chemical composition, and microhardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fracturing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninterrupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to 93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline intermetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.

Unexpected Ground-State Structure and Mechanical Properties of Ir₂Zr Intermetallic Compound.

PubMed

Zhang, Meiguang; Cao, Rui; Zhao, Meijie; Du, Juan; Cheng, Ke

2018-01-10

Using an unbiased structure searching method, a new orthorhombic Cmmm structure consisting of ZrIr 12 polyhedron building blocks is predicted to be the thermodynamic ground-state of stoichiometric intermetallic Ir₂Zr in Ir-Zr systems. The formation enthalpy of the Cmmm structure is considerably lower than that of the previously synthesized Cu₂Mg-type phase, by ~107 meV/atom, as demonstrated by the calculation of formation enthalpy. Meanwhile, the phonon dispersion calculations further confirmed the dynamical stability of Cmmm phase under ambient conditions. The mechanical properties, including elastic stability, rigidity, and incompressibility, as well as the elastic anisotropy of Cmmm -Ir₂Zr intermetallic, have thus been fully determined. It is found that the predicted Cmmm phase exhibits nearly elastic isotropic and great resistance to shear deformations within the (100) crystal plane. Evidence of atomic bonding related to the structural stability for Ir₂Zr were manifested by calculations of the electronic structures.

Fiber Laser Welding-Brazing Characteristics of Dissimilar Metals AZ31B Mg Alloys to Copper with Mg-Based Filler

NASA Astrophysics Data System (ADS)

Zhao, Xiaoye; Tan, Caiwang; Meng, Shenghao; Chen, Bo; Song, Xiaoguo; Li, Liqun; Feng, Jicai

2018-03-01

Fiber laser welding-brazing of 1-mm-thick AZ31B Mg alloys to 1.5-mm-thick copper (T2) with Mg-based filler was performed in a lap configuration. The weld appearance, interfacial microstructure and mechanical properties were investigated with different heat inputs. The results indicated that processing windows for optimizing appropriate welding parameters were relatively narrow in this case. Visually acceptable joints with certain strength were achieved at appropriate welding parameters. The maximum tensile-shear fracture load of laser-welded-brazed Mg/Cu joint could reach 1730 N at the laser power of 1200 W, representing 64.1% joint efficiency relative to AZ31Mg base metal. The eutectic structure (α-Mg + Mg2Cu) and Mg-Cu intermetallic compound was observed at the Mg/Cu interface, and Mg-Al-Cu ternary intermetallic compound were identified between intermetallics and eutectic structure at high heat input. All the joints fractured at the Mg-Cu interface. However, the fracture mode was found to differ. For laser power of 1200 W, the surface was characterized by tearing edge, while that with poor joint strength was almost dominated by smooth surface or flat tear pattern.

The role of zinc on the chemistry of complex intermetallic compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Weiwei

2014-01-01

Combining experiments and electronic structure theory provides the framework to design and discover new families of complex intermetallic phases and to understand factors that stabilize both new and known phases. Using solid state synthesis and multiple structural determinations, ferromagnetic β-Mn type Co 8+xZn 12–x was analyzed for their crystal and electronic structures.

X-Ray Diffraction of Intermetallic Compounds: A Physical Chemistry Laboratory Experiment

ERIC Educational Resources Information Center

Varberg, Thomas D.; Skakuj, Kacper

2015-01-01

Here we describe an experiment for the undergraduate physical chemistry laboratory in which students synthesize the intermetallic compounds AlNi and AlNi3 and study them by X-ray diffractometry. The compounds are synthesized in a simple one-step reaction occurring in the solid state. Powder X-ray diffractograms are recorded for the two compounds…

Heat shock factors HsfB1 and HsfB2b are involved in the regulation of Pdf1.2 expression and pathogen resistance in Arabidopsis.

PubMed

Kumar, Mukesh; Busch, Wolfgang; Birke, Hannah; Kemmerling, Birgit; Nürnberger, Thorsten; Schöffl, Friedrich

2009-01-01

In order to assess the functional roles of heat stress-induced class B-heat shock factors in Arabidopsis, we investigated T-DNA knockout mutants of AtHsfB1 and AtHsfB2b. Micorarray analysis of double knockout hsfB1/hsfB2b plants revealed as strong an up-regulation of the basal mRNA-levels of the defensin genes Pdf1.2a/b in mutant plants. The Pdf expression was further enhanced by jasmonic acid treatment or infection with the necrotrophic fungus Alternaria brassicicola. The single mutant hsfB2b and the double mutant hsfB1/B2b were significantly improved in disease resistance after A. brassicicola infection. There was no indication for a direct interaction of Hsf with the promoter of Pdf1.2, which is devoid of perfect HSE consensus Hsf-binding sequences. However, changes in the formation of late HsfA2-dependent HSE binding were detected in hsfB1/B2b plants. This suggests that HsfB1/B2b may interact with class A-Hsf in regulating the shut-off of the heat shock response. The identification of Pdf genes as targets of Hsf-dependent negative regulation is the first evidence for an interconnection of Hsf in the regulation of biotic and abiotic responses.

Heat Shock Factors HsfB1 and HsfB2b Are Involved in the Regulation of Pdf1.2 Expression and Pathogen Resistance in Arabidopsis

PubMed Central

Kumar, Mukesh; Busch, Wolfgang; Birke, Hannah; Kemmerling, Birgit; Nürnberger, Thorsten; Schöffl, Friedrich

2009-01-01

In order to assess the functional roles of heat stress-induced class B-heat shock factors in Arabidopsis, we investigated T-DNA knockout mutants of AtHsfB1 and AtHsfB2b. Micorarray analysis of double knockout hsfB1/hsfB2b plants revealed as strong an up-regulation of the basal mRNA-levels of the defensin genes Pdf1.2a/b in mutant plants. The Pdf expression was further enhanced by jasmonic acid treatment or infection with the necrotrophic fungus Alternaria brassicicola. The single mutant hsfB2b and the double mutant hsfB1/B2b were significantly improved in disease resistance after A. brassicicola infection. There was no indication for a direct interaction of Hsf with the promoter of Pdf1.2, which is devoid of perfect HSE consensus Hsf-binding sequences. However, changes in the formation of late HsfA2-dependent HSE binding were detected in hsfB1/B2b plants. This suggests that HsfB1/B2b may interact with class A-Hsf in regulating the shut-off of the heat shock response. The identification of Pdf genes as targets of Hsf-dependent negative regulation is the first evidence for an interconnection of Hsf in the regulation of biotic and abiotic responses. PMID:19529832

Hydrides of intermetallic compounds with a H/M ratio greater than unity obtained at high hydrogen pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Semenenko, K.N.; Klyamkin, S.N.

1993-11-01

Novel hydride phases with H/M > 1 based on Zr{sub 2}Pd, Hf{sub 2}Pd, and Hf{sub 2}Cu (structures of the MoSi{sub 2} type) have been synthesized at high H{sub 2} pressures. The X-ray diffraction investigations of the resulting hydrides have been carried out. Some factors determining the maximum hydrogen content in the hydrides of intermetallic compounds are discussed. A model structure of the hydrides obtained is proposed, which assumes the possibility of direct H-H interactions when the interatomic distances are less than 1 {angstrom}.

The characteristics of hot swaged NiAl intermetallic compounds with ternary additions consolidated by HIP techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishiyama, S.; Eto, M.; Mishima, Y.

Stoichiometric and non-stoichiometric NiAl intermetallics with ternary additives, such as Ti, Zr, Hf, V, Nb, Ta, Cr, Mo or Mo/e, W, Mn, Fe, Cu and B, fabricated with the combination of Hot Isostatic Pressing (HIP) and hot swaging techniques have been investigated. The mechanical properties of hot swaged NiAl with various ternary additives, consolidated by ion beam casting or HIP techniques, have been tested at temperatures ranging from R.T. to 1,000 C. It is found that significant tensile elongation at room temperature can be achieved by hot swaged as-HIP`ed NiAl compounds with Mo or Mo/Re additives, whereas cast and hotmore » swaged compounds with Mo addition resulted in some elongation above 400 C.« less

Amino Acids Aided Sintering for the Formation of Highly Porous FeAl Intermetallic Alloys

PubMed Central

Karczewski, Krzysztof; Stepniowski, Wojciech J.

2017-01-01

Fabrication of metallic foams by sintering metal powders mixed with thermally degradable compounds is of interest for numerous applications. Compounds releasing gaseous nitrogen, minimizing interactions between the formed gases and metallic foam by diluting other combustion products, were applied. Cysteine and phenylalanine, were used as gas releasing agents during the sintering of elemental Fe and Al powders in order to obtain metallic foams. Characterization was carried out by optical microscopy with image analysis, scanning electron microscopy with energy dispersive spectroscopy, and gas permeability tests. Porosity of the foams was up to 42 ± 3% and 46 ± 2% for sintering conducted with 5 wt % cysteine and phenylalanine, respectively. Chemical analyses of the formed foams revealed that the oxygen content was below 0.14 wt % and the carbon content was below 0.3 wt %. Therefore, no brittle phases could be formed that would spoil the mechanical stability of the FeAl intermetallic foams. The gas permeability tests revealed that only the foams formed in the presence of cysteine have enough interconnections between the pores, thanks to the improved air flow through the porous materials. The foams formed with cysteine can be applied as filters and industrial catalysts. PMID:28773106

Water vapor effect on high-temperature oxidation behavior of Fe3Al intermetallics

PubMed Central

Chevalier, Sebastian; Juzon, Pitor; Przybylski, Kazimierz; Larpin, Jean-Pierre

2009-01-01

Fe3Al intermetallics (Fe3Al, Fe3Al-Zr, Fe3Al-Zr,Mo and Fe3Al-Zr, Mo, Nb) were oxidized at 950 °C in dry and humid (11 vol% water) synthetic air. Thermogravimetric measurements showed that the oxidation rates of the tested intermetallics were lower in humid air than in dry air (especially for Fe3Al-Zr, Mo and Fe3Al-Zr, Mo, Nb). The addition of small amounts of Zr, Mo or Nb improved the kinetics compared with that of the undoped Fe3Al. Fe3Al showed massive spallation, whereas Fe3Al-Zr, Fe3Al-Zr, Mo and Fe3Al-Zr, Mo, Nb produced a flat, adherent oxide layer. The rapid transformation of transient alumina into alpha alumina may explain the decrease in the oxidation rate in humid air. PMID:27877306

Intermetallic Al-, Fe-, Co- and Ni-Based Thermal Barrier Coatings Prepared by Cold Spray for Applications on Low Heat Rejection Diesel Engines

NASA Astrophysics Data System (ADS)

Leshchinsky, E.; Sobiesiak, A.; Maev, R.

2018-02-01

Conventional thermal barrier coating (TBC) systems consist of a duplex structure with a metallic bond coat and a ceramic heat insulating topcoat. They possess the desired low thermal conductivity, but at the same time they are very brittle and sensitive to thermal shock and thermal cycling due to the inherently low coefficient of thermal expansion. Recent research activities are focused on the developing of multilayer TBC structures obtained using cold spraying and following annealing. Aluminum intermetallics have demonstrated thermal and mechanical properties that allow them to be used as the alternative TBC materials, while the intermetallic layers can be additionally optimized to achieve superior thermal physical properties. One example is the six layer TBC structure in which cold sprayed Al-based intermetallics are synthesized by annealing in nitrogen atmosphere. These multilayer coating systems demonstrated an improved thermal fatigue capability as compared to conventional ceramic TBC. The microstructures and properties of the coatings were characterized by SEM, EDS and mechanical tests to define the TBC material properties and intermetallic formation mechanisms.

Vortex lattice structures in YNi{sub 2}B{sub 2}C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yethiraj, M.; Paul, D.M.; Tomy, C.V.

The authors observe a flux lattice with square symmetry in the superconductor YNi{sub 2}B{sub 2}C when the applied field is parallel to the c-axis of the crystal. A square lattice observed previously in the isostructural magnetic analog ErNi{sub 2}B{sub 2}C was attributed to the interaction between magnetic order in that system and the flux lattice. Since the Y-based compound does not order magnetically, it is clear that the structure of the flux lattice is unrelated to magnetic order. In fact, they show that the flux lines have a square cross-section when the applied field is parallel to the c-axis ofmore » the crystal, since the measured penetration depth along the 100 crystal direction is larger than the penetration depth along the 110 by approximately 60%. This is the likely reason for the square symmetry of the lattice. Although they find considerable disorder in the arrangement of the flux lines at 2.5T, no melting of the vortex lattice was observed.« less

Vortex lattice structures in YNi{sub 2}B{sub 2}C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yethiraj, M.; Paul, D.M.; Tomy, C.V.

We observe a flux lattice with square symmetry in the superconductor YNi{sub 2}B{sub 2}C when the applied field is parallel to the c-axis of the crystal. A square lattice observed previously in the isostructural magnetic analog ErNi{sub 2}B{sub 2}C was attributed to the interaction between magnetic order in that system and the flux lattice. Since the Y-based compound does not order magnetically, it is clear that the structure of the flux lattice is unrelated to magnetic order. In fact, we show that the flux lines have a square cross-section when the applied field is parallel to the c-axis of themore » crystal, since the measured penetration depth along the 110 crystal direction is smaller than the penetration depth along the 100 by approximately 30%. This causes the square symmetry of the lattice. Although we find considerable disorder in the arrangement of the flux lines at 2.5T, no melting of the vortex lattice was observed.« less

The structure and ordering of ɛ-MnO 2

NASA Astrophysics Data System (ADS)

Kim, Chang-Hoon; Akase, Zentaro; Zhang, Lichun; Heuer, Arthur H.; Newman, Aron E.; Hughes, Paula J.

2006-03-01

The presence of ɛ-MnO 2 as a major component of electrolytic manganese dioxide (EMD) has been demonstrated by a combined X-ray diffraction/transmission electron microscopy (TEM) study. ɛ-MnO 2 usually has a partially ordered defect NiAs structure containing 50% cation vacancies; these vacancies can be fully ordered by a low temperature (200 °C) heat treatment to form a pseudohexagonal but monoclinic superlattice. Numerous fine-scale anti-phase domain boundaries are present in ordered ɛ-MnO 2 and cause extensive peak broadening and a massive shift of a very intense, 0.37 nm superlattice peak. This suggests a radically different explanation of the ubiquitous, very broad ˜0.42 nm peak (˜21-22° 2 θ, Cu Kα radiation) in EMDs, which heretofore has been attributed to Ramsdellite containing numerous planar defects. This work confirms the multi-phase model of equiaxed EMDs proposed by Heuer et al. [ITE Lett. 1(6) (2000) B50; Proc. Seventh Int. Symp. Adv. Phys. Fields 92 (2001)], rather than the defective single-phase model of Chabre and Pannetier [Prog. Solid State Chem. 23 (1995) 1] and Bowden et al. [ITE Lett. 4(1) (2003) B1].

On the Formation of Sludge Intermetallic Particles in Secondary Aluminum Alloys

NASA Astrophysics Data System (ADS)

Ferraro, Stefano; Bjurenstedt, Anton; Seifeddine, Salem

2015-08-01

The primary precipitation of Fe-rich intermetallics in AlSi9Cu3(Fe) type alloys is studied for different Fe, Mn, and Cr contents and cooling rates. Differential scanning calorimetry, thermal analysis, and interrupted solidification with a rapid quenching technique were used in combination in order to assess the nucleation temperature of sludge particles, as well as to follow their evolution. The results revealed that the sludge nucleation temperature and the release of latent heat during sludge formation are functions of Fe, Mn, and Cr levels in the molten alloy ( i.e., the sludge factor, SF) and cooling rate. Moreover, it can be concluded that sensitivity to sludge formation is not affected by cooling rate; i.e., a decrease in the SF will reduce sludge nucleation temperature to the same extent for a higher cooling rate as for a lower cooling rate. The sludge formation temperature detected will assist foundries in setting the optimal molten metal temperature for preventing sludge formation in holding furnaces and plunger systems.

Effect of Mn and AlTiB Addition and Heattreatment on the Microstructures and Mechanical Properties of Al-Si-Fe-Cu-Zr Alloy.

PubMed

Yoo, Hyo-Sang; Kim, Yong-Ho; Lee, Seong-Hee; Son, Hyeon-Taek

2018-09-01

The microstructure and mechanical properties of as-extruded Al-0.1 wt%Si-0.2 wt%Fe- 0.4 wt%Cu-0.04 wt%Zr-xMn-xAlTiB (x = 1.0 wt%) alloys under various annealing processes were investigated and compared. After the as-cast billets were kept at 400 °C for 1 hr, hot extrusion was carried out with a reduction ratio of 38:1. In the case of the as-extruded Al-Si-Fe-Cu-Zr alloy at annealed at 620 °C, large equiaxed grain was observed. When the Mn content is 1.0 wt%, the phase exhibits a skeleton morphology, the phase formation in which Mn participated. Also, the volume fraction of the intermetallic compounds increased with Mn and AlTiB addition. For the Al-0.1Si-0.2Fe-0.4Cu-0.04Zr alloy with Mn and AlTiB addition from 1.0 wt%, the ultimate tensile strength increased from 100.47 to 119.41 to 110.49 MPa. The tensile strength of the as-extruded alloys improved with the addition of Mn and AlTiB due to the formation of Mn and AlTiB-containing intermetallic compounds.

Effect of elastic collisions and electronic excitation on lattice structure of NiTi bulk intermetallic compound irradiated with energetic ions

NASA Astrophysics Data System (ADS)

Ochi, M.; Kojima, H.; Hori, F.; Kaneno, Y.; Semboshi, S.; Saitoh, Y.; Okamoto, Y.; Ishikawa, N.; Iwase, A.

2018-07-01

NiTi bulk intermetallic compound with the B19‧ structure was irradiated with 1 MeV He, 5 MeV Al, 16 MeV Au and 200 MeV Xe ions, and the change in lattice structure near the surface by the ion bombardment was investigated by using the grazing incidence X-ray diffraction (GIXD) and the extended X-ray absorption fine structure (EXAFS). The lattice structure transformation by the irradiation strongly depends on ion species and/or energies. For the 1 MeV He irradiation, the lattice structure changed from B19‧ to the A2 structure, but did not show an amorphization even after the high fluence irradiation. For the 5 MeV Al irradiation, the samples are partially amorphized. For the 16 MeV Au irradiation, the lattice structure of the NiTi samples changed nearly completely from the B19‧ structure to the amorphous state via the A2 structure. The value of dpa (displacement per atom) which is needed for the amorphization is, however, much smaller than the case of the Al ion irradiation. For the 200 MeV Xe ion irradiation, the lattice structure completely changed to the A2 structure even by a small ion fluence. The dependence of the lattice structure transformation on elastic collisions (dpa), the spectrum of the primary knock-on (PKA) atoms and the density of energy deposited through electronic excitation was discussed.

The Vaporization of B2O3(l) to B2O3(g) and B2O2(g)

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Myers, Dwight L.

2011-01-01

The vaporization of B2O3 in a reducing environment leads to formation of both B2O3(g) and B2O2(g). While formation of B2O3(g) is well understood, many questions about the formation of B2O2(g) remain. Previous studies using B(s) + B2O3(l) have led to inconsistent thermodynamic data. In this study, it was found that after heating, B(s) and B2O3(l) appear to separate and variations in contact area likely led to the inconsistent vapor pressures of B2O2(g). To circumvent this problem, an activity of boron is fixed with a two-phase mixture of FeB and Fe2B. Both second and third law enthalpies of formation were measured for B2O2(g) and B2O3(g). From these the enthalpies of formation at 298.15 K are calculated to be -479.9 +/- 41.5 kJ/mol for B2O2(g) and -833.4 +/- 13.1 kJ/mol for B2O3(g). Ab initio calculations to determine the enthalpies of formation of B2O2(g) and B2O3(g) were conducted using the W1BD composite method and show good agreement with the experimental values.

Doped YbRh2Si2: not only ferromagnetic correlations but ferromagnetic order.

PubMed

Lausberg, S; Hannaske, A; Steppke, A; Steinke, L; Gruner, T; Pedrero, L; Krellner, C; Klingner, C; Brando, M; Geibel, C; Steglich, F

2013-06-21

YbRh2Si2 is a prototypical system for studying unconventional antiferromagnetic quantum criticality. However, ferromagnetic correlations are present which can be enhanced via isoelectronic cobalt substitution for rhodium in Yb(Rh(1-x)Co(x))2Si2. So far, the magnetic order with increasing x was believed to remain antiferromagnetic. Here, we present the discovery of ferromagnetism for x = 0.27 below T(C) = 1.30  K in single crystalline samples. Unexpectedly, ordering occurs along the c axis, the hard crystalline electric field direction, where the g factor is an order of magnitude smaller than in the basal plane. Although the spontaneous magnetization is only 0.1 μB/Yb it corresponds to the full expected saturation moment along c taking into account partial Kondo screening.

Ab Initio Studies of Shock-Induced Chemical Reactions of Inter-Metallics

NASA Astrophysics Data System (ADS)

Zaharieva, Roussislava; Hanagud, Sathya

2009-06-01

Shock-induced and shock assisted chemical reactions of intermetallic mixtures are studied by many researchers, using both experimental and theoretical techniques. The theoretical studies are primarily at continuum scales. The model frameworks include mixture theories and meso-scale models of grains of porous mixtures. The reaction models vary from equilibrium thermodynamic model to several non-equilibrium thermodynamic models. The shock-effects are primarily studied using appropriate conservation equations and numerical techniques to integrate the equations. All these models require material constants from experiments and estimates of transition states. Thus, the objective of this paper is to present studies based on ab initio techniques. The ab inito studies, to date, use ab inito molecular dynamics. This paper presents a study that uses shock pressures, and associated temperatures as starting variables. Then intermetallic mixtures are modeled as slabs. The required shock stresses are created by straining the lattice. Then, ab initio binding energy calculations are used to examine the stability of the reactions. Binding energies are obtained for different strain components super imposed on uniform compression and finite temperatures. Then, vibrational frequencies and nudge elastic band techniques are used to study reactivity and transition states. Examples include Ni and Al.

Fractographic Analysis of HfB2-SiC and ZrB2-SiC Composites

NASA Technical Reports Server (NTRS)

Mecholsky, J.J., Jr.; Ellerby, D. T.; Johnson, S. M.; Stackpoole, M. M.; Loehman, R. E.; Arnold, Jim (Technical Monitor)

2001-01-01

Hafnium diboride-silicon carbide and zirconium diboride-silicon carbide composites are potential materials for high temperature leading edge applications on reusable launch vehicles. In order to establish material constants necessary for evaluation of in-situ fracture, bars fractured in four point flexure were examined using fractographic principles. The fracture toughness was determined from measurements of the critical crack sizes and the strength values, and the crack branching constants were established to use in forensic fractography of materials for future flight applications. The fracture toughnesses range from about 13 MPam (sup 1/2) at room temperature to about 6 MPam (sup 1/2) at 1400 C for ZrB2-SiC composites and from about 11 MPam (sup 1/2) at room temperature to about 4 MPam (sup 1/2) at 1400 C for HfB2-SiC composites.

Crystallographic and magnetic structure of UCu{sub 1.5}Sn{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purwanto, A.; Robinson, R.A.; Nakotte, H.

1996-04-01

We report on the crystallographic and magnetic structures of the antiferromagnet UCu{sub 1.5}Sn{sub 2}, as determined by x-ray and neutron powder diffraction. It crystallizes in the tetragonal CaBe{sub 2}Ge{sub 2} structure type, with space group P/4nmm, and we find no site disorder between two different Sn2{ital c} sites, in contrast with a previous report. UCu{sub 1.5}Sn{sub 2} orders antiferromagnetically with a N{acute e}el temperature of about 110 K. This is unusually high among uranium intermetallics. The uranium moments align along the {ital c} axis in a collinear arrangement but alternating along the {ital c} axis. The low-temperature uranium moment ismore » 2.01{mu}{sub {ital B}}. {copyright} {ital 1996 American Institute of Physics.}« less

[Interferon alpha-2b modified with polyethylene glycol].

PubMed

Wu, Yingxin; Zhai, Yanqin; Lei, Jiandu; Ma, Guanghui; Su, Zhiguo

2008-09-01

In order to obtain a more stable PEGylated interferon alpha-2b, and prolong its half life, interferon alpha-2b (IFN alpha-2b) was modified with monomethoxy polyethylene glycol propionaldehyde (mPEG-ALD) 20000. It was found that the optimized reaction condition for the maximum bioactivity and highest PEGylation degree of the mono PEGylated interferon alpha-2b was as follows: in 20 mmol/L, pH 6.5, citric acid and sodium dihydrogen phosphate buffer, the concentration of IFN alpha-2b was 4 mg/mL, and the molar ratio of PEG/IFN alpha-2b was 8:1, and the reaction time was 20 h at 4 degrees C. Under the optimized reaction condition, the mono PEGylation degree reached to 55%. Ion exchange chromatography was used to separate and purify mono PEGylated interferon alpha-2b from the reaction mixture. The purity of mono PEGylated interferon alpha-2b was higher than 97% characterized by HPLC. The bioactivity of the mono PEGylated interferon alpha-2b was 13.4% of the native IFN alpha-2b, while its half life in SD rat is much longer than the native IFN alpha-2b. The mono PEGylated interferon alpha-2b is also stable in aqueous.

The effect of pH on the corrosion behavior of intermetallic compounds Ni{sub 3}(Si,Ti) and Ni{sub 3}(Si,Ti) + 2Mo in sodium chloride solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Priyotomo, Gadang, E-mail: gada001@lipi.go.id; Nuraini, Lutviasari, E-mail: Lutviasari@gmail.com; Kaneno, Yasuyuki, E-mail: kaneno@mtr.osakafu-u.ac.id

The corrosion behavior of the intermetallic compounds, Ni{sub 3}(Si,Ti) (L1{sub 2}: single phase) and Ni{sub 3}(Si,Ti) + 2Mo (L1{sub 2} and (L12 + Ni{sub ss}) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EDAX: Energy Dispersive X-ray) in 0.5 kmol/m{sup 3} NaCl solutions at various pH. The corrosion behavior of nickel alloy C-276 was studied under the same experimental conditions as a reference. It was found that the uniform attack was observed on Ni{sub 3}(Si,Ti) for the immersion test at lower pH, while the pitting attack was observedmore » on this compound for this test at neutral solution. Furthermore, Ni{sub 3}(Si,Ti)+2Mo had the preferential dissolution of L1{sub 2} compared to (L1{sub 2} + Ni{sub ss}) mixture region at lower pH, while pitting attack occurred in (L1{sub 2} + Ni{sub ss}) mixture region at neutral solution. For both intermetallic compounds, the magnitude of pitting and uniform attack decrease with increasing pH of solutions. From the immersion test and polarization curves, the corrosion resistance of Ni{sub 3}(Si,Ti)+2Mo is lower than that of Ni{sub 3}(Si,Ti), while the nickel alloy C-276 is the highest one at various pH of solutions. On the other hand, in the lower pH of solutions, the corrosion resistance of tested materials decreased significantly compared to those in neutral and higher pH of solutions.« less

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

NASA Astrophysics Data System (ADS)

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

1996-01-01

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

Theoretical investigation of thermoelectric and elastic properties of intermetallic compounds ScTM (TM = Cu, Ag, Au and Pd)

NASA Astrophysics Data System (ADS)

Iqbal, R.; Bilal, M.; Jalali-Asadabadi, S.; Rahnamaye Aliabad, H. A.; Ahmad, Iftikhar

2018-01-01

In this paper, we explore the structural, electronic, thermoelectric and elastic properties of intermetallic compounds ScTM (TM = Cu, Ag, Au and Pd) using density functional theory. The produced results show high values of Seebeck coefficients and electrical conductivity for these materials. High power factor for these materials at room-temperature shows that these materials may be beneficial for low-temperature thermoelectric devices and alternative energy sources. Furthermore, elastic properties of these compounds are also calculated, which are used to evaluate their mechanical properties. The Cauchy’s pressure and B/G ratio figure out that these compounds are ductile in nature. The calculated results also predict that these compounds are stable against deforming force.

Itinerant G-type antiferromagnetic order in SrCr2As2

NASA Astrophysics Data System (ADS)

Das, Pinaki; Sangeetha, N. S.; Lindemann, George R.; Heitmann, T. W.; Kreyssig, A.; Goldman, A. I.; McQueeney, R. J.; Johnston, D. C.; Vaknin, D.

2017-07-01

Neutron-diffraction and magnetic susceptibility studies of polycrystalline SrCr2As2 reveal that this compound is an itinerant G-type antiferromagnet below the Néel temperature TN = 590(5) K with the Cr magnetic moments aligned along the tetragonal c axis. The system remains tetragonal to the lowest measured temperature (˜12 K). The lattice parameter ratio c /a and the magnetic moment saturate at about the same temperature below ˜200 K, indicating a possible magnetoelastic coupling. The ordered moment μ =1.9 (1 ) μB /Cr , measured at T =12 K, is significantly reduced compared to its localized value (4 μB /Cr ) due to the itinerant character brought about by hybridization between the Cr 3 d and As 4 p orbitals.

Unusual behaviour of (Np,Pu)B2C

NASA Astrophysics Data System (ADS)

Klimczuk, Tomasz; Boulet, Pascal; Griveau, Jean-Christophe; Colineau, Eric; Bauer, Ernst; Falmbigl, Matthias; Rogl, Peter; Wastin, Franck

2015-02-01

Two transuranium metal boron carbides, NpB2C and PuB2C have been synthesized by argon arc melting. The crystal structures of the {Np,Pu}B2C compounds were determined from single-crystal X-ray data to be isotypic with the ThB2C-type (space group ?, a = 0.6532(2) nm; c = 1.0769(3) nm for NpB2C and a = 0.6509(2) nm; c = 1.0818(3) nm for PuB2C; Z = 9). Physical properties have been derived from polycrystalline bulk material in the temperature range from 2 to 300 K and in magnetic fields up to 9 T. Magnetic susceptibility and heat capacity data indicate the occurrence of antiferromagnetic ordering for NpB2C with a Neel temperature TN = 68 K. PuB2C is a Pauli paramagnet most likely due to a strong hybridization of s(p,d) electrons with the Pu-5f states. A pseudo-gap, as concluded from the Sommerfeld value and the electronic transport, is thought to be a consequence of the hybridization. The magnetic behaviour of {Np,Pu}B2C is consistent with the criterion of Hill.

Electronic and optical properties of RESn{sub 3} (RE=Pr & Nd) intermetallics: A first principles study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pagare, G., E-mail: gita-pagare@yahoo.co.in; Abraham, Jisha A.; Department of Physics, National Defence Academy, Pune-411023

2015-06-24

A theoretical study of structural, electronic and optical properties of RESn{sub 3} (RE = Pr & Nd) intermetallics have been investigated systematically using first principles density functional theory. The calculations are carried out within the PBE-GGA and LSDA for the exchange correlation potential. The ground state properties such as lattice parameter (a{sub 0}), bulk modulus (B) and its pressure derivative (B′) are calculated and the calculated lattice parameters show well agreement with the experimental results. We first time predict elastic constants for these compounds. From energy dispersion curves, it is found that these compounds are metallic in nature. The linearmore » optical response of these compounds are also studied and the higher value of static dielectric constant shows the possibility to use them as good dielectric materials.« less

Formation of intermetallic phases in AlSi7Fe1 alloy processed under microgravity and forced fluid flow conditions and their influence on the permeability

NASA Astrophysics Data System (ADS)

Steinbach, S.; Ratke, L.; Zimmermann, G.; Budenkova, O.

2016-03-01

Ternary Al-6.5wt.%Si-0.93wt.%Fe alloy samples were directionally solidified on-board of the International Space Station ISS in the ESA payload Materials Science Laboratory (MSL) equipped with Low Gradient Furnace (LGF) under both purely diffusive and stimulated convective conditions induced by a rotating magnetic field. Using different analysis techniques the shape and distribution of the intermetallic phase β-Al5SiFe in the dendritic microstructure was investigated, to study the influence of solidification velocity and fluid flow on the size and spatial arrangement of intermetallics. Deep etching as well as 3-dimensional computer tomography measurements characterized the size and the shape of β-Al5SiFe platelets: Diffusive growth results in a rather homogeneous distribution of intermetallic phases, whereas forced flow promotes an increase in the amount and the size of β-Al5SiFe platelets in the centre region of the samples. The β-Al5SiFe intermetallics can form not only simple platelets, but also be curved, branched, crossed, interacting with dendrites and porosity located. This leads to formation of large and complex groups of Fe-rich intermetallics, which reduce the melt flow between dendrites leading to lower permeability of the mushy zone and might significantly decrease feeding ability in castings.

Investigation of Laser Generation and Detection of Ultrasound in Ceramic Matrix Composites and Intermetallics

NASA Technical Reports Server (NTRS)

Ehrlich, Michael J.

1998-01-01

The goal of this program is to assess the feasibility of using laser based ultrasonic techniques for inspecting and characterizing materials of interest to NASA, specifically those used in propulsion and turbomachinery applications, such as ceramic composites, metal matrix composites, and intermetallics.

Final Report, Volume 2, The Development of Qualification Standards for Cast Duplex Stainless Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, Steven, W.; Lundin, Carl, W.

2005-09-30

wrought DSS and tested per ASTM A923 method B (Charpy impact test). Method A (sodium hydroxide etch test) was performed on one half of a fractured Charpy V-notch impact sample and Method C (ferric chloride corrosion weight loss test) was performed on another half. Test results for the three cast lots and one wrought lot indicate that ASTM A923 is relevant for detecting intermetallic phases in cast DSS. In the ASTM A923 round robin study, five laboratories conducted ASTM A923 Methods A & C on cast DSS material and the lab-to-lab reproducibility of the data was determined. Two groups of samples were sent to the participants. Group 1 samples were tested per ASTM A923 Method A, group 2 samples were tested by ASTM A923 Method C. Testing procedures for this round robin study were identical to those used in the ASTM A923 applicability study. Results from this round robin indicate that there is excellent lab-to-lab reproducibility of ASTM A923 with respect to cast DSS and that ASTM A923 could be expanded to cover both wrought and cast DSS. In the ASTM A923 study of the effectiveness of existing foundry solution annealing procedures for producing cast DSS without intermetallic phases, Ten heats of ASTM A890-4A (CD3MN) in the foundry solution annealed condition were tested per ASTM A923 Methods A, B, & C. Testing of these materials per ASTM A923 was used to determine if the foundry solution anneal procedures were adequate to completely eliminate any intermetallic phases, which may have precipitated during the casting and subsequent heat treatment processes. All heats showed no sign of intermetallic phase per Method A, passed minimum Charpy impact energy requirements per Method B (> 40 ft-lbs @ -40°C (-40°F)), and showed negligible weight loss per Method C (< 10 mdd). These results indicate that the solution annealing procedure used by foundries is adequate to produce a product free from intermetallic phases.« less

Final Report, Volume 2, The Development of Qualification Standards for Cast Duplex Stainless Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, Steven, W.; Lundin, Carl, D.

2005-09-30

the castings and wrought DSS and tested per ASTM A923 method B (Charpy impact test). Method A (sodium hydroxide etch test) was performed on one half of a fractured Charpy V-notch impact sample and Method C (ferric chloride corrosion weight loss test) was performed on another half. Test results for the three cast lots and one wrought lot indicate that ASTM A923 is relevant for detecting intermetallic phases in cast DSS. In the ASTM A923 round robin study, five laboratories conducted ASTM A923 Methods A & C on cast DSS material and the lab-to-lab reproducibility of the data was determined. Two groups of samples were sent to the participants. Group 1 samples were tested per ASTM A923 Method A, group 2 samples were tested by ASTM A923 Method C. Testing procedures for this round robin study were identical to those used in the ASTM A923 applicability study. Results from this round robin indicate that there is excellent lab-to-lab reproducibility of ASTM A923 with respect to cast DSS and that ASTM A923 could be expanded to cover both wrought and cast DSS. In the ASTM A923 study of the effectiveness of existing foundry solution annealing procedures for producing cast DSS without intermetallic phases, Ten heats of ASTM A890-4A (CD3MN) in the foundry solution annealed condition were tested per ASTM A923 Methods A, B, & C. Testing of these materials per ASTM A923 was used to determine if the foundry solution anneal procedures were adequate to completely eliminate any intermetallic phases, which may have precipitated during the casting and subsequent heat treatment processes. All heats showed no sign of intermetallic phase per Method A, passed minimum Charpy impact energy requirements per Method B (> 40 ft-lbs {at} -40 C (-40 F)), and showed negligible weight loss per Method C (< 10 mdd). These results indicate that the solution annealing procedure used by foundries is adequate to produce a product free from intermetallic phases.« less

Prediction and characterization of an Mg-Al intermetallic compound with potentially improved ductility via orbital-free and Kohn-Sham density functional theory

NASA Astrophysics Data System (ADS)

Zhuang, Houlong L.; Chen, Mohan; Carter, Emily A.

2017-10-01

Magnesium-aluminum (Mg-Al) intermetallic compounds that form as precipitates can significantly influence the mechanical properties of Mg-Al alloys. A computational evaluation of known and unknown Mg-Al intermetallic compounds could help design new Mg-Al alloy microstructures with optimal properties. Here, we employ the cluster-expansion method with energies efficiently calculated with orbital-free density functional theory (OFDFT) and predict a new, metastable intermetallic compound Mg3Al with a D019 hexagonal structure that is slightly more stable than an alternative L12 cubic structure. We apply Kohn-Sham DFT (KSDFT) to accurately evaluate various metastability criteria for D019 and L12 Mg3Al, including Born’s criterion and phonon dispersion. We show that both Mg3Al crystalline phases satisfy the metastability criteria and hence should be at least metastable. We further compare ductility metrics for D019 and L12 Mg3Al to that of hexagonal-close-packed Mg by computing Pugh’s ratio and generalized stacking fault energies. The ductility is predicted to follow the order: D019 Mg3Al > L12 Mg3Al > Mg, based on the highest Pugh’s ratio and the lowest unstable stacking and twinning fault energies of D019 Mg3Al compared to that of Mg. We also predict a very low antiphase boundary energy for Mg3Al and therefore expect D019 Mg3Al to be beneficial for improving the ductility of Mg-rich Mg-Al alloys. A computational design of Mg-Al alloy microstructures may become possible by combining the strengths of both OFDFT and KSDFT, i.e., the efficiency of the former and the accuracy of the latter, as demonstrated here.

B B ¯ angular correlations at the LHC in the parton Reggeization approach merged with higher-order matrix elements

NASA Astrophysics Data System (ADS)

Karpishkov, A. V.; Nefedov, M. A.; Saleev, V. A.

2017-11-01

We calculate the angular distribution spectra between beauty (B ) and antibeauty (B ¯) mesons in proton-proton collisions in the leading order approximation of the parton Reggeization approach consistently merged with the next-to-leading order corrections from the emission of an additional hard gluon. To describe b-quark hadronization we use the universal scale-dependent parton-to-meson fragmentation functions extracted from the world e+e- annihilation data. We have obtained good agreement between our predictions and data from the CMS Collaboration at the energy √{S }=7 TeV for B B ¯ angular correlations within uncertainties and without free parameters. Predictions for analogous correlation observables at √{S }=13 TeV are provided.

Itinerant G-type antiferromagnetic order in SrCr 2 As 2

DOE PAGES

Das, Pinaki; Sangeetha, N. S.; Lindemann, George R.; ...

2017-07-07

Here, neutron-diffraction and magnetic susceptibility studies of polycrystalline SrCr 2As 2 reveal that this compound is an itinerant G-type antiferromagnet below the Néel temperature T N = 590(5) K with the Cr magnetic moments aligned along the tetragonal c axis. The system remains tetragonal to the lowest measured temperature (~12 K). The lattice parameter ratio c/a and the magnetic moment saturate at about the same temperature below ~200 K, indicating a possible magnetoelastic coupling. The ordered moment μ = 1.9(1)μ B/Cr, measured at T = 12 K, is significantly reduced compared to its localized value (4μ B/Cr) due to themore » itinerant character brought about by hybridization between the Cr 3d and As 4p orbitals.« less

Itinerant G-type antiferromagnetic order in SrCr 2 As 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Pinaki; Sangeetha, N. S.; Lindemann, George R.

Here, neutron-diffraction and magnetic susceptibility studies of polycrystalline SrCr 2As 2 reveal that this compound is an itinerant G-type antiferromagnet below the Néel temperature T N = 590(5) K with the Cr magnetic moments aligned along the tetragonal c axis. The system remains tetragonal to the lowest measured temperature (~12 K). The lattice parameter ratio c/a and the magnetic moment saturate at about the same temperature below ~200 K, indicating a possible magnetoelastic coupling. The ordered moment μ = 1.9(1)μ B/Cr, measured at T = 12 K, is significantly reduced compared to its localized value (4μ B/Cr) due to themore » itinerant character brought about by hybridization between the Cr 3d and As 4p orbitals.« less

Phase stability and B-site ordering in La{sub 2}NiMnO{sub 6} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Xiao-Wei; Lu, Lu; Liu, Ming

2016-07-18

Thin films of multiferroic double-perovskite La{sub 2}NiMnO{sub 6} are prepared on (001)-oriented SrTiO{sub 3}, (La{sub 0.289}Sr{sub 0.712})(Al{sub 0.633}Ta{sub 0.356})O{sub 3}, and LaSrAlO{sub 4} substrates by pulsed laser deposition. Microstructure investigation by advanced electron microscopy shows that the La{sub 2}NiMnO{sub 6} films have a monoclinic structure on the SrTiO{sub 3} substrates and a rhombohedral structure on the (La{sub 0.289}Sr{sub 0.712})(Al{sub 0.633}Ta{sub 0.356})O{sub 3} and LaSrAlO{sub 4} substrates. Atomic-scale elemental maps of the monoclinic and rhombohedral phases reveal a short-range and/or partial ordering of the B-sites. In addition, domains and columnar grains are found in the films. Our results demonstrate that themore » phase and microstructure of the La{sub 2}NiMnO{sub 6} films can be tuned by epitaxial strains induced by different substrates.« less

K2-30 b and K2-34 b: Two inflated hot Jupiters around solar-type stars

NASA Astrophysics Data System (ADS)

Lillo-Box, J.; Demangeon, O.; Santerne, A.; Barros, S. C. C.; Barrado, D.; Hébrard, G.; Osborn, H. P.; Armstrong, D. J.; Almenara, J.-M.; Boisse, I.; Bouchy, F.; Brown, D. J. A.; Courcol, B.; Deleuil, M.; Delgado Mena, E.; Díaz, R. F.; Kirk, J.; Lam, K. W. F.; McCormac, J.; Pollacco, D.; Rajpurohit, A.; Rey, J.; Santos, N. C.; Sousa, S. G.; Tsantaki, M.; Wilson, P. A.

2016-10-01

We report the discovery of the two hot Jupiters K2-30 b and K2-34 b. The two planets were detected during campaigns 4 and 5 of the extension of the Kepler mission, K2; they transit their main-sequence stars with periods of ~4.099 and ~2.996 days. Subsequent ground-based radial velocity follow-up with SOPHIE, HARPS-N, and CAFE established the planetary nature of the transiting objects. We analyzed the transit signal, radial velocity, and spectral energy distributions of the two systems to characterize their properties. Both planets (K2-30 b and K2-34 b) are bloated hot Jupiters (1.20 RJup and 1.22 RJup) around relatively bright (V = 13.5 and V = 11.5) slow rotating main-sequence (G8 and F9) stars. Thus, these systems are good candidates for detecting the Rossiter-MacLaughlin effect in order to measure their obliquity and for atmospheric studies. Full Tables 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/594/A50

The impact of e-marketing orientation on performance in Asian SMEs: a B2B perspective

NASA Astrophysics Data System (ADS)

Chong, Woon Kian; Man, Ka Lok; Kim, Mucheol

2018-01-01

Business-to-business (B2B) organisations are increasingly utilising electronic devices in their business operations in order to succeed in increasingly competitive markets. This trend is prevalent in the growing Asian markets, especially in the small and medium-sized enterprises (SMEs) sector. While prior research has focused on this issue in the context of large business-to-customer (B2C) organisations in Asia, there have hardly been any studies that have shed light on the B2B sector in the SME setting. This study aims to critically explore B2B e-marketing critical success factors (B2B-eM-CSFs) for SMEs operating in the Asian B2B marketplace. A key finding is the development of a theoretical framework for SMEs, emerging from the analysis of 406 companies from various industrial sectors. The study shows that interaction with the B2B-eM-CSFs is an important dimension and has a positive and significant impact on e-business efficiency and marketing improvements for Asian SMEs.

Effect of Si on Fe-rich intermetallic formation and mechanical properties of heat-treated Al–Cu–Mn–Fe alloys

NASA Astrophysics Data System (ADS)

Zhao, Yuliang; Zhang, Weiwen; Yang, Chao; Zhang, Datong; Wang, Zhi

2018-04-01

The effect of Si on Fe-rich intermetallics formation and mechanical properties of heat-treated squeeze cast Al-5.0Cu-0.6Mn-0.7Fe alloy was investigated. Our results show that increasing Si content promotes the formation of Al15(FeMn)3(SiCu)2 (${\\alpha}$-Fe), and varying the morphology of T (Al20Cu3Mn2) where the size decreases and the amount increases. The major reason is that Si promotes heterogeneous nucleation of the intermetallics leading to finer precipitates. Si addition significantly enhances ultimate tensile strength and yield strength of the alloys. The strengthening effect is mainly owing to the dispersoid strengthening by increasing volume fraction of T phase and less harmful ${\\alpha}$-Fe with a compact structure, which make the cracks more difficult to initiate and propagation during tensile test. The squeeze cast Al-5.0Cu-0.6Mn-0.7Fe alloy with 1.1% Si shows significantly improved mechanical properties than the alloy without Si addition, which has tensile strength of 386 MPa, yield strength of 280 MPa and elongation of 8.6%.

Layered Structures and Disordered Polyanionic Nets in the Cation-Poor Polar Intermetallics CsAu 1.4 Ga 2.8 and CsAu 2 Ga 2.6

DOE PAGES

Smetana, Volodymyr; Steinberg, Simon; Mudring, Anja-Verena

2016-12-27

Gold intermetallics are known for their unusual structures and bonding patterns. Two new compounds have been discovered in the cation-poor part of the Cs–Au–Ga system. We obtained both compounds directly by heating the elements at elevated temperatures. Structure determinations based on single-crystal X-ray diffraction analyses revealed two structurally and compositionally related formations: CsAu 1.4Ga 2.8 (I) and CsAu 2Ga 2.6 (II) crystallize in their own structure types (I: Rmore » $$\\bar{3}$$, a = 11.160(2) Å, c = 21.706(4) Å, Z = 18; II: R$$\\bar{3}$$, a = 11.106(1) Å, Å, c = 77.243(9) Å, Z = 54) and contain hexagonal cationic layers of cesium. Furthermore, this is a unique structural motif, which has never been observed for the other (lighter) alkali metals in combination with Au and post transition elements. The polyanionic part is characterized in contrast by Au/Ga tetrahedral stars, a structural feature that is characteristic for light alkali metal representatives, and disordered sites with mixed Au/Ga occupancies that occur in both structures with a more significant disorder in the polyanionic component of CsAu 2Ga 2.6. Examinations of the electronic band structure for a model approximating the composition of CsAu 1.4Ga 2.8 have been completed using density-functional-theory-based methods and reveal a deep pseudogap at E F. Bonding analysis by evaluating the crystal orbital Hamilton populations show dominant heteroatomic Au–Ga bonds and only a negligible contribution from Cs pairs.« less

A Model-based B2B (Batch to Batch) Control for An Industrial Batch Polymerization Process

NASA Astrophysics Data System (ADS)

Ogawa, Morimasa

This paper describes overview of a model-based B2B (batch to batch) control for an industrial batch polymerization process. In order to control the reaction temperature precisely, several methods based on the rigorous process dynamics model are employed at all design stage of the B2B control, such as modeling and parameter estimation of the reaction kinetics which is one of the important part of the process dynamics model. The designed B2B control consists of the gain scheduled I-PD/II2-PD control (I-PD with double integral control), the feed-forward compensation at the batch start time, and the model adaptation utilizing the results of the last batch operation. Throughout the actual batch operations, the B2B control provides superior control performance compared with that of conventional control methods.

Crystal field effects in the intermetallic R Ni3Ga9 (R =Tb , Dy, Ho, and Er) compounds

NASA Astrophysics Data System (ADS)

Silva, L. S.; Mercena, S. G.; Garcia, D. J.; Bittar, E. M.; Jesus, C. B. R.; Pagliuso, P. G.; Lora-Serrano, R.; Meneses, C. T.; Duque, J. G. S.

2017-04-01

In this paper, we report temperature-dependent magnetic susceptibility, electrical resistivity, and heat-capacity experiments in the family of intermetallic compounds R Ni3Ga9 (R = Tb, Dy, Ho, and Er). Single-crystalline samples were grown using Ga self-flux method. These materials crystallize in a trigonal ErNi3Al9 -type structure with space group R 32 . They all order antiferromagnetically with TN<20 K . The anisotropic magnetic susceptibility presents large values of the ratio χeasy/χhard indicating strong crystalline electric-field (CEF) effects. The evolution of the crystal-field scheme for each R was analyzed in detail by using a spin model including anisotropic nearest-neighbor Ruderman-Kittel-Kasuya-Yosida interaction and the trigonal CEF Hamiltonian. Our analysis allows one to understand the distinct direction of the ordered moments along the series—the Tb-, Dy-, and Ho-based compounds have the ordered magnetic moments in the easy ab plane and the Er sample magnetization easy axis is along the c ̂ direction.

Strain rate dependence in the nanoindentation-induced deformation of Mg-Al intermetallic compounds produced by packed powder diffusion coating

NASA Astrophysics Data System (ADS)

Chang, Haiwei; Lu, Mingyuan; Zhang, Mingxing; Atrens, Andrej; Huang, Han

2015-09-01

Nanoindentation was performed on τ-Mg32(Al, Zn)49 and β-Mg17Al12 intermetallic coatings and on a AZ91E Mg alloy substrate using loading rates of 0.03 to 30 mNs-1. Pop-in phenomenon was observed during loading in the two intermetallic coatings and in the substrate. Both the magnitude of the pop-ins and the time interval between two consecutive pop-ins increased with increasing loads. The phenomenon was attributed to plastic instability, which is known as the Portevin-Le Châtelier effect. The morphologies of the indent impressions at different strain rates on the t phase, the β phase and the substrate were also investigated using atomic force microscopy. Pile-up occurred in the τ and β phases and was found independent of the strain rate; no obvious pile-up occurred on the AZ91E substrate. The AZ91E substrate exhibited creep rates greater than those of the intermetallic phases, and all of the creep rates increased with the loading rate.

Increasing strength and conductivity of Cu alloy through abnormal plastic deformation of an intermetallic compound

PubMed Central

Han, Seung Zeon; Lim, Sung Hwan; Kim, Sangshik; Lee, Jehyun; Goto, Masahiro; Kim, Hyung Giun; Han, Byungchan; Kim, Kwang Ho

2016-01-01

The precipitation strengthening of Cu alloys inevitably accompanies lowering of their electric conductivity and ductility. We produced bulk Cu alloys arrayed with nanofibers of stiff intermetallic compound through a precipitation mechanism using conventional casting and heat treatment processes. We then successfully elongated these arrays of nanofibers in the bulk Cu alloys to 400% of original length without breakage at room temperature using conventional rolling process. By inducing such an one-directional array of nanofibers of intermetallic compound from the uniform distribution of fine precipitates in the bulk Cu alloys, the trade-off between strength and conductivity and between strength and ductility could be significantly reduced. We observed a simultaneous increase in electrical conductivity by 1.3 times and also tensile strength by 1.3 times in this Cu alloy bulk compared to the conventional Cu alloys. PMID:27488621

Ordered porous mesostructured materials from nanoparticle-block copolymer self-assembly

DOEpatents

Warren, Scott; Wiesner, Ulrich; DiSalvo, Jr., Francis J

2013-10-29

The invention provides mesostructured materials and methods of preparing mesostructured materials including metal-rich mesostructured nanoparticle-block copolymer hybrids, porous metal-nonmetal nanocomposite mesostructures, and ordered metal mesostructures with uniform pores. The nanoparticles can be metal, metal alloy, metal mixture, intermetallic, metal-carbon, metal-ceramic, semiconductor-carbon, semiconductor-ceramic, insulator-carbon or insulator-ceramic nanoparticles, or combinations thereof. A block copolymer/ligand-stabilized nanoparticle solution is cast, resulting in the formation of a metal-rich (or semiconductor-rich or insulator-rich) mesostructured nanoparticle-block copolymer hybrid. The hybrid is heated to an elevated temperature, resulting in the formation of an ordered porous nanocomposite mesostructure. A nonmetal component (e.g., carbon or ceramic) is then removed to produce an ordered mesostructure with ordered and large uniform pores.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

You, Tae-Soo; Bobev, Svilen, E-mail: bobev@udel.ed

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

AN ATTEMPT TO LOCATE INTERMETALLIC PARTICLES IN ZIRCONIUM ALLOYS USING A BITTER FIGURE TECHNIQUE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cox, B.; Harder, B.R.

1961-10-01

The compound ZrFe/sub 2/ is known to be ferromagnetic, and an attempt to locate particles of magnetic material in zircaloy-2 and dilute Zr- Fe alloys by a Bitter figure technlque is described. An Fe/sub 3/O/sub 4/ sol in water-soluble plastic was used to prepare Bitter figures of the alloy surfaces in the form of replicas, which were then examined in an electron microscope. No magnetic particles were located in either zircaloy-2 or a Zr-O.3% Fe alloy. Subsequent work on specimens of ZrFe/sub 2/ showed that the failure to detect it in the dilute alloys arose because the size of themore » intermetallic particles in the latter was smaller than the size of the magnetic domains. (auth)« less

Derivation of mechanical characteristics for Ni/Au intermetallic surface with SAC305 solder

NASA Astrophysics Data System (ADS)

Kim, Jong-Min; Lee, Hyun-Boo; Chang, Yoon-Suk; Choi, Jae-Boong

2013-03-01

Many surface finish methods are used to connect a substrate with the electric components of IT products in the micro-packaging process, and various types of lead-free solder have been developed as alternative materials to lead-based solder to reduce environmental contamination. However, there has been little research on the mechanical properties of the inter-metallic surface which is generated in the bumping process between the lead-free solder and surface films such as Ni/Au. The present work is to derive the material properties of a Ni/Au inter-metallic surface with SAC305 solder. A series of indentation tests were carried out by changing four nano-scale indentation depths and two strain rates. Also, a reverse algorithm method was adopted to determine the elastic-plastic stress-strain curve based on the load-displacement curve from the indentation test data. As a result of the material characterization effort, the mean elastic modulus, yield strength and strain hardening exponent of IMC with Ni/Au finish were determined.

Complex magnetism of lanthanide intermetallics and the role of their valence electrons: Ab Initio theory and experiment

DOE PAGES

Petit, L.; Paudyal, D.; Mudryk, Y.; ...

2015-11-09

We explain a profound complexity of magnetic interactions of some technologically relevant gadolinium intermetallics using an ab initio electronic structure theory which includes disordered local moments and strong f-electron correlations. The theory correctly finds GdZn and GdCd to be simple ferromagnets and predicts a remarkably large increase of Curie temperature with a pressure of +1.5 K kbar –1 for GdCd confirmed by our experimental measurements of +1.6 K kbar –1. Moreover, we find the origin of a ferromagnetic-antiferromagnetic competition in GdMg manifested by noncollinear, canted magnetic order at low temperatures. As a result, replacing 35% of the Mg atoms withmore » Zn removes this transition, in excellent agreement with long-standing experimental data.« less

Spark plasma sintering of titanium aluminide intermetallics and its composites

NASA Astrophysics Data System (ADS)

Aldoshan, Abdelhakim Ahmed

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.

Slow plastic strain rate compressive flow in binary CoAl intermetallics

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.

1985-01-01

Constant-velocity elevated temperature compression tests have been conducted on a series of binary CoAl intermetallics produced by hot extrusion of blended prealloyed powders. The as-extruded materials were polycrystalline, and they retained their nominal 10-micron grain size after being tested between 1100 and 1400 K at strain rates ranging from 2 x 10 to the -4th to 2 x 10 to the -7th per sec. Significant plastic flow was obtained in all cases; while cracking was observed, much of this could be due to failure at matrix-oxide interfaces along extrusion stringers rather than to solely intergranular fracture. A maximum in flow strength occurs at an aluminum-to-cobalt ratio of 0.975, and the stress exponent appears to be constant for aluminum-to-cobalt ratios of 0.85 or more. It is likely that very aluminum-deficient materials deform by a different mechanism than do other compositions.

Influence of Al grain boundaries segregations and La-doping on embrittlement of intermetallic NiAl

NASA Astrophysics Data System (ADS)

Kovalev, Anatoly I.; Wainstein, Dmitry L.; Rashkovskiy, Alexander Yu.

2015-11-01

The microscopic nature of intergranular fracture of NiAl was experimentally investigated by the set of electron spectroscopy techniques. The paper demonstrates that embrittlement of NiAl intermetallic compound is caused by ordering of atomic structure that leads to formation of structural aluminum segregations at grain boundaries (GB). Such segregations contain high number of brittle covalent interatomic bonds. The alloying by La increases the ductility of material avoiding Al GB enrichment and disordering GB atomic structure. The influence of La alloying on NiAl mechanical properties was investigated. GB chemical composition, atomic and electronic structure transformations after La doping were investigated by AES, XPS and EELFS techniques. To qualify the interatomic bonds metallicity the Fermi level (EF) position and electrons density (neff) in conduction band were determined in both undoped and doped NiAl. Basing on experimental results the physical model of GB brittleness formation was proposed.

Sc(2)MgGa(2) and Y(2)MgGa(2).

PubMed

Sahlberg, Martin; Andersson, Yvonne

2009-03-01

Scandium magnesium gallide, Sc(2)MgGa(2), and yttrium magnesium gallide, Y(2)MgGa(2), were synthesized from the corresponding elements by heating under an argon atmosphere in an induction furnace. These intermetallic compounds crystallize in the tetragonal Mo(2)FeB(2)-type structure. All three crystallographically unique atoms occupy special positions and the site symmetries of (Sc/Y, Ga) and Mg are m2m and 4/m, respectively. The coordinations around Sc/Y, Mg and Ga are pentagonal (Sc/Y), tetragonal (Mg) and triangular (Ga) prisms, with four (Mg) or three (Ga) additional capping atoms leading to the coordination numbers [10], [8+4] and [6+3], respectively. The crystal structure of Sc(2)MgGa(2 )was determined from single-crystal diffraction intensities and the isostructural Y(2)MgGa(2) was identified from powder diffraction data.

Cyclic Deformation, Damage, and Effects of Environment in the Ni3Al Ordered Alloy at Elevated Temperature

DTIC Science & Technology

1991-03-29

restricts atomic mobility leading to slower diffusion and perhaps better creep resistance. Ordered intermetallics such as aluminides and silicides are...evaluation of the mechanical properties of these materials (specifically creep , oxidation and fatigue) must be evaluated before implementation in...rate by an order of magnitude (frcm 0.001/s to 0.01/s) doubled the fatigue life at a given plastic strain range. When tested in vacuum environments

ZrB 2-HfB 2 solid solutions as electrode materials for hydrogen reaction in acidic and basic solutions

DOE PAGES

Sitler, Steven J.; Raja, Krishnan S.; Charit, Indrajit

2016-11-09

Spark plasma sintered transition metal diborides such as HfB 2, ZrB 2 and their solid solutions were investigated as electrode materials for electrochemical hydrogen evolutions reactions (HER) in 1 M H 2SO 4 and 1 M NaOH electrolytes. HfB 2 and ZrB 2 formed complete solid solutions when mixed in 1:1, 1:4, and 4:1 ratios and they were stable in both electrolytes. The HER kinetics of the diborides were slower in the basic solution than in the acidic solutions. The Tafel slopes in 1 M H 2SO 4 were in the range of 0.15 - 0.18 V/decade except for puremore » HfB 2 which showed a Tafel slope of 0.38 V/decade. In 1 M NaOH the Tafel slopes were in the range of 0.12 - 0.27 V/decade. The composition of Hf xZr 1-xB 2 solid solutions with x = 0.2 - 0.8, influenced the exchange current densities, overpotentials and Tafel slopes of the HER. As a result, the EIS data were fitted with a porous film equivalent circuit model in order to better understand the HER behavior. In addition, modeling calculations, using density functional theory approach, were carried out to estimate the density of states and band structure of the boride solid solutions.« less

H2MBH2 and M(μ-H)2BH2 Molecules Isolated in Solid Argon: Interelement M-B and M-H-B Bonds (M = Ge, Sn).

PubMed

Zhao, Jie; Beckers, Helmut; Huang, Tengfei; Wang, Xuefeng; Riedel, Sebastian

2018-02-19

Laser-ablated boron atoms react with GeH 4 molecules to form novel germylidene borane H 2 GeBH 2 , which undergoes a photochemical rearrangement to the germanium tetrahydroborate Ge(μ-H) 2 BH 2 upon irradiation with light of λ = 405 nm. For comparison, the boron atom reactions with SnH 4 only gave the tin tetrahydroborate Sn(μ-H) 2 BH 2 . Infrared matrix-isolation spectroscopy with deuterium substitution and the state-of-the-art quantum-chemical calculations are used to identify these species in solid argon. A planar structure of H 2 GeBH 2 with an electron-deficient B-Ge bond with a partial multiple bond character (bond order = 1.5) is predicted by quantum-chemical calculations. In the case of M(μ-H) 2 BH 2 (M = Ge, Sn) two 3c-2e B-H-M hydrogen bridged bonds are formed by donation of electrons from the B-H σ-bonds into empty p-orbitals of M.

Clusters, Assemble: Growth of Intermetallic Compounds from Metal Flux Reactions.

PubMed

Latturner, Susan E

2018-01-16

Metal flux synthesis involves the reaction of metals and metalloids in a large excess of a low-melting metal that acts as a solvent. This technique makes use of an unusual temperature regime (above the temperatures used for solvothermal methods and below the temperatures used in traditional solid state synthesis) and facilitates the growth of products as large crystals. It has proven to be a fruitful method to discover new intermetallic compounds. However, little is known about the chemistry occurring within a molten metal solvent; without an understanding of the nature of precursor formation and assembly, it is difficult to predict product structures and target properties. Organic chemists have a vast toolbox of well-known reagents and reaction mechanisms to use in directing their synthesis toward a desired molecular structure. This is not yet the case for the synthesis of inorganic extended structures. We have carried out extensive explorations of the growth of new magnetic intermetallic compounds from a variety of metal fluxes. This Account presents a review of some of our results and recent reports by other groups; this work indicates that products with common building blocks and homologous series with identical structural motifs are repeatedly seen in metal flux chemistry. For instance, fluorite-type layers comprised of transition metals coordinated by eight main group metal atoms are found in the Th 2 (Au x Si 1-x )[AuAl 2 ] n Si 2 and R[AuAl 2 ] n Al 2 (Au x Si 1-x ) 2 series grown from aluminum flux, the Ce n PdIn 3n+2 series grown from indium flux, and CePdGa 6 and Ce 2 PdGa 10 grown from gallium flux. Similarly, our investigations of reactions of heavy main group metals, M, in rare earth/transition metal eutectic fluxes reveal that the R/T/M/M' products usually feature M-centered rare earth clusters M@R 8-12 , which share faces to form layers and networks that surround transition metal building blocks. These structural trends, temperature dependence of

A New Ordered Si/SiO2 phase: Infrared Spectroscopy Analysis and Modeling

NASA Astrophysics Data System (ADS)

Bradley, J.; Herbots, N.; Shaw, J.; Atluri, V.; Queeney, K. T.; Chabal, Y. J.

2003-10-01

A new ordered Si/SiO2 phase is grown by conventional oxidation on ordered, OH-terminated (1x1)Si(100) surfaces formed at room temperature in ambient using a wet chemical cleaning method [1, 2] combined with conventional oxidation. Si atoms within 1-2.5 nm thick SiO2 are found to be in registry with respect to Si atoms in the Si(100). The degree of ordering is characterized by combining ion channeling with nuclear resonance analysis, as well as Reflective High Energy Electron Diffraction (RHEED), and High Resolution Transmission Electron Microscopy (HRTRM) and is found to be confined to a 2nm region in the SiO2[1]. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Elastic Recoil Deflection (ERD) were used to profile silicon, oxygen, carbon, and hydrogen coverage within the ordered interphase. Most recently, infrared spectroscopy [2] was employed to investigate the bonding at the ordered Si/SiO2 interface and compare the suboxides region to conventional thermal oxides. Infrared spectroscopy shows that the TO red-shift due to SiOx cross-bonding at the Si/SiO2 interface is 50 % smaller and occurs more abruptly than in conventional thermal oxides. This indicates a more homogeneous bonding environment between Si and SiO2, which is consistent with the presence of an ordered phase. Using these results, we are modeling the structure of the 2 nm interphase with 3DSTRING [3]. This Monte Carlo Simulation enables us to compare the channeling spectra with the experimental data for the possible phase configuration in ordered SiOx on Si. [1] N. Herbots, V. Atluri, J. D. Bradley, J. Xiang, S. Banerjee, Q.Hurst, US Patent #6,613,677, Granted 9/2/2003 [2] N. Herbots, J. M. Shaw, Q. B. Hurst, M. P. Grams, R. J. Culbertson, D. J. Smith, V. Atluri, P. Zimmerman, and K. T. Queeney, Mat. Sci. Eng. B B87, 303-316 (2001). [3] K. T. Queeney, N. Herbots, Justin, M. Shaw, V. Atluri, Y. J. Chabal (to be published)

VizieR Online Data Catalog: Sgr B2(N) and Sgr B2(M) IRAM 30m line survey (Belloche+, 2013)

NASA Astrophysics Data System (ADS)

Belloche, A.; Mueller, H. S. P.; Menten, K. M.; Schilke, P.; Comito, C.

2013-08-01

The list of line identifications corresponding to the blue labels in Figs. 2 to 7 where the labels are often too crowded to be easily readable are available in ASCII format. The lists are split into six files, three for Sgr B2(N) and three for Sgr B2(M). For each source, there is one file per atmospheric window (3, 2, and 1mm). Each file is ordered by increasing frequency. The observed and synthetic spectra of Sgr B2(N) and Sgr B2(M) between 80 and 116GHz are available both in ASCII and FITS formats. The synthetic spectra were resampled to the same frequency channels as the observed spectra. The blanking value is -1000K for the ASCII files. There is one ASCII file per source. There are two FITS files per source, one for the observed spectrum and one for the synthetic spectrum. The intensities are in main-beam temperature scale in K. The blanking value is 42.75234K for the observed spectrum of SgrB2(N) and 53.96533K for the observed spectrum of SgrB2(M). (9 data files).

Effects of Fragmented Fe Intermetallic Compounds on Ductility in Al-Si-Mg Alloys.

PubMed

Kim, JaeHwang; Kim, DaeHwan

2018-03-01

Fe is intentionally added in order to form the Fe intermetallic compounds (Fe-IMCs) during casting. Field emission scanning electron microscope with energy dispersive spectrometer (EDS) was conducted to understand microstructural changes and chemical composition analyses. The needlelike Fe-IMCs based on two dimensional observation with hundreds of micro size are modified to fragmented particles with the minimum size of 300 nm through clod rolling with 80% thickness reduction. The ratio of Fe:Si on the fragmented Fe-IMCs after 80% reduction is close to 1:1, representing the β-Al5FeSi. The yield and tensile strengths are increased with increasing reduction rate. On the other hand, the elongation is decreased with the 40% reduction, but slightly increased with the 60% reduction. The elongation is dramatically increased over two times for the specimen of 80% reduction compared with that of the as-cast. Fracture behavior is strongly affected by the morphology and size of Fe-IMCs. The fracture mode is changed from brittle to ductile with the microstructure modification of Fe-IMCs.

Intermediate coupled superconductivity in yttrium intermetallics

NASA Astrophysics Data System (ADS)

Sharma, Ramesh; Ahmed, Gulzar; Sharma, Yamini

2017-09-01

Non-magnetic YIn3, LaIn3 and LuIn3 with a superconducting transition temperature Tc of 0.78, 0.71 and 0.24 K were investigated for superconductivity. Similarly, rare-earth compound LaSn3 has been reported to exhibit superconductivity around 6.25 K, whereas the non-magnetic YSn3 is a superconductor with Tc of 7 K. The substitution of 13th group In-atoms by 14th group Sn-atoms is seen to enhance Tc by nearly one order, although the lattice parameters increase by ∼1.0% in YSn3 compared to YIn3 compound. It is observed from the ground state properties that the slight difference in the energy band structures of YIn3, YIn2Sn and YSn3 gives rise to various complex Fermi surfaces which are multiply connected and exhibit vast differences. The Fermi level lies on a sharp peak in YSn3 which has a higher density of states N(EF), whereas Fermi level lies on the shoulder of a sharp peak in YIn3. The electron localization function (ELF) and difference charge density maps clearly illustrate the difference in the nature of bonding; the Ysbnd Sn bonds are clearly more ionic (due to larger bond length) than Ysbnd In bonds. These results are consistent with the Bader charges which show loss of charges from Y-atoms and a gain of charges by In/Sn atoms. The dynamical properties also clearly illustrate the difference in the nature of bonds in YX3 intermetallics. A softening of the lowermost acoustic modes is observed in YIn3, whereas all the modes in YSn3 are observed to have positive frequencies which imply its greater stability. Since λel-ph < 1, both YIn3 and YSn3 compounds exhibit type I superconductivity according to BCS theory. However, the smaller N(EF) obtained from the density of states (DOS); the electron-phonon coupling constant λel-ph obtained from the temperature dependent specific heat as well as the instability in phonon modes due to stronger Ysbnd In and Insbnd In bonds in YIn3 may be the cause of lower Tc and filamentary nature of superconductivity. Insertion of Sn

Emission lineshapes of the B850 band of light-harvesting 2 (LH2) complex in purple bacteria: a second order time-nonlocal quantum master equation approach.

PubMed

Kumar, Praveen; Jang, Seogjoo

2013-04-07

The emission lineshape of the B850 band in the light harvesting complex 2 of purple bacteria is calculated by extending the approach of 2nd order time-nonlocal quantum master equation [S. Jang and R. J. Silbey, J. Chem. Phys. 118, 9312 (2003)]. The initial condition for the emission process corresponds to the stationary excited state density where exciton states are entangled with the bath modes in equilibrium. This exciton-bath coupling, which is not diagonal in either site excitation or exciton basis, results in a new inhomogeneous term that is absent in the expression for the absorption lineshape. Careful treatment of all the 2nd order terms are made, and explicit expressions are derived for both full 2nd order lineshape expression and the one based on secular approximation that neglects off-diagonal components in the exciton basis. Numerical results are presented for a few representative cases of disorder and temperature. Comparison of emission line shape with the absorption line shape is also made. It is shown that the inhomogeneous term coming from the entanglement of the system and bath degrees of freedom makes significant contributions to the lineshape. It is also found that the perturbative nature of the theory can result in negative portion of lineshape in some situations, which can be removed significantly by inclusion of the inhomogeneous term and completely by using the secular approximation. Comparison of the emission and absorption lineshapes at different temperatures demonstrates the role of thermal population of different exciton states and exciton-phonon couplings.

Structural building principles of complex face-centered cubic intermetallics.

PubMed

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

2011-08-01

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

Enhancing Friction Stir Weldability of 6061-T6 Al and AZ31B Mg Alloys Assisted by External Non-rotational Shoulder

NASA Astrophysics Data System (ADS)

Ji, Shude; Huang, Ruofei; Meng, Xiangchen; Zhang, Liguo; Huang, Yongxian

2017-05-01

In order to increase cooling rate and then reduce the amounts of intermetallic compounds, external non-rotational shoulder tool system derived from traditional tool in friction stir welding was used to join dissimilar Al and Mg alloys. In this study, based on the external non-rotational shoulder, the weldability of Al and Mg alloys was significantly improved. The non-rotational shoulder tool is propitious to make more materials into weld, increase cooling rate and then reduce material adhesion of rotational pin, obtaining sound joint with smaller flashes and smooth surface. Importantly, the thickness of intermetallic compounds layer is reduced compared with traditional tool. Meanwhile, hardness values of dissimilar joint present uneven distribution, resulting from complex intercalated structures in nugget zone (NZ) featured by intermetallic compound layers and fine recrystallized Mg and Al grains. Compared with traditional tool, non-rotational shoulder is beneficial to higher tensile properties of joint. Due to the intermetallic compound layer formed in the interface of Al-Mg, the welding joint easily fractures at the NZ, presenting the typical brittle fracture mode.

Compressibility behaviour of conducting ceramic TiB2

NASA Astrophysics Data System (ADS)

Arpita Aparajita, A. N.; Kumar, N. R. Sanjay; Shekar, N. V. Chandra; Kalavathi, S.

2017-09-01

To address the large spread in the bulk modulus value of TiB2 reported in literature, high pressure compressibility study of a phase pure polycrystalline sample has been carried out using in situ high pressure x-ray diffraction technique (HPXRD) in angle dispersive mode. The study has been done up to 23 GPa at ambient temperature with methanol-ethanol-water (MEW) as pressure transmitting medium. The hexagonal lattice has been found to be stable in the pressure range studied. The isothermal bulk modulus is estimated to be 333(6) GPa by employing 3rd order Birch-Murnaghan equation of state. The obtained high value of bulk modulus is understood in terms of band filling effect, and the nature of bonding between B-B and Ti-B in TiB2. Compressibility along ‘a’ and ‘c’ axis is found to be anisotropic with compressibility values of 0.93(2) TPa-1 and 1.14(2) TPa-1 respectively. From the estimated bond lengths for Ti-B and B-B it is found that B-B bonds are less compressible compared to Ti-B bonds which is in accordance with the respective nature of Ti-B and B-B bonds. A change in the rate of bond contraction was seen around 12 GPa which is due to the bond hardening for both Ti-B and B-B bonds with pressure.

B11 NMR in the layered diborides OsB2 and RuB2

NASA Astrophysics Data System (ADS)

Suh, B. J.; Zong, X.; Singh, Y.; Niazi, A.; Johnston, D. C.

2007-10-01

B11 nuclear magnetic resonance (NMR) measurements have been performed on B11 enriched OsB2 and RuB2 polycrystalline powder samples in an external field of 4.7T and in the temperature range, 4.2KB2 and RuB2 , respectively. The experimental results indicate that a p character dominates the conduction electron wave function at the B site with a negligibly small s character in both compounds.

Kondo lattice heavy fermion behavior in CeRh2Ga2

NASA Astrophysics Data System (ADS)

Anand, V. K.; Adroja, D. T.; Bhattacharyya, A.; Klemke, B.; Lake, B.

2017-04-01

The physical properties of an intermetallic compound CeRh2Ga2 have been investigated by magnetic susceptibility χ (T) , isothermal magnetization M(H), heat capacity {{C}\\text{p}}(T) , electrical resistivity ρ (T) , thermal conductivity κ (T) and thermopower S(T) measurements. CeRh2Ga2 is found to crystallize with CaBe2Ge2-type primitive tetragonal structure (space group P4/nmm). No evidence of long range magnetic order is seen down to 1.8 K. The χ (T) data show paramagnetic behavior with an effective moment {μ\\text{eff}}≈ 2.5~{μ\\text{B}} /Ce indicating Ce3+ valence state of Ce ions. The ρ (T) data exhibit Kondo lattice behavior with a metallic ground state. The low-T {{C}\\text{p}}(T) data yield an enhanced Sommerfeld coefficient γ =130(2) mJ/mol K2 characterizing CeRh2Ga2 as a moderate heavy fermion system. The high-T {{C}\\text{p}}(T) and ρ (T) show an anomaly near 255 K, reflecting a phase transition. The κ (T) suggests phonon dominated thermal transport with considerably higher values of Lorenz number L(T) compared to the theoretical Sommerfeld value L 0.

Directed Self-Assembly of Poly(2-vinylpyridine)-b-polystyrene-b-poly(2-vinylpyridine) Triblock Copolymer with Sub-15 nm Spacing Line Patterns Using a Nanoimprinted Photoresist Template.

PubMed

Sun, Zhiwei; Chen, Zhenbin; Zhang, Wenxu; Choi, Jaewon; Huang, Caili; Jeong, Gajin; Coughlin, E Bryan; Hsu, Yautzong; Yang, XiaoMin; Lee, Kim Y; Kuo, David S; Xiao, Shuaigang; Russell, Thomas P

2015-08-05

Low molecular weight P2VP-b-PS-b-P2VP triblock copolymer (poly(2-vinlypyridine)-block-polystyrene-block-poly(2-vinylpyridine)] is doped with copper chloride and microphase separated into lamellar line patterns with ultrahigh area density. Salt-doped P2VP-b-PS-b-P2VP triblock copolymer is self-assembled on the top of the nanoimprinted photoresist template, and metallic nanowires with long-range ordering are prepared with platinum-salt infiltration and plasma etching. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Melt-Spun Fe-Sb Intermetallic Alloy Anode for Performance Enhanced Sodium-Ion Batteries.

PubMed

Edison, Eldho; Sreejith, Sivaramapanicker; Madhavi, Srinivasan

2017-11-15

Owing to the high theoretical sodiation capacities, intermetallic alloy anodes have attracted considerable interest as electrodes for next-generation sodium-ion batteries (SIBs). Here, we demonstrate the fabrication of intermetallic Fe-Sb alloy anode for SIBs via a high-throughput and industrially viable melt-spinning process. The earth-abundant and low-cost Fe-Sb-based alloy anode exhibits excellent cycling stability with nearly 466 mAh g -1 sodiation capacity at a specific current of 50 mA g -1 with 95% capacity retention after 80 cycles. Moreover, the alloy anode displayed outstanding rate performance with ∼300 mAh g -1 sodiation capacity at 1 A g -1 . The crystalline features of the melt-spun fibers aid in the exceptional electrochemical performance of the alloy anode. Further, the feasibility of the alloy anode for real-life applications was demonstrated in a sodium-ion full-cell configuration which could deliver a sodiation capacity of over 300 mAh g -1 (based on anode) at 50 mA g -1 with more than 99% Coulombic efficiency. The results further exhort the prospects of melt-spun alloy anodes to realize fully functional sodium-ion batteries.

Crystal structures of the new ternary stannides La3Mg4-xSn2+x and LaMg3-xSn2

NASA Astrophysics Data System (ADS)

Solokha, P.; De Negri, S.; Minetti, R.; Proserpio, D. M.; Saccone, A.

2016-01-01

Synthesis and structural characterization of the two new lanthanum-magnesium-stannides La3Mg4-xSn2+x (0.12≤x≤0.40) and LaMg3-xSn2 (0.33≤x≤0.78) are reported. The crystal structures of these intermetallics were determined by single crystal X-ray diffraction analysis and confirmed by Rietveld refinement of powder X-ray diffraction patterns of the corresponding samples. The La3Mg4-xSn2+x phase crystallizes in the hexagonal Zr3Cu4Si2 structure type (P6bar2m, hP9, Z=3, x=0.12(1), a=7.7974(7), c=4.8384(4) Å), which represents an ordered derivative of the hP9-ZrNiAl prototype, ubiquitous among equiatomic intermetallics. The LaMg3-xSn2 phase is the second representative of the trigonal LaMg3-xGe2 type, which is a superstructure of the LaLi3Sb2 structure type (P3bar1c, hP34-0.12, Z=6, x=0.35(1), a=8.3222(9), c=14.9546(16) Å). The scheme describing the symmetry reduction/coloring with respect to the parent type is reported here with the purpose to discuss the LaMg3-xSn2 off-stoichiometry from the geometrical point of view. Structural relationships between the La-Mg-Sn ternary phases, including the already known equiatomic LaMgSn compound (oP12-TiNiSi), are presented in the framework of the AlB2-related compounds family and discussed with the aid of group-subgroup relations in the Bärnighausen formalism.

Selective field evaporation in field-ion microscopy for ordered alloys

NASA Astrophysics Data System (ADS)

Ge, Xi-jin; Chen, Nan-xian; Zhang, Wen-qing; Zhu, Feng-wu

1999-04-01

Semiempirical pair potentials, obtained by applying the Chen-inversion technique to a cohesion equation of Rose et al. [Phys. Rev. B 29, 2963 (1984)], are employed to assess the bonding energies of surface atoms of intermetallic compounds. This provides a new calculational model of selective field evaporation in field-ion microscopy (FIM). Based on this model, a successful interpretation of FIM image contrasts for Fe3Al, PtCo, Pt3Co, Ni4Mo, Ni3Al, and Ni3Fe is given.

Production of B atoms and BH radicals from B2H6/He/H2 mixtures activated on heated W wires.

PubMed

Umemoto, Hironobu; Kanemitsu, Taijiro; Tanaka, Akihito

2014-07-17

B atoms and BH radicals could be identified by laser-induced fluorescence when B2H6/He/H2 mixtures were activated on heated tungsten wires. The densities of these radical species increased not only with the wire temperature but also with the partial pressure of H2. The densities in the presence of 0.026 Pa of B2H6 and 2.6 Pa of H2 were on the order of 10(11) cm(-3) both for B and BH when the wire temperature was 2000 K. Densities in the absence of a H2 flow were much smaller, suggesting that the direct production of these species on wire surfaces is minor. B and BH must be produced in the H atom shifting reactions, BH(x) + H → BH(x-1) + H2 (x = 1-3), in the gas phase, while H atoms are produced from H2 on wire surfaces. The B atom density increased monotonously with the H atom density, while the BH density showed saturation. These tendencies could be reproduced by simple modeling based on ab initio potential energy calculations and the transition-state theoretical calculations of the rate constants. The absolute densities could also be reproduced within a factor of 2.5.

Influence of Electron Doping on Magnetic Order in CeRu 2Al 10

DOE PAGES

Kobayashi, Riki; Kaneko, Koji; Saito, Kotaro; ...

2014-09-17

The effect of electron doping by the substitution of Rh for Ru on unconventional magnetic order in CeRu 2Al 10 was investigated via neutron powder diffraction. In Ce(Ru 1-xRh x) 2Al 10 with x = 0.05, 0.12, and 0.2, reorientation of the ordered moment from the c- to the a-axis takes place in all samples, while the ordering vector q=(0 1 0) remains unchanged within this concentration range. The moment reorientation is accompanied by an enhancement in its size by a factor of ~2.4, from μ=0.43 μ B at x=0 to μ =1.06, 1.04, and 1.02 μ B for x=0.05,more » 0.12 and 0.2, respectively. The continuous decrease in N´eel temperature T 0(T N), despite an abrupt increase in μ , underlines the strong anisotropy in the exchange interaction in CeRu 2Al 10, and the fact that this anisotropy is easily suppressed by electron doping.« less

High-Resolution Synchrotron Infrared Spectroscopy of Thiophosgene: the νb{1}, νb{5}, 2νb{4}, and νb{2} + 2νb{6} bands

NASA Astrophysics Data System (ADS)

McKellar, Bob; Billinghurst, Brant E.

2015-06-01

Thiophosgene (Cl_2CS) is a favorite model system for studies of photophysics, vibrational dynamics, and intersystem interactions. But at high resolution its infrared spectrum is very congested due to hot bands and multiple isotopic species. Previously, we reported the first high resolution IR study of this molecule, analyzing the νb{2} (504 wn) and νb{4} (471 wn) fundamental bands. Here we continue, with analysis of the νb{1} (1139 wn) and νb{5} (820 wn) fundamentals for the two most abundant isotopologues, 35Cl2CS and 35Cl37ClCS, based on spectra with a resolution of about 0.001 wn obtained at the Canadian Light Source far-infrared beamline using synchrotron radiation and a Bruker IFS125 Fourier transform spectrometer. The νb{2} + νb{4} (942 wn) and νb{2} + 2νb{6} (1104 wn) bands are also studied here. But so far the νb{2} + νb{6} combination band (795 wn) resists analysis, as do the weak νb{3} (292.9 wn) and νb{6} (≈300? wn) fundamentals. A.R.W. McKellar, B.E.Billinghurst, J. Mol. Spectrosc. 260, 66 (2010).

DOE-EPSCoR. Exchange interactions in epitaxial intermetallic layered systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

LeClair, Patrick R.; Gary, Mankey J.

2015-05-25

The goal of this research is to develop a fundamental understanding of the exchange interactions in epitaxial intermetallic alloy thin films and multilayers, including films and multilayers of Fe-Pt, Co-Pt and Fe-P-Rh alloys deposited on MgO and Al2O3 substrates. Our prior results have revealed that these materials have a rich variety of ferromagnetic, paramagnetic and antiferromagnetic phases which are sensitive functions of composition, substrate symmetry and layer thickness. Epitaxial antiferromagnetic films of FePt alloys exhibit a different phase diagram than bulk alloys. The antiferromagnetism of these materials has both spin ordering transitions and spin orienting transitions. The objectives include themore » study of exchange-inversion materials and the interface of these materials with ferromagnets. Our aim is to formulate a complete understanding of the magnetic ordering in these materials, as well as developing an understanding of how the spin structure is modified through contact with a ferromagnetic material at the interface. The ultimate goal is to develop the ability to tune the phase diagram of the materials to produce layered structures with tunable magnetic properties. The alloy systems that we will study have a degree of complexity and richness of magnetic phases that requires the use of the advanced tools offered by the DOE-operated national laboratory facilities, such as neutron and x-ray scattering to measure spin ordering, spin orientations, and element-specific magnetic moments. We plan to contribute to DOE’s mission of producing “Materials by Design” with properties determined by alloy composition and crystal structure. We have developed the methods for fabricating and have performed neutron diffraction experiments on some of the most interesting phases, and our work will serve to answer questions raised about the element-specific magnetizations using the magnetic x-ray dichroism techniques and interface magnetism in layered

A Fast Healthcare Interoperability Resources (FHIR) layer implemented over i2b2.

PubMed

Boussadi, Abdelali; Zapletal, Eric

2017-08-14

Standards and technical specifications have been developed to define how the information contained in Electronic Health Records (EHRs) should be structured, semantically described, and communicated. Current trends rely on differentiating the representation of data instances from the definition of clinical information models. The dual model approach, which combines a reference model (RM) and a clinical information model (CIM), sets in practice this software design pattern. The most recent initiative, proposed by HL7, is called Fast Health Interoperability Resources (FHIR). The aim of our study was to investigate the feasibility of applying the FHIR standard to modeling and exposing EHR data of the Georges Pompidou European Hospital (HEGP) integrating biology and the bedside (i2b2) clinical data warehouse (CDW). We implemented a FHIR server over i2b2 to expose EHR data in relation with five FHIR resources: DiagnosisReport, MedicationOrder, Patient, Encounter, and Medication. The architecture of the server combines a Data Access Object design pattern and FHIR resource providers, implemented using the Java HAPI FHIR API. Two types of queries were tested: query type #1 requests the server to display DiagnosticReport resources, for which the diagnosis code is equal to a given ICD-10 code. A total of 80 DiagnosticReport resources, corresponding to 36 patients, were displayed. Query type #2, requests the server to display MedicationOrder, for which the FHIR Medication identification code is equal to a given code expressed in a French coding system. A total of 503 MedicationOrder resources, corresponding to 290 patients, were displayed. Results were validated by manually comparing the results of each request to the results displayed by an ad-hoc SQL query. We showed the feasibility of implementing a Java layer over the i2b2 database model to expose data of the CDW as a set of FHIR resources. An important part of this work was the structural and semantic mapping between the

Influence of severe plastic deformation on intermetallic particles in Mg-12 wt.%Zn alloy investigated using transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Němec, M., E-mail: nemecm@fzu.cz

The in-depth microstructural characterization of intermetallic particles in an Mg-12 wt.%Zn binary alloy subjected to a severe plastic deformation is presented. The alloy was processed by four passes via equal channel angular pressing with an applied back pressure at a gradually decreasing temperature and analyzed using transmission electron microscopy techniques to observe the influence of processing on intermetallic particles. The results are compared with the initial state of the material prior to severe plastic deformation. The microstructural evolution of the α-Mg matrix and the Mg{sub 21}Zn{sub 25}, Mg{sub 51}Zn{sub 20} and MgZn{sub 2} was analyzed using bright field imaging, selectedmore » area electron diffraction, high-resolution transmission electron microscopy and high-angle annular dark field imaging in scanning mode. The plastic deformation process influenced the α-Mg matrix and each type of intermetallic particle. The α-Mg matrix consisted of two types of areas. The first type of area had a highly deformed structure, and the second type of area had a partially recrystallized structure with an average grain size of approximately 250 nm. The Mg{sub 21}Zn{sub 25} microparticles exhibited distinct forms in the α-Mg matrix that were characterized as a single-crystalline form, a nano-crystalline form and a broken up form. No evidence of Mg{sub 51}Zn{sub 20} nanoparticles within the α-Mg matrix was found in the microstructure, which indicates their dissolution or phase transformation during the deformation process. MgZn{sub 2} nanoparticles exhibited different behavior in both types of α-Mg matrix. Two orientation relationships toward the highly deformed α-Mg matrix were observed; however, there was no relationship toward the partially recrystallized α-Mg matrix. Additionally, the growth of the MgZn{sub 2} nanoparticles was different in the two types of α-Mg matrix. The Mg{sub 51}Zn{sub 20} nanoparticles inside Mg{sub 21}Zn{sub 25} microparticles

A theoretical investigation of mixing thermodynamics, age-hardening potential, and electronic structure of ternary M11–xM2xB2 alloys with AlB2 type structure

PubMed Central

Alling, B.; Högberg, H.; Armiento, R.; Rosen, J.; Hultman, L.

2015-01-01

Transition metal diborides are ceramic materials with potential applications as hard protective thin films and electrical contact materials. We investigate the possibility to obtain age hardening through isostructural clustering, including spinodal decomposition, or ordering-induced precipitation in ternary diboride alloys. By means of first-principles mixing thermodynamics calculations, 45 ternary M11–xM2xB2 alloys comprising MiB2 (Mi = Mg, Al, Sc, Y, Ti, Zr, Hf, V, Nb, Ta) with AlB2 type structure are studied. In particular Al1–xTixB2 is found to be of interest for coherent isostructural decomposition with a strong driving force for phase separation, while having almost concentration independent a and c lattice parameters. The results are explained by revealing the nature of the electronic structure in these alloys, and in particular, the origin of the pseudogap at EF in TiB2, ZrB2, and HfB2. PMID:25970763

Method of fabricating a homogeneous wire of inter-metallic alloy

DOEpatents

Ohriner, Evan Keith; Blue, Craig Alan

2001-01-01

A method for fabricating a homogeneous wire of inter-metallic alloy comprising the steps of providing a base-metal wire bundle comprising a metal, an alloy or a combination thereof; working the wire bundle through at least one die to obtain a desired dimension and to form a precursor wire; and, controllably heating the precursor wire such that a portion of the wire will become liquid while simultaneously maintaining its desired shape, whereby substantial homogenization of the wire occurs in the liquid state and additional homogenization occurs in the solid state resulting in a homogenous alloy product.

Chemical Frustration. A Design Principle for the Discovery of New Complex Alloy and Intermetallic Phases, Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fredrickson, Daniel C

2015-06-23

Final technical report for "Chemical Frustration: A Design Principle for the Discovery of New Complex Alloy and Intermetallic Phases" funded by the Office of Science through the Materials Chemistry Program of the Office of Basic Energy Sciences.

Order, viscoelastic, and dielectric properties of symmetric and asymmetric alkyl[1]benzothieno[3,2-b][1]benzothiophenes.

PubMed

Grigoriadis, Christos; Niebel, Claude; Ruzié, Christian; Geerts, Yves H; Floudas, George

2014-02-06

The morphology, the viscoelastic, the dielectric properties and the dynamics of phase transformation are studied in symmetrically and asymmetrically substituted alkyl[1]benzothieno[3,2-b][1]benzothiophenes (C8-BTBT) by X-ray scattering, rheology, and dielectric spectroscopy. The interlayer spacing reflects the molecular and supramolecular ordering, respectively, in the symmetrically and asymmetrically substituted BTBTs. In the asymmetric BTBT, the core layer is double in size with a broader network of intermolecular interactions though the increased S-S contacts that is prerequisite for the development of high performance OFET devices. Two crystal states with elastic and viscoelastic responses were identified in the symmetric compound. In contrast, the SmA phase in the asymmetric compound is a viscoelastic solid. A path-dependent dielectric environment with a switchable dielectric permittivity was found in both compounds by cooling below 0 °C with possible implications to charge transport. The kinetics of phase transformation to the crystalline and SmA phases revealed a nucleation and growth mechanism with rates dominated by the low activation barriers.

Novel Gold Intermetallics with Unique Properties and Bonding Patterns

NASA Astrophysics Data System (ADS)

Celania, Christopher Ranger

Gold has drawn the fascination of society through its brilliant color, malleability, and chemical resistance (hence its chemical nobility) since its discovery in ancient times. Today, this material is still highly coveted by consumers, but also for research within the scientific realm. The inclusion of gold in intermetallics often leads to notably unique structural and bonding features due to the pronounced relativistic effects on its 5d and 6s orbitals. Examples include quasicrystals and their approximants, unique gold clusters such as isolated Au7 clusters in A4Au7X2 (A = K, Rb, Cs; X = Ge, Sn), one dimensional columns such as Au zig-zag chains through Ca3Au3In, two dimensional slabs, such as in K2 Au3, as well as three dimensional gold networks as observed in the interconnected trigonal bipyramids in KAu5, hexagonal diamond-like frameworks of Au tetrahedra in Au-rich Sr-Au-Al systems; and combinations of tetrahedral and fourfold planar Au atoms in Rb3Au7. In recent years, compounds in the gold-rich region of the R-Au- M system (R = rare earth, M = groups 13-15) have come under increased study. Many compounds within this system produce varied electronic and magnetic properties such as Pauli paramagnetism, superconductivity, thermoelectricity, etc. The shielded 4f electrons of the added rare earth elements provide the unpaired spins that lead to the wealth of interesting magnetic properties in their compounds. Metals and metalloids from groups 13-15 may then be used as a bank of available options useful in tuning the valence electron count of the R-Au system toward the formation of stable compounds. Exploration of the Gd-Au-Sb system by utilizing common solid state synthesis techniques frequently used for the production of intermetallics (such as arc melting and high-temperature furnaces for self-flux reactions with low melting components) has yielded rich outcomes. These results include the discovery of a new R3Au9Pn series of compounds (R = Y, Gd-Ho; Pn = Sb, Bi

Friction stir welding joint of dissimilar materials between AZ31B magnesium and 6061 aluminum alloys: Microstructure studies and mechanical characterizations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohammadi, J.; Behnamian, Y.; Mostafaei, A., E-mail: amir.mostafaei@gmail.com

2015-03-15

Friction stir welding is an efficient manufacturing method for joining dissimilar alloys, which can dramatically reduce grain sizes and offer high mechanical joint efficiency. Lap FSW joints between dissimilar AZ31B and Al 6061 alloy sheets were made at various tool rotation and travel speeds. Rotation and travel speeds varied between 560–1400 r/min and 16–40 mm/min respectively, where the ratio between these parameters was such that nearly constant pitch distances were applied during welding. X-ray diffraction pattern (XRD), optical microscopy images (OM), electron probe microanalysis (EPMA) and scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM-EDS) were used to investigatemore » the microstructures of the joints welded. Intermetallic phases including Al{sub 12}Mg{sub 17} (γ) and Al{sub 3}Mg{sub 2} (β) were detected in the weld zone (WZ). For different tool rotation speeds, the morphology of the microstructure in the stir zone changed significantly with travel speed. Lap shear tensile test results indicated that by simultaneously increasing the tool rotation and travel speeds to 1400 r/min and 40 mm/min, the joint tensile strength and ductility reached a maximum. Microhardness measurements and tensile stress–strain curves indicated that mechanical properties were affected by FSW parameters and mainly depended on the formation of intermetallic compounds in the weld zone. In addition, a debonding failure mode in the Al/Mg dissimilar weld nugget was investigated by SEM and surface fracture studies indicated that the presence of intermetallic compounds in the weld zone controlled the failure mode. XRD analysis of the fracture surface indicated the presence of brittle intermetallic compounds including Al{sub 12}Mg{sub 17} (γ) and Al{sub 3}Mg{sub 2} (β). - Highlights: • Dissimilar Al/Mg joint was obtained by lap friction stir welding technique. • Effect of rotation and travel speeds on the formation of intermetallic

Hidden order signatures in the antiferromagnetic phase of U (Ru1-xFex) 2Si2

NASA Astrophysics Data System (ADS)

Williams, T. J.; Aczel, A. A.; Stone, M. B.; Wilson, M. N.; Luke, G. M.

2017-03-01

We present a comprehensive set of elastic and inelastic neutron scattering measurements on a range of Fe-doped samples of U (Ru1-xFex) 2Si2 with 0.01 ≤x ≤0.15 . All of the samples measured exhibit long-range antiferromagnetic order, with the size of the magnetic moment quickly increasing to 0.51 μB at 2.5% doping and continuing to increase monotonically with doping, reaching 0.69 μB at 15% doping. Time-of-flight and inelastic triple-axis measurements show the existence of excitations at (1 0 0) and (1.4 0 0) in all samples, which are also observed in the parent compound. While the excitations in the 1% doping are quantitatively identical to the parent material, the gap and width of the excitations change rapidly at 2.5% Fe doping and above. The 1% doped sample shows evidence for a separation in temperature between the hidden order and antiferromagnetic transitions, suggesting that the antiferromagnetic state emerges at very low Fe dopings. The combined neutron scattering data suggest not only discontinuous changes in the magnetic moment and excitations between the hidden order and antiferromagnetic phases, but that these changes continue to evolve up to at least x =0.15 .

Neutron diffraction study of Tb0.5Ho0.5Mn2Si2

NASA Astrophysics Data System (ADS)

Pandey, Swati; Siruguri, Vasudeva; Rawat, Rajeev

2018-02-01

The magnetic properties of tetragonal polycrystalline intermetallic compound Tb0.5Ho0.5Mn2Si2 have been investigated using temperature dependent dc magnetic susceptibility and neutron powder diffraction studies. Results of high temperature susceptibility data shows anomaly at TN = 510 K while low temperature susceptibility data indicate two successive anomalies at T1 = 11 K and T2 = 25 K. Metamagnetic transition is observed in magnetization versus field curves. Our neutron diffraction results indicate three different magnetic regions with different magnetic structures. Neutron diffraction data shows that below T2, the intensities of some of the nuclear peaks get enhanced indicating ferromagnetic ordering, while additional magnetic reflections are observed below T1, indicating antiferromagnetic order. Ordering of rare earth sublattice at low temperature rearranges the ordering of Mn sublattice and results in reorientation of Mn spins at T1. At 2 K Tb/Ho moments are aligned along c-axis while Mn moments are aligned perpendicular to c-axis.

Launch Load Resistant Spacecraft Mechanism Bearings Made From NiTi Superelastic Intermetallic Materials

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher; Moore, Lewis E.

2014-01-01

Compared to conventional bearing materials (tool steel and ceramics), emerging Superelastic Intermetallic Materials (SIMs), such as 60NiTi, have significantly lower elastic modulus and enhanced strain capability. They are also immune to atmospheric corrosion (rusting). This offers the potential for increased resilience and superior ability to withstand static indentation load without damage. In this paper, the static load capacity of hardened 60NiTi 50mm bore ball-bearing races are measured to correlate existing flat-plate indentation load capacity data to an actual bearing geometry through the Hertz stress relations. The results confirmed the validity of using the Hertz stress relations to model 60NiTi contacts; 60NiTi exhibits a static stress capability (3.1GPa) between that of 440C (2.4GPa) and REX20 (3.8GPa) tool steel. When the reduced modulus and extended strain capability are taken into account, 60NiTi is shown to withstand higher loads than other bearing materials. To quantify this effect, a notional space mechanism, a 5kg mass reaction wheel, was modeled with respect to launch load capability when supported on 440C, 60NiTi and REX20 tool steel bearings. For this application, the use of REX20 bearings increased the static load capability of the mechanism by a factor of three while the use of 60NiTi bearings resulted in an order of magnitude improvement compared to the baseline 440C stainless steel bearings.

Ab-initio thermodynamic and elastic properties of AlNi and AlNi3 intermetallic compounds

NASA Astrophysics Data System (ADS)

Yalameha, Shahram; Vaez, Aminollah

2018-04-01

In this paper, thermodynamic and elastic properties of the AlNi and AlNi3 were investigated using density functional theory (DFT). The full-potential linearized augmented plane-wave (APW) in the framework of the generalized gradient approximation as used as implemented in the Wien2k package. The temperature dependence of thermal expansion coefficient, bulk modulus and heat capacity in a wide range of temperature (0-1600 K) were investigated. The calculated elastic properties of the compounds show that both intermetallic compounds of AlNi and AlNi3 have surprisingly negative Poisson’s ratio (NPR). The results were compared with other experimental and computational data.

Influence of the Heterogeneous Nucleation Sites on the Kinetics of Intermetallic Phase Formation in Aged Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Melo, Elis Almeida; Magnabosco, Rodrigo

2017-11-01

The aim of this work is to study the influence of the heterogeneous nucleation site quantity, observed in different ferrite and austenite grain size samples, on the phase transformations that result in intermetallic phases in a UNS S31803 duplex stainless steel (DSS). Solution treatment was conducted for 1, 24, 96, or 192 hours at 1373 K (1100 °C) to obtain different ferrite and austenite grain sizes. After solution treatment, isothermal aging treatments for 5, 8, 10, 20, 30, or 60 minutes at 1123 K (850 °C) were performed to verify the influence of different amounts of heterogeneous nucleation sites in the kinetics of intermetallic phase formation. The sample solution treated for 1 hour, with the highest surface area between matrix phases, was the one that presented, after 60 minutes at 1123 K (850 °C), the smaller volume fraction of ferrite (indicative of greater intermetallic phase formation), higher volume of sigma (that was present in coral-like and compact morphologies), and chi phase. It was not possible to identify which was the first nucleated phase, sigma or chi. It was also observed that the phase formation kinetics is higher for the sample solution treated for 1 hour. It was evidenced that, from a certain moment on, the chi phase begins to be consumed due to the sigma phase formation, and the austenite/ferrite interface presents higher S V for all solution treatment times. It was also observed that intermetallic phases form preferably in austenite-ferrite interfaces, although the higher occupation rate occurs at triple junction ferrite-ferrite-ferrite. It was verified that there was no saturation of nucleation sites in any interface type nor triple junction, and the equilibrium after 1 hour of aging at 1123 K (850 °C) was not achieved. It was then concluded that sigma phase formation is possibly controlled by diffusional processes, without saturation of nucleation sites.

Melt impregnation as a post processing treatment for performance enhancement in high capacity 3D microporous tin-copper-nickel intermetallic anode for Li-ion battery supported by electrodeposited nickel scaffold: A structural study

NASA Astrophysics Data System (ADS)

Sengupta, Srijan; Patra, Arghya; Mitra, Arijit; Jena, Sambedan; Das, Karabi; Majumder, Subhasish Basu; Das, Siddhartha

2018-05-01

This paper communicates stabilization of a Sn anode by impregnating it within the porous framework of a Ni-scaffold. The impregnation is carried out by electrodeposition Sn on Ni-foam followed by heating at 300 °C for 1 h. The Ni-foam was also electrodeposited on a Cu foil prior to deposition of Sn. The melting step leads to the formation of Nisbnd Sn and Cusbnd Sn intermetallics within pores of the Ni-scaffold. Snsbnd Cu/Ni intermetallics lithiate following the active-inactive strategy in which the inactive Cu/Ni buffers the volume expansion while Sn lithiates. Furthermore, this entire process takes place within Ni-scaffold which resists material pulverization and delamination and provide better electronic pathway for charge transfer. This active-inactive Sn:Snsbnd Cu/Ni intermetallic within a protected Ni-scaffold assembly results in 100th cycle discharge capacity of 587.9 mA h/g at a rate of 500 mA/g (0.5 C), and superior rate capability delivering 463 mAh/g at a rate of 2 A/g (2 C) while retaining structural integrity as compared to pure Sn electrodeposited (without heat-treatment) on the nickel scaffold.

Spectroscopic Properties of B2O3-PbO-Nd2O3 Glasses

NASA Astrophysics Data System (ADS)

Simon, V.; Ardelean, I.; Milea, I.; Peteanu, M.; Simon, S.

Samples belonging to xNd2O3(100-x) [2B2O3·PbO] glass system, with 0≤ x≤ 40 mol%, are investigated by IR and UV-VIS spectroscopies in order to obtain evidence for the influence of Nd2O3 on the local order from 2B2O3·PbO glass matrix. Besides the IR absorption bands characteristic to lead and boron arrangements, typical absorption lines of Nd3+ ions around 4000 cm-1 and 6000 cm-1 are recorded. The 6000 cm-1 band appears only for the samples with x≥25 mol% Nd2O3. The split of some UV-VIS absorption bands arising from transitions of neodymium ions in doublet lines as well as the shift of the absorption bands as the Nd2O3 content increases denote the influence of the lead-borate matrix on the radiative transitions of the lanthanide ion.

Degradation kinetics of aflatoxin B1 and B2 in solid medium by using pulsed light irradiation.

PubMed

Wang, Bei; Mahoney, Noreen E; Khir, Ragab; Wu, Bengang; Zhou, Cunshan; Pan, Zhongli; Ma, Haile

2018-04-10

Pulsed light (PL) is a new potential technology to degrade aflatoxin. The objective of this study was to investigate the degradation characters of aflatoxin B 1 (AFB 1 ) and B 2 (AFB 2 ) treated under PL irradiation. A kinetic degradation study of AFB 1 and AFB 2 in solid medium was performed under PL irradiation at different initial concentrations of AFB 1 (229.9, 30.7 and 17.8 μg kg -1 ) and AFB 2 (248.2, 32.2 and 19.5 μg kg -1 ) and irradiation intensities (2.86, 1.60 and 0.93 W cm -2 ) of PL. A second-order reaction model was applied to describe degradation of AFB 1 and AFB 2 . The results showed that the degradation of AFB 1 and AFB 2 followed the second-order reaction kinetic model well (R 2  > 0.97). The degradation rate was proportional to the intensities of PL irradiation and the initial concentrations of aflatoxins. It is concluded that the degradation of AFB 1 and AFB 2 with the use of PL could be accurately described using the second-order reaction kinetic model. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

Towards next-to-next-to-leading-log accuracy for the width difference in the {B}_s-{\\overline{B}}_s system: fermionic contributions to order ( m c /m b )0 and ( m c /m b )1

NASA Astrophysics Data System (ADS)

Asatrian, H. M.; Hovhannisyan, A.; Nierste, U.; Yeghiazaryan, A.

2017-10-01

We calculate a class of three-loop Feynman diagrams which contribute to the next-to-next-to-leading logarithmic approximation for the width difference ΔΓ s in the {B}_s-{\\overline{B}}_s system. The considered diagrams contain a closed fermion loop in a gluon propagator and constitute the order α s 2 N f , where N f is the number of light quarks. Our results entail a considerable correction in that order, if ΔΓ s is expressed in terms of the pole mass of the bottom quark. If the \\overline{MS} scheme is used instead, the correction is much smaller. As a result, we find a decrease of the scheme dependence. Our result also indicates that the usually quoted value of the NLO renormalization scale dependence underestimates the perturbative error.

First-principles investigation of thermodynamic, elastic and electronic properties of Al{sub 3}V and Al{sub 3}Nb intermetallics under pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zhe; Zhang, Peng; Chen, Dong

2015-02-28

The thermodynamic, elastic, and electronic properties of D0{sub 22}-type Al{sub 3}V and Al{sub 3}Nb intermetallics were studied using the first-principle method. The results showed the pressure has profound effects on the structural, mechanical and electronic properties in both Al{sub 3}V and Al{sub 3}Nb. Thermodynamically, the formation enthalpies for Al{sub 3}V and Al{sub 3}Nb were derived, which agreed well with available experimental and theoretical values. Comparably, Al{sub 3}Nb was a more stable phase with the more negative H{sub f} than Al{sub 3}V. Mechanically, the calculated elastic constants showed linearly increasing tendencies, and satisfied the Born's criteria from 0–20 GPa, indicating the mechanicallymore » stability of Al{sub 3}V and Al{sub 3}Nb under this pressure range. Further, the mechanical parameters (i.e., bulk modulus (B), shear modulus (G), and Young's modulus (E)) were derived using the Voigt-Reuss-Hill (VRH) method, and in good agreement with available experimental results at the ground state. All these parameters presented the linearly increasing dependences on the external pressure. The B/G ratios and Poisson's ratio indicated that the Al{sub 3}V and Al{sub 3}Nb crystals should exhibit brittle behavior at 0–20 GPa. Additionally, the bulk modulus can be obtained through fitting the Birch-Murnaghan equation (B{sub 0}), computing by VRH method (B{sub H}), and deriving from the elastic theory (B{sub relax}) in both intermetallics. The uniformity of these calculated bulk moduli in each compound exhibited the excellent reliability and self-consistency. In addition, Debye temperature was estimated from the average sound velocity. The Debye temperature showed an increasing dependence on the pressures. Finally, through density of states analysis, Al{sub 3}V and Al{sub 3}Nb were suggested to possess naturally metallic behavior. Under pressures, it was noted that the shapes of peaks and pseudogaps exhibited relative few changes

Ternary aurides La4In3Au10 and Yb4In3Au10 and platinide U4In3Pt10 with ordered Zr7Ni10 type structure

NASA Astrophysics Data System (ADS)

Muts, Ihor; Kharkhalis, Anton; Hlukhyy, Viktor; Kaczorowski, Dariusz; Rodewald, Ute Ch.; Pöttgen, Rainer; Zaremba, Vasyl` I.

2017-09-01

The ternary aurides La4In3Au10 and Yb4In3Au10 and the platinide U4In3Pt10 with ordered Zr7Ni10 type structure were synthesized from the elements by induction-melting in sealed tantalum tubes or via arc-melting. The polycrystalline samples were characterized by powder X-ray diffraction and the structures were refined from single crystal X-ray diffractometer data: Cmce, a = 1426.7(3), b = 1020.3(2), c = 1025.2(2) pm, wR2 = 0.0441, 1510 F2 values, 46 variables for La4In3Au10, a = 1361.5(3), b = 998.3(2), c = 1007.8(2), wR2 = 0.0804, 1404 F2 values, 46 variables for Yb4In3Au10 and a = 1344.4(3), b = 973.9(2), c = 978.9(2), wR2 = 0.0922, 741 F2 values, 48 variables for U4.15In3.03Pt9.82 (with small degrees of In/U, respectively Pt/In mixing on Wyckoff sites 4a and 8 f). The La4In3Au10, Yb4In3Au10 and U4In3Pt10 structures contain pronounced two-dimensional gold, respectively platinum substructures which are filled and condensed by two crystallographically independent indium and rare earth atoms. The crystal chemical features clearly classify these intermetallics as aurides and platinides. The physical properties of U4In3Pt10 were characterized by means of magnetic and electrical transport measurements. The compound exhibits metallic conductivity and shows no magnetic ordering down to 1.72 K. Its magnetic behavior is governed by hybridization between 5f and ligand electrons that results in significant delocalization of the 5f states.

Site preference, magnetism and lattice vibrations of intermetallics Lu₂Fe 17–xT x (T=Cr, Mn, Ru)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jin-Chun; Qian, Ping, E-mail: qianpinghu@sohu.com; Zhang, Zhen-Feng

We present an atomistic study on the phase stability, site preference and lattice constants of the rare earth intermetallics Lu₂Fe 17–xT x (T=Cr, Mn, Ru). The calculated preferential occupation site of ternary element T is found to be the 4f site. The order of site preference is given as 4f, 12k, 12j and 6g for Lu₂Fe 17–xT x. The calculated lattice parameters are corresponding to the experimental results. We have calculated the magnetic moments of Lu₂Fe 17–xT x compounds. Results show that the calculated total magnetic moment of Lu₂Fe₁₇ compound is M=37.34 μ B/f.u. In addition, the total and partialmore » phonon densities of states are evaluated first for these complicated structures. - Graphical abstract: The vibrational modes are mostly excited by Fe atoms, Lu contributes to the lower frequencies modes, and the contribution of Ru atoms is the same as Fe atoms. Highlights: • There are no reports on lattice vibrations of Lu₂(Fe, T) 17–x (T=Cr, Mn, Ru) compounds. • The phase stability and site preference are evaluated first for the complex structures of Lu₂(Fe, T) 17–x (T=Cr, Mn, Ru) compounds. • The lattice inversion method to obtain the interatomic pair potential is the unique one.« less

Corrosion behavior of binary titanium aluminide intermetallics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saffarian, H.M.; Gan, Q.; Hadkar, R.

1996-08-01

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

Intermetallic Compound Growth and Stress Development in Al-Cu Diffusion Couple

NASA Astrophysics Data System (ADS)

Mishler, M.; Ouvarov-Bancalero, V.; Chae, Seung H.; Nguyen, Luu; Kim, Choong-Un

2018-01-01

This paper reports experimental observations evidencing that the intermetallic compound phase interfaced with Cu in the Al-Cu diffusion couple is most likely α2-Cu3Al phase, not γ-Cu9Al4 phase as previously assumed, and that its growth to a critical thickness may result in interface failure by stress-driven fracture. These conclusions are made based on an interdiffusion study of a diffusion couple made of a thick Cu plate coated with ˜ 2- μm-thick Al thin film. The interface microstructure and lattice parameter were characterized using scanning electron microscopy and x-ray diffraction analysis. Specimens aged at temperature between 623 K (350°C) and 723 K (450°C) for various hours produced consistent results supporting the main conclusions. It is found that disordered α2-Cu3Al phase grows in a similar manner to solid-state epitaxy, probably owing to its structural similarity to the Cu lattice. The increase in the interface strain that accompanies the α2-Cu3Al phase growth ultimately leads to interface fracture proceeding from crack initiation and growth along the interface. This mechanism provides the most consistent explanation for interface failures observed in other studies.

Thermodynamic properties and solidification kinetics of intermetallic Ni{sub 7}Zr{sub 2} alloy investigated by electrostatic levitation technique and theoretical calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, L. H.; Hu, L.; Yang, S. J.

2016-01-21

The thermodynamic properties, including the density, volume expansion coefficient, ratio of specific heat to emissivity of intermetallic Ni{sub 7}Zr{sub 2} alloy, have been measured using the non-contact electrostatic levitation technique. These properties vary linearly with temperature at solid and liquid states, even down to the obtained maximum undercooling of 317 K. The enthalpy, glass transition, diffusion coefficient, shear viscosity, and surface tension were obtained by using molecular dynamics simulations. Ni{sub 7}Zr{sub 2} has a relatively poor glass forming ability, and the glass transition temperature is determined as 1026 K. The inter-diffusivity of Ni{sub 7}Zr{sub 2} alloy fitted by Vogel–Fulcher–Tammann law yields amore » fragility parameter of 8.49, which indicates the fragile nature of this alloy. Due to the competition of increased thermodynamic driving force and decreased atomic diffusion, the dendrite growth velocity of Ni{sub 7}Zr{sub 2} compound exhibits double-exponential relationship to the undercooling. The maximum growth velocity is predicted to be 0.45 m s{sup −1} at the undercooling of 335 K. Theoretical analysis reveals that the dendrite growth is a diffusion-controlled process and the atomic diffusion speed is only 2.0 m s{sup −1}.« less

Bu-2470, a new peptide antibiotic complex. II. Structure determination of Bu-2470 A, B1, B2a and B2b.

PubMed

Sugawara, K; Yonemoto, T; Konishi, M; Matsumoto, K; Miyaki, T; Kawaguchi, H

1983-06-01

The structures of Bu-2470 A, B1, B2a, and B2b have been determined. Bu-2470 A is a simple octapeptide having no fatty acid moiety, while Bu-2470 B1, B2a and B2b are octapeptides that have been acylated with a beta-hydroxy C11 or C10 fatty acid. The octapeptide structure of Bu-2470 components was found identical with that of octapeptin C1, hence generic names of octapeptin C0, C2, C3 and C4 are proposed for Bu-2470 A, B1, B2a and B2b, respectively.

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

NASA Astrophysics Data System (ADS)

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

2013-03-01

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.

Cu-Sn Intermetallic Compound Joints for High-Temperature Power Electronics Applications

NASA Astrophysics Data System (ADS)

Lee, Byung-Suk; Yoon, Jeong-Won

2018-01-01

Cu-Sn solid-liquid interdiffusion (SLID) bonded joints were fabricated using a Sn-Cu solder paste and Cu for high-temperature power electronics applications. The interfacial reaction behaviors and the mechanical properties of Cu6Sn5 and Cu3Sn SLID-bonded joints were compared. The intermetallic compounds formed at the interfaces in the Cu-Sn SLID-bonded joints significantly affected the die shear strength of the joint. In terms of thermal and mechanical properties, the Cu3Sn SLID-bonded joint was superior to the conventional solder and the Cu6Sn5 SLID-bonded joints.

Magnetic interactions in equi-atomic rare-earth intermetallic alloys RScGe (R = Ce, Pr, Nd and Gd) studied by time differential perturbed angular correlation spectroscopy and ab initio calculations.

PubMed

Mishra, S N

2009-03-18

Applying the time differential perturbed angular correlation (TDPAC) technique we have measured electric and magnetic hyperfine fields of the (111)Cd impurity in equi-atomic rare-earth intermetallic alloys RScGe (R = Ce, Pr and Gd) showing antiferro- and ferromagnetism with unusually high ordering temperatures. The Cd nuclei occupying the Sc site show high magnetic hyperfine fields with saturation values B(hf)(0) = 21 kG, 45 kG and 189 kG in CeScGe, PrScGe and GdScGe, respectively. By comparing the results with the hyperfine field data of Cd in rare-earth metals and estimations from the RKKY model, we find evidence for the presence of additional spin density at the probe nucleus, possibly due to spin polarization of Sc d band electrons. The principal electric field gradient component V(zz) in CeScGe, PrScGe and GdScGe has been determined to be 5.3 × 10(21) V m(-2), 5.5 × 10(21) V m(-2) and 5.6 × 10(21) V m(-2), respectively. Supplementing the experimental measurements, we have carried out ab initio calculations for pure and Cd-doped RScGe compounds with R = Ce, Pr, Nd and Gd using the full potential linearized augmented plane wave (FLAPW) method based on density functional theory (DFT). From the total energies calculated with and without spin polarization we find ferrimagnetic ground states for CeScGe and PrScGe while NdScGe and GdScGe are ferromagnetic. In addition, we find a sizable magnetic moment at the Sc site, increasing from ≈0.10 μ(B) in CeScGe to ≈0.3 μ(B) in GdScGe, confirming the spin polarization of Sc d band electrons. The calculated electric field gradient and magnetic hyperfine fields of the Cd impurity closely agree with the experimental values. We believe spin polarization of Sc 3d band electrons, strongly hybridized with spin polarized 5d band electrons of the rare-earth, enables a long range Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between RE 4f moments which in turn leads to high magnetic ordering temperatures in

Thermal stress effects in intermetallic matrix composites

NASA Technical Reports Server (NTRS)

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

1993-01-01

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

B2B Models for DoD Acquisition

DTIC Science & Technology

2007-07-30

Internet, extranets, intranets, or private networks • In 2003 it represented about 11% of total B2B trade estimated at $13.5 trillion • Predicted to... B2B Models for DoD Acquisition 30 July 2007 by Magdi N. Kamel, Associate Professor Graduate School of Operational & Information Sciences...number. 1. REPORT DATE 30 JUL 2007 2. REPORT TYPE 3. DATES COVERED 00-00-2007 to 00-00-2007 4. TITLE AND SUBTITLE B2B Models for DoD

B2B Models for DoD Acquisition

DTIC Science & Technology

2008-01-15

unlimited. Prepared for: Naval Postgraduate School, Monterey, California 93943 B2B Models for DoD Acquisition 15 January 2008 by Magdi N...TYPE AND DATES COVERED 1 Oct 2006 through 30 Sept 2007 4. TITLE AND SUBTITLE B2B Models for DoD Acquisition 5. FUNDING 6. AUTHOR (S...public release; distribution is unlimited 12b. DISTRIBUTION CODE 13. ABSTRACT (Maximum 200 words.) A central vision of B2B e-commerce is that

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

NASA Astrophysics Data System (ADS)

Gao, Mao

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

Telecom 2-B and 2-C (TC2B and TC2C)

NASA Technical Reports Server (NTRS)

Dulac, J.; Alvarez, H.

1991-01-01

The DSN (Deep Space Network) mission support requirements for Telecom 2-B and 2-C (TC2B and TC2C) are summarized. These Telecom missions will provide high-speed data link applications, telephone, and television service between France and overseas territories as a follow-on to TC2A. Mission objectives are outlined and the DSN support requirements are defined through the presentation of tables and narratives describing the spacecraft flight profile; DSN support coverage; frequency assignments; support parameters for telemetry, command and support systems; and tracking support responsibility.

Report on inspection of compliance with DOE Order 2030.4B at the Savannah River Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1997-03-01

The purpose of this inspection was to evaluate contractor compliance at the Savannah River Site (SRS) with Department of Energy (DOE) Order 2030.4B, {open_quotes}Reporting Fraud, Waste, And Abuse To The Office Of Inspector General.{close_quotes} The specific objective was to determine if the SRS management and operating (M&O) contractors were complying with the requirements in Paragraph 6.c. of DOE Order 2030.4B. These requirements are: (1) annual notification to employees of their duty to report allegations of fraud, waste, abuse, corruption, or mismanagement; (2) display and publish the DOE Office of Inspector General (OIG) Hotline telephone number in common areas of buildings;more » (3) display and publish the DOE OIG Hotline number in telephone books and newsletters; and (4) notify the OIG cases referred to other law enforcement entities.« less

Launch Load Resistant Spacecraft Mechanism Bearings Made From NiTi Superelastic Intermetallic Materials

NASA Technical Reports Server (NTRS)

DellaCorte, Christopher; Moore, Lewis E., III

2014-01-01

Compared to conventional bearing materials (tool steel and ceramics), emerging Superelastic Intermetallic Materials (SIMs), such as 60NiTi, have significantly lower elastic modulus and enhanced strain capability. They are also immune to atmospheric corrosion (rusting). This offers the potential for increased resilience and superior ability to withstand static indentation load without damage. In this paper, the static load capacity of hardened 60NiTi 50-mm-bore ball bearing races are measured to correlate existing flat-plate indentation load capacity data to an actual bearing geometry through the Hertz stress relations. The results confirmed the validity of using the Hertz stress relations to model 60NiTi contacts; 60NiTi exhibits a static stress capability (approximately 3.1 GPa) between that of 440C (2.4 GPa) and REX20 (3.8 GPa) tool steel. When the reduced modulus and extended strain capability are taken into account, 60NiTi is shown to withstand higher loads than other bearing materials. To quantify this effect, a notional space mechanism, a 5-kg mass reaction wheel, was modeled with respect to launch load capability when supported on standard (catalogue geometry) design 440C; 60NiTi and REX20 tool steel bearings. For this application, the use of REX20 bearings increased the static load capability of the mechanism by a factor of three while the use of 60NiTi bearings resulted in an order of magnitude improvement compared to the baseline 440C stainless steel bearings

Grb2 regulates B-cell maturation, B-cell memory responses and inhibits B-cell Ca2+ signalling.

PubMed

Ackermann, Jochen A; Radtke, Daniel; Maurberger, Anna; Winkler, Thomas H; Nitschke, Lars

2011-04-20

Grb2 is a ubiquitously expressed adaptor protein, which activates Ras and MAP kinases in growth factor receptor signalling, while in B-cell receptor (BCR) signalling this role is controversial. In B cell lines it was shown that Grb2 can inhibit BCR-induced Ca(2+) signalling. Nonetheless, the physiological role of Grb2 in primary B cells is still unknown. We generated a B-cell-specific Grb2-deficient mouse line, which had a severe reduction of mature follicular B cells in the periphery due to a differentiation block and decreased B-cell survival. Moreover, we found several changes in important signalling pathways: enhanced BCR-induced Ca(2+) signalling, alterations in mitogen-activated protein kinase activation patterns and strongly impaired Akt activation, the latter pointing towards a defect in PI3K signalling. Interestingly, B-cell-specific Grb2-deficient mice showed impaired IgG and B-cell memory responses, and impaired germinal centre formation. Thus, Grb2-dependent signalling pathways are crucial for lymphocyte differentiation processes, as well as for control of secondary humoral immune responses.

Vacancy-ordering effects in AlB2-type ErGe2 - x(0.4 < x < or = 0.5).

PubMed

Christensen, Jeppe; Lidin, Sven; Malaman, Bernard; Venturini, Gerard

2008-06-01

In the Er-Ge system, the compostion range ErGe(2) to Er(2)Ge(3) has been investigated. Eight samples were produced by arc melting of the elements, and analyzed using X-ray powder diffraction. Nine crystal structures were found to be present in the samples. The structures are described as a homologous series and presented within the superspace formalism using the superspace group X2/m(alpha0gamma)0s, X representing the centring vector ((1/2), (1/2), 0, (1/2)). In this description the modulation vector q = (alphaa* + gammac*) is shown to be a direct measure of the Ge content as ErGe(2 - alpha) (alpha falls in the range 1\\over 3 to (1/2)). The large composition range is achieved by extended vacancy ordering in the planar 6(3) net of Ge with subsequent relaxation.

The Influence of Ultrasonic Cavitation on the Formation of Fe-Rich Intermetallics in A383 Alloy

NASA Astrophysics Data System (ADS)

Xuan, Yang; Liu, Tao; Nastac, Laurentiu; Brewer, Luke; Levin, Ilya; Arvikar, Vish

2018-06-01

The effect of ultrasonic treatment (UST) on the formation of Fe-rich intermetallics (including sludge) in the A383 alloy is investigated for different processing temperatures in the present study. Differential scanning calorimetry is used to analyze the precipitation temperature of the sludge phase. The results revealed that the sludge will precipitate at a temperature above that of the Al matrix and the precipitation temperature decreases with an increasing cooling rate. UST cavitation applied at different temperatures (600 °C to 750 °C) during the solidification process breaks the sludge into small island-like pieces. However, the aggregation trend of the sludge is not changed. Sludge with small size and uniform distribution is obtained when UST is applied at 600 °C, which is lower than the precipitation temperature of the sludge. At the highest temperature (850 °C), the application of UST has no effect on the formation of either sludge or α-Fe intermetallics. At 750 °C, UST promotes the formation of the sludge when applied at 750 °C.

Competition between magnetism and superconductivity in Eu-based intermetallic compounds

NASA Astrophysics Data System (ADS)

Stavinoha, Macy; Green, Lance; Chan, Julia; Morosan, Emilia

Eu-based intermetallic compounds present a path to discover new correlated electronic behavior in quantum materials. Reports of superconductivity, intermediate valence behavior, and heavy fermions indicate that Eu-based compounds are promising routes to study the relationship between crystallography and electronic properties. The present work is focused on EuGa4, an antiferromagnet with TN = 16 K isostructural with the tetragonal RT2M2 (R = rare earth, T = transition metal, M = metal or metalloid) family that exhibits heavy fermion behavior and unconventional superconductivity. Single crystals of the doped series (Eu1-xLax)Ga4, (Eu1-xCax)Ga4, and Eu(Ga1-xAlx)4 have been grown using the self-flux method and tested for change in unit cell volume and magnetic susceptibility. Results show that doping with Ca (isoelectronic doping) and La (hole doping) reduce TN to 12.4 K and 2.3 K, respectively, for Ca doping up to x = 0.11 and La doping up to x = 0.74 without an associated change in unit cell volume. The series Eu(Ga1-xAlx)4 has shown incommensurate-to-commensurate magnetic transitions. Future studies will aim to further decrease TN and the unit cell volume using physical pressure and chemical pressure through doping. ICAM, Gordon and Betty Moore Foundation.