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Sample records for system ni kansuru

  1. Ternary system Er-Ni-In at T=870 K

    SciTech Connect

    Dzevenko, M.; Tyvanchuk, Yu.; Bratash, L.; Zaremba, V.; Havela, L.; Kalychak, Ya.

    2011-10-15

    Isothermal section of the Er-Ni-In system at T=870 K was constructed by means of X-ray powder diffraction and EDX-analyses. Nine ternary compounds, namely ErNi{sub 9}In{sub 2} (YNi{sub 9}In{sub 2}-type), Er{sub 1-1.22}Ni{sub 4}In{sub 1-0.78} (MgCu{sub 4}Sn-type), Er{sub 10}Ni{sub 9.07}In{sub 20} (Ho{sub 10}Ni{sub 9}In{sub 20}-type), ErNi{sub 1-0.60}In{sub 1-1.40} (ZrNiAl-type), Er{sub 2}Ni{sub 2}In (Mn{sub 2}AlB{sub 2}-type), Er{sub 2}Ni{sub 1.78}In (Mo{sub 2}FeB{sub 2}-type), Er{sub 5}Ni{sub 2}In{sub 4} (Lu{sub 5}Ni{sub 2}In{sub 4}-type), Er{sub 5}Ni{sub 2}In (Mo{sub 5}SiB{sub 2}-type), and Er{sub 13.53}Ni{sub 3.14}In{sub 3.33} (Lu{sub 14}Co{sub 2}In{sub 3}-type), exist in the Er-Ni-In system at this temperature. The substitution of Ni for In was observed for ErNi{sub 1-0.60}In{sub 1-1.40} and In for Er in the case of related compounds ErNi{sub 2} and ErNi{sub 4}In. Er can enter NiIn (CoSn-type) leading to including-substitution type of compound Er{sub 0-0.12}NiIn{sub 1-0.89}. Basic magnetic properties of the Er{sub 0.04}NiIn{sub 0.97}, ErNi{sub 2}, Er{sub 0.9}Ni{sub 2}In{sub 0.1}, and ErNi{sub 4}In phases were inspected. Electrical-resistivity studies were performed on the ErNiIn, ErNi{sub 0.9}In{sub 1.1}, and ErNi{sub 4}In phases. - Graphical Abstract: Phase relations in the ternary system Er-Ni-In have been established for the isothermal section at T=870 K based on X-ray phase and EDX-analyses. Nine ternary compounds were observed. Highlights: > Isothermal section of Er-Ni-In system at T=870 K was constructed. > Nine ternary compounds were detected. > Basic magnetic properties of Er{sub 0.04}NiIn{sub 0.97} and ErNi{sub 4}In phases were inspected.

  2. Measured Activities of Al and Ni in gamma-(Ni) and gamma'-(Ni)3Al in the Ni-Al-Pt System

    NASA Technical Reports Server (NTRS)

    Copland, Evan

    2007-01-01

    Adding Pt to Ni-Al coatings is critical to achieving the required oxidation protection of Ni-based superalloys, but the nature of the Pt effect remains unresolved. This research provides a fundamental part of the answer by measuring the influence of Pt on the activities of Al and Ni in gamma-(Ni), gamma prime-(Ni)3Al and liquid in the Ni-Al-Pt system. Measurements have been made at 25 compositions in the Ni-rich corner over the temperature range, T = 1400-1750 K, by the vapor pressure technique with a multiple effusion-cell mass spectrometer (multi-cell KEMS). These measurements clearly show adding Pt (for X(sub Pt) less than 0.25) decreases a(Al) while increasing a(Ni). This solution behavior supports the idea that Pt increases Al transport to an alloy / Al2O3 interface and also limits the interaction between the coating and substrate alloys in the gamma-(Ni) + gamma prime-(Ni)3Al region. This presentation will review the progress of this study.

  3. Thickness and ordering temperature of surface NiO/Ni systems

    SciTech Connect

    Shih, Ying-Ta; Su, Chien-Yu; Tsai, Chung-Wei; Pan, Wei

    2014-02-15

    We estimate the thickness and ordering temperature of an antiferromagnetic and passivation surface oxide through exchange bias coupling. The surface NiO, which is generated through the exposure of a Ni/Cu(001) surface to oxygen, is taken as a model system on which to perform the estimation. Since no exchange bias is found in the surface NiO/Ni/Cu(001), we have built a sandwich structure of NiO/n ML Ni/10 ML Co/Cu(001) to measure the n dependence of exchange bias. With n ⩽ 2, a large exchange bias field is found above 300 K, which could be due to the direct contact between the oxides and the Co layer. With 3 ⩽ n ⩽ 6, a smaller exchange bias field is found with a blocking temperature of 190 K. This implies that the thickness of NiO is, at most, 3 ML. Discovering the thickness and ordering temperature of the surface NiO provides us to explore the potential applications by using surface NiO.

  4. Interdiffusion in the Ni/TD-NiCr and Cr/TD-NiCr systems

    NASA Technical Reports Server (NTRS)

    Pawar, A. V.; Tenney, D. R.

    1974-01-01

    The diffusion of Ni and Cr into TD-NiCr has been studied over the 900 to 1100 C temperature range. The diffusion couples were prepared by electroplating Cr and Ni on polished TD-NiCr wafers. Concentration profiles produced as a result of isothermal diffusion at 905, 1000, and 1100 C were determined by electron microprobe analysis. The Boltzmann-Matano analysis was used to determine concentration-dependent diffusion coefficients which were found to compare favorably with previously reported values. These data suggest that 2 vol % ThO2 distribution has no appreciable effect on the rates of diffusion in TD-NiCr with a large grain size. This supports the view that an inert dispersoid in an alloy matrix will not in itself lead to enhanced diffusion unless a short-circuit diffusion structure is stabilized.

  5. Peculiarities of thermoelectric half-Heusler phase formation in Gd-Ni-Sb and Lu-Ni-Sb ternary systems

    NASA Astrophysics Data System (ADS)

    Romaka, V. V.; Romaka, L.; Horyn, A.; Rogl, P.; Stadnyk, Yu; Melnychenko, N.; Orlovskyy, M.; Krayovskyy, V.

    2016-07-01

    The phase equilibria in the Gd-Ni-Sb and Lu-Ni-Sb ternary systems were studied at 873 K by X-ray and metallographic analyses in the whole concentration range. The interaction of the elements in the Gd-Ni-Sb system results the formation of five ternary compounds at investigated temperature: Gd5Ni2Sb (Mo5SiB2-type), Gd5NiSb2 (Yb5Sb3-type), GdNiSb (MgAgAs-type), Gd3Ni6Sb5 (Y3Ni6Sb5-type), and GdNi0.72Sb2 (HfCuSi2-type). At investigated temperature the Lu-Ni-Sb system is characterized by formation of the LuNiSb (MgAgAs-type), Lu5Ni2Sb (Mo5SiB2-type), and Lu5Ni0.56Sb2.44 (Yb5Sb3-type) compounds. The disordering in the crystal structure of half-Heusler GdNiSb and LuNiSb was revealed by EPMA and studied by means of Rietveld refinement and DFT modeling. The performed electronic structure calculations are in good agreement with electrical transport property studies.

  6. Phase competition in ternary Ti-Ni-Al system

    NASA Astrophysics Data System (ADS)

    Wierzba, Bartek

    2016-07-01

    In this paper the reactive diffusion in Ti-Ni-Al system is discussed at 1173 K. The calculation method based on the binary approach is presented. The key kinetic parameter is Wagner integral diffusion coefficient. The experimental and simulation results of reactive diffusion between pure Ti and β-NiAl are compared at 1173 K after 100 h.

  7. The isothermal section of Gd-Ni-Si system at 1070 K

    NASA Astrophysics Data System (ADS)

    Morozkin, A. V.; Knotko, A. V.; Yapaskurt, V. O.; Manfrinetti, P.; Pani, M.; Provino, A.; Nirmala, R.; Quezado, S.; Malik, S. K.

    2016-03-01

    The Gd-Ni-Si system has been investigated at 1070 K by X-ray and microprobe analyses. The existence of the known compounds, i.e.: GdNi10Si2, GdNi8Si3, GdNi5Si3, GdNi7Si6, GdNi6Si6, GdNi4Si, GdNi2Si2, GdNiSi3, Gd3Ni6Si2, GdNiSi, GdNiSi2, GdNi0.4Si1.6, Gd2Ni2.35Si0.65, Gd3NiSi2, Gd3NiSi3 and Gd6Ni1.67Si3, has been confirmed. Moreover, five new phases have been identified in this system. The crystal structure for four of them has been determined: Gd2Ni16-12.8Si1-4.2 (Th2Zn17-type), GdNi6.6Si6 (GdNi7Si6-type), Gd3Ni8Si (Y3Co8Si-type) and Gd3Ni11.5Si4.2(Gd3Ru4Ga12-type). The compound with composition ~Gd2Ni4Si3 still remains with unknown structure. Quasi-binary phases, solid solutions, were detected at 1070 K to be formed by the binaries GdNi5, GdNi3, GdNi2, GdNi, GdSi2 and GdSi1.67; while no appreciable solubility was observed for the other binary compounds of the Gd-Ni-Si system. Magnetic properties of the GdNi6Si6, GdNi6.6Si6 and Gd3Ni11.5Si4.2 compounds have also been investigated and are here reported.

  8. Near-barrier fusion of Sn+Ni and Te+Ni Systems: Examining the influence of neutron transfer couplings

    SciTech Connect

    Liang, J Felix; Kohley, Zachary W; Shapira, Dan; Varner Jr, Robert L; Gross, Carl J; Allmond, J M; Lagergren, Karin B; Mueller, Paul Edward

    2011-01-01

    The fusion excitation functions for radioactive 132Sn+58Ni and stable 130Te+58;64Ni were measured at energies near the Coulomb barrier. The role of transfer couplings in heavy-ion fusion was examined through a comparison of Sn+Ni and Te+Ni systems, which have large variations in the number of positive Q-value nucleon transfer channels. In contrast with previous comparisons, where increased sub-barrier fusion cross sections were observed in the systems with positive Q-value neutron transfer channels, the reduced excitation functions were equivalent for the different Sn+Ni and Te+Ni systems. The present results suggest a significant change in the influence of transfer couplings on the fusion process for the Sn+Ni and Te+Ni systems.

  9. Characteristics of Reactive Ni3Sn4 Formation and Growth in Ni-Sn Interlayer Systems

    NASA Astrophysics Data System (ADS)

    Lis, Adrian; Kenel, Christoph; Leinenbach, Christian

    2016-06-01

    The near-isothermal growth and formation of Ni3Sn4 intermetallic compounds (IMC) in Ni-Sn interlayer systems was studied in the solid state at 473 K (200 °C) and under solid-liquid conditions at 523 and 573 K (250 °C and 300 °C) from an initial state of a few seconds. Scalloped solid-state IMC formation was mainly driven by grain boundary diffusion of Ni through the IMC layer combined with the grain coarsening of the IMC layer. Under solid-liquid conditions, the formation of faceted and needle-shaped Ni3Sn4 grains as well as an atypical IMC growth behavior with similar parabolic growth constants for 523 K and 573 K (250 °C and 300 °C) was observed within the first 180 seconds of the holding time, and IMC growth occurred as an isothermal solidification from the Ni-saturated Sn melt. Due to the progressive densification of the IMC layer and the diffusion-controlled growth, the kinetics slowed down by approximately one order of magnitude after 180 seconds of annealing. The final stage was characterized by the formation of IMC islands ahead of the interfacial Ni3Sn4 layer. Needle-like IMC growth was effectively suppressed under combined solid-state and solid-liquid conditions. Textured Ni3Sn4 IMC formation at the Ni-Sn interface was approved with pole figure measurements. The activation energy Q for solid-liquid IMC formation was calculated as 43.3 kJ/mol, and processing maps for IMC growth and Sn consumption were derived as functions of temperature and time, respectively.

  10. Characteristics of Reactive Ni3Sn4 Formation and Growth in Ni-Sn Interlayer Systems

    NASA Astrophysics Data System (ADS)

    Lis, Adrian; Kenel, Christoph; Leinenbach, Christian

    2016-03-01

    The near-isothermal growth and formation of Ni3Sn4 intermetallic compounds (IMC) in Ni-Sn interlayer systems was studied in the solid state at 473 K (200 °C) and under solid-liquid conditions at 523 and 573 K (250 °C and 300 °C) from an initial state of a few seconds. Scalloped solid-state IMC formation was mainly driven by grain boundary diffusion of Ni through the IMC layer combined with the grain coarsening of the IMC layer. Under solid-liquid conditions, the formation of faceted and needle-shaped Ni3Sn4 grains as well as an atypical IMC growth behavior with similar parabolic growth constants for 523 K and 573 K (250 °C and 300 °C) was observed within the first 180 seconds of the holding time, and IMC growth occurred as an isothermal solidification from the Ni-saturated Sn melt. Due to the progressive densification of the IMC layer and the diffusion-controlled growth, the kinetics slowed down by approximately one order of magnitude after 180 seconds of annealing. The final stage was characterized by the formation of IMC islands ahead of the interfacial Ni3Sn4 layer. Needle-like IMC growth was effectively suppressed under combined solid-state and solid-liquid conditions. Textured Ni3Sn4 IMC formation at the Ni-Sn interface was approved with pole figure measurements. The activation energy Q for solid-liquid IMC formation was calculated as 43.3 kJ/mol, and processing maps for IMC growth and Sn consumption were derived as functions of temperature and time, respectively.

  11. Microstructure of the Al-La-Ni-Fe system

    SciTech Connect

    Vasil’ev, A. L.; Ivanova, A. G.; Bakhteeva, N. D.; Kolobylina, N. N.; Orekhov, A. S.; Presnyakov, M. Yu.; Todorova, E. V.

    2015-01-15

    The microstructure of alloys based on the Al-La-Ni-Fe system, which are characterized by a unique ability to form metal glasses and nanoscale composites in a wide range of compositions, has been investigated. Al{sub 85}Ni{sub 7}Fe{sub 4}La{sub 4} and Al{sub 85}Ni{sub 9}Fe{sub 2}La{sub 4} alloys have been analyzed by electron microscopy (including high-resolution scanning transmission electron microscopy), energy-dispersive X-ray microanalysis, electron diffraction (ED), and X-ray diffraction (XRD). It is found that, along with fcc Al and Al{sub 4}La (Al{sub 11}La{sub 3}) particles, these alloys contain a ternary phase Al{sub 3}Ni{sub 1−x}Fe{sub x} (sp. gr. Pnma) isostructural to the Al{sub 3}Ni phase and a quaternary phase Al{sub 8}Fe{sub 2−x}Ni{sub x}La isostructural to the Al{sub 8}Fe{sub 2}Eu phase (sp. gr. Pbam). The unit-cell parameters of the Al{sub 3}Ni{sub 1−x}Fe{sub x} and Al{sub 8}Fe{sub 2−x}Ni{sub x}La compounds, determined by ED and refined by XRD, are a = 0.664(1) nm, b = 0.734(1) nm, and c = 0.490(1) nm for Al{sub 3}Ni{sub 1−x}Fe{sub x} and a = 1.258(3) nm, b = 1.448(3) nm, and c = 0.405(8) nm for Al{sub 8}Fe{sub 2−x}Ni{sub x}La. In both cases Ni and Fe atoms are statistically arranged, and no ordering is found. Al{sub 8}Fe{sub 2−x}Ni{sub x}La particles contain inclusions in the form of Al{sub 3}Fe δ layers.

  12. NiAl-based Polyphase in situ Composites in the NiAl-Ta-X (X = Cr, Mo, or V) Systems

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Polyphase in situ composites were generated by directional solidification of ternary eutectics. This work was performed to discover if a balance of properties could be produced by combining the NiAl-Laves phase and the NiAl-refractory metal phase eutectics. The systems investigated were the Ni-Al-Ta-X (X = Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and the eutectic composition, temperature, and morphology were determined. The ternary eutectic systems examined were the NiAl-NiAlTa-(Mo, Ta), NiAl-(Cr, Al) NiTa-Cr, and the NiAl-NiAlTa-V systems. Each eutectic consists of NiAl, a C14 Laves phase, and a refractory metal phase. Directional solidification was performed by containerless processing techniques in a levitation zone refiner to minimize alloy contamination. Room temperature fracture toughness of these materials was determined by a four-point bend test. Preliminary creep behavior was determined by compression tests at elevated temperatures, 1100-l400 K. Of the ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr, Al)NiTa-Cr eutectic was intermediate between the values of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  13. Solidification Behavior of gamma'-Ni3Al Containing Alloys in the Ni-Al-O System

    NASA Technical Reports Server (NTRS)

    Copland, Evan

    2007-01-01

    The chemical activities of Al and Ni in gamma(prime)-Ni3Al-containing systems were measured using the multi-cell Knudsen effusion-cell mass spectrometry technique (multi-cell KEMS), over the composition range 8 - 32 at.%Al and temperature range T = 1400 - 1750 K. From these measurements a better understanding of the equilibrium solidification behaviour of gamma(prime)-Ni3Al-containing alloys in the Ni-Al-O system was established. Specifically, these measurements revealed that (1) gamma(prime)-Ni3Al forms via the peritectiod reaction, gamma + Beta (+ A12O3) = gamma (prime) (+ Al2O3), at 1633 +/- 1 K, (2) the {gamma + Beta + Al2O3} phase field is stable over the temperature range 1633 through 1640 K, and (3) equilibrium solidification occurs by the eutectic reaction, L (+ Al2O3) = gamma + Beta (+ Al2O3), at 1640 +/- 1 K and a liquid composition of 24.8 +/- 0.2 at.%Al (at an unknown oxygen content). When projected onto the Ni-Al binary, this behaviour is inconsistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady-state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma(prime)-Ni3Al phase field.

  14. Interdiffusion and intrinsic diffusion in the NiAl /delta/ phase of the Al-Ni system

    NASA Technical Reports Server (NTRS)

    Shankar, S.; Seigle, L. L.

    1978-01-01

    Interdiffusion coefficients at 950 to 1150 C and the ratio of intrinsic diffusion coefficients at 1100 C were measured as functions of composition in the NiAl (delta) phase of the Al-Ni system, using a vapor-solid technique. Diffusivity values were also obtained for the Ni3Al (epsilon) and Ni (Al) solid solution (zeta) phases from 950 to 1150 C. The interdiffusion coefficient in NiAl (delta) varies several orders of magnitude over the delta phase field with a deep minimum in the diffusivity-composition curve at 48 to 49 at% Al. The ratio of intrinsic diffusion coefficients DNi/DAl, in the delta phase also varies with composition from a value of 3 to 3.5 below 50 at% Al to 0.1 or less above 50 at% Al.

  15. Oxygen potentials in Ni + NiO and Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4] systems

    SciTech Connect

    Kale, G.M.; Fray, D.J. . Dept. of Mining and Mineral Engineering)

    1994-06-01

    The chemical potential of O for the coexistence of Ni + NiO and Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4] equilibria has been measured employing solid-state galvanic cells, (+) Pt, Cu + Cu[sub 2]O [vert bar][vert bar] (Y[sub 2]O[sub 3])ZrO[sub 2] [vert bar][vert bar] Ni + NiO, Pt (-) and (+) Pt, Ni + NiO [vert bar][vert bar] (Y[sub 2]O[sub 3])ZrO[sub 2] [vert bar][vert bar] Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4], Pt (-) in the temperature range of 800 to 1,300 K and 1,100 to 1,460 K, respectively. The electromotive force (emf) of both he cells was reversible, reproducible on thermal cycling, and varied linearly with temperature. for the coexistence of the two-phase mixture of Ni + NiO, [Delta][mu][sub O[sub 2

  16. Phase equilibria, formation, crystal and electronic structure of ternary compounds in Ti-Ni-Sn and Ti-Ni-Sb ternary systems

    SciTech Connect

    Romaka, V.V.; Rogl, P.; Romaka, L.; Stadnyk, Yu.; Melnychenko, N.; Grytsiv, A.; Falmbigl, M.; Skryabina, N.

    2013-01-15

    The phase equilibria of the Ti-Ni-Sn and Ti-Ni-Sb ternary systems have been studied in the whole concentration range by means of X-ray and EPM analyses at 1073 K and 873 K, respectively. Four ternary intermetallic compounds TiNiSn (MgAgAs-type), TiNi{sub 2-x}Sn (MnCu{sub 2}Al-type), Ti{sub 2}Ni{sub 2}Sn (U{sub 2}Pt{sub 2}Sn-type), and Ti{sub 5}NiSn{sub 3} (Hf{sub 5}CuSn{sub 3}-type) are formed in Ti-Ni-Sn system at 1073 K. The TiNi{sub 2}Sn stannide is characterized by homogeneity in the range of 50-47 at% of Ni. The Ti-Ni-Sb ternary system at 873 K is characterized by formation of three ternary intermetallic compounds, Ti{sub 0.8}NiSb (MgAgAs-type), Ti{sub 5}Ni{sub 0.45}Sb{sub 2.55} (W{sub 5}Si{sub 3}-type), and Ti{sub 5}NiSb{sub 3} (Hf{sub 5}CuSn{sub 3}-type). The solubility of Ni in Ti{sub 0.8}NiSb decreases number of vacancies in Ti site up to Ti{sub 0.91}Ni{sub 1.1}Sb composition. - Graphical abstract: Isothermal section of the Ti-Ni-Sn phase diagram and DOS distribution in hypothetical TiNi{sub 1+x}Sn solid solution. Highlights: Black-Right-Pointing-Pointer Ti-Ni-Sn phase diagram was constructed at 1073 K. Black-Right-Pointing-Pointer Four ternary compounds are formed: TiNiSn, TiNi{sub 2-x}Sn, Ti{sub 2}Ni{sub 2}Sn, and Ti{sub 5}NiSn{sub 3}. Black-Right-Pointing-Pointer Three ternary compounds exist in Ti-Ni-Sb system at 873 K. Black-Right-Pointing-Pointer The TiNi{sub 2}Sb compound is absent.

  17. Study of phase stability in NiPt systems

    NASA Astrophysics Data System (ADS)

    Paudyal, Durga; Saha-Dasgupta, Tanusri; Mookerjee, Abhijit

    2003-02-01

    We have studied the problem of phase stability in NiPt alloy systems. We have used the augmented space recursion based on the tight binding-linearized muffin-tin orbital as the method for studying the electronic structure of the alloys. In particular, we have used the relativistic generalization of our earlier technique. We note that, in order to predict the proper ground state structures and energetics, in addition to relativistic effects, we have to take into account charge transfer effects with precision.

  18. Diffusion, phase equilibria and partitioning experiments in the Ni-Fe-Ru system

    NASA Technical Reports Server (NTRS)

    Blum, Joel D.; Wasserburg, G. J.; Hutcheon, I. D.; Beckett, J. R.; Stolper, E. M.

    1989-01-01

    Results are presented on thin-film diffusion experiments designed to investigate phase equilibria in systems containing high concentrations of Pt-group elements, such as Ni-Fe-Ru-rich systems containing Pt, at temperatures of 1273, 1073, and 873 K. The rate of Ru diffusion in Ni was determined as a function of temperature, and, in addition, the degree of Pt and Ir partitioning between phases in a Ni-Fe-Ru-rich system and of V between phases in a Ni-Fe-O-rich system at 873 were determined. It was found that Pt preferentially partitions into the (gamma)Ni-Fe phase, whereas Ir prefers the (epsilon)Ru-Fe phase. V partitions strongly into Fe oxides relative to (gamma)Ni-Fe. These results have direct application to the origin and thermal history of the alloys rich in Pt-group elements in meteorites.

  19. Access to Formally Ni(I) States in a Heterobimetallic NiZn System

    PubMed Central

    Uyeda, Christopher

    2014-01-01

    Heterobimetallic NiZn complexes featuring metal centers in distinct coordination environments have been synthesized using diimine-dioxime ligands as binucleating scaffolds. A tetramethylfuran-containing ligand derivative enables a stable one-electron-reduced S = 1/2 species to be accessed using Cp2Co as a chemical reductant. The resulting pseudo-square planar complex exhibits spectroscopic and crystallographic characteristics of a ligand-centered radical bound to a Ni(II) center. Upon coordination of a π-acidic ligand such as PPh3, however, a five-coordinate Ni(I) metalloradical is formed. The electronic structures of these reduced species provide insight into the subtle effects of ligand structure on the potential and reversibility of the NiII/I couple for complexes of redox-active tetraazamacrocycles. PMID:25614786

  20. Phase Equilibria of the Fe-Ni-Sn Ternary System at 270°C

    NASA Astrophysics Data System (ADS)

    Huang, Tzu-Ting; Lin, Shih-Wei; Chen, Chih-Ming; Chen, Pei Yu; Yen, Yee-Wen

    2016-07-01

    The Fe-42 wt.% Ni alloy, also known as a 42 invar alloy (Alloy 42), is used as a lead-frame material because its thermal expansion coefficient is much closer to Si substrate than Cu or Ni substrates. In order to enhance the wettability between the substrate and solder, the Sn layer was commonly electroplated onto the Alloy 42 surface. A clear understanding of the phase equilibria of the Fe-Ni-Sn ternary system is necessary to ensure solder-joint reliability between Sn and Fe-Ni alloys. To determine the isothermal section of the Fe-Ni-Sn ternary system at 270°C, 26 Fe-Ni-Sn alloys with different compositions were prepared. The experimental results confirmed the presence of the Fe3Ni and FeNi phases at 270°C. Meanwhile, it observed that the isothermal section of the Fe-Ni-Sn ternary system was composed of 11 single-phase regions, 19 two-phase regions and nine tie-triangles. Moreover, no ternary compounds were found in the Fe-Ni-Sn system at 270°C.

  1. Bulk-alloy microstructural analogues for transient liquid-phase bonds in the NiAl/Cu/Ni system

    SciTech Connect

    Gale, W.F.; Abdo, Z.A.M.

    1999-12-01

    Transient liquid-phase (TLP) bonds between dissimilar materials can have complex microstructures that evolve both during holding at the bonding temperature and on cooling. In this article, an examination is made of the feasibility of producing bulk-alloy microstructural analogues for individual microstructural features of dissimilar material TLP bonds. The ultimate intent of this work is to enable the contribution of individual microstructural features to the overall properties of TLP bonds to be determined. Specifically, the article focuses on the production, characterization, and applications of microstructural analogues for TLP bonds in an NiAl/Cu/Ni model system. The article examines the use of five different cast Ni-Al-Cu alloys, together with heat treatment of selected materials, as bulk analogues for six distinct microstructural regions of the NiAl/Cu/Ni bonds. Each of these analogues is characterized in detail by transmission electron microscopy (TEM) and compared to the relevant target region of the bond. An initial examination is also made of the use of bulk alloys in aiding an understanding of phase transformations and structure-property relationships in these bonds.

  2. Realization of magnetostructural coupling by modifying structural transitions in MnNiSi-CoNiGe system with a wide Curie-temperature window.

    PubMed

    Liu, Jun; Gong, Yuanyuan; Xu, Guizhou; Peng, Guo; Shah, Ishfaq Ahmad; Ul Hassan, Najam; Xu, Feng

    2016-01-01

    The magnetostructural coupling between structural and magnetic transitions leads to magneto-multifunctionalities of phase-transition alloys. Due to the increasing demands of multifunctional applications, to search for the new materials with tunable magnetostructural transformations in a large operating temperature range is important. In this work, we demonstrate that by chemically alloying MnNiSi with CoNiGe, the structural transformation temperature of MnNiSi (1200 K) is remarkably decreased by almost 1000 K. A tunable magnetostructural transformation between the paramagnetic hexagonal and ferromagnetic orthorhombic phase over a wide temperature window from 425 to 125 K is realized in (MnNiSi)1-x(CoNiGe)x system. The magnetic-field-induced magnetostructural transformation is accompanied by the high-performance magnetocaloric effect, proving that MnNiSi-CoNiGe system is a promising candidate for magnetic cooling refrigerant. PMID:26979284

  3. Realization of magnetostructural coupling by modifying structural transitions in MnNiSi-CoNiGe system with a wide Curie-temperature window

    PubMed Central

    Liu, Jun; Gong, Yuanyuan; Xu, Guizhou; Peng, Guo; Shah, Ishfaq Ahmad; ul Hassan, Najam; Xu, Feng

    2016-01-01

    The magnetostructural coupling between structural and magnetic transitions leads to magneto-multifunctionalities of phase-transition alloys. Due to the increasing demands of multifunctional applications, to search for the new materials with tunable magnetostructural transformations in a large operating temperature range is important. In this work, we demonstrate that by chemically alloying MnNiSi with CoNiGe, the structural transformation temperature of MnNiSi (1200 K) is remarkably decreased by almost 1000 K. A tunable magnetostructural transformation between the paramagnetic hexagonal and ferromagnetic orthorhombic phase over a wide temperature window from 425 to 125 K is realized in (MnNiSi)1−x(CoNiGe)x system. The magnetic-field-induced magnetostructural transformation is accompanied by the high-performance magnetocaloric effect, proving that MnNiSi-CoNiGe system is a promising candidate for magnetic cooling refrigerant. PMID:26979284

  4. Realization of magnetostructural coupling by modifying structural transitions in MnNiSi-CoNiGe system with a wide Curie-temperature window

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Gong, Yuanyuan; Xu, Guizhou; Peng, Guo; Shah, Ishfaq Ahmad; Ul Hassan, Najam; Xu, Feng

    2016-03-01

    The magnetostructural coupling between structural and magnetic transitions leads to magneto-multifunctionalities of phase-transition alloys. Due to the increasing demands of multifunctional applications, to search for the new materials with tunable magnetostructural transformations in a large operating temperature range is important. In this work, we demonstrate that by chemically alloying MnNiSi with CoNiGe, the structural transformation temperature of MnNiSi (1200 K) is remarkably decreased by almost 1000 K. A tunable magnetostructural transformation between the paramagnetic hexagonal and ferromagnetic orthorhombic phase over a wide temperature window from 425 to 125 K is realized in (MnNiSi)1‑x(CoNiGe)x system. The magnetic-field-induced magnetostructural transformation is accompanied by the high-performance magnetocaloric effect, proving that MnNiSi-CoNiGe system is a promising candidate for magnetic cooling refrigerant.

  5. Threshold behavior of interaction potential for the system 7Li + 64Ni: Comparison with 6Li + 64Ni

    NASA Astrophysics Data System (ADS)

    Shaikh, Md. Moin; Das, Mili; Roy, Subinit; Sinha, M.; Pradhan, M. K.; Basu, P.; Datta, U.; Ramachandran, K.; Shrivastava, A.

    2016-09-01

    The elastic scattering angular distributions for the system 7Li + 64Ni were measured in the bombarding energy range of 12 MeV ≤Elab ≤ 26.4 MeV. A phenomenological optical model analysis was performed for the measured data. The strengths of the fitted potential components at the surface were estimated to extract their variation with energy. Further analyses of the measured angular distributions were performed with a hybrid potential composed of a renormalized folded real and a phenomenological imaginary potential. Both the model potentials predict similar energy dependent behavior for the effective interaction potential around the barrier. Unlike the heavy targets, 7Li + 64Ni does not show a normal threshold behavior. It also does not clearly exhibit a behavior similar to 6Li + 64Ni. The real potential for 7Li + 64Ni does not exhibit any significant energy dependence and the imaginary potential strength remains almost independent of energy above the Coulomb barrier (∼ 14 MeV). However, at energies below the barrier, a sudden drop in the imaginary potential strength is observed.

  6. Sub-barrier fusion and transfers in the 40Ca + 58,64Ni systems

    NASA Astrophysics Data System (ADS)

    Bourgin, D.; Courtin, S.; Haas, F.; Goasduff, A.; Stefanini, A. M.; Montagnoli, G.; Montanari, D.; Corradi, L.; Huiming, J.; Scarlassara, F.; Fioretto, E.; Simenel, C.; Rowley, N.; Szilner, S.; Mijatović, T.

    2016-05-01

    Fusion cross sections have been measured in the 40Ca + 58Ni and 40Ca + 64Ni systems at energies around and below the Coulomb barrier. The 40Ca beam was delivered by the XTU Tandem accelerator of the Laboratori Nazionali di Legnaro and evaporation residues were measured at very forward angles with the LNL electrostatic beam deflector. Coupled-channels calculations were performed which highlight possible strong effects of neutron transfers on the fusion below the barrier in the 40Ca + 64Ni system. Microscopic time-dependent Hartree-Fock calculations have also been performed for both systems. Preliminary results are shown.

  7. The Effect of Ni on the Fe-S system to 36 GPa

    NASA Astrophysics Data System (ADS)

    Stewart, A. J.; Schmidt, M. W.; van Westrenen, W.; Liebske, C.

    2005-12-01

    The metallic cores of the terrestrial planets are dominated by an iron-nickel-light element alloy. Sulfur is a major candidate for the dominant light element component, as such its phase relations with Fe-Ni metals are of paramount importance to understanding the nature of the cores of differentiated planets. Much previous work has focused on examining the phase diagram of the Fe-S binary, however only a few studies have yet included nickel as a major element. Here we present equilibrium multi-anvil research into metallic core phases to pressures equivalent to the center of Mars. In this work a series of experiments have been performed in both the Fe-S and Fe-Ni-S systems at 23 and 36 GPa and temperatures between 850 and 1600°C. The aim of these experiments was to determine the effect of nickel on the eutectic temperature and composition of the Fe-S system and to establish the Fe-S binary phase relations at much increased pressures. Four starting materials were prepared (in wt%): Fe60Ni34S6; Fe77Ni17S6; Fe86Ni8S6 (roughly corresponding to the Earth's core Fe:Ni ratio) and Fe94S6 from pure iron, pure sulfur and a Fe64Ni36 pre-alloy. Multi-anvil experiments were run at ETH Zurich using a 10/3.5 assembly on WC cubes and a 7/2 assemblage on sintered diamond cubes in a true split sphere apparatus. Both assemblies are symmetrical with respect to the furnace' mid-plane and use a radial thermocouple, allowing for two experimental charges within one run. This setup greatly reduces the number of experiments to be performed. Results indicate that nickel has a strong effect on the eutectic temperature, but only a minor effect on the composition of eutectic liquids. At 23 GPa, increasing nickel quantities, to maximum 34 wt%, increase the amount of divergence of the eutectic point from the pure Fe-S system. We find the eutectic point for the Fe-S system at 23 GPa to occur at 14.5 wt% sulfur and a temperature of 1025°C while the addition of up to 34 wt% Ni progressively shifts

  8. Experimental determination and thermodynamic modeling of the Ni-Re binary system

    NASA Astrophysics Data System (ADS)

    Yaqoob, Khurram; Joubert, Jean-Marc

    2012-12-01

    The phase diagram of the Ni-Re binary system has been partially reinvestigated by chemical, structural and thermal characterization of the arc melted alloys. The experimental results obtained during the present investigation were combined with the literature data and a new phase diagram of the Ni-Re binary system is proposed. In comparison with the Ni-Re phase diagram proposed by Nash et al. in 1985 [1], significant differences in the homogeneity domains, freezing ranges and peritectic reaction temperature were evidenced. On the other hand, thermodynamic modeling of the studied system by using the new experimental information has also been carried out with the help of the CALPHAD method. The calculated Ni-Re phase diagram showed a good agreement with the selected experimental information.

  9. Transient liquid-phase bonding in the Ni-Al-B system

    NASA Astrophysics Data System (ADS)

    Campbell, C. E.; Boettinger, W. J.

    2000-11-01

    Transient liquid-phase (TLP) bonding experiments were performed using a Ni-10.3 at. pct Al alloy and a Ni-10 at. pct B filler material, and the results were compared to simulations performed using the finite-difference diffusion code, DICTRA. For the simulations, a thermodynamic assessment of the Ni-Al-B system was used to define the phase diagram and the thermodynamic factors of the diffusion coefficients. Composition-dependent diffusion mobilities were assessed for the ternary system. Predicted liquid widths as functions of time were in good agreement with the experiments. The calculated and experimental Al composition profiles agree in the matrix but not in the liquid. The simulations qualitatively predicted the observed precipitation and later dissolution of the intermetallic τ phase (Ni20Al3B6) in the base material. This research demonstrated the potential for modeling the formation of spurious phases during TLP bonding of practical superalloy systems.

  10. Experimental determination and thermodynamic modeling of the Ni-Re binary system

    SciTech Connect

    Yaqoob, Khurram; Joubert, Jean-Marc

    2012-12-15

    The phase diagram of the Ni-Re binary system has been partially reinvestigated by chemical, structural and thermal characterization of the arc melted alloys. The experimental results obtained during the present investigation were combined with the literature data and a new phase diagram of the Ni-Re binary system is proposed. In comparison with the Ni-Re phase diagram proposed by Nash et al. in 1985 [1], significant differences in the homogeneity domains, freezing ranges and peritectic reaction temperature were evidenced. On the other hand, thermodynamic modeling of the studied system by using the new experimental information has also been carried out with the help of the CALPHAD method. The calculated Ni-Re phase diagram showed a good agreement with the selected experimental information. - Graphical abstract: Ni-Re phase diagram according to the present study. Highlights: Black-Right-Pointing-Pointer Re-investigation of the Ni-Re phase diagram. Black-Right-Pointing-Pointer Extended phase field of the hcp phase. Black-Right-Pointing-Pointer Different freezing ranges and peritectic reaction temperature. Black-Right-Pointing-Pointer Thermodynamic modeling of the studied system by using the CALPHAD method.

  11. Molecular dynamics simulation of surface segregation, diffusion and reaction phenomena in equiatomic Ni-Al systems

    NASA Astrophysics Data System (ADS)

    Evteev, A. V.; Levchenko, E. V.; Belova, I. V.; Murch, G. E.

    2012-12-01

    The molecular dynamics method is used to provide fundamental insights into surface segregation, bulk diffusion and alloying reaction phenomena in equiatomic Ni-Al systems. This knowledge can serve as a guide for the search and development of economic routes for controlling microstructure and properties of the intermetallic compound NiAl. This paper gives an overview of recent molecular dynamics simulations in the area along with other theoretical calculations and experimental measurements.

  12. Hydrogen evolution in [NiFe] hydrogenases and related biomimetic systems: similarities and differences.

    PubMed

    Das, Ranjita; Neese, Frank; van Gastel, Maurice

    2016-09-21

    In this work, a detailed quantum chemical study of the mechanism of [Ni(bdt)(dppf)] (Ni(II)L) catalyzed hydrogen formation [A. Gan, T. L. Groy, P. Tarakeshwar, S. K. S. Mazinani, J. Shearer, V. Mujica and A. K. Jones, J. Am. Chem. Soc., 2015, 137, 1109-1115] following an electro-chemical-electro-chemical (ECEC) pathway is reported. The complex exclusively catalyzes the reduction of protons to molecular hydrogen. The calculations suggest that the first one-electron reduction of the [Ni(II)L] catalyst is the rate limiting step of the catalytic cycle and hence, the buildup of detectable reaction intermediates is not expected. The catalytic activity of the [Ni(II)L] complex is facilitated by the flexibility of the ligand system, which allows the ligand framework to adapt to changes in the Ni oxidation state over the course of the reaction. Additionally, a comparison is made with the catalytic activity of [NiFe] hydrogenase. It is argued that the directionality of the reversible hydrogen formation reaction is controlled by the ligand field of the nickel ion and the possibility for side-on (η(2)) binding of H2: if the ligand framework does not allow for η(2) binding of H2, as is the case for [Ni(II)L], the catalyst irreversibly reduces protons. If the ligand field allows η(2) binding of H2, the catalyst can in principle work reversibly. The conditions for η(2) binding are discussed. PMID:27545687

  13. Antiferromagnetic proximity effect in epitaxial CoO/NiO/MgO(001) systems

    PubMed Central

    Li, Q.; Liang, J. H.; Luo, Y. M.; Ding, Z.; Gu, T.; Hu, Z.; Hua, C. Y.; Lin, H.-J.; Pi, T. W.; Kang, S. P.; Won, C.; Wu, Y. Z.

    2016-01-01

    Magnetic proximity effect between two magnetic layers is an important focus of research for discovering new physical properties of magnetic systems. Antiferromagnets (AFMs) are fundamental systems with magnetic ordering and promising candidate materials in the emerging field of antiferromagnetic spintronics. However, the magnetic proximity effect between antiferromagnetic bilayers is rarely studied because detecting the spin orientation of AFMs is challenging. Using X-ray linear dichroism and magneto-optical Kerr effect measurements, we investigated antiferromagnetic proximity effects in epitaxial CoO/NiO/MgO(001) systems. We found the antiferromagnetic spin of the NiO underwent a spin reorientation transition from in-plane to out-of-plane with increasing NiO thickness, with the existence of vertical exchange spring spin alignment in thick NiO. More interestingly, the Néel temperature of the CoO layer was greatly enhanced by the adjacent NiO layer, with the extent of the enhancement closely dependent on the spin orientation of NiO layer. This phenomenon was attributed to different exchange coupling strengths at the AFM/AFM interface depending on the relative spin directions. Our results indicate a new route for modifying the spin configuration and ordering temperature of AFMs through the magnetic proximity effect near room temperature, which should further benefit the design of AFM spintronic devices. PMID:26932164

  14. Antiferromagnetic proximity effect in epitaxial CoO/NiO/MgO(001) systems.

    PubMed

    Li, Q; Liang, J H; Luo, Y M; Ding, Z; Gu, T; Hu, Z; Hua, C Y; Lin, H-J; Pi, T W; Kang, S P; Won, C; Wu, Y Z

    2016-01-01

    Magnetic proximity effect between two magnetic layers is an important focus of research for discovering new physical properties of magnetic systems. Antiferromagnets (AFMs) are fundamental systems with magnetic ordering and promising candidate materials in the emerging field of antiferromagnetic spintronics. However, the magnetic proximity effect between antiferromagnetic bilayers is rarely studied because detecting the spin orientation of AFMs is challenging. Using X-ray linear dichroism and magneto-optical Kerr effect measurements, we investigated antiferromagnetic proximity effects in epitaxial CoO/NiO/MgO(001) systems. We found the antiferromagnetic spin of the NiO underwent a spin reorientation transition from in-plane to out-of-plane with increasing NiO thickness, with the existence of vertical exchange spring spin alignment in thick NiO. More interestingly, the Néel temperature of the CoO layer was greatly enhanced by the adjacent NiO layer, with the extent of the enhancement closely dependent on the spin orientation of NiO layer. This phenomenon was attributed to different exchange coupling strengths at the AFM/AFM interface depending on the relative spin directions. Our results indicate a new route for modifying the spin configuration and ordering temperature of AFMs through the magnetic proximity effect near room temperature, which should further benefit the design of AFM spintronic devices. PMID:26932164

  15. Antiferromagnetic proximity effect in epitaxial CoO/NiO/MgO(001) systems

    NASA Astrophysics Data System (ADS)

    Li, Q.; Liang, J. H.; Luo, Y. M.; Ding, Z.; Gu, T.; Hu, Z.; Hua, C. Y.; Lin, H.-J.; Pi, T. W.; Kang, S. P.; Won, C.; Wu, Y. Z.

    2016-03-01

    Magnetic proximity effect between two magnetic layers is an important focus of research for discovering new physical properties of magnetic systems. Antiferromagnets (AFMs) are fundamental systems with magnetic ordering and promising candidate materials in the emerging field of antiferromagnetic spintronics. However, the magnetic proximity effect between antiferromagnetic bilayers is rarely studied because detecting the spin orientation of AFMs is challenging. Using X-ray linear dichroism and magneto-optical Kerr effect measurements, we investigated antiferromagnetic proximity effects in epitaxial CoO/NiO/MgO(001) systems. We found the antiferromagnetic spin of the NiO underwent a spin reorientation transition from in-plane to out-of-plane with increasing NiO thickness, with the existence of vertical exchange spring spin alignment in thick NiO. More interestingly, the Néel temperature of the CoO layer was greatly enhanced by the adjacent NiO layer, with the extent of the enhancement closely dependent on the spin orientation of NiO layer. This phenomenon was attributed to different exchange coupling strengths at the AFM/AFM interface depending on the relative spin directions. Our results indicate a new route for modifying the spin configuration and ordering temperature of AFMs through the magnetic proximity effect near room temperature, which should further benefit the design of AFM spintronic devices.

  16. Phase relations and structural features in the system Ni-Zn-B

    SciTech Connect

    Malik, Z.; Grytsiv, A.; Rogl, P.; Giester, G.; Bursik, J.

    2013-02-15

    Phase relations for the system Ni-Zn-B have been established in the isothermal section at 800 Degree-Sign C based on X-ray powder diffraction and electron microprobe analyses of about 60 samples, which have been prepared by hot pressing of pre-annealed powder compacts of arc-melted master alloys Ni{sub x}B{sub y} and Zn-filings. Six ternary compounds (labeled {tau}{sub 1} to {tau}{sub 6}) were found to exist, which in some cases exhibit considerable mutual solid solubilities mostly as an exchange of Ni-Zn at constant B-content, but in the case of the so-called {tau}-phase {tau}{sub 1}-(Ni{sub 1-x}Zn{sub x}){sub 21}[Zn{sub 1-y-z}{open_square}{sub y}(B{sub 4}){sub z}]{sub 2}B{sub 6} (0.07{<=}x{<=}0.11, 0.07{<=}y{<=}0.53, 0{<=}z{<=}0.3) also with Zn/B substitution. Single crystal X-ray data analysis for the composition x=0.07, y=0.125, z=0.30, and a=1.05800(3) nm confirmed the Cr{sub 23}C{sub 6} type with space group Fm3{sup Macron }m, but revealed partial replacement of Zn-atoms by B{sub 4}-tetrahedra (R{sub F}=0.014). Whereas Ni/Zn exchange (at constant B-content) ranges at about 4-5 at% for {tau}{sub 4}-Ni{sub 3}ZnB{sub 2} and {tau}{sub 5}-Ni{sub 48}Zn{sub 32}B{sub 20}, it is below 3 at% for {tau}{sub 2}-Ni{sub 12}ZnB{sub 8-x} (x=0.43), {tau}{sub 3}-Ni{sub 21}Zn{sub 2}B{sub 20} and {tau}{sub 6}-Ni{sub 47}Zn{sub 23}B{sub 30}. The crystal structures of {tau}{sub 2}-Ni{sub 12}ZnB{sub 8-x} (x=0.43; Ni{sub 12}AlB{sub 8} type), {tau}{sub 3}-Ni{sub 21}Zn{sub 2}B{sub 20} (own type) and {tau}{sub 4}-Ni{sub 3}ZnB{sub 2} (own type) have been determined in our foregoing paper [8]. Due to the non-availability of suitable single crystals, the crystal structures of {tau}{sub 5}-Ni{sub 48}Zn{sub 32}B{sub 20} (body-centered orthorhombic; a=1.6(2) nm, b=0.63(7) nm, and c=0.27(0) nm, determined from TEM) and of {tau}{sub 6}-Ni{sub 47}Zn{sub 23}B{sub 30} have not been elucidated yet. Phase equilibria at 800 Degree-Sign C are dominated by a large three-phase field ({beta}B)+Ni{sub 2}Zn

  17. Proposed long-range empirical potential to study the metallic glasses in the Ni-Nb-Ta system.

    PubMed

    Dai, Y; Li, J H; Che, X L; Liu, B X

    2009-05-21

    An n-body potential is constructed for the Ni-Nb-Ta ternary metal system in the newly proposed form of long-range empirical potential. The constructed Ni-Nb-Ta potential can well reproduce the lattice constants, cohesive energies, and elastic modulus of the metals and some compounds as well as the equations of state of the system. Applying the constructed Ni-Nb-Ta potential, molecular dynamics simulations and Voronoi tessellations are carried out to study the issues related to the Ni-Nb-Ta metallic glasses. It is found that increasing the Ni content can obviously improve the glass-forming ability of the binary Nb-Ta system, which features a isomorphous phase diagram unfavoring for forming glass, indicating that the Ni solute plays a decisive role in forming the Nb-based or Ta-based Ni-Nb-Ta metallic glasses. Concerning the atomic structure, the Voronoi cell volume and coordination number (CN) of Ta are generally larger than those of Ni in the binary Ni-Ta metallic glasses. With increasing the Ni concentration, the fraction of icosidihedron (CN=13) increases, while the fractions of icosihexahedron (CN=15) and icosioctahedron (CN=16) decrease. Meanwhile, with increasing the Ni concentration, the dominating coordination numbers of Ta atoms increase. Interestingly, similar feature in the atomic structure with variation of Ni concentration is also observed in the Ni-Nb metallic glasses. For the ternary Ni-Nb-Ta alloys, it is observed from the CN distributions that the structure of the metallic glasses is mostly affected by the Ni concentration. PMID:19438281

  18. Experimental study and thermodynamic assessment of the Ni-Mo-Ta ternary system

    SciTech Connect

    Cui, Y.; Lu, X.; Jin, Z.

    1999-11-01

    Phase equilibrium data of the Ni-Mo-Ta system at 1,473, 1,373, and 1,173 K were determined by means of diffusion triple and electron probe microanalysis (EPMA) techniques in this article. From the present experimental results and literature data, the Ni-Mo-Ta system was thermodynamically assessed using the CALPHAD method. A set of consistent thermodynamic parameters of each phase was obtained. A number of calculated isothermal sections are presented and compared with experimental data. They are in reasonable agreement. The present calculation was successfully used to analyze the solidification behavior of two alloys. Two subsystems, Ni-Mo and Mo-Ta, were assessed prior to the assessment of the ternary system.

  19. The As-Cu-Ni System: A Chemical Thermodynamic Model for Ancient Recycling

    NASA Astrophysics Data System (ADS)

    Sabatini, Benjamin J.

    2015-12-01

    This article is the first thermodynamically reasoned ancient metal system assessment intended for use by archaeologists and archaeometallurgists to aid in the interpretation of remelted/recycled copper alloys composed of arsenic and copper, and arsenic, copper, and nickel. These models are meant to fulfill two main purposes: first, to be applied toward the identification of progressive and regressive temporal changes in artifact chemistry that would have occurred due to recycling, and second, to provide thermodynamic insight into why such metal combinations existed in antiquity. Built on well-established thermodynamics, these models were created using a combination of custom-written software and published binary thermodynamic systems data adjusted to within the boundary conditions of 1200°C and 1 atm. Using these parameters, the behavior of each element and their likelihood of loss in the binaries As-Cu, As-Ni, Cu-Ni, and ternary As-Cu-Ni, systems, under assumed ancient furnace conditions, was determined.

  20. Highly efficient removal of chromium(VI) by Fe/Ni bimetallic nanoparticles in an ultrasound-assisted system.

    PubMed

    Zhou, Xiaobin; Jing, Guohua; Lv, Bihong; Zhou, Zuoming; Zhu, Runliang

    2016-10-01

    Highly active Fe/Ni bimetallic nanocomposites were prepared by using the liquid-phase reduction method, and they were proven to be effective for Cr(VI) removal coupled with US irradiation. The US-assisted Fe/Ni bimetallic system could maintain a good performance for Cr(VI) removal at a wide pH range of 3-9. Based on the characterization of the Fe/Ni nanoparticles before and after reaction, the high efficiency of the mixed system could attribute to the synergistic effects of the catalysis of Ni(0) and US cavitation. Ni(0) could facilitate the Cr(VI) reduction through electron transfer and catalytic hydrogenation. Meanwhile, US could fluidize the Fe/Ni nanoparticles to increase the actual reactive surface area and clean off the co-precipitated Fe(III)-Cr(III) hydroxides to maintain the active sites on the surface of the Fe/Ni nanoparticles. Thus, compared with shaking, the US-assisted Fe/Ni system was more efficient on Cr(VI) removal, which achieved 94.7% removal efficiency of Cr(VI) within 10 min. The pseudo-first-order rate constant (kobs) in US-assisted Fe/Ni system (0.5075 min(-1)) was over 5 times higher than that under shaking (0.0972 min(-1)). Moreover, the Fe/Ni nanoparticles still have a good performance under US irradiation after 26 days aging as well as regeneration. PMID:27393969

  1. Advanced thermal barrier system bond coatings for use on Ni, Co-, and Fe-base alloy substrates

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1985-01-01

    New and improved Ni-, Co-, and Fe-base bond coatings have been identified for the ZrO2-Y2O3 thermal barrier coatings to be used on NI-, Co-, and Fe-base alloy substrates. These bond coatings were evaluated in a cyclic furnace between 1120 and 1175 C. It was found that MCrAlYb (where M = Ni, Co, or Fe) bond coating thermal barrier systems. The longest life was obtained with the FeCrAlYb thermal barrier system followed by NiCrAlYb and CoCrAlYb thermal barrier systems in that order.

  2. Effective temperatures in complete fusion for the system {sup 58}Ni + {sup 58}Ni at 500 MeV bombarding energy

    SciTech Connect

    D`Onofrio, A.; Campajola, L.; Inglima, G.; Roca, V.

    1996-12-01

    Triple coincidences between complex fragments with Z > 3, light charged particles and {gamma} transitions have been measured for the system {sup 58}Ni+{sup 58}Ni at 500 MeV incident energy. To this end the HILI detector and a 19 pack BaF{sub 2} cluster made of 19 crystals of TAPS geometry have been used. Effective temperatures have been obtained from the ratios of the bound excited level cross sections to the ground states ones for C. N and 0 evaporated after complete fusion of {sup 58}Ni +{sup 58}Ni at 500 MeV incident energy. The dependence of the effective temperature on the charged light particle multiplicity has been investigated.

  3. Low temperature diffusion coefficients in the Fe-Ni and FeNiP systems: Application to meteorite cooling rates

    NASA Technical Reports Server (NTRS)

    Dean, D. C.; Goldstein, J. I.

    1984-01-01

    The interdiffusion coefficient of FeNi in fcc taenite (gamma) of Fe-Ni and Fe-Ni-0.2 P alloys was measured as a function of temperature between 600 and 900 C. This temperature range is directly applicable to the nucleation and growth of the Widmanstatten pattern in iron meteorites and metal regions of stony and stony-iron meteorites. Diffusion couples were made from FeNi or FeNiP alloys which ensured that the couples were in the taenite phase at the diffusion temperature. The presence or absence of grain boundary diffusion was determined by measuring the Ni profile normal to the existing grain boundaries with the AEM. Ignoring any variation of interdiffusion coefficient with composition, the measured data was plotted versus the reciprocal of the diffusion temperature. The FeNi data generally follow the extrapolated Goldstein, et al. (1965) data from high temperatures. The FeNiP data indicates that small additions of P (0.2 wt%) cause a 3 to 10 fold increase in the FeNi interdifussion coefficient increasing with decreasing temperature. This increase is about the same as that predicted by Narayan and Goldstein (1983) at the Widmanstatten growth temperature.

  4. Corrosion and oxidation properties of NiCr coatings sprayed in presence of gas shroud system

    NASA Astrophysics Data System (ADS)

    Morks, M. F.; Berndt, C. C.

    2010-04-01

    The oxidation of a NiCr bond coat during air plasma spraying was controlled by designing a gas shroud system attached to the plasma torch nozzle. Two nozzles, termed as "normal" and "high-speed" nozzles examined the effect of nozzle internal design on the microstructure and phase structure of coatings. X-ray diffraction and SEM morphologies showed that the shroud system reduced the oxidation of NiCr particles during the spray process. Compared with conventional air plasma spraying, the argon gas shroud reduced the coating hardness because the volume fraction of partially melted particles increased. The high-speed nozzle reduced the oxidation and hardness of NiCr coatings due to the increase of partially melted particles in the coatings.

  5. The Pd2Si - /Pd/ - Ni - solder plated metallization system for silicon solar cells

    NASA Technical Reports Server (NTRS)

    Coleman, M. G.; Pryor, R. A.; Sparks, T. G.

    1978-01-01

    The rationale and application of a plated metal system, Pd2Si Pd - Ni - solder, is presented. This metallization system is particularly useful on shallow p-n junction solar cells. The advantages of such plated solar cell contacts are discussed. A process sequence for applying the metallization system is outlined. A specific example is presented, including chemical plating solution formulations and detailed process step descriptions. Electrical test data for solar cells metallized with the palladium-nickel-solder system are provided.

  6. NiSi formation at the silicide/Si interface on the NiPt/Si system

    NASA Astrophysics Data System (ADS)

    Ottaviani, G.; Tu, K. N.; Chu, W. K.; Hung, L. S.; Mayer, J. W.

    1982-07-01

    Alloy films of NiPt were e-beam codeposited on n-type Si and annealed up to 700 °C in a purified- He ambient furnace. Silicide formation was monitored using MeV4 He Rutherford backscattering and glancing-angle x-ray diffraction. At low temperatures (300-350 °C), Ni segregates at the Si/ silicide interface and the first phases detected are NiSi and PtSi. At intermediate temperatures (400- 500 °C), there is further accumulation of Ni at the Si/silicide interface, and at later stages an incursion of Pt to the interface. The barrier height increase reflects the presence of Pt. At 700 °C, the Ni and Pt redistribute to form a uniform ternary.

  7. Direct Metal Deposition by Laser in TiNi-Al System for Graded Structure Fabrication

    NASA Astrophysics Data System (ADS)

    Shishkovsky, I.; Kakovkina, N.; Missemer, F.

    2016-07-01

    Intermetallic phase formation was studied in powdered TiNi-Al system under layerwise laser cladding with the aim of forming a gradient of properties due to a change in the concentration relation of Al in the NiTi powder mixture from one layer to another. The relationship between the laser cladding parameters and the intermetallic phase structures in consecutively cladded layers were determined. The structure of intermetallic compounds formed by laser synthesis was studied by optical microscopy, measurement of microhardness, SEM with EDX analysis. Microhardness doubling from 500 HV to 1000 HV was achieved due to nitinol matrix enrichment by Al, which is promising for aerospace applications.

  8. Magnetic transition in NiPt alloy systems: experiment and theory

    NASA Astrophysics Data System (ADS)

    Kumar, Uday; Padmalekha, K. G.; Mukhopadhyay, P. K.; Paudyal, Durga; Mookerjee, Abhijit

    2005-04-01

    We report here the preparation and measurements on the susceptibility, sound velocity and internal friction for NiPt systems. We then compare these experimental results with the first principle theoretical predictions and show that there is reasonable agreement with experiment and theory.

  9. Experimental study and thermodynamic modeling of the Al-Co-Cr-Ni system

    NASA Astrophysics Data System (ADS)

    Gheno, Thomas; Liu, Xuan L.; Lindwall, Greta; Liu, Zi-Kui; Gleeson, Brian

    2015-10-01

    A thermodynamic database for the Al-Co-Cr-Ni system is built via the Calphad method by extrapolating re-assessed ternary subsystems. A minimum number of quaternary parameters are included, which are optimized using experimental phase equilibrium data obtained by electron probe micro-analysis and x-ray diffraction analysis of NiCoCrAlY alloys spanning a wide compositional range, after annealing at 900 °C, 1100 °C and 1200 °C, and water quenching. These temperatures are relevant to oxidation and corrosion resistant MCrAlY coatings, where M corresponds to some combination of nickel and cobalt. Comparisons of calculated and measured phase compositions show excellent agreement for the β-γ equilibrium, and good agreement for three-phase β-γ-σ and β-γ-α equilibria. An extensive comparison with existing Ni-base databases (TCNI6, TTNI8, NIST) is presented in terms of phase compositions.

  10. Thermodynamic Modeling of Poorly Complexing Metals in Concentrated Electrolyte Solutions: An X-Ray Absorption and UV-Vis Spectroscopic Study of Ni(II) in the NiCl2-MgCl2-H2O System

    PubMed Central

    Zhang, Ning; Brugger, Joël; Etschmann, Barbara; Ngothai, Yung; Zeng, Dewen

    2015-01-01

    Knowledge of the structure and speciation of aqueous Ni(II)-chloride complexes is important for understanding Ni behavior in hydrometallurgical extraction. The effect of concentration on the first-shell structure of Ni(II) in aqueous NiCl2 and NiCl2-MgCl2 solutions was investigated by Ni K edge X-ray absorption (XAS) and UV-Vis spectroscopy at ambient conditions. Both techniques show that no large structural change (e.g., transition from octahedral to tetrahedral-like configuration) occurs. Both methods confirm that the Ni(II) aqua ion (with six coordinated water molecules at RNi-O = 2.07(2) Å) is the dominant species over the whole NiCl2 concentration range. However, XANES, EXAFS and UV-Vis data show subtle changes at high salinity (> 2 mol∙kg-1 NiCl2), which are consistent with the formation of small amounts of the NiCl+ complex (up to 0.44(23) Cl at a Ni-Cl distance of 2.35(2) Å in 5.05 mol∙kg-1 NiCl2) in the pure NiCl2 solutions. At high Cl:Ni ratio in the NiCl2-MgCl2-H2O solutions, small amounts of [NiCl2]0 are also present. We developed a speciation-based mixed-solvent electrolyte (MSE) model to describe activity-composition relationships in NiCl2-MgCl2-H2O solutions, and at the same time predict Ni(II) speciation that is consistent with our XAS and UV-Vis data and with existing literature data up to the solubility limit, resolving a long-standing uncertainty about the role of chloride complexing in this system. PMID:25885410

  11. Reaction dynamics studies for the system 7Be+58Ni

    NASA Astrophysics Data System (ADS)

    Torresi, D.; Mazzocco, M.; Acosta, L.; Boiano, A.; Boiano, C.; Diaz-Torres, A.; Fierro, N.; Glodariu, T.; Grilj, L.; Guglielmetti, A.; Keeley, N.; La Commara, M.; Martel, I.; Mazzocchi, C.; Molini, P.; Pakou, A.; Parascandolo, C.; Parkar, V. V.; Patronis, N.; Pierroutsakou, D.; Romoli, M.; Rusek, K.; Sanchez-Benitez, A. M.; Sandoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Stiliaris, E.; Strano, E.; Stroe, L.; Zerva, K.

    2015-04-01

    The study of reactions induced by exotic weakly bound nuclei at energies around the Coulomb barrier had attracted a large interest in the last decade, since the features of these nuclei can deeply affect the reaction dynamics. The discrimination between different reaction mechanisms is, in general, a rather difficult task. It can be achieved by using detector arrays covering high solid angle and with high granularity that allow to measure the reaction products and, possibly, coincidences between them, as, for example, recently done for stable weakly bound nuclei [1, 2]. We investigated the collision of the weakly bound nucleus 7Be on a 58Ni target at the beam energy of 1.1 times the Coulomb barrier, measuring the elastic scattering angular distribution and the energy and angular distributions of 3He and 4He. The 7Be radioactive ion beam was produced by the facility EXOTIC at INFN-LNL with an energy of 22 MeV and an intensity of ~3×105 pps. Results showed that the 4He yeld is about 4 times larger than 3He yield, suggesting that reaction mechanisms other than the break-up mostly produce the He isotopes. Theoretical calculations for transfer channels and compound nucleus reactions suggest that complete fusion accounts for (41±5%) of the total reaction cross section extracted from optical model analysis of the elastic scattering data, and that 3He and 4He stripping are the most populated reaction channels among direct processes. Eventually estimation of incomplete fusion contributions to the 3,4He production cross sections was performed through semi-classical calculations with the code PLATYPUS [3].

  12. Superconducting proximity effect in NiBi3-Ni-NiBi3 trilayer system with sharp superconductor-ferromagnet boundaries

    NASA Astrophysics Data System (ADS)

    Siva, Vantari; Pradhan, Paresh C.; Santosh Babu, G.; Nayak, Maheswar; Sahoo, Pratap K.; Senapati, Kartik

    2016-02-01

    We have studied the superconducting proximity effect in a series of e-beam evaporated Bi-Ni-Bi trilayers, where diffusion of Bi into Ni spontaneously formed superconducting NiBi3 layers at both Ni-Bi interfaces, effectively resulting in superconductor-ferromagnet-superconductor (S-F-S) trilayers. The thickness of top and bottom superconducting layers was found to be different with slightly different transition temperatures. Both resistive transition temperatures in the series of S-F-S trilayers showed 0-π crossover as a function of ferromagnetic Ni thickness. The zero bias conductance calculated from the in-plane current-voltage measurements also confirmed the 0-π crossovers. The possibility of proximity effect in the superconducting fluctuation regime, above transition temperature, was investigated via in-plane magneto-transport measurements at 4 K. We observed clear modulations in magneto-resistance (MR) and in low-field MR-hysteresis at 4 K, in contrast to their monotonic behavior at 10 K. Although the period of these modulations was commensurate with the observed periodicity of 0-π crossovers, the nature of these modulations was found to be the same in both 0 and π regimes. This observation suggested that in the superconducting fluctuation regime the apparent modulations of MR and MR-hysteresis were due to the variations in densities of superconducting fluctuations in individual NiBi3 layers, and not due to the proximity coupling between the superconducting layers.

  13. The study of threshold behaviour of effective potential for Li6+Ni58,64 systems

    NASA Astrophysics Data System (ADS)

    Biswas, M.; Roy, Subinit; Sinha, M.; Pradhan, M. K.; Mukherjee, A.; Basu, P.; Majumdar, H.; Ramachandran, K.; Shrivastava, A.

    2008-04-01

    The elastic scattering for 6Li + 64Ni system was measured in the bombarding energy range of 13 MeV⩽E⩽26 MeV. A phenomenological optical model analysis was performed and the behaviour of the surface strengths of the potential components with decreasing energy was extracted. A further analysis of the measured angular distributions, along with the existing data for 6Li + 58Ni, was performed with two different model potentials—one with the folded potential normalized with a complex factor (OMP1) and the other with a hybrid potential composed of a renormalized folded real and a phenomenological imaginary (OMP2) potential components. All the model potentials predict similar energy dependent behaviour for the interaction potential around the barrier. The observed energy dependence of the strengths of the real and imaginary potentials corroborate with the dispersion relation prediction for both the 6Li + 64Ni and 6Li + 58Ni systems. Though the evidence of breakup is distinct in the energy variation of the potential strengths, close to the barrier the variation is more in the line of conventional threshold anomaly. Also the threshold behaviour of the interaction potential does not indicate any distinct isotopic dependence.

  14. Orbital management and design considerations for NiCd satellite power systems

    NASA Technical Reports Server (NTRS)

    Tausch, Benjamin J., II

    1994-01-01

    Several recently manufactured 50 and 60 ampere hour aerospace NiCd battery cell lots, produced by Gates Aerospace Batteries, are prone to premature on orbit performance degradation. The failure mechanism is cadmium migration, and the consequent development of soft shorts. A Martin Marietta Astronautics satellite program instituted an orbital management strategy for a set of these batteries that reduced the rate of degradation and brought the system to stable operation. This strategy involves: (1) minimizing the accumulated battery overcharge; (2) regular discharge exercises; and (3) periodic battery reconditioning. Because of changes in the NiCd cell manufacturing process, the actual performance of subsequent lots of NiCd cells is open to question. Future NiCd based power system designs should therefore allow for fine control of charge parameters, and an on orbit battery reconditioning capability. To minimize risk, it is much better to perform a full life test to qualify the cells before launch, rather than in parallel with orbital operations. If there are any changes in the manufacturing process of cells, it is extremely important to maintain very strong cognizance of secondary subcontractors, recognizing that the cell and battery manufacturing discipline is easily atrophied.

  15. Phase equilibria and structural investigations in the Ni-poor part of the system Al–Ge–Ni

    PubMed Central

    Reichmann, Thomas L.; Duarte, Liliana I.; Effenberger, Herta S.; Leinenbach, Christian; Richter, Klaus W.

    2012-01-01

    The ternary phase diagram Al–Ge–Ni was investigated between 0 and 50 at.% Ni by a combination of differential thermal analysis (DTA), powder- and single-crystal X-ray diffraction (XRD), metallography and electron probe microanalysis (EPMA). Ternary phase equilibria and accurate phase compositions of the equilibrium phases were determined within two partial isothermal sections at 400 and 700 °C, respectively. The two binary intermediate phases AlNi and Al3Ni2 were found to form extended solid solutions with Ge in the ternary. Three new ternary phases were found to exist in the Ni-poor part of the phase diagram which were designated as τ1 (oC24, CoGe2-type), τ2 (at approximately Al67.5Ge18.0Ni14.5) and τ3 (cF12, CaF2-type). The ternary phases show only small homogeneity ranges. While τ1 was investigated by single crystal X-ray diffraction, τ2 and τ3 were identified from their powder diffraction pattern. Ternary phase reactions and melting behaviour were studied by means of DTA. A total number of eleven invariant reactions could be derived from these data, which are one ternary eutectic reaction, six transition reactions, three ternary peritectic reactions and one maximum. Based on the measured DTA values three vertical sections at 10, 20 and 35 at.% Ni were constructed. Additionally, all experimental results were combined to a ternary reaction scheme (Scheil diagram) and a liquidus surface projection. PMID:27087753

  16. Graphene as a diffusion barrier for isomorphous systems: Cu-Ni system

    NASA Astrophysics Data System (ADS)

    Roy, Apurba; Punith Kumar, M. K.; Srivastava, Chandan

    2016-02-01

    Electrochemical exfoliation technique using the pyrophosphate anion derived from tetra sodium pyrophosphate was employed to produce graphene. As-synthesized graphene was then drop dried over a cold rolled Cu sheet. Ni coating was then electrodeposited over bare Cu and graphene-Cu substrates. Both substrates were then isothermally annealed at 800 °C for 3 h. WDS analysis showed substantial atomic diffusion in annealed Ni-Cu sample. Cu-graphene-Ni sample, on the other hand, showed negligible diffusion illustrating the diffusion barrier property of the graphene coating.

  17. Breakup threshold anomaly for the 8B + 58Ni system at near-Coulomb barrier energies

    NASA Astrophysics Data System (ADS)

    Gómez Camacho, A.; Aguilera, E. F.; Gomes, P. R. S.; Lubian, J.

    2011-09-01

    By using recent fusion cross section measurements for the system 8B + 58Ni, a simultaneous analysis of elastic scattering, fusion, and total reaction cross sections is performed for the weakly bound system 8B + 58Ni at energies close to the Coulomb barrier. The analysis is carried out with an optical potential with fusion and direct reaction parts (i.e., the nuclear polarization potential U is split into a volume part UF, which accounts for fusion reactions and a surface part UDR, responsible for direct reactions). The parameters of the Woods-Saxon potentials are determined by a χ2 analysis of the data. The presence of the threshold anomaly is investigated from the energy dependence of both the fusion and direct reaction parts of the polarization potential.

  18. Threshold anomaly for the 7Be +58Ni system at near-Coulomb-barrier energies

    NASA Astrophysics Data System (ADS)

    Gómez Camacho, A.; Aguilera, E. F.

    2014-12-01

    By using recent fusion cross section measurements for the weakly bound system 7Be+58Ni around the Coulomb barrier, a simultaneous χ2 analysis of elastic scattering and fusion cross section data is performed. The analysis is carried out with optical polarization potentials for the fusion and direct reaction processes. That is, the nuclear polarization potential UN is split into a volume part UF which accounts for fusion reactions and a surface part UD R that is responsible for direct reactions. The parameters of fusion and direct reaction Woods-Saxon polarization potentials are determined by the analysis of the data. The presence of the threshold anomaly is investigated from the energy dependence of these polarization potentials. It is found that, contrary to other weakly bound systems, the 7Be+58Ni reaction presents the usual threshold anomaly.

  19. Volume dependent quasiparticle spectral weight in NiS2-xSex system

    NASA Astrophysics Data System (ADS)

    Marini, C.; Perucchi, A.; Dore, P.; Topwal, D.; Sarma, D. D.; Lupi, S.; Postorino, P.

    2012-05-01

    We discuss the evolution of Infrared reflectivity at room temperature under various pressures (P) and Se alloying concentration in the strongly correlated NiS2-xSex pyrite. Measurements gave a complete picture of the optical response of the system on approaching the P-induced and Se-induced metallic state. A peculiar non-monotonic (V-shaped) volume dependence was found for the quasiparticle spectral weight of both pure and Se-doped compounds.

  20. Experimental investigations of trace element fractionation in iron meteorites. III - Elemental partitioning in the system Fe-Ni-S-P

    NASA Technical Reports Server (NTRS)

    Malvin, D. J.; Jones, J. H.; Drake, M. J.

    1986-01-01

    Measurements of solid metal/liquid metal trace element partition coefficients, which are used to interpret the crystallization history of magmatic iron meteorite groups differ greatly between different research groups, using different experimental techniques. Specifically, partition coefficients measured utilizing 'static' experiments which approach equilibrium cannot be reconciled with the results of 'dynamic' experiments which mimic fractional crystallization. We report new tests of our 'static' experimental technique and demonstrate that our methodology yields reliable equilibrium values for Ni, P and Ge partition coefficients. Partition coefficients in the Fe-Ni-S-P system are well matched by interpolation between the Fe-Ni-S and Fe-Ni-P subsystems. In contrast, the predictions of 'dynamic' experiments do not agree with our measurements and, consequently, the ability of 'dynamic' experiments to reproduce iron meteorite Ge vs. Ni fractionation trends successfully must be regarded as fortuitous.

  1. Monte Carlo calculation of backscattering factor for Ni C multilayer system

    NASA Astrophysics Data System (ADS)

    Zommer, Ludomir; Jablonski, Alexander; Kotis, László; Menyhárd, Miklós

    2008-08-01

    Auger electron spectroscopy (AES) depth profiles using the NiMVV (61 eV), CKLL (272 eV) and NiLMM (848 eV) lines were recorded for a 3 × (Ni(40 nm)/C(28 nm))/Si substrate sample. It was found that the Auger intensities corresponding to pure regions of the depth profile changed with depth. The behaviour of the change was different for the different layers and different Auger lines. The changes can be attributed to the change in the backscattering factor (BF) as the thickness of the sample changes due to the sputter removal. Zommer and Jablonski developed a Monte Carlo (MC) algorithm to calculate the BF for systems with a buried layer. This algorithm was applied to the present case; the intensities of the monitored Auger lines were calculated for the sample with decreasing thickness similarly to the Auger depth profiling. The agreement between the measured and calculated AES depth profiles is excellent. The MC calculation verifies that several layers contribute to the BF and thus the expressions developed for overlayer/substrate systems cannot be used.

  2. Electronic structure of Zr-Ni-Sn systems: role of clustering and nanostructures in half-Heusler and Heusler limits.

    PubMed

    Do, Dat T; Mahanti, S D; Pulikkoti, Jiji J

    2014-07-01

    Half-Heusler and Heusler compounds have been of great interest for several decades for thermoelectric, magnetic, half-metallic and many other interesting properties. Among these systems, Zr-Ni-Sn compounds are interesting thermoelectrics which can go from semiconducting half-Heusler (HH) limit, ZrNiSn, to metallic Heusler (FH) limit, ZrNi2Sn. Recently Makongo et al (2011 J. Am. Chem. Soc. 133 18843) found that dramatic improvement in the thermoelectric power factor of HH can be achieved by putting excess Ni into the system. This was attributed to an energy filtering mechanism due to the presence of FH nanostructures in the HH matrix. Using density functional theory we have investigated clustering and nanostructure formation in ZrNi1+xSn (0 ⩽ x ⩽ 1) systems near the HH (x = 0) and FH (x = 1) ends and have found that excess Ni atoms in HH tend to stay close to each other and form nanoclusters. On the other hand, there is competing interaction between Ni-vacancies occupying different sites in FH which prevents them from forming vacancy nanoclusters. Effects of nano-inclusions on the electronic structure near HH and FH ends are discussed. PMID:24925669

  3. Magnetodielectric coupling in frustrated spin systems: the spinels MCr₂O₄ (M = Mn, Co and Ni).

    PubMed

    Mufti, N; Nugroho, A A; Blake, G R; Palstra, T T M

    2010-02-24

    We have studied the magnetodieletric coupling of polycrystalline samples of the spinels MCr(2)O(4) (M = Mn, Co and Ni). Dielectric anomalies are clearly observed at the onset of the magnetic spiral structure (T(s)) and at the 'lock-in' transition (T(f)) in MnCr(2)O(4) and CoCr(2)O(4), and also at the onset of the canted structure (T(s)) in NiCr(2)O(4). The strength of the magnetodielectric coupling in this system can be explained by spin-orbit coupling. Moreover, the dielectric response in an applied magnetic field scales with the square of the magnetization for all three samples. Thus, the magnetodielectric coupling in this state appears to originate from the P(2)M(2) term in the free energy. PMID:21386397

  4. Reaction studies near the barrier for medium heavy systems: Ni + Sn

    SciTech Connect

    Henning, W.

    1985-01-01

    Cross sections for elastic and inelastic scattering, single- and multi-nucleon transfer, fusion followed by particle evaporation leaving an evaporation residue, and fusion followed by fission have been measured for /sup 58/ /sup 64/Ni beams incident on even Sn targets at energies from below to above the Coulomb barrier. The Ni beams were provided by the Argonne Superconducting Linac. The aim of these measurements is a comprehensive study of the reaction systematics in a medium-heavy collision system. At present, a small fraction of the data has been fully analyzed and published, a larger part is presently being compared to model calculations. Some of the data needs to be confirmed by additional measurements. This summary should be viewed as a status report and an attempt to formulate some of the open questions. 9 references.

  5. Influence of Ni nanoparticle addition and spark plasma sintering on the TiNiSn–Ni system: Structure, microstructure, and thermoelectric properties

    SciTech Connect

    Birkel, Christina S.; Douglas, Jason E.; Lettiere, Bethany R.; Seward, Gareth; Zhang, Yichi; Pollock, Tresa M.; Seshadri, Ram; Stucky, Galen D.

    2013-12-01

    The electronic and thermal properties of thermoelectric materials are highly dependent on their microstructure and therefore on the preparation conditions, including the initial synthesis and, if applicable, densification of the obtained powders. Introduction of secondary phases on the nano- and/or microscale is widely used to improve the thermoelectric figure of merit by reduction of the thermal conductivity. In order to understand the effect of the preparation technique on structure and properties, we have studied the thermoelectric properties of the well-known half-Heusler TiNiSn with addition of a small amount of nickel nanoparticles. The different parameters are the initial synthesis (levitation melting and microwave heating), the amount of nickel nanoparticles added and the exact pressing profile using spark plasma sintering. The resulting materials have been characterized by synchrotron X-ray diffraction and microprobe measurements and their thermoelectric properties are investigated. We found the lowest (lattice) thermal conductivity in samples with full-Heusler TiNi2Sn and Ni3Sn4 as secondary phases.

  6. Theoretical study on the reaction mechanism of the gas-phase H2/CO2/Ni(3D) system.

    PubMed

    Qin, Song; Hu, Changwei; Yang, Huaqing; Su, Zhishan

    2005-07-28

    The ground-state potential energy surface (PES) in the gas-phase H2/CO2/Ni(3D) system is investigated at the CCSD(T)//B3LYP/6-311+G(2d,2p) levels in order to explore the possible reaction mechanism of the reverse water gas shift reaction catalyzed by Ni(3D). The calculations predict that the C-O bond cleavage of CO2 assisted by co-interacted H2 is prior to the dissociation of the H2, and the most feasible reaction path for Ni(3D) + H2 + CO2 --> Ni(3D) + H2O + CO is endothermic by 12.5 kJ mol(-1) with an energy barrier of 103.9 kJ mol(-1). The rate-determining step for the overall reaction is predicted to be the hydrogen migration with water formation. The promotion effect of H2 on the cleavage of C-O bond in CO2 is also discussed and compared with the analogous reaction of Ni(3D) + CO2 --> NiO + CO, and the difference between triplet and singlet H2/CO2/Ni systems is also discussed. PMID:16833994

  7. Experimental study and thermodynamic modeling of the Al–Co–Cr–Ni system

    DOE PAGESBeta

    Gheno, Thomas; Liu, Xuan L.; Lindwall, Greta; Liu, Zi -Kui; Gleeson, Brian

    2015-09-21

    In this study, a thermodynamic database for the Al–Co–Cr–Ni system is built via the Calphad method by extrapolating re-assessed ternary subsystems. A minimum number of quaternary parameters are included, which are optimized using experimental phase equilibrium data obtained by electron probe micro-analysis and x-ray diffraction analysis of NiCoCrAlY alloys spanning a wide compositional range, after annealing at 900 °C, 1100 °C and 1200 °C, and water quenching. These temperatures are relevant to oxidation and corrosion resistant MCrAlY coatings, where M corresponds to some combination of nickel and cobalt. Comparisons of calculated and measured phase compositions show excellent agreement for themore » β–γ equilibrium, and good agreement for three-phase β–γ–σ and β–γ–α equilibria. An extensive comparison with existing Ni-base databases (TCNI6, TTNI8, NIST) is presented in terms of phase compositions.« less

  8. Experimental study and thermodynamic modeling of the Al–Co–Cr–Ni system

    SciTech Connect

    Gheno, Thomas; Liu, Xuan L.; Lindwall, Greta; Liu, Zi -Kui; Gleeson, Brian

    2015-09-21

    In this study, a thermodynamic database for the Al–Co–Cr–Ni system is built via the Calphad method by extrapolating re-assessed ternary subsystems. A minimum number of quaternary parameters are included, which are optimized using experimental phase equilibrium data obtained by electron probe micro-analysis and x-ray diffraction analysis of NiCoCrAlY alloys spanning a wide compositional range, after annealing at 900 °C, 1100 °C and 1200 °C, and water quenching. These temperatures are relevant to oxidation and corrosion resistant MCrAlY coatings, where M corresponds to some combination of nickel and cobalt. Comparisons of calculated and measured phase compositions show excellent agreement for the β–γ equilibrium, and good agreement for three-phase β–γ–σ and β–γ–α equilibria. An extensive comparison with existing Ni-base databases (TCNI6, TTNI8, NIST) is presented in terms of phase compositions.

  9. Enhancement of perpendicular magnetic anisotropy of Co layer in exchange-biased Au/Co/NiO/Au polycrystalline system

    NASA Astrophysics Data System (ADS)

    Kuświk, P.; Szymański, B.; Anastaziak, B.; Matczak, M.; Urbaniak, M.; Ehresmann, A.; Stobiecki, F.

    2016-06-01

    The perpendicular exchange bias in NiO(antiferromagnet)/Co(ferromagnet) polycrystalline layer films is studied. It is found that the NiO layer forces the Co layer magnetization to be oriented perpendicular to the film plane in a greater thickness range than is found in the Au/Co/Au system. Simultaneously, a large coercivity and a significant perpendicular exchange bias field were observed that are owing to the interlayer exchange bias coupling between NiO and Co, which supports the perpendicular magnetic anisotropy of the Co layer. These findings are confirmed by magnetometry and magnetoresistance measurements.

  10. Nucleon transfer in the (35,37)Cl + (58,60,62,64)Ni systems

    NASA Astrophysics Data System (ADS)

    Kurz, Kristin Lynn

    1998-07-01

    Nucleon transfer measurements were carried out for the 35,37Cl + 58,60,62,64Ni systems at energies above the Coulomb barrier (Ecm/VC/approx 1.55 and 1.75) using the Enge split-pole spectrograph at the Nuclear Structure Research Laboratory at the University of Rochester. The Rochester recoil mass spectrometer was used to measure one-nucleon transfer cross sections for these systems below the Coulomb barrier at Elab = 88 MeV (Ecm/VC/approx 0.85). These measurements were used to study the influence of nucleon transfer on the enhancement of sub-barrier fusion cross sections for heavy systems compared to the one- dimensional barrier penetration model. Coupled-channel fusion calculations including couplings to inelastic and transfer degrees of freedom were performed for the 37Cl + 58,60,62,64Ni systems. Coupled- channel calculations for other systems for which measurements of both fusion and transfer cross sections in the region of the barrier exist were also carried out. The results suggest that there is a strong correlation between transfer strength and sub-barrier fusion enhancement.

  11. Bulk metallic glass formation in the Pd-Ni-P and Pd-Cu-P alloy systems

    SciTech Connect

    Schwarz, R.B.; He, Y.

    1996-12-11

    Bulk metallic glasses were prepared in the Pd-Ni-P and Pd-Cu-P systems using a fluxing technique. The formation of bulk amorphous Pd-Cu-P alloys was reported here for the first time. For both alloy systems, bulk glass formation requires maintaining the phosphorus content near 20 at.%. In the Pd-Ni-P system, 10-mm diameter amorphous Pd{sub x}Ni{sub 80{minus}x}P{sub 20} rods can be formed for 25 {le} x {le} 60. In the Pd-Cu-P system, 7-mm diameter amorphous Pd{sub x}Cu{sub 80{minus}x}P{sub 20} rods can be produced for 40 {le} x {le} 60. From all the ternary alloys studied, Pd{sub 40}Ni{sub 40}P{sub 20} has the highest glass formability, and 25-mm diameter amorphous cylinders, 50 mm in length, can be easily fabricated. The glass stability of the Pd-Ni-P system is wider than that of the Pd-Cu-P system. For most bulk Pd-Ni-P glasses, {Delta}T > 90 K. The {Delta}T values of bulk amorphous Pd-Cu-P alloys are considerably smaller, ranging from 27 to 73 K. The elastic constants of bulk amorphous Pd-Ni-P and Pd-Cu-P alloys were determined using a resonant ultrasound spectroscopy technique. The Pd-Ni-P glasses are slightly stiffer than the Pd-Cu-P glasses. Within each alloy system, the Young`s modulus and the bulk modulus show little change with alloy composition. Of all the bulk glass forming systems so far investigated, the ternary Pd-Ni-P system has the best glass formability. This alloy was one of the first bulk glasses discovered, yet it still remains the best in terms of glass formability. Upon replacing part of Ni by Cu, the critical cooling rates are expected to be further reduced.

  12. A comprehensive study on photocatalytic activity of supported Ni/Pb sulfide and oxide systems onto natural zeolite nanoparticles.

    PubMed

    Babaahamdi-Milani, Majid; Nezamzadeh-Ejhieh, Alireza

    2016-11-15

    The Ni(II)-Pb(II) exchanged clinoptilolite nanoparticles (NCP) were transformed to corresponding oxides and sulfides via calcination and sulfiding processes, respectively. The obtained catalysts were characterized by XRD, FT-IR, TEM and DRS and used in photodegradation of p-nitrophenol (4-NP) aqueous solution under Hg-lamp irradiation. Results showed considerable increase in activity of the coupled semiconductors with respect to monocomponent one. In NiO-PbO-NCP system, conduction band (CB) of NiO is enough negative for easily migration of photogenerated electrons to CB-PbO level, while such phenomena take place from more negative CB-PbS level to CB-NiS level in NiS-PbS-NCP. These phenomena significantly prevented from electron-hole recombination which increased photocatalytic activity of the coupled semiconductors. Best photodegradation activities obtained by NiO1.3%-PbO14.7%-NCP and NiS2.1%-PbS10.0%-NCP, confirming semiconductors' mass-ratio dependence of the photocatalytic process. The supported coupled semiconductors showed blue shifts in band gap energies with respect to the bulk semiconductors which confirm formation of semiconductors nanoparticles inside the zeolite framework. The highest degradation percentage of 4-NP was obtained at: 0.5gL(-1) photocatalysts, 15mgL(-1) 4-NP at pH 7.5. PMID:27427895

  13. Hybrid Co-Cr/W-WC and Ni-W-Cr-B/W-WC Coating Systems

    NASA Astrophysics Data System (ADS)

    Vernhes, L.; Azzi, M.; Bousser, E.; Schmitt, T.; Lamarre, J. M.; Klemberg-Sapieha, J. E.

    2016-01-01

    The aim of this study was to investigate the effects of subsurface materials on the performance of a wear-resistant thin film. The mechanical, tribological, and corrosion properties were assessed for two hybrid coating systems: (1) W-WC thin film and a laser cladded Co-Cr interlayer applied to a 316 stainless steel substrate and (2) the same W-WC thin film and a spray-and-fused Ni-W-Cr-B interlayer applied to an Inconel® 718 substrate. They were then compared to the same systems without an interlayer. The microstructures were analyzed by XRD, EDS, and SEM. The hardness and surface load-carrying capacity of the coating systems were determined by micro- and macrohardness testing. Rockwell indentation was used to assess coating adhesion (CEN/TS 1071-8). Tribological properties were assessed with a reciprocating tribometer, and corrosion resistance was determined by potentiodynamic polarization and electrochemical impedance spectroscopy. The originality of this work lies in the finding that, except for the Inconel 718/Ni-W-Cr-B/W-WC system, the wear rate decreases with decreasing hardness of the subsurface materials carrying the thin film due to the decreasing contact pressure for a given load. Another novel finding is the stress-induced phase transformation of the Co-Cr interlayer, which occurs beneath the thin film under high load.

  14. Phase relations and crystal structures in the system Ce-Ni-Zn at 800 Degree-Sign C

    SciTech Connect

    Malik, Z.; Grytsiv, A.; Rogl, P.; Giester, G.

    2012-10-15

    Phase relations have been established for the system Ce-Ni-Zn in the isothermal section at 800 Degree-Sign C using electron microprobe analysis and X-ray powder diffraction. Phase equilibria at 800 Degree-Sign C are characterized by a large region for the liquid phase covering most of the Ce-rich part of the diagram, whereas a Zn-rich liquid is confined to a small region near the Zn-corner of the Gibbs triangle. Whereas solubility of Ce in the binary Ni-Zn phases is negligible, mutual solubilities of Ni and Zn at a constant Ce content are large at 800 Degree-Sign C for most Ce-Zn and Ce-Ni compounds. The solid solution Ce(Ni{sub 1-x}Zn{sub x}){sub 5} with the CaCu{sub 5}-type is continuous throughout the entire section and for the full temperature region from 400 to 800 Degree-Sign C. Substitution of Zn by Ni is found to stabilize the structure of CeZn{sub 11} to higher temperatures. At 800 Degree-Sign C Ce(Ni{sub x}Zn{sub 1-x}){sub 11} (0.03{<=}x{<=}0.22) appears as a ternary solution phase. Similarly, a rather extended solution forms for Ce{sub 2}(Ni{sub x}Zn{sub 1-x}){sub 17} (0{<=}x{<=}0.53). Detailed data on atom site occupation and atom parameters were derived from X-ray structure analyses for single crystals of Ce{sub 2+y}(Ni{sub x}Zn{sub 1-x}){sub 17}, y=0.02, x=0.49 (a=0.87541(3), c=1.25410(4) nm; Th{sub 2}Zn{sub 17} type with space group R3{sup Macron }m,R{sub F{sup 2}}=0.018) and Ce(Ni{sub 0.18}Zn{sub 0.82}){sub 11} (a=1.04302(2), c=0.67624(3)nm, BaCd{sub 11} type with space group I4{sub 1}/amd, R{sub F{sup 2}}=0.049). - Graphical abstract: Ce-Ni-Zn isothermal section at 800 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Phase relations were determined for the system Ce-Ni-Zn in the section at 800 Degree-Sign C. Black-Right-Pointing-Pointer A continuous solid solution Ce(Ni{sub 1-x}Zn{sub x}){sub 5}, 0{<=}x{<=}1, forms between 400 and 800 Degree-Sign C. Black-Right-Pointing-Pointer Zn/Ni substitution stabilizes the ternary phase Ce(Zn{sub 1-x}Ni

  15. Observing Natural Hazards: Tsunami, Hurricane, and El Niño Observations from the NDBC Ocean Observing System of Systems

    NASA Astrophysics Data System (ADS)

    O'Neil, K.; Bouchard, R.; Burnett, W. H.; Aldrich, C.

    2009-12-01

    The National Oceanic and Atmospheric Administration’s (NOAA) National Data Buoy Center (NDBC) operates and maintains the NDBC Ocean Observing Systems of Systems (NOOSS), comprised of 3 networks that provide critical information before and during and after extreme hazards events, such as tsunamis, hurricanes, and El Niños. While each system has its own mission, they have in common the requirement to remain on station in remote areas of the ocean to provide reliable and accurate observations. After the 2004 Sumatran Tsunami, NOAA expanded its network of tsunameters from six in the Pacific Ocean to a vast network of 39 stations providing information to Tsunami Warning Centers to enable faster and more accurate tsunami warnings for coastal communities in the Pacific, Atlantic, Caribbean and the Gulf of Mexico. The tsunameter measurements are used to detect the amplitude and period of the tsunamis, and the data can be assimilated into models for the prediction and impact of the tsunamis to coastal communities. The network has been used for the detection of tsunamis generated by earthquakes, including the 2006 and 2007 Kuril Islands, 2007 Peru, and Solomon Islands, and most recently for the 2009 Dusky Sound, New Zealand earthquake. In August 2009, the NOAA adjusted its 2009 Atlantic Hurricane Seasonal Outlooks from above normal to near or below normal activity, primarily due to a strengthening El Niño. A key component in the detection of that El Niño was the Tropical Atmosphere Ocean Array (TAO) operated by NDBC. TAO provides real-time data for improved detection, understanding, and prediction of El Niño and La Niña. The 55-buoy TAO array spans the central and eastern equatorial Pacific providing real-time and post-deployment recovery data to support climate analysis and forecasts. Although, in this case, the El Niño benefits the tropical Atlantic, the alternate manifestation, La Niña typically enhances hurricane activity in the Atlantic. The various phases of

  16. Magmatic Conduit Metallogenic System in Jinchuan Cu-Ni (PGE) Sulfide Deposit

    NASA Astrophysics Data System (ADS)

    Su, S.; Tang, Z.; Zhou, M.; Song, C.

    2014-12-01

    The Jinchuan Cu-Ni (PGE) sulfide deposit is located in the southwestern margin of North China Craton. Jinchuan ultramafic intrusion hosts the third largest magmatic Cu-Ni deposit in the world. There are mainly four orebodies, namely, orebody-58, orebody-24, orebody-1, and orebody-2, respectively from west to east in the deposit. The primary characteristics of Jinchuan Cu-Ni sulfide deposit are the following: (1) There is an obvious boundary between orebodys and country rocks, usually orebodys intruded into country rocks. (2) "sulfide melts" migrate and settle in the later stage of magma evolution. (3) Fluid Minerals Assemblages are found in the sulfide ores, there is Phl+Cc+Pn+Ccp+Po in orebody-2; Phl+Dol+AP+Pn+Ccp+Po in orebody-24; Q+Mag+AP+Pn+Ccp+Po in orebody-58. (4) Massive sulfides mainly occur in orebody-2, and its PGE content is very rare. Pt-Pd enrichment zones mainly occur in orebody-1; orebody-24 and orebody-58. Ir vs. Ru, Rh, Pt, Pd show positive relationship in orebody-2, but Ir vs. Ru, Rh show positive relationship, Ir vs. Pt, Pd exhibit negative relationship in orebody-1, orebody-24 and orebody-58. The modeling of Ir-Pd shows that the massive sulfide in orebody-2 maybe the origin of MSS. Pt-Pd enrichment zones in orebody-1 orebody-24 and orebody-58 are the relic liquid of monosulfide solid solution segregation; (5) Cu/Ni value is 1.24 in orebody-58, 1.56 in orebody-24, 1.83 in orebody-1, and 2.06 in orebody-2. These features imply that (1) "ore magma" or "melt-fluid bearing metal" formed in the staging chamber in depth; (2) "ore magma" might contain a lot of fluids; (3) "melt-fluid bearing metal" flow moves as a whole; (4) The moving direction of melt-fluid bearing metal flow is form west to east. The ores are enriched in Ni in the front, and enriched in Cu, Pt, Pd in the back of Jinchuan Magmatic Conduit Metallogenic System.

  17. Electronic Structure and Ground State Properties of Non-Magnetic NiPt Systems

    NASA Astrophysics Data System (ADS)

    PAUDYAL, DURGA; MOOKERJEE, ABHIJIT

    We have studied the electronic properties like density of states and band structures and also the ground state properties like formation energy, cohesive energy, bulk modulus and structural energy of NiPt system using the linearized muffin-tin orbital method introduced by Andersen.1,2 In an earlier communication we had argued that both charge neutrality and scalar relativistic corrections are very important for the high concentration of Pt alloys. The calculations here, were, therefore, carried out with charge neutrality as well as with and without scalar relativistic correction for comparison.

  18. NMR study of hydrogen diffusion and phase determination of the Mg2NiHx system

    NASA Astrophysics Data System (ADS)

    Goren, S. D.; Korn, C.; Mintz, M. H.; Gavra, Z.; Hadari, Z.

    1980-11-01

    We have measured the temperature dependence of the hydrogen spin lattice relaxation time in the hydride (β, β', γ, δ) and solid solution phases of the Mg2NiHx system. These gave the temperature ranges of the various phases. The hydrogen diffusion activation energy for the β, β', γ and δ hydride phases were found to be 10.6±0.4, ?17, 12.0±0.3 and ?20 kcal/mole, respectively, and 8.7±0.7 kcal/mole for the α phase solution.

  19. Long-Time Stability of Ni-Ti-Shape Memory Alloys for Automotive Safety Systems

    NASA Astrophysics Data System (ADS)

    Strittmatter, Joachim; Gümpel, Paul

    2011-07-01

    In automotive a lot of electromagnetically, pyrotechnically or mechanically driven actuators are integrated to run comfort systems and to control safety systems in modern passenger cars. Using shape memory alloys (SMA) the existing systems could be simplified, performing the same function through new mechanisms with reduced size, weight, and costs. A drawback for the use of SMA in safety systems is the lack of materials knowledge concerning the durability of the switching function (long-time stability of the shape memory effect). Pedestrian safety systems play a significant role to reduce injuries and fatal casualties caused by accidents. One automotive safety system for pedestrian protection is the bonnet lifting system. Based on such an application, this article gives an introduction to existing bonnet lifting systems for pedestrian protection, describes the use of quick changing shape memory actuators and the results of the study concerning the long-time stability of the tested NiTi-wires. These wires were trained, exposed up to 4 years at elevated temperatures (up to 140 °C) and tested regarding their phase change temperatures, times, and strokes. For example, it was found that A P-temperature is shifted toward higher temperatures with longer exposing periods and higher temperatures. However, in the functional testing plant a delay in the switching time could not be detected. This article gives some answers concerning the long-time stability of NiTi-wires that were missing till now. With this knowledge, the number of future automotive applications using SMA can be increased. It can be concluded, that the use of quick changing shape memory actuators in safety systems could simplify the mechanism, reduce maintenance and manufacturing costs and should be insertable also for other automotive applications.

  20. Nano-structured FGM of the system AlN-Ni

    SciTech Connect

    Atarashiya, Koji; Uda, Masahiro

    1993-12-31

    A nano-structured FGM block of the system AlN-Ni was prepared by the method of powder metallurgy. The raw material i.e. an ultrafine particle, whose size was 200 nm in average diameter, was prepared by means of the arc-plasma processing that a vaporized substance was collected in a bag filter. A compositionally gradient mixture of a nickel ultrafine particle and an aluminum-aluminum nitride ultrafine particle was pressed (200 MPa) in a steel die, followed by two-step sintering (873K and 1273K) in flowing nitrogen under null pressure. In this process, the aluminum ultrafine particle reacted with nitrogen into aluminum nitride, but the nickel ultrafine particle did not react with any species. Thus, FGM block of the system AlN-Ni was completely accomplished. The techniques of an ultrafine-particle mixing and sintering without crystal-grain growth were invented. Generally speaking the preparation of FGM block especially in the metal nitride systems, needs an extremely high temperature and high pressure. However, in this work using an ultrafine particle, the nano-structured FGM block was easily prepared. The nitriding reaction of aluminum is exothermic. Thus, it considerably progresses by self-propagating high temperature synthesis (SHS) when it has once begun. The structure and the compositional distributions of the FGM block were examined by SEM and EDX. The physical properties of the FGM block such as density, thermal expansion coefficient and micro harness were measured.

  1. Characterization of NiTi Shape Memory Damping Elements designed for Automotive Safety Systems

    NASA Astrophysics Data System (ADS)

    Strittmatter, Joachim; Clipa, Victor; Gheorghita, Viorel; Gümpel, Paul

    2014-07-01

    Actuator elements made of NiTi shape memory material are more and more known in industry because of their unique properties. Due to the martensitic phase change, they can revert to their original shape by heating when subjected to an appropriate treatment. This thermal shape memory effect (SME) can show a significant shape change combined with a considerable force. Therefore such elements can be used to solve many technical tasks in the field of actuating elements and mechatronics and will play an increasing role in the next years, especially within the automotive technology, energy management, power, and mechanical engineering as well as medical technology. Beside this thermal SME, these materials also show a mechanical SME, characterized by a superelastic plateau with reversible elongations in the range of 8%. This behavior is based on the building of stress-induced martensite of loaded austenite material at constant temperature and facilitates a lot of applications especially in the medical field. Both SMEs are attended by energy dissipation during the martensitic phase change. This paper describes the first results obtained on different actuator and superelastic NiTi wires concerning their use as damping elements in automotive safety systems. In a first step, the damping behavior of small NiTi wires up to 0.5 mm diameter was examined at testing speeds varying between 0.1 and 50 mm/s upon an adapted tensile testing machine. In order to realize higher testing speeds, a drop impact testing machine was designed, which allows testing speeds up to 4000 mm/s. After introducing this new type of testing machine, the first results of vertical-shock tests of superelastic and electrically activated actuator wires are presented. The characterization of these high dynamic phase change parameters represents the basis for new applications for shape memory damping elements, especially in automotive safety systems.

  2. Phase relations in the Fe-Ni-Cr-S system and the sulfidation of an austenitic stainless steel

    NASA Technical Reports Server (NTRS)

    Jacob, K. T.; Rao, D. B.; Nelson, H. G.

    1977-01-01

    The stability fields of various sulfide phases that form on Fe-Cr, Fe-Ni, Ni-Cr and Fe-Cr-Ni alloys were developed as a function of temperature and the partial pressure of sulfur. The calculated stability fields in the ternary system were displayed on plots of log P sub S sub 2 versus the conjugate extensive variable which provides a better framework for following the sulfidation of Fe-Cr-Ni alloys at high temperatures. Experimental and estimated thermodynamic data were used in developing the sulfur potential diagrams. Current models and correlations were employed to estimate the unknown thermodynamic behavior of solid solutions of sulfides and to supplement the incomplete phase diagram data of geophysical literature. These constructed stability field diagrams were in excellent agreement with the sulfide phases and compositions determined during a sulfidation experiment.

  3. Redistribution of concentration of components during interdiffusion in Cu-Fe-Ni system

    NASA Astrophysics Data System (ADS)

    Ugaste, Yu. E.; Kodentsov, A. A.; van Loo, F.

    2012-12-01

    Interdiffusion in a Cu-Ni-Fe system was studied at a temperature of 1000°C for three different diffusion couples. It has been shown that, in the studied diffusion couples, the distributions of some components of the system have a distinctly nonmonotonous character and, apart from the local extremes of the concentration curves, there are also zero flux planes in five diffusion zones. Special features of the behavior of the concentration curves and diffusion paths are discussed using thermodynamic data for the system. It has been found that diffusion fluxes of the components are unambiguously associated with a derivative of thermodynamic activity by the concentration taken along the diffusion path. There are experimental data in the appendix concerning the concentration profiles for all of the studied components of the diffusion couples.

  4. Structural and physical properties of Ni-Tb-Fe-O system

    SciTech Connect

    Khan, M. Azhar Islam, M.U.; Ishaque, M.; Rahman, I.Z.; Genson, A.; Hampshire, S.

    2009-01-15

    A series of soft ferrites in the system Ni{sub 1-x}Tb{sub x}Fe{sub 2}O{sub 4} (0 {<=} x {<=} 0.2), was prepared by a standard ceramic technique. The influence of terbium content was investigated by means of X-ray diffraction, Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy. The X-ray diffraction analysis reveals that the samples have a cubic spinel (single phase) structure for 0 {<=} x {<=} 0.08; for x > 0.08 a small peak of orthorhombic phase (TbFeO{sub 3}) appears and becomes more conspicuous with increased terbium substitution. The lattice parameter changes in a non-linear way as a function of terbium content which may be attributed to differences in the ionic radii of the cations involved and the solubility limit of terbium ions. A gradual increase in the bulk density was observed with the increase of terbium concentration, from 5.13 g/cm{sup 3} to 5.69 g/cm{sup 3}. FTIR absorption spectra of the Ni-Tb-Fe-O system were investigated in the wave number range 370-1500 cm{sup -1}. Each spectrum exhibited two main absorption bands, thereby confirming the spinel structure.

  5. The Major and Minor Relaxations in Polymeric Ni-Zn-Cu-Co Complex Nanocomposite Systems

    NASA Astrophysics Data System (ADS)

    Akbulut, S.; şentürk, E.; Köseoğlu, Y.

    2015-02-01

    Nanocrystalline polymeric complex (Ni0.5Zn0.4Cu0.1) ferrite substituted cobalt (Co) ferrite system has been synthesized by chemical co precipitation method. The dielectric properties of polymeric spinel ferrite system (Ni0.5Zn0.4Cu0.1Fe2O4)x (CoFe2O4)1-x have been investigated. Some of the dielectric parameters such as dielectric permittivity ɛ' and loss tangent (tan δ) were studied as a function of frequency in the range 1 Hz-1 MHz and of temperature in the range 230-410 K. Excessive dependency of dielectric properties on frequency and temperature with the presence of two relaxation mechanisms, which are called as major and minor, have been observed. From Argand diagram analysis α and Δɛ values for these two kinds of relaxation curves have been determined for all the samples in the measured temperatures. The reported dielectric properties are thought to be meaningful for future applications.

  6. New Stable Crystal Structures for Cu-Au and Ni-Pt Alloy Systems

    NASA Astrophysics Data System (ADS)

    Sanati, Mahdi; Wang, L. G.; Zunger, A.

    2003-10-01

    Cu-Au and Ni-Pt are among the best studied fcc alloy systems, exhibiting the famous L10 (AB) and L12 (A_3B) phases. We were wondering if a complete configurational search of the T=0 LDA total energies would reveal any unexpected phases. Total-energy calculations of ˜ 30 arbitrarily chosen structures were used to construct a generalized (momentum-space) Ising Hamiltonian containing ˜ 20 pair-interactions, ˜ 5-10 many-body terms, as well as the long-range strain term. This Hamiltonian was tested carefully as to its ability to predict the LDA energies of other structures. We searched the energies of all fcc configurations with 20 or less atoms per primitive cell ( ˜ 2,700,000 structures), found known L1_0, L12 as well as new, unsuspected structures. The new ground state structures are NiPt_7, Cu_2Au, and Cu_2Au_3. We also found a composition range in which there is quasicontinuum of stable, ordered structures made of (001) repeat units of simple structural motifs. This structural adaptivity is explained in terms of anisotropic, long-range strain energy.

  7. Bridge Structure for the graphene/Ni(111) system: A first principles study

    SciTech Connect

    Fuentes-Cabrera, Miguel A; Baskes, Mike I.; Melechko, Anatoli Vasilievich; Simpson, Michael L

    2008-01-01

    The structure of graphene on Ni(111) is studied with density functional theory (DFT). Six different structures, i.e., top-fcc, top-hcp, hcp-fcc, bridge-top, bridge-fcc, and bridge-hcp, were investigated. Bridge-top, bridge-fcc, and bridge-hcp are studied here. Top-fcc and hcp-fcc have been considered before, experimentally and theoretically, and regarded as energetically stable structures. The calculations employed the local density approximation (LDA) and the Perdew, Burke, and Ernzerhof (PBE) generalized-gradient approximation to DFT. The results showed that with PBE, none of the structures is stable at the experimentally relevant temperatures; with LDA, only bridge-top and top-fcc are stable. These findings suggest that it will be worthwhile to carry on new experimental studies to revisit the structural determination of the graphene/Ni(111) system, with special emphasis on testing whether bridge-top could exist by itself or coexist with other structures.

  8. Potential High-Temperature Shape-Memory Alloys Identified in the Ti(Ni,Pt) System

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.; Biles, Tiffany A.; Garg, Anita; Nathal, Michael V.

    2004-01-01

    "Shape memory" is a unique property of certain alloys that, when deformed (within certain strain limits) at low temperatures, will remember and recover to their original predeformed shape upon heating. It occurs when an alloy is deformed in the low-temperature martensitic phase and is then heated above its transformation temperature back to an austenitic state. As the material passes through this solid-state phase transformation on heating, it also recovers its original shape. This behavior is widely exploited, near room temperature, in commercially available NiTi alloys for connectors, couplings, valves, actuators, stents, and other medical and dental devices. In addition, there are limitless applications in the aerospace, automotive, chemical processing, and many other industries for materials that exhibit this type of shape-memory behavior at higher temperatures. But for high temperatures, there are currently no commercial shape-memory alloys. Although there are significant challenges to the development of high-temperature shape-memory alloys, at the NASA Glenn Research Center we have identified a series of alloy compositions in the Ti-Ni-Pt system that show great promise as potential high-temperature shape-memory materials.

  9. Stable Ni Isotope Fractionation In Systems Relevant To Banded Iron-Formations

    NASA Astrophysics Data System (ADS)

    Howe, H.; Spivak-Birndorf, L.; Newkirk, D.; Wasylenki, L. E.

    2013-12-01

    An important event in the evolution of life was the rise of atmospheric oxygen during the Proterozoic. Preceding the rise in O2 was a decline in atmospheric methane concentrations, likely due to decreased productivity of methanogenic Archaea. Based on Ni concentrations in banded iron formations (BIF), Konhauser et al. (2009) hypothesized that mantle cooling during the Archaean reduced the amount of Ni present in igneous rocks and in oceans, causing a Ni shortage for methanogens. Methanogens use Ni for cofactor F430, a catalyst during methanogenesis. To confirm Konhauser's hypothesis, a proxy for methanogen productivity in the rock record is necessary, in order to determine whether a decline in methanogen populations correlated with the observed decrease in maximum Ni contents in rocks from the Archaean. Ni isotope ratios recorded in BIF (oceanic sediments consisting of layered iron oxides and cherts) may provide evidence of a decline in methane production. Cameron et al. (2009) have shown that methanogens preferentially assimilate light Ni isotopes. Thus Ni isotopes in BIF have potential use as biomarkers for methanogenesis. Ferrihydrite was almost certainly the dominant Fe-oxide phase precipitating during BIF deposition. Ferrihydrite nanoparticles have large surface areas and are able to remove aqueous metals from solution through multiple sorption mechanisms. Thus we investigated experimentally the relationship between Ni isotopes in solution and Ni associated with ferrihydrite. We experimented with two different sorption mechanisms: adsorption of aqueous Ni onto surfaces of synthetic ferrihydrite and coprecipitation of aqueous Ni with ferrihydrite. Preliminary results indicate that light isotopes are preferentially associated with ferrihydrite in both adsorption and coprecipitation experiments, with an average fractionation of 0.3‰ in terms of δ60/58 Ni. Future experiments will investigate whether the observed isotope fractionations reflect kinetics or

  10. Chemical Convection in the Lunar Core from Melting Experiments on the Fe-Ni-S System

    NASA Astrophysics Data System (ADS)

    Liu, J.; Chen, B.; Wang, Y.; Jing, Z.; Li, Z.; Li, J.

    2012-12-01

    The thermal and chemical states of the lunar interior are directly related to the origin and evolution of the Moon. Recent seismic study suggested the lunar core is partially molten, consisting of a liquid outer shell and a solid inner sphere (Weber et al., 2011). The volume fraction of the lunar inner core is 38%, which is much higher than that for the Earth (~ 4%). This volume fraction can be used to establish the relation between the bulk composition of the lunar core and its temperature profile if the liquidi of relevant compositions at lunar inner core boundary (ICB) pressure (~ 5.1 GPa) are known. Moreover, knowledge on the extent of core solidification can be used to evaluate the role of compositional convection in the origin of early lunar core dynamo (Stegman et al., 2003). We have conducted melting experiments at 5.1 GPa and 900-1600 °C for the Fe-rich portion of Fe-Ni-S system, using the multi-anvil apparatus and synchrotron and laboratory-based analytical methods. Our data show that in the iron-rich portion of the Fe-S binary system, the liquidus curve reflects nearly ideal mixing between iron and FeS end-members. In contrast, the liquidus curve of the Fe-Ni-S ternary contains two inflection points with a turning point at a sulfur content of 10 wt.%, resulting from a departure from ideal solution behavior. Given that the compositional buoyancy force scales with the slope of the liquidus curve at the ICB pressure and temperature, the contribution of compositional convection to sustain the early lunar dynamo can be estimated from our data: for a simplified model of Fe-S binary core, the role of chemical convection was probably negligible in the early history of the Moon and would have remained nearly constant since the inception of the inner core. The lunar core, however, likely contains nickel, the turning points in liquidus curve of the Fe-Ni-S ternary system may lead to dynamo initiation if the sulfur content of the bulk lunar core is less than 10 wt

  11. The microstructure and electrical properties of contacts formed in the Ni/Al/Si system due to rapid thermal processing

    NASA Astrophysics Data System (ADS)

    Katz, A.; Komem, Y.

    1988-06-01

    The microstructure and electrical properties of the contacts formed in the Ni(30 nm)/Al(10 nm)/100-line n-Si system due to rapid thermal processing were studied at temperatures between 300 and 900 C. A melting at the intermediate Al layer was observed already at about 580 C after 2-s heat treatments. This rapid eutectic melting, assumed to initiate at the Al-Si interface, resulted in the formation of a unique contact composed of the Ni(Al/0.5/Si/0.5/)/Al3Ni/Ni(x)Si(y)/n-Si structure with fairly smooth interfaces between the layers. The sheet resistance of the layers and the Schottky barrier height of the contact were measured as a function of the rapid thermal processing temperatures. As a result of the eutectic melting reaction at 580 C, the sheet resistance of the formed layers decreased from 3.2 to 2.6 ohm/unit area, the Schottky barrier height between the layers and Si increased from 0.61-0.76 eV, and the effective electrically active area of the contact increased. These electrical properties are discussed in correlation with the microstructure formed in the Ni/Al/Si system due to the rapid thermal processing.

  12. Fatigue of NiTi SMA–pulley system using Taguchi and ANOVA

    NASA Astrophysics Data System (ADS)

    Mohd Jani, Jaronie; Leary, Martin; Subic, Aleksandar

    2016-05-01

    Shape memory alloy (SMA) actuators can be integrated with a pulley system to provide mechanical advantage and to reduce packaging space; however, there appears to be no formal investigation of the effect of a pulley system on SMA structural or functional fatigue. In this work, cyclic testing was conducted on nickel–titanium (NiTi) SMA actuators on a pulley system and a control experiment (without pulley). Both structural and functional fatigues were monitored until fracture, or a maximum of 1E5 cycles were achieved for each experimental condition. The Taguchi method and analysis of the variance (ANOVA) were used to optimise the SMA–pulley system configurations. In general, one-way ANOVA at the 95% confidence level showed no significant difference between the structural or functional fatigue of SMA–pulley actuators and SMA actuators without pulley. Within the sample of SMA–pulley actuators, the effect of activation duration had the greatest significance for both structural and functional fatigue, and the pulley configuration (angle of wrap and sheave diameter) had a greater statistical significance than load magnitude for functional fatigue. This work identified that structural and functional fatigue performance of SMA–pulley systems is optimised by maximising sheave diameter and using an intermediate wrap-angle, with minimal load and activation duration. However, these parameters may not be compatible with commercial imperatives. A test was completed for a commercially optimal SMA–pulley configuration. This novel observation will be applicable to many areas of SMA–pulley system applications development.

  13. Displacement reactions in the Ni-Al-O system resulting in periodic layer structures

    SciTech Connect

    Song, D.W.; Subramanian, R.; Dieckmann, R.

    1995-10-01

    Displacement reactions may play an important role in in situ processing technologies for the production of metal-ceramic composites. To better understand such reactions displacement reactions between NiO and Al were studied at high temperatures. Different reaction layers with periodic structures were observed involving Al{sub 2}O{sub 3}, Al{sub 3}Ni, Al{sub 3}Ni{sub 2}, Ni and Al. The experimental observations are presented and discussed with regard to the reaction mechanism.

  14. Vapor phase oxidation of benzoic acid to phenol over a novel catalyst system consisting of NiO and NiFe{sub 2}O{sub 4}

    SciTech Connect

    Miki, Jun; Asanuma, Minoru; Tachibana, Yakudo

    1995-02-01

    NiO and Fe{sub 2}O{sub 3} were found to show the catalytic activities for the vapor phase oxidation of benzoic acid to form phenol. Furthermore, the enhancement of the activity and phenol selectivity were achieved by combined Ni and Fe components prepared by precipitation. The calcination temperature and the atomic ratio of Ni to Fe were found to be important for the enhancement of activity. The homogeneous distribution profile of NiO and NiFe{sub 2}O{sub 4} on the surface and in the bulk of the catalyst is essential for the optimization of phenol formation. 32 refs., 7 figs., 4 tabs.

  15. Optimization of the NiCrAl-Y/ZrO-Y2O3 thermal barrier system

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1985-01-01

    The effects of bond and thermal barrier coating compositions, thicknesses, and densities on air plasma spray deposited Ni-Cr-Al-Y/ZrO2-Y2O3 life were evaluated in cyclic furnace oxidation tests at temperatures from 1110 to 1220 C. An empirical relation was developed to give life as a function of the above parameters. The thermal barrier system tested which had the longest life consisted of Ni-35.0 wt% Cr-5.9 wt% Al-0.95 wt% Y bond coating and ZrO2-6.1 wt% Y2O3 thermal barrier coating.

  16. X-Ray And Polarized Neutron Reflectometry: Characterization Of Si/Co/Si And Si/Ni/Si Systems

    SciTech Connect

    Bhattacharya, Debarati; Basu, Saibal; Poswal, A. K.; Roy, S.; Dev, B. N.

    2010-12-01

    Technologically important metal silicides formed through interdiffusion in metal/Si systems has been probed using two complementary techniques viz. x-ray reflectivity (XRR) and polarized neutron reflectivity (PNR). Both structural and magnetic characterization with good depth resolution has been achieved in these systems. We have studied two systems Si/Co/Si and Si/Ni/Si which relate to important applications in ferromagnetic/ non-magnetic semiconductor layered structures for memory devices.

  17. The effect of silicon on the oxidation behavior of NiAlHf coating system

    NASA Astrophysics Data System (ADS)

    Dai, Pengchao; Wu, Qiong; Ma, Yue; Li, Shusuo; Gong, Shengkai

    2013-04-01

    Two types of NiAlHf coatings doped with different content of Si (1 at.% and 2 at.%) were deposited on a Ni3Al based single crystal superalloy IC32 by electron beam physical vapor deposition (EB-PVD) method, respectively. For comparison, NiAlHf coating with 0 at.% Si was also prepared. The oxidation tests were carried out at 1423 K in air. At the initial stage of oxidation, large amount of flake-like θ-Al2O3 was found on NiAlHf coating surface. However, no θ-Al2O3 was observed in 2 at.% Si doped NiAlHf coating except α-Al2O3. It revealed that the Si additions could contribute to the transformation from θ-Al2O3 to α-Al2O3. When oxidation time prolonged to 100 h, it was found that the degradation of NiAlHf coating was very severe with no residual β-phase, which was due to the serious inter-diffusion between the coating and substrate. In contrast, the inter-diffusion in Si-doped coating was reduced with some residual β-phase and R-Ni(Mo, Re) precipitates. The presence of Si could retard the inter-diffusion of elements between coating and substrate, indicating a barrier diffusion effect. As a result, the oxidation resistance of NiAlHf coating was improved significantly.

  18. Degradation study of the ZrNiH_1.5 system

    NASA Astrophysics Data System (ADS)

    Prina, M.; Kulleck Bowman, J. G., Jr.

    2001-03-01

    The ZrNi hydride has been assessed as reversible hydrogen storage material in actuators of gas gap heat switches for applications involving hydride compressors in closed-cycle Joule-Thomson sorption cryocoolers. Three ZrNiHx samples have been cycled between 280 K (ZrNiH_1.5) and 450 K (ZrNiH_1.47) for more than 20,000 cycles to evaluate the hydride phase stability and durability for conditions simulating device operation. Changes in the hydrogen absorption and desorption were evaluated by measuring the pressure and temperature dynamic relationship during each cycle and by x-ray diffraction methods. No significant traces of degradation were observed although disproportionation had been seen previously for ZrNiHx heated above 570 K. The resistance of the present samples to degradation is primarily attributed to the lower desorption temperature during cycling.

  19. The Effects of Ni-Plating and Prolonged High Temperature Oxidation at 1423 K (1150 °C) on a CMSX-10 Single-Crystal Ni-Based Super-Alloy and Coating System

    NASA Astrophysics Data System (ADS)

    Clancy, Marie; Pomeroy, Michael J.

    2013-07-01

    A hypothesis was investigated, to assess if Ni-plating a 3rd-generation single-crystal alloy could favorably alter the diffusion profile of critical elements such that brittle, deleterious topologically close-packed (TCP) phases did not form or at least the extent to which they did was reduced. In conjunction with delaying the onset of these phases, it was hoped that more favorable alternatives could be promoted, such as martensite (β'). This study showed that Ni-plating did have some positive effects on the super-alloy/coating system. While the coating produced on the Ni-plated alloy was thinner, it retained a higher Al content than its unplated counterpart when subjected to oxidation. The retention of Al within the coating delayed the phase evolution of the coating from a β or β + β' to a γ'-dominant coating as the Ni-plated system had a greater driving force for Ni and Al diffusion, which helped to establish the Ni-rich diffusion barrier that entrapped Al in the coating. Unfortunately, Ni-plating does not sufficiently alter the diffusion profiles within the alloy to prevent precipitation of the TCP phases. Four pairs of the CMSX-10 alloy were used for this study. While they were all aluminized, only half of them, one in each pair, were Ni plated prior to aluminizing. Three of the four pairs were then oxidized at 1423 K (1150 °C), while the first pair was kept as a standard. X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy were used to characterize each alloy-coating system in an effort to better understand their performance under high temperature oxidation.

  20. LaFe0.6Sb2: Strongly to weakly correlated system with Ni doping

    NASA Astrophysics Data System (ADS)

    Misuraca, J. C.; Simonson, J. W.; Kistner-Morris, J. J.; Puri, A.; Orvis, T.; Greene, L. H.; Aronson, M. C.

    2014-03-01

    Since the discovery of superconducting Ca1-xLaxFeAs2 with a Tc of 34 K, there has been an increasing interest in growing 112 iron pnictides in the search for high Tc superconductivity. We have grown large single crystals of LaFe0.6Sb2, which form in a tetragonal 112 structure with a significant amount of Fe vacancies, confirmed via single crystal x-ray diffraction. We present a doping study utilizing Ni which replaces both the Fe and vacancies while transforming the material from strongly to weakly correlated, as determined by low temperature heat capacity measurements. The Sommerfeld coefficient γ of the undoped crystal is 50 mJ/mol Fe K2, indicating a large mass enhancement, while LaNiSb2 is 5 mJ/mol Ni K2 with no vacancies and up to 18% interstitial Ni according to energy-dispersive x-ray spectroscopy. When doping LaFeSb2 with Ni, γ remains constant when normalized per transition metal, possibly indicating a constant density of states. A divergence appears in C/T vs. T2 once the vacancies are filled, at 89% Ni, and the divergence remains until the LaNiSb2 sample, which is a weakly correlated 1 K superconductor. We acknowledge funding via an NSSEFF from the Office of Assistant Secretary of Defense for Research and Engineering and via ICAM from the NSF International Materials Institute Award: DMR-0844115.

  1. Interface stability in the Ni-Cr-AI system: Part I. morphological stability of β-γ diffusion couple interfaces at 1150°C

    NASA Astrophysics Data System (ADS)

    Merchant, Sailesh M.; Notis, Michael R.; Goldstein, Joseph I.

    1990-07-01

    Aluminide coatings on Ni-base superalloys offer resistance to oxidation and hot corrosion at elevated temperatures. Complex depositional and subsequent diffusional interactions of the coating with the substrate result in a multiphase product consisting primarily of β-NiAl and γ'-Ni3Al intermediate phases. An understanding of interfacial stability between the coating and the substrate is therefore necessary in order to explain the formation of such phases. The Ni-Cr-AI system serves to simplify the complex chemistry of most Ni-base superalloys. In this study, reaction diffusion and interfacial stability were investigated in solid-solid diffusion couples, consisting of a common β-Ni50Al end-member and a series of γ-pure Ni, binary Ni-Cr, and ternary Ni-Cr-Al alloys, isothermally annealed at 1150 °C for 49 hours. The morphological development of the interface was examined using optical metallography and quantitative information obtained using electron-probe microanalysis. A transition from a stable or planar to an unstable or nonplanar interface in the β-γ diffusion couples was observed with the systematic variation in Cr content of the γ end-member. Interface breakdown in the β-γ couples was explained by means of microstructural information gathered about interfaces, measured diffusion paths, and a knowledge of phase constitution relationships.

  2. C-Axis Properties of DyNi2B2C System

    NASA Astrophysics Data System (ADS)

    Lee, W. C.

    2012-02-01

    We have measured the electrical resistivity along c-axis ρc(T, H) of the DyNi2B2C single crystal with the magnetic fields perpendicular to the c-axis and the magnetization isotherms M(H) of the DyNi2B2C single crystal with magnetic fields perpendicular and parallel to the c-axis. We confirmed that Neel temperature TN is 10.3K from the ρc(T) result which is consistent with that from previous ρab(T) result. In addition, the constructed critical fields Hc2(T) curve and magnetic transitions diagram of DyNi2B2C from ρc(T) magnetic fields perpendicular to c-axis is similar to that of ρab(T) result, which is thought to arise that 3 D magnetic structure of DyNi2B2C.

  3. Degradation study of the ZrNiH(sub 1.5) system

    NASA Technical Reports Server (NTRS)

    Prina, M.; Kulleck, J. G.; Bowman, R. C., Jr.

    2000-01-01

    The ZrNi hydride has been assessed as reversible hydrogen storage material in actuators of gas gap heat switches for applications involving hydride compressors in closed-cycle Joule-Thomson sorption cryocoolers.

  4. El Niño as a consequence of the global oscillation in the dynamics of the earth's climatic system

    NASA Astrophysics Data System (ADS)

    Byshev, V. I.; Neiman, V. G.; Romanov, Yu. A.; Serykh, I. V.

    2012-09-01

    During study of the physical nature and potential precursor features of the El Niño phenomenon in the Pacific, it was found that a negative large-scale temperature anomaly on the Indian Ocean surface may be one of its significant precursors. This anomaly appears prior to the occurrence of El Niño and is accompanied by growth in atmospheric pressure. It gradually extends eastwards along the equator until the zone of planetary convection in the area of the Indonesian Region. The west wind that emerges on the eastern peripherals of the mentioned pressure anomaly leads to reversal of the Pacific segment of the Walker equatorial atmospheric circulation and to a subsequent change in the zonal thermal dipole polarity in the tropical zone of the Pacific (the latter means culmination of the El Niño phenomenon). In addition to the mentioned thermobaric anomaly in the Indian Ocean, other obvious signs of large-scale pressure anomalies have been found in the global atmospheric pressure field; these anomalies may be interpreted as manifestations of the intradecadal global oscillation in the dynamics of the modern climatic system. It is suggested that the whole known complex of events related to the El Niño phenomenon in the Pacific is a consequence and a regional link of the planetary structure of this global atmospheric phenomenon.

  5. Discovery of a thermally persistent h.c.p. solid-solution phase in the Ni-W system

    SciTech Connect

    Kurz, S. J. B. Leineweber, A.; Maisel, S. B.; Höfler, M.; Müller, S.; Mittemeijer, E. J.

    2014-08-28

    Although the accepted Ni-W phase diagram does not reveal the existence of h.c.p.-based phases, h.c.p.-like stacking sequences were observed in magnetron-co-sputtered Ni-W thin films at W contents of 20 to 25 at. %, by using transmission electron microscopy and X-ray diffraction. The occurrence of this h.c.p.-like solid-solution phase could be rationalized by first-principles calculations, showing that the vicinity of the system's ground-state line is populated with metastable h.c.p.-based superstructures in the intermediate concentration range from 20 to 50 at. % W. The h.c.p.-like stacking in Ni-W films was observed to be thermally persistent, up to temperatures as high as at least 850 K, as evidenced by extensive X-ray diffraction analyses on specimens before and after annealing treatments. The tendency of Ni-W for excessive planar faulting is discussed in the light of these new findings.

  6. Fabrication and Characterization of Multi-Walled Carbon Nanotube (MWCNT) and Ni-Coated Multi-Walled Carbon Nanotube (Ni-MWCNT) Repair Patches for Carbon Fiber Reinforced Composite Systems

    NASA Technical Reports Server (NTRS)

    Johnson, Brienne; Caraccio, Anne; Tate, LaNetra; Jackson, Dionne

    2011-01-01

    Multi-walled carbon nanotube (MWCNT)/epoxy and nickel-coated multi-walled carbon nanotube (Ni-MWCNT)/epoxy systems were fabricated into carbon fiber composite repair patches via vacuum resin infusion. Two 4 ply patches were manufactured with fiber orientations of [90/ 90/ 4590] and [0/90/ +45/ -45]. Prior to resin infusion, the MWCNT/Epoxy system and NiMWCNT/ epoxy systems were optimized for dispersion quality. Scanning electron microscopy (SEM) and optical microscopy (OM) were used to determine the presence ofcarbon nanotubes and assess dispersion quality. Decomposition temperatures were determined via thermogravametric analysis (TGA). SEM and TGA were also used to evaluate the composite repair patches.

  7. Bonding in zerovalent Ni compounds - NiN2 and Ni(N2)4 compared with NiCO and Ni(CO)4

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Barnes, Leslie A.

    1989-01-01

    Calculations are carried out on NiN2, which may be considered a prototypical metal surface-ligand system. A large Gaussian basis set and an MCPF treatment of electron correlation are used. Consideration is also given to the 2Sigma(+) states of NiN2(-), NiCO(-), and NiN2(+), the low-lying 2Delta and 2Pi states of NiN2(+), and the 1A1 states of Ni(CO)4 and Ni(N2)4.

  8. Re Os isotopic systematics of the Voisey's Bay Ni Cu Co magmatic ore system, Labrador, Canada

    NASA Astrophysics Data System (ADS)

    Lambert, D. D.; Foster, J. G.; Frick, L. R.; Li, C.; Naldrett, A. J.

    1999-06-01

    Re and Os concentrations and Os isotopic compositions have been obtained for massive, matrix, and disseminated sulphide ores from three environments within the Voisey's Bay intrusion (the `Ovoid', Eastern Deeps, and Discovery Hill Zone) in order to assess the role of crustal contamination in the genesis of this large Cu-Ni-Co deposit. These samples have high Re concentrations (148 to 288 ppb, in 100% sulphide) for their common Os concentrations (4.8 to 24 ppb, in 100% sulphide), yielding high Re/Os ratios (12 to 33). These data confirm that the magma parental to the Voisey's Bay ore system was broadly basaltic in major element chemistry rather than picritic, consistent with the low Ni/Cu ratio of the ores (˜1.5). Re-Os isotopic data exhibit a limited spread in 187Re/ 188Os (57 to 157) and define an imprecise 1323±135 Ma `model 3' isochron, likely the result of small R-factor variations within the ore system. The Re-Os isochron age is within error of 1334 Ma U-Pb ages obtained for baddeleyite from the ore-bearing troctolites, demonstrating that whole rock Re-Os isotopic systematics have remained closed since crystallisation. The initial Os isotopic composition of the isochron ( γOs=1040±200) implies significant magma interactions with radiogenic Os that most likely resides in the Nain-Churchill Province crust. These data are, therefore, consistent with the parental magma achieving sulphide saturation as a result of contamination by radiogenic crustal components, with further addition of base and precious metals as a function of R-factor. Analyses of sulphide separates from the Proterozoic Tasiuyak (Churchill) and Archaean Nain gneisses confirm that both units contained significant Os (8.6 ppb and 0.38 ppb, respectively) that was very radiogenic at 1334 Ma ( γOs=1908 and 5202, respectively), yielding crustal residence TCHUR model ages of 2200 to 2400 Ma. However, these model ages may have been affected by Re and/or Os mobility during the 1.85 Ga Torngat and 1

  9. Magnetic structure of the UCu 4- xNi xAl 8 system

    NASA Astrophysics Data System (ADS)

    André, G.; Bourée, F.; Wochowski, K.; Suski, W.

    1997-10-01

    The results of the neutron powder diffraction (NPD) experiments performed on the alloys with x = 1 and 2 between 1.4 K and 42 K are presented. The nuclear structure refinements at 42 K confirmed for both compounds the ThMn 12 structure with uranium atom located in position 2(a), copper and nickel in position 8(f) and aluminium atoms in positions 8(i) and 8(j). The presence of extra phases has been detected in both UCu 3NiAl 8 and UCu 2Ni 2Al 8 samples: NiAl and Al for x = 1, Al 3Ni 2, NiAl and Al for x = 2. The NPD patterns recorded at 1.4 K show pure magnetic reflections which can be indexed in the crystallographic tetragonal unit cell. Magnetic structure consists of a plus (+)-minus (-) sequence of ferromagnetically ordered (0 0 1) sheets. The magnetic moments are located in the uranium position only. The values of the Néel temperatures are 26 and 24 K for x = 1 and 2, respectively.

  10. Blanch Resistant and Thermal Barrier NiAl Coating Systems for Advanced Copper Alloys

    NASA Technical Reports Server (NTRS)

    Raj, Sai V. (Inventor)

    2005-01-01

    A method of forming an environmental resistant thermal barrier coating on a copper alloy is disclosed. The steps include cleansing a surface of a copper alloy, depositing a bond coat on the cleansed surface of the copper alloy, depositing a NiAl top coat on the bond coat and consolidating the bond coat and the NiAl top coat to form the thermal barrier coating. The bond coat may be a nickel layer or a layer composed of at least one of copper and chromium-copper alloy and either the bond coat or the NiAl top coat or both may be deposited using a low pressure or vacuum plasma spray.

  11. Bridging exchange bias effect in NiO and Ni(core)@NiO(shell) nanoparticles

    NASA Astrophysics Data System (ADS)

    Rinaldi-Montes, Natalia; Gorria, Pedro; Martínez-Blanco, David; Fuertes, Antonio B.; Fernández Barquín, Luis; Puente-Orench, Inés; Blanco, Jesús A.

    2016-02-01

    Among all bi-magnetic core(transition metal)@shell(transition metal oxide) nanoparticles (NPs), Ni@NiO ones show an onset temperature for the exchange bias (EB) effect far below the Néel temperature of bulk antiferromagnetic NiO. In this framework, the role played by the magnetism of NiO at the nanoscale is investigated by comparing the microstructure and magnetic properties of NiO and Ni@NiO NPs. With the aim of bridging the two systems, the diameter of the NiO NPs (~4 nm) is chosen to be comparable to the shell thickness of Ni@NiO ones (~2 nm). The EB effect in Ni@NiO NPs is attributed to the exchange coupling between the core and the shell, with an interfacial exchange energy of ΔE~0.06 erg cm-2, thus comparable to previous reports on Ni/NiO interfaces both in thin film and NP morphologies. In contrast, the EB detected in NiO NPs is explained in a picture where uncompensated spins located on a magnetically disordered surface shell are exchange coupled to the antiferromagnetic core. In all the studied NPs, the variation of the EB field as a function of temperature is described according to a negative exponential law with a similar decay constant, yielding a vanishing EB effect around T~40-50 K. In addition, the onset temperature for the EB effect in both NiO and Ni@NiO NPs seems to follow a universal dependence with the NiO crystallite size.

  12. Corrosion of NiCoCrAlY Coatings and TBC Systems Subjected to Water Vapor and Sodium Sulfate

    NASA Astrophysics Data System (ADS)

    Eriksson, Robert; Yuan, Kang; Li, Xin-Hai; Lin Peng, Ru

    2015-08-01

    Thermal barrier coating (TBC) systems are commonly used in gas turbines for protection against high-temperature degradation. Penetration of the ceramic top coat by corrosive species may cause corrosion damage on the underlying NiCoCrAlY bond coat and cause failure of the TBC system. In the current study, four oxidation/corrosion conditions were tried: (i) lab air, (ii) water vapor, (iii) sodium sulfate deposited on the specimens, and (iv) water vapor + sodium sulfate. The test was done at 750 °C in a cyclic test rig with 48 h cycles. The corrosion damage was studied on NiCoCrAlY-coated specimens, thin APS TBC specimens, and thick APS TBC specimens. Water vapor was found to have very minor influence on the oxidation, while sodium sulfate increased the TGO thickness both for NiCoCrAlY specimens and TBC-coated specimens; the influence of the TBC thickness was found to be very small. Sodium sulfate promoted thicker TGO; more Cr-rich TGO; the formation of Y oxides, and internally, Y sulfides; pore formation in the coating as well as in the substrate; and the formation of a Cr-depleted zone in the substrate.

  13. Estimation of excess energies and activity coefficients for the penternary Ni-Cr-Co-Al-Mo system and its subsystems

    NASA Astrophysics Data System (ADS)

    Dogan, A.; Arslan, H.; Dogan, T.

    2015-06-01

    Using different prediction methods, such as the General Solution Model of Kohler and Muggianu, the excess energy and activities of molybdenum for the sections of the phase diagram for the penternary Ni-Cr-Co-Al-Mo system with mole ratios xNi/ xMo = 1, xCr/ xMo = 1, xCo/ xMo = 1, and xAl/ xMo = r = 0.5 and 1, were thermodynamically investigated at a temperature of 2000 K, whereas the excess energy and activities of Bi for the section corresponding to the ternary Bi-Ga-Sb system with mole ratio xGa/ xSb = 1/9 were thermodynamically investigated at a temperature of 1073 K. In the case of r = 0.5 and 1 in the alloys Ni-Cr-Co-Al-Mo, a positive deviation in the activity coefficient was revealed, as molybdenum content increased. Moreover, in the calculations performed in Chou's GSM model, the obtained values for excess Gibbs energies are negative in the whole concentration range of bismuth at 1073 K and exhibit the minimum of about -2.2 kJ/mol at the mole ratio xGa/ xSb = 1/9 in the alloy Bi-Ga-Sb.

  14. Influence of the nonmagnetic impurities on the spin-1 Heisenberg chain SrNi2V2O8 system

    NASA Astrophysics Data System (ADS)

    Giapintzakis, J.; Androulakis, J.; Syskakis, E.; Papageorgiou, Th. P.; Apostolopoulos, G.; Thanos, S.; Papastaikoudis, C.

    Dc-magnetization and heat capacity measurements on polycrystalline samples of SrNi2-x Mgx V2O8 (x = 0 and 0.05) are reported. The magnetization data suggest that both compounds are S = 1 quasi one-dimensional Heisenberg antiferromagnets. The substitution of non-magnetic impurity Mg2+ ions for Ni2+ induces a magnetic phase transition at ?3.7 K. A simple Hamiltonian model is proposed for these systems giving good quantitative agreement with the experimental magnetization data. The intrachain magnetic exchange constant (J 1/k B) and the Haldane gap (? ) for both compounds are estimated to be ?105 K and ?58.3 K (5.02 meV), respectively.

  15. Elastic scattering and total reaction cross section for the {sup 6}He+{sup 58}Ni system

    SciTech Connect

    Morcelle, V.; Lichtenthäler, R.; Lépine-Szily, A.; Guimarães, V.; Gasques, L.; Scarduelli, V.; Condori, R. Pampa; Leistenschneider, E.; Mendes Jr, D. R.; Faria, P. N. de; Pires, K. C. C.; Barioni, A.; Morais, M. C.; Shorto, J. M. B.; Zamora, J. C.

    2014-11-11

    Elastic scattering measurements of {sup 6}He + {sup 58}Ni system have been performed at the laboratory energy of 21.7 MeV. The {sup 6}He secondary beam was produced by a transfer reaction {sup 9}Be ({sup 7}Li, {sup 6}He) and impinged on {sup 58}Ni and {sup 197}Au targets, using the Radioactive Ion Beam (RIB) facility, RIBRAS, installed in the Pelletron Laboratory of the Institute of Physics of the University of São Paulo, Brazil. The elastic angular distribution was obtained in the angular range from 15° to 80° in the center of mass frame. Optical model calculations have been performed using a hybrid potential to fit the experimental data. The total reaction cross section was derived.

  16. Simulation of atomic diffusion in the Fcc NiAl system: A kinetic Monte Carlo study

    SciTech Connect

    Alfonso, Dominic R.; Tafen, De Nyago

    2015-04-28

    The atomic diffusion in fcc NiAl binary alloys was studied by kinetic Monte Carlo simulation. The environment dependent hopping barriers were computed using a pair interaction model whose parameters were fitted to relevant data derived from electronic structure calculations. Long time diffusivities were calculated and the effect of composition change on the tracer diffusion coefficients was analyzed. These results indicate that this variation has noticeable impact on the atomic diffusivities. A reduction in the mobility of both Ni and Al is demonstrated with increasing Al content. As a result, examination of the pair interaction between atoms was carried out for the purpose of understanding the predicted trends.

  17. The role of the non-magnetic material in spin pumping and magnetization dynamics in NiFe and CoFeB multilayer systems

    SciTech Connect

    Ruiz-Calaforra, A. Brächer, T.; Lauer, V.; Pirro, P.; Heinz, B.; Geilen, M.; Chumak, A. V.; Conca, A.; Leven, B.; Hillebrands, B.

    2015-04-28

    We present a study of the effective magnetization M{sub eff} and the effective damping parameter α{sub eff} by means of ferromagnetic resonance spectroscopy on the ferromagnetic (FM) materials Ni{sub 81}Fe{sub 19} (NiFe) and Co{sub 40}Fe{sub 40}B{sub 20} (CoFeB) in FM/Pt, FM/NM, and FM/NM/Pt systems with the non-magnetic (NM) materials Ru, Cr, Al, and MgO. Moreover, for NiFe layer systems, the influence of interface effects is studied by way of thickness dependent measurements of M{sub eff} and α{sub eff}. Additionally, spin pumping in NiFe/NM/Pt is investigated by means of inverse spin Hall effect (ISHE) measurements. We observe a large dependence of M{sub eff} and α{sub eff} of the NiFe films on the adjacent NM layer. While Cr and Al do not induce a large change in the magnetic properties, Ru, Pt, and MgO affect M{sub eff} and α{sub eff} in different degrees. In particular, NiFe/Ru and NiFe/Ru/Pt systems show a large perpendicular surface anisotropy and a significant enhancement of the damping. In contrast, the magnetic properties of CoFeB films do not have a large influence of the NM adjacent material and only CoFeB/Pt systems present an enhancement of α{sub eff}. However, this enhancement is much more pronounced in NiFe/Pt. By the introduction of the NM spacer material, this enhancement is reduced. Furthermore, a difference in symmetry between NiFe/NM/Pt and NiFe/NM systems in the output voltage signal from the ISHE measurements reveals the presence of spin pumping into the Pt layer in all-metallic NiFe/NM/Pt and NiFe/Pt systems.

  18. Stresses and Cracking During Chromia-Spinel-NiO Cluster Formation in TBC Systems

    NASA Astrophysics Data System (ADS)

    Eriksson, Robert; Gupta, Mohit; Broitman, Esteban; Jonnalagadda, Krishna Praveen; Nylén, Per; Lin Peng, Ru

    2015-08-01

    Thermal barrier coatings (TBC) are used in gas turbines to reduce the temperatures in the underlying substrate. There are several mechanisms that may cause the TBC to fail; one of them is cracking in the coating interface due to extensive oxidation. In the present study, the role of so called chromia-spinel-NiO (CSN) clusters in TBC failure was studied. Such clusters have previously been found to be prone to cracking. Finite element modeling was performed on a CSN cluster to find out at which stage of its formation it cracks and what the driving mechanisms of cracking are. The geometry of a cluster was obtained from micrographs and modeled as close as possible. Nanoindentation was performed on the cluster to get the correct Young's moduli. The volumetric expansion associated with the formation of NiO was also included. It was found that the cracking of the CSN clusters is likely to occur during its last stage of formation as the last Ni-rich core oxidizes. Furthermore, it was shown that the volumetric expansion associated with the oxidation only plays a minor role and that the main reason for cracking is the high coefficient of thermal expansion of NiO.

  19. Systematics of Ni, Co, Cr and V in Olivine from Planetary Melt Systems: Martian Basalts

    NASA Technical Reports Server (NTRS)

    Herd, C. D. K.; Jones, J. H.; Shearer, C. K.; Papike, J. J.

    2001-01-01

    Secondary Ion Mass Spectrometry (SIMS) data for Ni, Co, Cr, and V in olivine in martian basalts is compared to data from lunar and terrestrial basalts. We use experimentally-derived and published D values to calculate as-yet unsampled, olivine-bearing, non-cumulus melt compositions. Additional information is contained in the original extended abstract.

  20. Highly processable bulk metallic glass-forming alloys in the Pt-Co-Ni-Cu-P system

    NASA Astrophysics Data System (ADS)

    Schroers, Jan; Johnson, William L.

    2004-05-01

    Highly processable bulk metallic glass alloys in the Pt-Co-Ni-Cu-P system were discovered. The alloys show low liquidus temperature below 900 K, excellent processability with low critical cooling rate reflecting in maximum casting thicknesses in quartz tubes of up to 20 mm, and a large supercooled liquid region. The Pt57.5Cu14.7Ni5.3P22.5 composition has a liquidus temperature of 795 K, a glass transition temperature of 508 K with a supercooled liquid region of 98 K. For medical and jewelry applications a Ni-free alloy, Pt60Cu16Co2P22 was discovered with a liquidus temperature of 881 K, a glass transition temperature of 506 K, and a supercooled liquid region of 63 K. Glass formation was observed in a wider composition range. Vickers hardness of these alloys is in the 400 Hv range. The alloys can be processed in the supercooled liquid region in air without any measurable oxidation. In this region, a large processing window is available in which the material does not embrittle. Embrittlement in these alloys is correlated with crystallization. It can be avoided as long as substantial crystallization does not take place during isothermal processing in the supercooled liquid region. Also, liquid processing can be performed in air when flux with B2O3.

  1. New complex bismuth oxides in the Bi2O3-NiO-Sb2O5 system and their properties

    NASA Astrophysics Data System (ADS)

    Egorysheva, A. V.; Ellert, O. G.; Zubavichus, Y. V.; Gajtko, O. M.; Efimov, N. N.; Svetogorov, R. D.; Murzin, V. Yu.

    2015-05-01

    Phase equilibria in the Bi2O3-NiO-Sb2O5 system have been investigated. The isothermal section of the system (650°) has been constructed. For the first time the existence of the pyrochlore structure solid solution, (Bi2-xNix)Ni2/3-ySb4/3+yO7±δ, x=0.1-0.35, y=0-0.1, and a new compound Bi3Ni2/3Sb7/3O11 of KSbO3 structure type have been discovered. The structures and properties of these compounds were studied by XRD, XAFS, diffuse reflection spectroscopy and magnetic methods. Rietveld refinement of synchrotron radiation-based powder XRD data for pyrochlore sample of 38.43Bi2O3-33.0NiO-28.57Sb2O5 composition and Bi3Ni2/3Sb7/3O11 compound was performed. The best possible refinement of the positional parameters for both pyrochlore and Bi3Ni2/3Sb7/3O11 structures was achieved for disordered models. Magnetic, diffuse reflection and an X-ray absorption spectroscopy study confirmed that in both compounds nickel ions are mainly in a 2+ oxidation state. According to magnetic data, Bi1.84Ni0.16(Ni0.63Sb1.37)O7 pyrochlore and Bi3Ni2/3Sb7/3O11 are overall paramagnetic in nature.

  2. Mg substitution effect on the hydrogenation behaviour, thermodynamic and structural properties of the La{sub 2}Ni{sub 7}-H(D){sub 2} system

    SciTech Connect

    Denys, R.V.; Riabov, A.B.; Yartys, V.A. Sato, Masashi; Delaplane, R.G.

    2008-04-15

    The present work is focused on studies of the influence of magnesium on the hydrogenation behaviour of the (La,Mg){sub 2}Ni{sub 7} alloys. Substitution of La in La{sub 2}Ni{sub 7} by Mg to form La{sub 1.5}Mg{sub 0.5}Ni{sub 7} preserves the initial Ce{sub 2}Ni{sub 7} type of the hexagonal P6{sub 3}/mmc structure and leads to contraction of the unit cell. The system La{sub 1.5}Mg{sub 0.5}Ni{sub 7}-H{sub 2} (D{sub 2}) was studied using in situ synchrotron X-ray and neutron powder diffraction in H{sub 2}/D{sub 2} gas and pressure-composition-temperature measurements. La replacement by Mg was found to proceed in an ordered way, only within the Laves-type parts of the hybrid crystal structure, yielding formation of LaMgNi{sub 4} slabs with statistic and equal occupation of one site by La and Mg atoms. Mg alters structural features of the hydrogenation process. Instead of a strong unilateral anisotropic expansion which takes place on hydrogenation of La{sub 2}Ni{sub 7}, the unit cell of La{sub 1.5}Mg{sub 0.5}Ni{sub 7}D{sub 9.1} is formed by nearly equal hydrogen-induced expansions proceeding in the basal plane ({delta}a/a=7.37%) and along [001] ({delta}c/c=9.67%). In contrast with La{sub 2}Ni{sub 7}D{sub 6.5} where only LaNi{sub 2} layers absorb hydrogen atoms, in La{sub 1.5}Mg{sub 0.5}Ni{sub 7}D{sub 9.1} both LaNi{sub 5} and LaMgNi{sub 4} layers become occupied. Nine types of sites were found to be filled by D in total, including tetrahedral (La,Mg){sub 2}Ni{sub 2}, (La,Mg)Ni{sub 3}, Ni{sub 4}, tetragonal pyramidal La{sub 2}Ni{sub 3} and trigonal bipyramidal (La,Mg){sub 3}Ni{sub 2} interstices. The hydrogen sublattice around the La/Mg site shows formation of two co-ordination spheres of D atoms: an octahedron MgD{sub 6} and a 16-vertex polyhedron LaD{sub 16} around La. The interatomic distances are in the following ranges: La-D (2.28-2.71), Mg-D (2.02-2.08), Ni-D (1.48-1.86 A). All D-D distances exceed 1.9 A. Thermodynamic PCT studies yielded the following values for the

  3. Mg substitution effect on the hydrogenation behaviour, thermodynamic and structural properties of the La 2Ni 7-H(D) 2 system

    NASA Astrophysics Data System (ADS)

    Denys, R. V.; Riabov, A. B.; Yartys, V. A.; Sato, Masashi; Delaplane, R. G.

    2008-04-01

    The present work is focused on studies of the influence of magnesium on the hydrogenation behaviour of the (La,Mg) 2Ni 7 alloys. Substitution of La in La 2Ni 7 by Mg to form La 1.5Mg 0.5Ni 7 preserves the initial Ce 2Ni 7 type of the hexagonal P6 3/ mmc structure and leads to contraction of the unit cell. The system La 1.5Mg 0.5Ni 7-H 2 (D 2) was studied using in situ synchrotron X-ray and neutron powder diffraction in H 2/D 2 gas and pressure-composition-temperature measurements. La replacement by Mg was found to proceed in an ordered way, only within the Laves-type parts of the hybrid crystal structure, yielding formation of LaMgNi 4 slabs with statistic and equal occupation of one site by La and Mg atoms. Mg alters structural features of the hydrogenation process. Instead of a strong unilateral anisotropic expansion which takes place on hydrogenation of La 2Ni 7, the unit cell of La 1.5Mg 0.5Ni 7D 9.1 is formed by nearly equal hydrogen-induced expansions proceeding in the basal plane (Δ a/ a=7.37%) and along [001] (Δ c/ c=9.67%). In contrast with La 2Ni 7D 6.5 where only LaNi 2 layers absorb hydrogen atoms, in La 1.5Mg 0.5Ni 7D 9.1 both LaNi 5 and LaMgNi 4 layers become occupied. Nine types of sites were found to be filled by D in total, including tetrahedral (La,Mg) 2Ni 2, (La,Mg)Ni 3, Ni 4, tetragonal pyramidal La 2Ni 3 and trigonal bipyramidal (La,Mg) 3Ni 2 interstices. The hydrogen sublattice around the La/Mg site shows formation of two co-ordination spheres of D atoms: an octahedron MgD 6 and a 16-vertex polyhedron LaD 16 around La. The interatomic distances are in the following ranges: La-D (2.28-2.71), Mg-D (2.02-2.08), Ni-D (1.48-1.86 Å). All D-D distances exceed 1.9 Å. Thermodynamic PCT studies yielded the following values for the Δ H and Δ S of hydrogenation/decomposition; Δ HH=-15.7±0.9 kJ (mol H) -1 and Δ SH=-46.0±3.7 J (K mol H) -1 for H 2 absorption, and Δ HH=16.8±0.4 kJ (mol H) -1 and Δ SH=48.1±1.5 J (K mol H) -1 for H 2 desorption.

  4. Sustainability assessment and comparison of waste management systems: The Cities of Sofia and Niš case studies.

    PubMed

    Milutinović, Biljana; Stefanović, Gordana; Kyoseva, Vanya; Yordanova, Dilyana; Dombalov, Ivan

    2016-09-01

    Sustainability assessment of a waste management system is a very complex problem for numerous reasons. Firstly, it is a problem of environmental assessment, economic viability and social acceptability, and also a choice of the most practical waste treatment technique, taking into account all the specific areas in which a waste management system is implemented. For these reasons, among others, it is very important to benchmark, cooperate and exchange experiences in areas with similar characteristics. In this study, a comparison of waste management scenarios in the Cities of Niš and Sofia was performed. Based on the amount and composition of municipal solid waste, and taking into account local specifics (economic conditions, social acceptance, etc.), different scenarios were developed: landfilling without energy recovery, landfilling with energy recovery, mechanical-biological treatment, anaerobic digestion with biogas utilization and incineration with energy recovery. Scenario ranking was done using multi-criteria analysis and 12 indicators were chosen as the criteria. The obtained results show that the most sustainable scenario in both case studies is the mechanical-biological treatment (recycling, composting and Refuse Derived Fuel production). Having in mind that this scenario is the current waste management system in Sofia, these results can help decision-makers in the City of Niš in choosing a successful and sustainable waste management system. PMID:27357562

  5. Simulation of atomic diffusion in the Fcc NiAl system: A kinetic Monte Carlo study

    DOE PAGESBeta

    Alfonso, Dominic R.; Tafen, De Nyago

    2015-04-28

    The atomic diffusion in fcc NiAl binary alloys was studied by kinetic Monte Carlo simulation. The environment dependent hopping barriers were computed using a pair interaction model whose parameters were fitted to relevant data derived from electronic structure calculations. Long time diffusivities were calculated and the effect of composition change on the tracer diffusion coefficients was analyzed. These results indicate that this variation has noticeable impact on the atomic diffusivities. A reduction in the mobility of both Ni and Al is demonstrated with increasing Al content. As a result, examination of the pair interaction between atoms was carried out formore » the purpose of understanding the predicted trends.« less

  6. Low-density open-cell foams in the NiTi system

    NASA Astrophysics Data System (ADS)

    Grummon, David S.; Shaw, John A.; Gremillet, Antoine

    2003-04-01

    It is shown that open-cell metallic foams having very low density, and that display martensite transformations required for shape memory and superelastic behavior, can be fabricated using a powder-metallurgy technique. Results are presented on experiments in which a polymeric precursor foam was coated with an equiatomic NiTi powder slurry and subsequently sintered to yield foams with relative densities as low as 0.039. Although contaminated with interstitial impurities, they displayed unambiguous calorimetric signature of the B2→B19' transformation. The results are of considerable significance to potential applications requiring ultralightweight structures with the unusual dissipative and strain-recovery properties of NiTi shape-memory materials.

  7. Near-Barrier Fusion of the B8+Ni58 Proton-Halo System

    NASA Astrophysics Data System (ADS)

    Aguilera, E. F.; Amador-Valenzuela, P.; Martinez-Quiroz, E.; Lizcano, D.; Rosales, P.; García-Martínez, H.; Gómez-Camacho, A.; Kolata, J. J.; Roberts, A.; Lamm, L. O.; Rogachev, G.; Guimarães, V.; Becchetti, F. D.; Villano, A.; Ojaruega, M.; Febbraro, M.; Chen, Y.; Jiang, H.; Deyoung, P. A.; Peaslee, G. F.; Guess, C.; Khadka, U.; Brown, J.; Hinnefeld, J. D.; Acosta, L.; , E. S. Rossi, Jr.; Huiza, J. F. P.; Belyaeva, T. L.

    2011-08-01

    Fusion cross sections were measured for the exotic proton-halo nucleus B8 incident on a Ni58 target at several energies near the Coulomb barrier. This is the first experiment to report on the fusion of a proton-halo nucleus. The resulting excitation function shows a striking enhancement with respect to expectations for normal projectiles. Evidence is presented that the sum of the fusion and breakup yields saturates the total reaction cross section.

  8. An investigation of electrical current induced phase transformations in the NiPtSi/polysilicon system

    NASA Astrophysics Data System (ADS)

    Kim, Deok-kee; Domenicucci, Anthony; Iyer, Subramanian S.

    2008-04-01

    We studied phase transformations and microstructural changes of NiPtSi/polysilicon fuses programmed with three different current densities (under, optimal, and over programming). Electromigration of NiPt toward the anode occurred in all three cases studied. Achieving high resistance after the fuse programming strongly depends on the kinetics of the electromigration and dopant diffusion processes which operate during the fuse blow. A thick silicide region was formed after electrically programmable fuse programming by the reaction of the electromigrated NiPt with the polysilicon layer underneath. The low tails of the underprogrammed fuses seemed to result from the incomplete electromigration and the incomplete dopant depletion due to the insufficient programming current density, while the depletion of the implanted dopants due to the sufficiently elevated temperature seemed to make the postresistance of the optimally programmed fuse higher. In the overprogrammed fuse, the newly formed silicide seemed to have further electromigrated due to the sufficiently high temperature during programming, which caused voids and hillocks. The high temperature caused melting of the polysilicon and the surrounding nitride layer, and their reaction as well. The conduction paths created by the unremoved silicide in fuse link caused the postprogramming resistance of the overprogrammed fuse to be low.

  9. Properties and structure of carbon nanotubes in the system C-Ni

    NASA Astrophysics Data System (ADS)

    Czerwosz, E.; Keczkowska, J.; Kowalska, E.; Kozłowski, M.; Radomska, J.; Suchańska, M.; Wronka, H.

    2014-11-01

    We present results of Raman studies of CNT-Ni films obtained in two steps method. In the first step an initial nanocomposite Ni-C film (produced by PVD method) was prepared. This initial film has multiphase composite-like structure with nanograins of fullerenes, amorphous carbon and nickel. In the second step CNTs were obtained by CVD method. In this process the initial films were placed in a quartz tube reactor where pyrolysis process were performed in xylene. Decomposition of xylene at 650°C was occurred. Products of this CVD decomposition process take part in nanotubes growth on Ni nanograins. These nanograins play a role of a catalyser of the growth process. SEM observations showed that form of nanotubes obtained with the various CVD process parameters is similar. Raman studies of initial films (obtained PVD process) confirm the presence of fullerenes C60 in and some forms of graphite-like objects in the samples. Raman spectra of MWCNTs films contained: bands characteristic for carbon nanotube's vibrations.

  10. Sub-barrier fusion of {sup 36}S + {sup 64}Ni and other medium-light systems

    SciTech Connect

    Montagnoli, G.; Scarlassara, F.; Stefanini, A. M.; Corradi, L.; Fioretto, E.; Silvestri, R.; Courtin, S.; Haas, F.; Lebhertz, D.; Szilner, S.

    2010-12-15

    Sub-barrier fusion cross sections of {sup 36}S + {sup 64}Ni have been measured down to {approx_equal}3 {mu}b. The logarithmic slope of the fusion excitation function has a steep rise in the barrier region with decreasing energy and saturates at lower energies. The data can be reproduced within the coupled-channels model using a Woods-Saxon potential with a large diffuseness. The slope saturation is analogous to what has been observed for {sup 36}S, {sup 48}Ca + {sup 48}Ca, while for heavier systems the slope increases steadily below the barrier.

  11. The influence of transfer reactions on the sub-barrier fusion enhancement in the systems {sup 58.64}Ni +, {sup 92,100}Mo

    SciTech Connect

    Rehm, K.E.; Jiang, C.L.; Esbensen, H.

    1995-08-01

    High resolution experiments performed during the past few years demonstrated that the various reaction modes occurring in heavy ion collisions can strongly influence each other. This interrelation of the different reaction modes brings a nuclear structure dependence to the fusion and deep-inelastic channels that were previously described in the framework of pure statistical models. In order to fully understand the interrelation between these reaction channels, a complete set of measurements including elastic and inelastic scattering, few-nucleon transfer and fusion is required. In continuation of our earlier measurements of the fusion cross sections in the system {sup 58,64}Ni + {sup 92,100}Mo we finished the studies of the quasielastic process in these systems. The experiments were done in inverse reaction kinematics using the split-pole spectrograph with its hybrid focal-plane detector for particle identification. The experiments with {sup 100}Mo beams were performed previously. First test runs with {sup 92}Mo showed the possible interference with {sup 98}Mo ions which could be eliminated by using the 13{sup +} charge state from the ECR source. The data from these experiments were completely analyzed. The smallest transfer cross sections are observed for the systems {sup 64}Ni + {sup 100}Mo and {sup 58}Ni + {sup 92}Mo, i.e., the most neutron-rich and neutron-deficient systems, respectively. For the other systems, {sup 64}Ni + {sup 92}Mo and {sup 58}Ni + {sup 100}Mo, the transfer cross sections at energies close to the barrier are about of equal magnitude. This observation does not correlate with the deviation of the experimental fusion cross sections from the coupled-channels predictions. While for {sup 58}Ni + {sup 100}Mo discrepancies between the experimental and theoretical fusion cross sections are observed, the system {sup 64}Ni + {sup 92}Mo which shows about the same transfer yields, is quite well described by the coupled-channels calculations.

  12. Improving simulation of El Niño Impacts on summer cropping systems of the Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Capa-Morocho, Mirian; Ruiz-Ramos, Margarita; Rodríguez-Fonseca, Belén

    2013-04-01

    El Niño event is a main driver of seasonal climate variability that greatly impacts agriculture and regional economies (Legler et al., 1999). The relationships found between El Niño and yield can be helpful to anticipate yield anomalies (higher or lower than usual) what can help us to adapt crop systems in advance: insurance coverage, changes in sowing dates, choice of species and varieties, as well as changes in the management of fertilization and irrigation and the establishment of an early warning system. In a previous work, we found that the ENSO affects maize yield differently depending on the location in the Iberian Peninsula (Capa et al., 2012), using observed data series for periods ranging from 22 to 46 years. The specific objective of this work is 1) to confirm these results using a longer time series from re-analysis data; 2) to evaluate the yield simulations done with re-analysis regarding observed crops yields and simulations obtained with observed climate data; and 3) to use re-analysis climate data to help to explain the mechanism of the influence of El Niño. Crop yield was simulated with the ecophysiological crop model CERES-maize, included in DSSAT v.4.5 (Decision Support System for Agrotechnology Transfer). To simulate maize yields, re-analysis daily data of radiation, maximum and minimum temperature and precipitation were used. The re-analysis climate data were obtained from NCEP/NCAR 40-year reanalysis project (NOAA National Center for Environmental Prediction) and ECMWF Data server (European Centre for Medium-Range Weather Forecasts: ERA 40 and ERA Interim). Simulations were made on three locations where site- specific calibrations were done and validated with independent field data: Lugo (northwestern), Getafe (centre) and Albacete (southeastern Spain). Re-analysis data confirm the preliminary results obtained with observed data (AEMET): El Niño phenomenon affects irrigated maize depending on the location in the Iberian Peninsula. Also

  13. Experiments on Lunar Core Composition: Phase Equilibrium Analysis of A Multi-Element (Fe-Ni-S-C) System

    NASA Technical Reports Server (NTRS)

    Go, B. M.; Righter, K.; Danielson, L.; Pando, K.

    2015-01-01

    Previous geochemical and geophysical experiments have proposed the presence of a small, metallic lunar core, but its composition is still being investigated. Knowledge of core composition can have a significant effect on understanding the thermal history of the Moon, the conditions surrounding the liquid-solid or liquid-liquid field, and siderophile element partitioning between mantle and core. However, experiments on complex bulk core compositions are very limited. One limitation comes from numerous studies that have only considered two or three element systems such as Fe-S or Fe-C, which do not supply a comprehensive understanding for complex systems such as Fe-Ni-S-Si-C. Recent geophysical data suggests the presence of up to 6% lighter elements. Reassessments of Apollo seismological analyses and samples have also shown the need to acquire more data for a broader range of pressures, temperatures, and compositions. This study considers a complex multi-element system (Fe-Ni-S-C) for a relevant pressure and temperature range to the Moon's core conditions.

  14. Effects of FeNi-phosphorus-carbon system on crystal growth of diamond under high pressure and high temperature conditions

    NASA Astrophysics Data System (ADS)

    Hu, Mei-Hua; Bi, Ning; Li, Shang-Sheng; Su, Tai-Chao; Zhou, Ai-Guo; Hu, Qiang; Jia, Xiao-Peng; Ma, Hong-An

    2015-03-01

    This paper reports the crystal growth of diamond from the FeNi-Carbon system with additive phosphorus at high pressures and high temperatures of 5.4-5.8 GPa and 1280-1360 °C. Attributed to the presence of additive phosphorus, the pressure and temperature condition, morphology, and color of diamond crystals change obviously. The pressure and temperature condition of diamond growth increases evidently with the increase of additive phosphorus content and results in the moving up of the V-shape region. The surfaces of the diamonds also become coarse as the additive phosphorus added in the growth system. Raman spectra indicate that diamonds grown from the FeNi-phosphorus-carbon system have more crystal defects and impurities. This work provides a new way to enrich the doping of diamond and improve the experimental exploration for future material applications. Project supported by the Doctoral Fund of Henan Polytechnic University, China (Grant Nos. B2013-013 and B2013-044) and the Research Projects of Science and Technology of the Education Department of Henan Province, China (Grant Nos. 14B430026 and 12A430010).

  15. Predicting stochastic systems by noise sampling, and application to the El Niño-Southern Oscillation.

    PubMed

    Chekroun, Mickaël David; Kondrashov, Dmitri; Ghil, Michael

    2011-07-19

    Interannual and interdecadal prediction are major challenges of climate dynamics. In this article we develop a prediction method for climate processes that exhibit low-frequency variability (LFV). The method constructs a nonlinear stochastic model from past observations and estimates a path of the "weather" noise that drives this model over previous finite-time windows. The method has two steps: (i) select noise samples--or "snippets"--from the past noise, which have forced the system during short-time intervals that resemble the LFV phase just preceding the currently observed state; and (ii) use these snippets to drive the system from the current state into the future. The method is placed in the framework of pathwise linear-response theory and is then applied to an El Niño-Southern Oscillation (ENSO) model derived by the empirical model reduction (EMR) methodology; this nonlinear model has 40 coupled, slow, and fast variables. The domain of validity of this forecasting procedure depends on the nature of the system's pathwise response; it is shown numerically that the ENSO model's response is linear on interannual time scales. As a result, the method's skill at a 6- to 16-month lead is highly competitive when compared with currently used dynamic and statistic prediction methods for the Niño-3 index and the global sea surface temperature field. PMID:21730171

  16. Siderophile element partitioning between cohenite and liquid in the Fe-Ni-S-C system and implications for geochemistry of planetary cores and mantles

    NASA Astrophysics Data System (ADS)

    Buono, Antonio S.; Dasgupta, Rajdeep; Lee, Cin-Ty A.; Walker, David

    2013-11-01

    We experimentally investigated the effects of pressure and S content on partition coefficients (D) between crystalline cohenite and liquid in the Fe-Ni-S-C system. Compositions with S contents of 0, 4.72, and 14.15 wt.%, in an Fe-rich mix containing a constant C (4.72 wt.%), Ni (5.23 wt.%), and W, Re, Os, Pt, and Co (totaling 0.43 wt.%) were equilibrated at 1150 °C and 3 and 6 GPa. Our cohenite-melt D data are compared to literature Fe-Ni-S and Fe-Ni-C experiments involving a crystalline phase of Fe. There is a change in D when the solid is cohenite rather than crystalline iron. Compared to solid-Fe/melt Ds, cohenite/melt Ds are lower for all elements except W.

  17. Geodynamics of magmatic Cu-Ni-PGE sulfide deposits: new insights from the Re-Os isotope system

    USGS Publications Warehouse

    Lambert, D.D.; Foster, J.G.; Frick, L.R.; Ripley, E.M.; Zientek, M.L.

    1998-01-01

    In this study, we reassess crustal contamination and sulfide ore-forming processes in some of the largest magmatic ore deposits, using published Re-Os isotope data and a modeling methodology that incorporates the R factor, defined as the effective mass of silicate magma with which a given mass of sulfide magma has equilibrated, in an Re-Os isotope mixing equation. We show that there is less disparity between conclusions based on Re-Os isotope data compared to other isotopic systems if the R factor is considered, Komatiite-associated Ni sulfide ore systems typically have high Os concentrations, low Re/Os ratios, and near-chondritic initial Os isotope compositions. For magmatic sulfide ores that are interpreted to have experienced relatively low R factors (2,000). Sulfide saturation in these ore systems may, therefore, have been achieved via changes in intensive parameters of the komatiite lavas (cooling or decompression) or changes in compositional parameters transparent to the Re-Os isotope system (e.g., fo2/fs2/fH2O)- Basalt-gabbro-associated Cu-Ni sulfide ore systems at Duluth, Sudbury, and Stillwater are quite distinct from those at Kambalda by having comparatively low Os concentrations, high Re/Os ratios, and high initial Os isotope compositions, These chemical and isotopic characteristics are indicative of significant interactions between their parental basaltic magmas and old crust because there are no known mantle reservoirs with such extreme geocheinical characteristics. Our modeling suggests that for Cu-Ni sulfide ores at Duluth, Sudbury, and Stillwater to maintain the observed high initial Os isotope compositions inherited from a crustal contaminant, R factors for these systems must have been low (< 10,000), consistent with their low metal concentrations. Thus, we interpret this style of base metal sulfide mineralization to be derived from crustally contaminated but less dynamic magmatic systems that did not permit extensive equilibration of sulfide magma

  18. Predicting stochastic systems by noise sampling, and application to the El Niño-Southern Oscillation

    PubMed Central

    Chekroun, Mickaël David; Kondrashov, Dmitri; Ghil, Michael

    2011-01-01

    Interannual and interdecadal prediction are major challenges of climate dynamics. In this article we develop a prediction method for climate processes that exhibit low-frequency variability (LFV). The method constructs a nonlinear stochastic model from past observations and estimates a path of the “weather” noise that drives this model over previous finite-time windows. The method has two steps: (i) select noise samples—or “snippets”—from the past noise, which have forced the system during short-time intervals that resemble the LFV phase just preceding the currently observed state; and (ii) use these snippets to drive the system from the current state into the future. The method is placed in the framework of pathwise linear-response theory and is then applied to an El Niño–Southern Oscillation (ENSO) model derived by the empirical model reduction (EMR) methodology; this nonlinear model has 40 coupled, slow, and fast variables. The domain of validity of this forecasting procedure depends on the nature of the system’s pathwise response; it is shown numerically that the ENSO model’s response is linear on interannual time scales. As a result, the method’s skill at a 6- to 16-month lead is highly competitive when compared with currently used dynamic and statistic prediction methods for the Niño-3 index and the global sea surface temperature field. PMID:21730171

  19. Performance of two-layer thermal barrier systems on directionally solidified Ni-Al-Mo and comparative effects of alloy thermal expansion on system life

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1980-01-01

    A promising two-layer thermal barrier coating system (TBS), Ni-16.4Cr-5.1A1-0.15Y/ZrO2-6.1Y2O3 (all in weight percent), was identified for directionally solidified Ni-Al-Mo (gamma/gamma' alpha). In cyclic furnace tests at 1095 C this system on gamma/gamma' alpha was better than Ni-16. 4Cr-5.1Al-0.15Y/ZrO2-7.8Y2O3 by about 50 percent. In natural gas - oxygen torch rig tests at 1250 C the ZrO2-6.1Y2O3 coating was better than the ZrO2-7.8Y2O3 coating by 95 percent, on MAR-M509 substrates and by 60 percent on gamma/gamma' alpha substrates. Decreasing the coefficient of thermal expansion of the substrate material from 17-18x10 to the -6 power/C (MAR-M200 + Hf and MAR-M509) to 11x10 to the -6 power/C (gamma/gamma' alpha) also resulted in improved TBS life. For example, in natural gas - oxygen torch rig tests at 1250 C, the life of Ni-16.4Cr-5.1Al-0.15Y/ZrO26.1Y2O3 was about 30 percent better on gamma/gamma' alpha than on MAR-M509 substrates. Thus compositional changes in the bond and thermal barrier coatings were shown to have a greater effect on TBS life than does the coefficient of thermal expansion.

  20. Petrogenesis of the Ni-Cu-PGE sulfide-bearing Tamarack Intrusive Complex, Midcontinent Rift System, Minnesota

    NASA Astrophysics Data System (ADS)

    Taranovic, Valentina; Ripley, Edward M.; Li, Chusi; Rossell, Dean

    2015-01-01

    The Tamarack Intrusive Complex (TIC, 1105.6 ± 1.2 Ma) in NE Minnesota, was emplaced during the early stages of the development of the Midcontinent Rift System (MRS, "Early Stage": 1110-1106 Ma). Country rocks of the TIC are those of the Paleoproterozoic Thomson Formation, part of the Animikie Group including sulfide-bearing metasedimentary black shale. The magmatic system is composed of at least two principal mafic-ultramafic intrusive sequences: the sulfide-barren Bowl Intrusion in the south and the "dike" area intrusions in the north which host Ni-Cu-Platinum Group Elements (PGE) mineralization with up to 2.33% Ni, 1.24% Cu, 0.34 g/t Pt, 0.23 g/t Pd and 0.18 g/t Au. Two distinct intrusive units in the "dike" area are the CGO (coarse-grained olivine-bearing) Intrusion, a sub-vertical dike-like body, and the overlying sub-horizontal FGO (fine-grained olivine-bearing) Intrusion. Both intrusions comprise peridotite, feldspathic peridotite, feldspathic pyroxenite, melatroctolite and melagabbro. Massive sulfides are volumetrically minor and mainly occur as lenses emplaced into the country rocks associated with both intrusions. Semi-massive (net-textured) sulfides are distributed at the core of the CGO Intrusion, surrounded by a halo of the disseminated sulfides. Disseminated sulfides also occur in lenses along the base of the FGO Intrusion. Olivine compositions in the CGO Intrusion are between Fo89 and Fo82 and in the FGO Intrusion from Fo84 to Fo82. TIC intrusions have more primitive olivine compositions than that of olivine in the sheet-like intrusions in the Duluth Complex (below Fo70), as well as olivine from the smaller, conduit-related, Eagle and East Eagle Intrusions in Northern Michigan (Fo86 to Fo75). The FeO/MgO ratios of the CGO and FGO Intrusion parental magmas, inferred from olivine compositions, are similar to those of picritic basalts erupted during the early stages of the MRS formation. Trace element ratios differ slightly from other intrusions in the

  1. Synthesis of Waste Form in the Gd-Fe-Al-Ni-Mn-Cr-O System

    SciTech Connect

    Chae, S.C.; Jang, Y.N.; Bae, I.K.; Ryu, K.W.

    2006-07-01

    Poly-phase waste form which was the mixture of Gd{sub 3}Fe{sub 2}Al{sub 3}O{sub 12} and (Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4} was synthesized. Also, we are intended to examine phase relation and physicochemical properties of coexisted phases in the compositions and to confirm accommodation relation of elements and phases. Two types of phase series were observed: Garnet-perovskite-spinel and Garnet-spinel. The compositions of garnets and spinels were nonstoichiometric, and especially, this poly-phase ceramics may be in a good waste form. The excessive Gd in garnets indicated the immobilization of higher content of actinides. The nonstoichiometric compositions of garnet and spinel were attributed to the formation of perovskite in that perovskite contained Gd, Fe and Al from garnet and Cr from spinel. (authors)

  2. High-Level Ab-Initio Calculation on the NiO₂ System

    SciTech Connect

    Song, Jie; Apra, Edoardo; Khait, Yuri; Hoffmann, Mark R.; Kowalski, Karol

    2006-09-20

    Several high-level ab-initio methods were employed in studies of the narrow singlet-triplet separation of the cyclic dorm of the nickel dioxide (NiO?). It is shown that the complete visions of the locally renormalized couples cluster method with singles, doubles, and noniterative triples (LR-CCSD(T)) approach, in contrast to the standard CCSD(T) method, provides results in concert with predictions of the density functional theory (DFT) and internally contracted multi-reference configuration interaction method (IIC-MCRCI), which favor the triplet state to be the lowest one. Relevant discussion of several aspects related to underlying CCSD calculations, indicate that the dominate roll of singly excited amplitudes violates the paradigm about the leading role to two-body effect in description of the correlation energy. These results are compared with the results of the second order Generalized Van Vleck Perturbation Theory (GVVPPT2) approach which supports the CCSD(T) predictions.

  3. Study of fatigue and fracture behavior of NbCr{sub 2}-based alloys: Phase stability in Nb-Cr-Ni ternary system

    SciTech Connect

    Zhu, J.H.; Liaw, P.K.; Liu, C.T.

    1997-12-01

    Phase stability in a ternary Nb-Cr-Ni Laves phase system was studied in this paper. Their previous study in NbCr{sub 2}-based transition-metal Laves phases has shown that the average electron concentration factor, e/a, is the dominating factor in controlling the phase stability of NbCr{sub 2}-based Laves phases when the atomic size ratios are kept identical. Since Ni has ten out-shell electrons, the substitution of Ni for Cr in NbCr{sub 2} will increase the average electron concentration of the alloy, thus leading to the change of the crystal structures from C15 to C14. In this paper, a number of pseudo-binary Nb(Cr,Ni){sub 2} alloys were prepared, and the crystal structures of the alloys after a long heat-treatment at 1000 C as a function of the Ni content were determined by the X-ray diffraction technique. The boundaries of the C15/C14 transition were determined and compared to their previous predictions. It was found that the electron concentration and phase stability correlation is obeyed in the Nb-Cr-Ni system. However, the e/a ratio corresponding to the C15/C14 phase transition was found to move to a higher value than the predicted one. The changes in the lattice constant, Vickers hardness and fracture toughness were also determined as a function of the Ni content, which were discussed in light of the phase stability difference of the alloys.

  4. Measurements of fusion cross sections in the systems {sup 58,64}Ni +, {sup 78,86}Kr

    SciTech Connect

    Rehm, K.E.; Jiang, C.L.; Esbensen, H.

    1995-08-01

    We investigated the nuclear structure dependence of the sub-barrier fusion enhancement in heavy-ion induced reactions by studying the systems {sup 58,64}Ni + {sup 78,86}Kr at energies in the vicinity of the Coulomb barrier. These {sup 78,86}Kr selected because, similar to the Mo case discussed isotopes were above, there are strong changes in nuclear structure as a function of the neutron number. However, contrary to Mo, where the {open_quotes}softness{close_quotes} of the nucleus increases with higher neutron number, the most collective nucleus for the Kr case is the neutron-deficient {sup 78}Kr. The experiment was performed with Kr beams from the positive-ion injector using enriched {sup 78,86}Kr gas in the ECR ion source. The separation of evaporation residues from the elastically-scattered particles was achieved by using their difference in time-of-flight and magnetic rigidity in the gas-filled spectrograph. The excitation functions for the four systems were compared to coupled-channels calculations including inelastic excitations of one- and two-phonon states in projectile and target. For systems involving {sup 86}Kr, good agreement between theory and experiment is obtained, while for {sup 78}Kr + {sup 58,64}Ni an additional enhancement of the cross sections persisted at the lowest energies. It was found that this fusion enhancement correlates with the nuclear structure of the individual nucleus. Characterizing the structure of vibrational even-even nuclei by their restoring force parameter C{sub 2}, which can be calculated from the energy of the lowest 2{sup +} state and the associated B(E2) value, one observes that nuclei with small C{sub 2} values exhibit a large sub-barrier fusion enhancement, while nuclei with high values of C{sub 2} (usually closed-shell nuclei), show smaller fusion yields.

  5. Electrodepositing behaviors and properties of nano Fe-Ni-Cr/SiC composite coatings from trivalent chromium baths containing compound carboxylate-urea system.

    PubMed

    He, Xinkuai; Hou, Bailong; Cai, Youxing; Li, Chen; Jiang, Yumei; Wu, Luye

    2013-06-01

    The nano Fe-Ni-Cr/SiC composite coatings were prepared using pulse electrodeposition method from trivalent chromium baths containing compound carboxylate-urea system and nano SiC in ultrasonic field. The effects of the carboxylate-urea system on the nano Fe-Ni-Cr/SiC composite coatings have been investigated. These results indicated that the SiC and Cr contents and the thickness of the Fe-Ni-Cr/SiC composite coatings could be obviously improved by the compound carboxylate-urea system. The steady-state polarization curves showed that the hydrogen evolution reaction (HER) could be significantly inhibited by the compound carboxylate-urea system, which was benefit to increase the SiC and Cr contents and the thickness of the composite coatings. The cyclic voltammetry (CV) curves showed that the cathodic polarization of the matrix metal ions could be increased in the bath containing the compound carboxylate-urea system. Thus, a compact Fe-Ni-Cr/SiC composite coating could be obtained using this technique. The surface morphology of the Fe-Ni-Cr/SiC composite coatings checked with the scanning electron micrographs (SEM) showed that the surface smoothness could be also improved and the microcracks and pinholes could be decreased due to the presence of the compound carboxylate-urea system. The phase composition of the as-posited coating was measured by the X-ray diffraction (XRD). XRD data showed that the as-posited coating was Fe-Ni-Cr/SiC composite coating. The chemical composition of the coating was investigated by energy dispersive spectrum (EDS) analysis. The result showed the functional Fe-Ni-Cr/SiC composite coatings with 4.1 wt.% SiC and 25.1 wt.% Cr, and 23.9 microm thickness were obtained in this study, which had best corrosion resistance according to the results of the typical potentiodynamic polarization curves of the Fe-Ni-Cr/SiC composite coatings. PMID:23862444

  6. [Effect of heat treatment on the structure of a Cu-Zn-Al-Ni system dental alloy].

    PubMed

    Guastaldi, A C; Adorno, A T; Beatrice, C R; Mondelli, J; Ishikiriama, A; Lacefield, W

    1990-01-01

    This article characterizes the structural phases present in the copper-based metallic alloy system "Cu-Zn-Al-Ni" developed for dental use, and relates those phases to other properties. The characterization was obtained after casting (using the lost wax process), and after heat treatment. In order to obtain better corrosion resistance by changing the microstructure, the castings were submitted to 30, 45 and 60 minutes of heat treatment at the following temperatures: 750 degrees C, 800 degrees C, and 850 degrees C. The various phases were analyzed using X-ray diffraction and scanning electron microscopy (SEM). The results after heat treatment showed a phase (probably Cu3Al), that could be responsible for the improvement in the alloy's resistance to corrosion as compared to the as-cast structure. PMID:2135444

  7. Methanation of CO{sub 2} on Ni(II)-bearing ferrite (Ni{sub x}Fe{sub 3{minus}x}O{sub 4{minus}{delta}}; x = 0.39, {delta} > 0) in flow system

    SciTech Connect

    Kato, H.; Tabata, M.; Tsuji, M.; Tamaura, Y.

    1994-12-31

    One of the clear solutions to the greenhouse effect by CO{sub 2} gas is the in situ selective conversion of CO{sub 2} to hydrocarbons such as methane by using the waste heat in each stationary source, e.g., power plant, ironworks, etc. The methanation of CO{sub 2} has been studied by using reduced Ni(II)-bearing ferrite (Ni{sub x}Fe{sub 3{minus}x}O{sub 4{minus}{delta}}; x = 0.39, {delta} = 0.1 {approximately} 0.2) in an H{sub 2}/CO{sub 2} mixed gas flow system. A yield of 31% and a high selectivity of 89% were obtained in the methanation for 6h using the H{sub 2}-reduced Ni(II)-bearing ferrite. The X-ray diffractometry showed that the reduced Ni(II)-bearing ferrite during the methanation retained the spinel-type structure whose lattice constant increased from 0.8375 to 0.8379 nm. The chemical analysis corroborated an increase in the mole ratio of Fe{sup 2+}/Fe{sub total} in the Ni(II)-bearing ferrite. These results suggest that oxygen-deficient sites were formed in the spinel structure of the reduced Ni(II)-bearing ferrite. It has been found from the analysis using the Langmuir isotherm for dissociative adsorption that CO{sub 2} is adsorbed onto oxygen-deficient sites to be decomposed to an elemental carbon and two oxygen-deficient ions. The methanation of CO{sub 2} is considered to proceed owing to the oxygen deficient sites. It is considered that the methanation consists of three elementary reaction steps: (1) formation of oxygen-deficient sites by H{sub 2}-reduction, (2) reduction of CO{sub 2} to carbon and Incorporation of two oxygen ions of the CO{sub 2} into the oxygen-deficient sites, and (3) hydrogenation of the deposited carbon to CH{sub 4}.

  8. Reaction of amorphous Ni-W and Ni-N-W films with substrate silicon

    NASA Technical Reports Server (NTRS)

    Zhu, M. F.; Suni, I.; Nicolet, M.-A.; Sands, T.

    1984-01-01

    Wiley et al. (1982) have studied sputtered amorphous films of Nb-Ni, Mo-Ni, Si-W, and Si-Mo. Kung et al. (1984) have found that amorphous Ni-Mo films as diffusion barriers between multilayer metallizations on silicon demonstrate good electrical and thermal stability. In the present investigation, the Ni-W system was selected because it is similar to the Ni-Mo system. However, W has a higher silicide formation temperature than Mo. Attention is given to aspects of sample preparation, sample characterization, the interaction between amorphous Ni-W films and Si, the crystallization of amorphous Ni(36)W(64) films on SiO2, amorphous Ni-N-W films, silicide formation and phase separation, and the crystallization of amorphous Ni(36)W(64) and Ni(30)N(21)W(49) layers.

  9. Determining the activation energies and slip systems for dislocation nucleation in body-centered cubic mo and face-centered cubic Ni single crystals

    SciTech Connect

    Wang, L.; Bei, Hongbin; Li, T.; Gao, Y. F.; George, Easo P; Nieh, T. G.

    2011-01-01

    Nanoindentation tests were performed on single crystals of Mo and Ni. The critical shear stress for the first pop-in was {approx}1/7 of the shear modulus in both crystals. The dependence of pop-in probability on load was understood in terms of a thermally activated dislocation nucleation process. Comparison of the activation energies suggests nucleation of full dislocations in Mo and partial dislocations in Ni. The activation energy analysis also offers information on the specific slip system on which dislocations are nucleated.

  10. Impacts of the 2015-2016 El Niño on the California Current System: Early assessment and comparison to past events

    NASA Astrophysics Data System (ADS)

    Jacox, Michael G.; Hazen, Elliott L.; Zaba, Katherine D.; Rudnick, Daniel L.; Edwards, Christopher A.; Moore, Andrew M.; Bograd, Steven J.

    2016-07-01

    The 2015-2016 El Niño is by some measures one of the strongest on record, comparable to the 1982-1983 and 1997-1998 events that triggered widespread ecosystem change in the northeast Pacific. Here we describe impacts of the 2015-2016 El Niño on the California Current System (CCS) and place them in historical context using a regional ocean model and underwater glider observations. Impacts on the physical state of the CCS are weaker than expected based on tropical sea surface temperature anomalies; temperature and density fields reflect persistence of multiyear anomalies more than El Niño. While we anticipate El Niño-related impacts on spring/summer 2016 productivity to be similarly weak, their combination with preexisting anomalous conditions likely means continued low phytoplankton biomass. This study highlights the need for regional metrics of El Niño's effects and demonstrates the potential to assess these effects before the upwelling season, when altered ecosystem functioning is most apparent.

  11. In situ spectroscopic detection of SMSI effect in a Ni/CeO2 system: hydrogen-induced burial and dig out of metallic nickel

    SciTech Connect

    Caballero, Alfonso; Holgado, Juan P.; Gonzalez-delaCruz, Victor M.; Habas, Susan e.; Herranz, Tirma; Salmeron, Miquel

    2010-06-29

    In situ APPES technique demonstrates that the strong metal support interaction effect (SMSI) in the Ni-ceria system is associated with the decoration and burial of metallic particles by the partially reduced support, a phenomenon reversible by evacuation at high temperature of the previously absorbed hydrogen.

  12. General laws of the effect of hydrogen on the crystallization of amorphous alloys based on the quasi-binary TiNi-TiCu system

    NASA Astrophysics Data System (ADS)

    Spivak, L. V.; Shelyakov, A. V.; Shchepina, N. E.

    2014-02-01

    The crystallization processes that occur during heating of hydrogen-containing melt-quenched alloys based on the quasi-binary TiNi-TiCu system alloyed with aluminum, iron, hafnium, and zirconium are studied by high-resolution differential scanning calorimetry. The general laws of the transition of the hydrogen-containing alloys from an amorphous into a crystalline state are determined.

  13. The Fe-Ni-(S) System at 23 GPa: The Possibility of Strong Chemical Fractionation Between Phases in the Cores of the Earth, Mars and Mercury

    NASA Astrophysics Data System (ADS)

    Stewart, A. J.; Schmidt, M. W.

    2004-12-01

    The presence of nickel in the Earths core is widely accepted based on cosmochemical and seismological arguments. However, experimental studies into core compositions rarely include nickel, thus adding a degree of simplicity to otherwise complex experiments. Diamond-anvil cell studies have discovered that Fe-Ni alloys appear to separate into two phases upon heating above 10 GPa: from a single hexagonally close-packed (hcp) phase to the presence of both hcp and face centered cubic (fcc) phases (Lin et al., 2002). Unfortunately, due to the small size of diamond-anvil cell samples, meaningful quantitative analysis is commonly impossible. We have conducted multi-anvil experiments at 23 GPa into the Fe-Ni system and have confirmed the presence of two phases in the sub-solidus system. The starting material for these experiments contains 6 wt% nickel, approximating the amount expected to be found in the Earths core (McDonough, 2003). In experiments to 1500° C (the highest temperature thus far examined), electron microprobe analyses show dramatic phase fractionation with charges separating into an iron-rich phase containing less than 1 wt% Ni and a nickel-rich phase containing as much as 98 wt% Ni. We have observed the effect over a range of more than 500° ºC; further experiments are underway to determine whether these phases both persist toward the melting point of the alloy. Multi-anvil experiments at 23 GPa have also been conducted to examine the effect of nickel on the Fe-S system. Sulphur is an element favoured by many researchers as the light element component in the core of the Earth as well as that of Mars. Previous research has suggested that the addition of nickel to the Fe-S system results in the lowering of eutectic temperatures by about 75° C (Pike et al., 1999). The starting material for these experiments is the same as that used for the pure Fe-Ni experiments discussed above, with the addition of sulphur. Our results indicate a pseudo-binary, (Fe, Ni

  14. Copper-based alloys, crystallographic and crystallochemical parameters of alloys in binary systems Cu-Me (Me=Co, Rh, Ir, Cu, Ag, Au, Ni, Pd, Pt)

    NASA Astrophysics Data System (ADS)

    Porobova, Svetlana; Markova, Tat'jana; Klopotov, Vladimir; Klopotov, Anatoliy; Loskutov, Oleg; Vlasov, Viktor

    2016-01-01

    The article presents the results of the analysis of phase equilibrium of ordered phases in binary systems based on copper Cu- Me (where Me - Co, Rh, Ir, Ag, Au, Ni, Pd, Pt) to find correlations of crystallochemical and crystallographic factors. It is established that the packing index in disordered solid solutions in binary systems based on copper is close to the value of 0.74 against the background of an insignificant deviation of atomic volumes from the Zen's law.

  15. Secondary dislocation structures in a Ni-TiN system from the GMS and O-lattice theory

    NASA Astrophysics Data System (ADS)

    Tang, Yiru; Dai, Fuzhi; Gu, Xinfu; Wang, Zhongchang; Zhang, Wenzheng

    2016-03-01

    The preferred state in an interface is the key to evaluating misfit strain, especially for the interphase interfaces in secondary preferred state. The structure of good matching site (GMS) in a GMS clusters offers a guidance for the preferred state, especially for identifying the coincidence site lattice in two dimension for secondary preferred state and the Burgers vectors in a large misfit system. Here, we combine the GMS with O-lattice theory to calculate the secondary dislocation structure in the habit planes of the type II and III TiN precipitates in a Ni-TiN system. We find that under a slight elastic strain, the type III habit plane contains a single set of secondary dislocations, consistent with the experimental observation. The type II habit plane contains three sets of secondary dislocations, two of which can be relaxed to be nearly parallel and another of which may be invisible in diffraction contrast due to its short Burgers vector. The present study provides a reasonable interpretation to the observed interfacial dislocations, and also suggests Burgers vectors for the dislocations that are not determined experimentally.

  16. Development of dispersion-strengthened Ni-Cr-ThOz alloys for the space shuttle thermal protection system

    NASA Technical Reports Server (NTRS)

    Blankenship, C. P.; Saunders, N. T.

    1972-01-01

    Manufacturing processes were developed for TD-NiCr providing small sheet (45 x 90 cm), and larger sheet (60 x 150 cm) and foil. The alternate alloy, DS-NiCr, was produced by pack-chromizing Ni-ThO2 sheet. Formability criteria are being established for basic sheet forming processes, which are brake forming, corrugation forming, joggling, dimpling, and beading. Resistance spot welding (fusion and solid state), resistance seam welding, solid state diffusion welding, and brazing are included in the joining programs. Major emphasis is centered on an Al-modified Ni-Cr-ThO2 alloy development. These alloys, containing 3 to 5% Al, form the protective Al2O3 scale. This enhances oxidation resistance under reentry conditions. Both TD-NiCrAl and DS-NiCrAl alloys are included. A tentative composition of Ni-16Cr-3.5Al-2ThO2 was selected based on oxidation resistance and fabricability.

  17. In situ x-ray and neutron powder diffraction study of LaNi5-xSnx-H systems

    NASA Technical Reports Server (NTRS)

    Bowman, Robert C., Jr.; Nakamara, Yumiko; Akiba, Etsuo

    2004-01-01

    This paper will present results of in situ XRD measurements of LaNi4.75Sn0.25 .during the initial absorption-desorption cycle, These measurements were performed under a similar condition to that for LaNi4.75Al0.25 previously reported [1]. The data were analyzed by the Rietveld method. Lattice parameter change and strain formation accompanying hydride phase formation and decomposition will be discussed. In addition, results of in situ neutron diffraction of LaNi4.78Sn0.22, focusing on hydrogen occupation in the hydride phase, will be presented.

  18. Electronic-network modelling of rechargeable NiCd cells and its application to the design of battery management systems

    NASA Astrophysics Data System (ADS)

    Bergveld, H. J.; Kruijt, W. S.; Notten, P. H. L.

    In the first part of this paper, the development of a simulation model for a sealed rechargeable NiCd cell is described. Based on the concept of this cell type, a mathematical description of the various physical and electrochemical processes occurring inside the cell can be given. Subsequently, these equations are introduced in the form of electronic components into an electronic-circuit simulator. This enables the user to simulate the most important cell characteristics like voltage, temperature and internal gas pressure simultaneously and coherently under a wide variety of charging, discharging and open-circuit conditions. The construction of the model enables the user to investigate the course of each of the various reactions taking place inside the cell. Moreover, the electrical and thermal interaction with the surrounding electronics attached to the cell and with other cells, e.g., in a battery pack, can also be simulated. In the second part of this paper, some examples of simulations of cell characteristics are presented. The results of the simulated phenomena show good qualitative agreement with measured cell characteristics. An understanding of phenomena such as charge efficiency, self-discharge and overdischarge is presented using the model. Simulation of battery behaviour in an electronic system enables a system designer to design the optimal Battery Management System around the battery. In the third part of this paper, an example of applying the model in an electronic system is given, i.e., a shaver. Also, simulations of several cells connected in series forming a battery or battery pack are described.

  19. Combinatorial Study of the Li-Ni-Mn-Co Oxide Pseudoquaternary System for Use in Li-Ion Battery Materials Research.

    PubMed

    Brown, Colby R; McCalla, Eric; Watson, Cody; Dahn, J R

    2015-06-01

    Combinatorial synthesis has proven extremely effective in screening for new battery materials for Li-ion battery electrodes. Here, a study in the Li-Ni-Mn-Co-O system is presented, wherein samples with nearly 800 distinct compositions were prepared using a combinatorial and high-throughput method to screen for single-phase materials of high interest as next generation positive electrode materials. X-ray diffraction is used to determine the crystal structure of each sample. The Gibbs' pyramid representing the pseudoquaternary system was studied by making samples within three distinct pseudoternary planes defined at fractional cobalt metal contents of 10%, 20%, and 30% within the Li-Ni-Mn-Co-O system. Two large single-phase regions were observed in the system: the layered region (ordered rocksalt) and cubic spinel region; both of which are of interest for next-generation positive electrodes in lithium-ion batteries. These regions were each found to stretch over a wide range of compositions within the Li-Ni-Mn-Co-O pseudoquaternary system and had complex coexistence regions existing between them. The sample cooling rate was found to have a significant effect on the position of the phase boundaries of the single-phase regions. The results of this work are intended to guide further research by narrowing the composition ranges worthy of study and to illustrate the broad range of applications where solution-based combinatorial synthesis can have significant impact. PMID:25970448

  20. Ductile phase toughened ceramics by partial reduction reactions in the Ni-Al-O system: Mechanical properties and effect of dopants

    SciTech Connect

    Uestuendag, E.; Ret, P.; Shapiro, Y.; Subramanian, R.; Dieckmann, R.; Sass, S.L.

    1995-10-01

    Partial reduction reactions in the Ni-Al-O system, starting with the spinel compound NiAl{sub 2}O{sub 4}, are used to form metal-ceramic microstructures in situ. Two different morphologies of nearly pure Ni particles, equiaxed and rod-like, form within a ceramic matrix depending on the choice of processing parameters. Electron microscopy studies were performed for microstructural characterization, phase identification and chemical analysis. The fracture toughness of the Ni-Al{sub 2}O{sub 3} mixture was significantly improved with respect to that of the original spinel phase. It is shown that cracking at the original spinel grain boundaries, likely due to the large volume changes associated with the reduction reaction, can be avoided by the addition of small amounts of ZrO{sub 2}. It is seen that ZrO{sub 2} also acts as a nucleation site for the precipitating metal and hence allows morphology control in microstructures obtained by partial reduction reactions.

  1. Self-Propagating High-Temperature Synthesis in the Ti-C-Ni-Mo System on Application of Powerful Ultrasound

    NASA Astrophysics Data System (ADS)

    Kulak, M. M.; Khina, B. B.

    2014-03-01

    An experimental setup has been developed and a study has been made of the self-propagating high-temperature synthesis in a Ti-C-Ni-Mo system under the conditions of action of ultrasonic vibrations. The influence of the amplitude of ultrasonic vibrations on the combustion rate and temperature and on the phase composition and structure of the derived composite material based on titanium carbide with a metal binder has been determined. The heat-transfer coefficient on the surface of a sample for vibrations at ultrasound frequency has been evaluated. Consideration has been given to possible mechanisms of influence of ultrasonic vibrations on the process of self-propagating high-temperature synthesis. It has been shown that the reduction in the synthesis temperature is due to the cooling of the sample because of the forced convection of the surrounding gas, whereas the change in the structure of the synthesized material is related to the change in the conditions of high-temperature heterogeneous interaction in the wave of self-propagating high-temperature synthesis.

  2. Exchange bias in sputtered FeNi/FeMn systems: Effect of short low-temperature heat treatments

    NASA Astrophysics Data System (ADS)

    Savin, Peter; Guzmán, Jorge; Lepalovskij, Vladimir; Svalov, Andrey; Kurlyandskaya, Galina; Asenjo, Agustina; Vas'kovskiy, Vladimir; Vazquez, Manuel

    2016-03-01

    Short (5 min) post-deposition thermal treatments under magnetic field at low temperature (up to 200 °C) performed in exchange-coupled FeNi(40 nm)/FeMn(20 nm) bilayer thin films prepared by magnetron sputtering are shown to be effective to significantly modify their exchange field (from around 40 Oe down to 27 Oe) between FeNi and FeMn layers. A similar exchange field decrease was observed for the first deposited FeNi layer of the FeNi(40 nm)/FeMn(20 nm)/FeNi(40 nm) trilayer films after the same thermal treatments. The exchange field value for the second FeNi layer was not substantially changed. The X-ray diffraction patterns indicates that such a heat treatment has no effect on the grain size and crystalline texture of the films, while atomic force microscope studies reveal an increase of the surface roughness after the treatment which is more noticeable in the case of the trilayer film. Analysis of the experimental results leads us to conclude that the variations of the exchange field after heat treatment are likely caused by a modification of interfacial roughness and/or interfacial magnetic structure, but unlikely by the changes in the microstructure and/or changes of composition of the antiferromagnetic FeMn layer.

  3. Phase equilibria in the FeO-Fe2O3-NiO-H2S-H2O-HCl system: An experimental study with implications for the stability of Ni-bearing phases at ultramafic-hosted hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Hoover, R. H.; Foustoukos, D.

    2010-12-01

    Nickel-bearing minerals commonly found in altered abyssal peridotites have been shown to be important catalysts for abiogenic formation of hydrocarbons in ultramafic-hosted hydrothermal systems (e.g. awaruite, pentlandite). Recent theoretical studies on the relative stability of these phases suggest that extremely low f O2 conditions are needed to allow formation of Ni-Fe alloys and sulfides at elevated temperatures and pressures. However, such redox conditions have never been established during hydrothermal experiments involving peridotite alteration, especially at conditions that promote ferric iron partitioning into secondary alteration phases (e.g. brucite, serpentine) and limit the extent of H2(aq) generation through magnetite formation (200°C-400°C). Thus, there is a strong disagreement on the stability of Ni-bearing minerals between petrological observations in altered peridotites and theoretical models. In addition, there is a complete lack of any experimental data on the stability of awaruite (Ni3Fe) coexisting with pentlandite (Fe4.5Ni4.5S8), heazlewoodite (Ni3S2) and magnetite (Fe3O4) at conditions reflecting serpentinization processes in the subseafloor reaction zones of ultramafic-hosted systems. Thus, a series of hydrothermal experiments has been conducted involving, magnetite, heazlewoodite, pentlandite, awaruite and a composite of native Ni, Fe (80:20) coexisting with a 3.2 wt% NaCl aqueous solution at 200°C to 400°C at 500 bars. To establish phase relations as a function of redox conditions, fluid samples were analyzed for dissolved H2(aq) and H2S(aq) by gas chromatography while the chemical composition of final solid products was retrieved by SEM/EDS. Results support formation of awaruite at redox conditions significantly less reducing than those predicted by theoretical phase equilibria models. For example, in experiments conducted at 400°C-500 bars utilizing the Ni:Fe-heazlewoodite-magnetite mineral assemblage, synthesis of awaruite is

  4. Ni5, Ni8, and Ni10 clusters with 2,6-diacetylpyridine-dioxime as a ligand.

    PubMed

    Escuer, Albert; Esteban, Jordi; Roubeau, Olivier

    2011-09-19

    In the present work, novel coordination possibilities for the system dapdoH(2)/Ni(II) (dapdoH(2) = 2,6-diacetylpyridine-dioxime) have been explored. Depending on the starting reagents and solution conditions, several clusters with nuclearities ranging from Ni(5) to Ni(10) were achieved and structurally characterized, namely, [Ni(5)(R-COO)(2)(dapdo)(2)(dapdoH)(2)(N(CN)(2))(2)(MeOH)(2)] in which R-COO(-) = benzoate (1) or 3-chlorobenzoate (2), [Ni(8)(dapdo)(4)(NO(3))(4)(OH)(4)(MeOH)(4)] (3), and [Ni(10)(dapdo)(8)(N(CN)(2))(2)(MeO)(MeOH)](NO(3)) (4). For the first time, pentadentate coordination for the dapdo(2-) ligand has been established. All compounds show a combination of square-planar and octahedrally coordinated nickel atoms. According to the Ni(2)(sp)Ni(3)(Oh) (1 and 2), Ni(4)(sp)Ni(4)(Oh) (3), and Ni(4)(sp)Ni(6)(Oh) (4) environments, these systems magnetically behave as trimer, tetramer, and hexanuclear clusters, respectively. dc magnetic measurements in the 2-300 K range of temperature reveal antiferromagnetic coupling for all compounds, and the correlation of the superexchange interaction with the torsion angles involving the oximato bridges is experimentally confirmed. PMID:21853990

  5. Solar-Driven Reduction of Aqueous Protons Coupled to Selective Alcohol Oxidation with a Carbon Nitride–Molecular Ni Catalyst System

    PubMed Central

    2016-01-01

    Solar water-splitting represents an important strategy toward production of the storable and renewable fuel hydrogen. The water oxidation half-reaction typically proceeds with poor efficiency and produces the unprofitable and often damaging product, O2. Herein, we demonstrate an alternative approach and couple solar H2 generation with value-added organic substrate oxidation. Solar irradiation of a cyanamide surface-functionalized melon-type carbon nitride (NCNCNx) and a molecular nickel(II) bis(diphosphine) H2-evolution catalyst (NiP) enabled the production of H2 with concomitant selective oxidation of benzylic alcohols to aldehydes in high yield under purely aqueous conditions, at room temperature and ambient pressure. This one-pot system maintained its activity over 24 h, generating products in 1:1 stoichiometry, separated in the gas and solution phases. The NCNCNx–NiP system showed an activity of 763 μmol (g CNx)−1 h–1 toward H2 and aldehyde production, a Ni-based turnover frequency of 76 h–1, and an external quantum efficiency of 15% (λ = 360 ± 10 nm). This precious metal-free and nontoxic photocatalytic system displays better performance than an analogous system containing platinum instead of NiP. Transient absorption spectroscopy revealed that the photoactivity of NCNCNx is due to efficient substrate oxidation of the material, which outweighs possible charge recombination compared to the nonfunctionalized melon-type carbon nitride. Photoexcited NCNCNx in the presence of an organic substrate can accumulate ultralong-lived “trapped electrons”, which allow for fuel generation in the dark. The artificial photosynthetic system thereby catalyzes a closed redox cycle showing 100% atom economy and generates two value-added products, a solar chemical, and solar fuel. PMID:27337491

  6. Solar-Driven Reduction of Aqueous Protons Coupled to Selective Alcohol Oxidation with a Carbon Nitride-Molecular Ni Catalyst System.

    PubMed

    Kasap, Hatice; Caputo, Christine A; Martindale, Benjamin C M; Godin, Robert; Lau, Vincent Wing-Hei; Lotsch, Bettina V; Durrant, James R; Reisner, Erwin

    2016-07-27

    Solar water-splitting represents an important strategy toward production of the storable and renewable fuel hydrogen. The water oxidation half-reaction typically proceeds with poor efficiency and produces the unprofitable and often damaging product, O2. Herein, we demonstrate an alternative approach and couple solar H2 generation with value-added organic substrate oxidation. Solar irradiation of a cyanamide surface-functionalized melon-type carbon nitride ((NCN)CNx) and a molecular nickel(II) bis(diphosphine) H2-evolution catalyst (NiP) enabled the production of H2 with concomitant selective oxidation of benzylic alcohols to aldehydes in high yield under purely aqueous conditions, at room temperature and ambient pressure. This one-pot system maintained its activity over 24 h, generating products in 1:1 stoichiometry, separated in the gas and solution phases. The (NCN)CNx-NiP system showed an activity of 763 μmol (g CNx)(-1) h(-1) toward H2 and aldehyde production, a Ni-based turnover frequency of 76 h(-1), and an external quantum efficiency of 15% (λ = 360 ± 10 nm). This precious metal-free and nontoxic photocatalytic system displays better performance than an analogous system containing platinum instead of NiP. Transient absorption spectroscopy revealed that the photoactivity of (NCN)CNx is due to efficient substrate oxidation of the material, which outweighs possible charge recombination compared to the nonfunctionalized melon-type carbon nitride. Photoexcited (NCN)CNx in the presence of an organic substrate can accumulate ultralong-lived "trapped electrons", which allow for fuel generation in the dark. The artificial photosynthetic system thereby catalyzes a closed redox cycle showing 100% atom economy and generates two value-added products, a solar chemical, and solar fuel. PMID:27337491

  7. From One Extreme to Another: Tsunami, Hurricane, and El Niño Observations from the NDBC Ocean Observing Systems of Systems

    NASA Astrophysics Data System (ADS)

    Bouchard, R. H.; Henderson, D.; Locke, L.

    2008-05-01

    NOAA`s National Data Buoy Center (NDBC) operates a system of ocean observing systems (NOOSS) to provide critical information in real-time during extreme events, such as tsunamis, hurricanes, and El Niños. NDBC recently completed the 39-station array of tsunameters that employ the second-generation Deep-ocean and Assessment and Reporting of Tsunamis (DART II) technology. The tsunameter array spans the Pacific Ocean and the western Atlantic Ocean providing real-time water-level measurements and tsunami detection times. At depths down to 6000 meters the tsunameters can send information in less than 3 minutes to the Tsunami Warning Centers in Hawaii and Alaska and to the international tsunami community. The tsunameters have provided data for the Kuril tsunamis of November 2006 and January 2007, the Peru tsunamis of August and September 2007, and the southern Sumatra tsunami of September 2007. In 2006, NDBC assumed operations of the Tropical Atmosphere Ocean Array (TAO), the "crown jewel" of the Global Climate Observation System. TAO provides real-time data for improved detection, understanding, and prediction of El Niño and La Niña. The 55-buoy TAO array spans the central and eastern equatorial Pacific. Real-time and post-deployment recovery data support climate analysis and forecasts. For more than 30 years, NDBC has operated a system of buoys and coastal automated stations for meteorological and oceanographic observations that support real-time weather analysis, forecasting, and warnings. These "traditional" NDBC stations measure winds, waves, temperature, and humidity routinely. Some stations are augmented with ocean current and temperature and salinity (conductivity) sensors. In recent years, among the Gulf of Mexico and Caribbean hurricanes passing in proximity to NDBC stations include Ivan in 2004, Cindy, Emily, Dennis, Katrina, Rita, and Wilma in 2005, Ernesto in 2006, and Dean and Felix in 2007 as well as numerous tropical storms. Not confined to tropical

  8. Cycling Stability Performance of La0.75Mg0.25Ni3.5Si0.10 Hydrogen Storage Alloy in Discharge-Charge System

    NASA Astrophysics Data System (ADS)

    Liu, Zhaojiang; Huang, Lei; Wan, Qi; Li, Xu; Guang, Ma; Li, Ping

    2014-12-01

    La0.75Mg0.25Ni3.5Si0.10 hydrogen storage alloy was prepared by vacuum induction melting furnace and subsequently heated treatment at 940°C for 8 h and cooled to room temperature in the oven. The electrochemical properties of La0.75Mg0.25Ni3.5Si0.10 compound were measured by LAND CT2001A battery test system. The morphologies of the samples were characterized by scanning electron microscopy (SEM). The surface state of samples was analyzed by X-ray photoelectron spectroscopy (XPS). It was found that the charge-discharge rate plays the key impact on the cycling stability of the alloy. During the cycle test, the prepared La0.75Mg0.25Ni3.5Si0.10 compound presented an excellent capacity retention at the charge-discharge of 1 C while the capacity of sample declined rapidly at 0.2 C. The excellent cycling stability performance of La0.75Mg0.25Ni3.5Si0.10 electrode at 1 C could be attributed to the less powder and less oxidation of surface effective active elements. The pulverization inevitably leads to the separation of the part of the cracking alloy and the electrode, resulting in reduction of the effective active substance and increasing attenuation of the capacity per cycle. In addition, on the analysis of the different cut-off potential effects on the electrode, it was found that the La0.75Mg0.25Ni3.5Si0.10 electrode shows good comprehensive electrochemical properties at 1 C cut-off 0.6-0.7 V. During charging, heavy overcharge will not be conducive to cycling stability performance during the charging test.

  9. Carbon Storage in the Mid- to Deep- Upper Mantle Constrained by Phase Relations in the Fe-Ni-Cu-C-S system

    NASA Astrophysics Data System (ADS)

    Tsuno, K.; Dasgupta, R.

    2014-12-01

    Carbon is a key element for evolution of terrestrial planets as it has influence on the chemistry and habitability of surficial environment as well as impact on mantle processes such as partial melting and element mobility. Because mantle is arguably the largest reservoir of extractable carbon, the stable form of carbon in various mantle domains needs to be constrained. In the reduced, mid- to deep- upper mantle, the host of deep carbon is graphite/diamond and/or Fe-Ni-bearing alloy melt [1]. However, high solubility of carbon in Fe-Ni alloy melt [2] suggests that diamond saturation may be restricted only to C-rich mantle domains. But such suggestions do not take into account the role of sulfides, which must interact with alloy-carbon mantle subsystems. In order to constrain the stable forms of carbon in the reduced mantle where Ni-rich alloy is likely present [3], we explore the phase relations and C solubility in Ni-rich portion of the Fe-Ni-±Cu-C-S systems. Experiments were performed in a MgO capsule using a multi-anvil with six starting mixes (Ni/(Fe+Ni) wt. ratio of 0.50-0.61, 8-16 % wt.% S, 2.0-2.5 wt.% C, and 0-0.7 wt.% Cu) at 6-8 GPa and 800-1400 °C. Low-temperature runs for all starting mixes contain C-bearing, solid Fe-Ni alloy + alloy melt + graphite, and solid alloy-out boundary is constrained, for example, at 1000-1050 °C at 6 GPa and 900-1000 °C at 8 GPa for the S-rich starting mix. The carbon solubility in the alloy melt (0.8~2.1 wt.% at 8 GPa and 1400 °C) decreases with increasing S content from 8 to 24 wt.%, increasing pressure for S-rich (18-24 wt.%) melt, and decreasing Ni/(Fe+Ni) from 0.65 to 0.53. For a mantle with ~0.1 wt.% alloy (~250 km depth) [3], diamond is likely stable coexisting with an S-rich alloy melt for ≥10 ppm bulk C. This is owing to the influence of S, which suppresses the incorporation of C in the alloy melt to stabilize diamond. Our results thus imply that diamond is a stable form of carbon even in depleted mantle

  10. Degradation behavior of Ni3Al plasma-sprayed boiler tube steels in an energy generation system

    NASA Astrophysics Data System (ADS)

    Sidhu, Buta Singh; Prakash, S.

    2005-06-01

    Boiler steels, namely, low-C steel, ASTM-SA210-Grade A1 (GrA1), 1Cr-0.5Mo steel, ASTM-SA213-T-11 (T11) and 2.25Cr-1Mo steel, ASTM-SA213-T-22 (T22) were plasma sprayed with Ni3Al. The alloy powder was prepared by mixing Ni and Al in the stoichiometric ratio of 3 to 1. The Ni-22Cr-10Al-1Y alloy powder was used as a bond coat, with a 150 µm thick layer sprayed onto the surface before applying the 200 µm coating of Ni3Al. Exposure studies have been performed in the platen superheater zone of a coal-fired boiler at around 755 °C for 10 cycles, each of 100 h duration. The protection to the base steel was minimal for the three steels. Scale spallation and the formation of a porous and nonadherent NiO scale were probably the main reasons for the lack of protection. In the case of T22-coated steel, cracks in the coatings have been observed after the first 100 h exposure cycle.

  11. Effect on structural and magnetic properties of aluminum substituted Ni-Zn nanoferrite system prepared via citrate-gel route

    NASA Astrophysics Data System (ADS)

    Babu, B. Rajesh; Prasad, M. S. R.; Ramesh, K. V.

    2015-12-01

    Nickel zinc aluminum nanoferrites with general formula Ni0.5Zn0.5Fe2-xAlxO4(x = 0.0, 0.05, 0.1, 0.15, 0.2 and 0.25) were prepared by citrate-gel autocombustion method and heat treated in air at 1100°C for 4 h. The crystallography, surface morphology and magnetic properties were studied by using X-ray diffraction (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer (VSM), respectively. XRD analysis confirms that the system exhibits polycrystalline single phase cubic spinel structure and absence of any secondary phases. The crystallite size estimated from Scherrer formula for the Gaussian peak (311) has been found to be around 30 nm. The results obtained show that with Al3+ doping, the lattice parameter decreases due to smaller ionic radii of Al3+ ions replaces larger Fe3+ ions. The distribution of Al3+ ions over tetrahedral (A) and octahedral (B) sites is estimated from X-ray intensity calculations. The arrangement of magnetic ions among the tetrahedral and octahedral sites due to the substitution of Al3+ ions modifies the saturation magnetization (Ms) and coercivity (Hc). The room temperature magnetization values increases up to x = 0.1 and then decreases for the increase in aluminum concentration above x > 0.1. Surface topography of the powder samples exhibits nearly spherical shape microstructure and the average grain size has been found to be 180 nm (x = 0.05). The observed variations in the structural and magnetic properties are discussed in the light of existing understanding.

  12. Competitive adsorption of Cd(II), Zn(II) and Ni(II) from their binary and ternary acidic systems using tourmaline.

    PubMed

    Liu, Haibin; Wang, Cuiping; Liu, Jingting; Wang, Baolin; Sun, Hongwen

    2013-10-15

    The adsorption of Cd(II), Zn(II) and Ni(II) from aqueous solutions in binary and ternary component systems by tourmaline was investigated. Kinetic data were accurately fitted to pseudo-second order and internal diffusion models, which indicated that the adsorption of heavy metals occurred on the interior surface of the sorbent and internal diffusion was the controlling mechanism during heavy metal ion adsorption but was not the only rate-controlling step. Additionally, tourmaline had a very good adsorption capacity for Cd(II), Zn(II) and Ni(II) in multi-component aqueous solutions at strongly acidic pH values (in contrast to industrial wastewater pH values). This good adsorption capacity is attributed to the fact that tourmaline can automatically adjust the pH values of acidic (except pH 2.0 and 3.0), neutral or alkaline aqueous solutions to 6.0. Adsorption isotherms and separation factors showed that tourmaline displays a high selectivity toward one metal in a two-component or a three-component system with an affinity order of Cd(II) > Zn(II) > Ni(II). Thermodynamic parameters indicated that heavy metal adsorption was feasible, spontaneous, and endothermic. Therefore, tourmaline should be explored as a material for removing pollutants from the strongly acidic wastewater. PMID:23851318

  13. Current-driven domain wall motion due to volume spin transfer torque in Co/Ni multilayer systems on Au underlayer

    NASA Astrophysics Data System (ADS)

    Ryu, Kwang-Su; Yang, See-Hun; Thomas, Luc; Parkin, Stuart

    2016-09-01

    We have studied the current-induced domain wall (CIDW) dynamics in perpendicularly magnetized Co/Ni multilayers deposited on Au underlayer, where the conventional spin transfer torque governs the domain wall dynamics, by the Kerr microscope. It is found that the DW angle tilting following Oersted field profile plays an important role in domain wall (DW) motion at high current density J by decreasing DW velocity with the increasing J, while distorting its DW morphology. Also we find that the DW pinning becomes pronounced as the anisotropy decreases by increasing number of Co/Ni repeats. Most remarkably, the DW tilting angle changes its sign by inserting ultrathin Pt layer between Au and Co layer, which suggests that the Dzyaloshinskii–Moriya interaction and spin Hall effect induces opposite effect in DW tilting. Our findings can be of use for application of CIDW to spintronics with perpendicularly magnetized systems.

  14. Phase relationships in the quaternary systems MS-Cr/sub 2/S/sub 3/-In/sub 2/S/sub 3/ (M=Mn,Fe,Co,Ni), miscibility gaps in spinel solid solutons

    SciTech Connect

    Lutz, H.D.; Jung, M.; Wussow, K.

    1986-02-01

    The phase diagrams of the quanternary systems MS-Cr/sub 2/S/sub 3/-In/sub 2/S/sub 3/ wth M=MN,Fe,Ni were studied by x-ray powder photographs of quenched samples. In the quasibinary sections MnIn/sub 2/S/sub 4/-MnCr/sub 2/S/sub 4/ and FeIn/sub 2/S/sub 4/-FeCr/sub 2/S/sub 4/, immiscibility domes exist below 800 and 850/sup 0/C, respectively. At higher temperatures complete series of spinel type solid solutions are formed, which can be quenched to ambient temperature without decomposition. In the NiIn/sub 2/S/sub 4/-NiCr/sub 2/S/sub 4/ section, spinel-type solid solutions are formed in the range from NiIn/sub 2/S/sub 4/ to NiCr/sub 1.7/In/sub 0.3/S/sub 4/ (800/sup 0/C). At lower temperatures decomposition to chromium and indium rich spinel solid solutions occurs. The phase width of Cr/sub 3/S/sub 4/ type NiCr/sub 2/S/sub 4/ is very small. The system NiCr/sub 2/S/sub 4/-In/sub 2/S/sub 3/ is similar to the NiCr/sub 2/S/sub 4/-NiIn/sub 2/S/sub 4/ system, but probably no quasibinary. The fir spectra of the NiCr/sub 2-2X/In/sub 2X/S/sub 4/ (and NiCr/sub 2-2X/Ga/sub 2X/S/sub 4/) solid solutions reveal that the hypothetical spinel NiCr/sub 2/S/sub 4/ is probably metallic. In the sections CoS-In/sub 2/S/sub 3/ and NiS-In/sub 2/S/sub 3/, spinel type solid solutions are formed in the range from In/sub 2/S/sub 3/ to MIN/sub 2/S/sub 4/. The unusually small reaction rates of the solid state equilibration reaction are discussed in terms of the Gibb's enthalpies of forming the spinel mixed crystals and the kinetic retardation of such reactions.

  15. Material properties of perovskites in the quasi-ternary system LaFeO3-LaCoO3-LaNiO3

    NASA Astrophysics Data System (ADS)

    Tietz, F.; Arul Raj, I.; Ma, Q.; Baumann, S.; Mahmoud, A.; Hermann, R. P.

    2016-05-01

    An overview is presented on the variation of electrical conductivity, oxygen permeation, and thermal expansion coefficient as a function of the composition of perovskites in the quasi-ternary system LaFeO3-LaCoO3-LaNiO3. Powders of thirteen nominal perovskite compositions were synthesized under identical conditions by the Pechini method. The powder X-ray diffraction data of two series, namely La(Ni0.5Fe0.5)1-xCoxO3 and LaNi0.5-xFexCo0.5O3, are presented after the powders had been sintered at 1100 °C for 6 h in air. The measurements revealed a rhombohedral structure for all compositions except LaNi0.5Fe0.5O3 for which 60% rhombohedral and 40% orthorhombic phase was found. The maximum DC electrical conductivity value of the perovskites at 800 °C was 1229 S cm-1 for the composition LaCoO3 and the minimum was 91 S cm-1 for the composition LaCo0.5Fe0.5O3. The oxygen permeation of samples with promising conductivities at 800 °C was one order of magnitude lower than that of La0.6Sr0.4Co0.8Fe0.2O3 (LSCF). The highest value of 0.017 ml cm-2 min-1 at 950 °C was obtained with LaNi0.5Co0.5O3. The coefficients of thermal expansion varied in the range of 13.2×10-6 K-1 and 21.9×10-6 K-1 for LaNi0.5Fe0.5O3 and LaCoO3, respectively. 57Fe Mössbauer spectroscopy was used as probe for the oxidation states, local environment and magnetic properties of iron ions as a function of chemical composition. The substitution had a great influence on the chemical properties of the materials.

  16. Material properties of perovskites in the quasi-ternary system LaFeO3 LaCoO3 LaNiO3

    DOE PAGESBeta

    Tietz, Frank; Raj, I. Arul; Ma, Q.; Baumann, S.; Mahmoud, A.; Hermann, Raphael P

    2016-01-01

    An overview is presented on the variation of electrical conductivity, oxygen permeation, oxygen surface exchange and thermal expansion coefficient as a function of the composition of perovskites in the quasi-ternary system LaFeO3-LaCoO3-LaNiO3. Powders of thirteen nominal perovskite compositions were synthesized under identical conditions by the Pechini method. The powder X-ray diffraction data of two series, namely La(Ni0.5Fe0.5)1-xCoxO3 and LaNi0.5- xFexCo0.5O3, are presented after the powders had been sintered at 1100 C for 6 h in air. The measurements revealed a rhombohedral structure for all compositions except LaNi0.5Fe0.5O3 for which 60% rhombohedral and 40% orthorhombic phase was found. The maximum DCmore » electrical conductivity value of the perovskites at 800 C was 1229 S cm-1 for the composition LaCoO3 and the minimum was 91 S cm-1 for the composition LaCo0.5Fe0.5O3. The oxygen permeation of samples with promising conductivities at 800 C was one order of magnitude lower than that of La0.6Sr0.4Co0.8Fe0.2O3 (LSCF). The highest value of 0.017 ml cm-2 min-1 at 950 C was obtained with LaNi0.5Co0.5O3. The coefficients of thermal expansion varied in the range of 13.2 x 10-6 K-1 and 21.9 x 10-6 K-1 for LaNi0.5Fe0.5O3 and LaCoO3, respectively. 57Fe M ssbauer spectroscopy was used as probe for the oxidation states, local environment and magnetic properties of iron ions as a function of chemical composition. The substitution had a great influence on the chemical properties of the materials.« less

  17. Material properties of perovskites in the quasi-ternary system LaFeO3–LaCoO3–LaNiO3

    DOE PAGESBeta

    Tietz, F.; Arul Raj, I.; Ma, Q.; Baumann, S.; Mahmoud, A.; Hermann, R. P.

    2016-02-02

    We present an overview on the variation of electrical conductivity, oxygen permeation, oxygen surface exchange and thermal expansion coefficient as a function of the composition of perovskites in the quasi-ternary system LaFeO3–LaCoO3–LaNiO3. Powders of thirteen nominal perovskite compositions were synthesized under identical conditions by the Pechini method. The powder X-ray diffraction data of two series, namely La(Ni0.5Fe0.5)1-xCoxO3 and LaNi0.5- xFexCo0.5O3, are presented after the powders had been sintered at 1100 C for 6 h in air. The measurements revealed a rhombohedral structure for all compositions except LaNi0.5Fe0.5O3 for which 60% rhombohedral and 40% orthorhombic phase was found. Moreover, the maximummore » DC electrical conductivity value of the perovskites at 800 C was 1229 S cm-1 for the composition LaCoO3 and the minimum was 91 S cm-1 for the composition LaCo0.5Fe0.5O3. The oxygen permeation of samples with promising conductivities at 800 C was one order of magnitude lower than that of La0.6Sr0.4Co0.8Fe0.2O3 (LSCF). The highest value of 0.017 ml cm-2 min-1 at 950 C was obtained with LaNi0.5Co0.5O3. The coefficients of thermal expansion varied in the range of 13.2 x 10-6 K-1 and 21.9 x 10-6 K-1 for LaNi0.5Fe0.5O3 and LaCoO3, respectively. 57Fe M ssbauer spectroscopy was used as probe for the oxidation states, local environment and magnetic properties of iron ions as a function of chemical composition. Ultimately, the substitution had a great influence on the chemical properties of the materials.« less

  18. Material properties of perovskites in the quasi-ternary system LaFeO3 LaCoO3 LaNiO3

    SciTech Connect

    Tietz, Frank; Raj, I. Arul; Ma, Q.; Baumann, S.; Mahmoud, A.; Hermann, Raphael P

    2016-01-01

    An overview is presented on the variation of electrical conductivity, oxygen permeation, oxygen surface exchange and thermal expansion coefficient as a function of the composition of perovskites in the quasi-ternary system LaFeO3-LaCoO3-LaNiO3. Powders of thirteen nominal perovskite compositions were synthesized under identical conditions by the Pechini method. The powder X-ray diffraction data of two series, namely La(Ni0.5Fe0.5)1-xCoxO3 and LaNi0.5- xFexCo0.5O3, are presented after the powders had been sintered at 1100 C for 6 h in air. The measurements revealed a rhombohedral structure for all compositions except LaNi0.5Fe0.5O3 for which 60% rhombohedral and 40% orthorhombic phase was found. The maximum DC electrical conductivity value of the perovskites at 800 C was 1229 S cm-1 for the composition LaCoO3 and the minimum was 91 S cm-1 for the composition LaCo0.5Fe0.5O3. The oxygen permeation of samples with promising conductivities at 800 C was one order of magnitude lower than that of La0.6Sr0.4Co0.8Fe0.2O3 (LSCF). The highest value of 0.017 ml cm-2 min-1 at 950 C was obtained with LaNi0.5Co0.5O3. The coefficients of thermal expansion varied in the range of 13.2 x 10-6 K-1 and 21.9 x 10-6 K-1 for LaNi0.5Fe0.5O3 and LaCoO3, respectively. 57Fe M ssbauer spectroscopy was used as probe for the oxidation states, local environment and magnetic properties of iron ions as a function of chemical composition. The substitution had a great influence on the chemical properties of the materials.

  19. Hydrogen atom distribution and hydrogen induced site depopulation for the La{sub 2-x}Mg{sub x}Ni{sub 7}-H system

    SciTech Connect

    Guzik, Matylda N.; Hauback, Bjorn C.; Yvon, Klaus

    2012-02-15

    opposed to nine proposed for La{sub 1.5}Mg{sub 0.5}Ni{sub 7}D{sub 8.9(9.1)}. The reported four remaining deuterium atom positions in La{sub 1.5}Mg{sub 0.5}Ni{sub 7}D{sub 8.9(9.1)} were not found in the investigated La{sub 1.63}Mg{sub 0.37}Ni{sub 7}D{sub 8.8}. The five Ni atoms have deuterium among their nearest neighbors, which surround them in a way similar to configurations observed in some complex transition metal hydrides and already reported for metallic hydrides. In the presented deuterium-rich phase, deformed tetrahedron, rigid trigonal pyramids as well as disordered and deformed saddle-like configuration are observed. Highlights: Black-Right-Pointing-Pointer Alpha- and beta-phase for La{sub 2-x}Mg{sub x}Ni{sub 7}-H system have been characterized. Black-Right-Pointing-Pointer Five different interstitial sites are occupied by deuterium/hydrogen atoms in the beta-phase. Black-Right-Pointing-Pointer One D/H site has been determined in the alpha-phase. Black-Right-Pointing-Pointer Deuterium/hydrogen induced site depopulation during phase transformation is observed. Black-Right-Pointing-Pointer Ni atoms tend to have tetrahedral-like D/H atom coordination.

  20. A novel asymmetric di-Ni(II) system as a highly efficient functional model for phosphodiesterase: synthesis, structures, physicochemical properties and catalytic kinetics.

    PubMed

    Ren, Yan-wei; Lu, Jia-xian; Cai, Bo-wei; Shi, Da-bin; Jiang, Huan-feng; Chen, Jun; Zheng, De; Liu, Bin

    2011-02-14

    A novel asymmetric phenol-based 'end-off' dinucleating ligand 2-{[(2-piperidylmethyl)amino]methyl}-4-bromo-6-[(1-methylhomopiperazine-4-yl)methyl]phenol (HL) and three dinuclear nickel(II) complexes, [Ni₂L(μ-OH)] (ClO₄)₂ (1), [Ni₂L(DNBA)₂(CH₃CN)₂]BPh₄ (2) and [Ni₂L(BPP)₂(CH₃CN)₂]BPh₄ (3) have been synthesized and characterized by a variety of techniques including: NMR, infrared and UV-vis spectroscopies, mass spectrometry, elemental analysis, molar conductivity, thermal analysis, magnetochemistry and single-crystal X-ray diffractometry. The UV-vis spectrum of complex 1 exhibits a strong peak at 510 nm, a characteristic absorption of a d-d transition of the square-planar four-coordinated Ni(II) center. Utilizing this feature, the stepwise formation of mono- and dinickel centers in solution can be monitored. Phosphodiesterase activity of a dinuclear Ni(II) system (complex 1), formed in situ by a 2 : 1 mixture of Ni(2+) ions and the ligand HL, was investigated using bis(4-nitrophenyl)phosphate (BNPP) as the substrate. The pH dependence of the BNPP cleavage in water-ethanol (1 : 1, v/v) reveals a bell-shaped pH-k(obs) profile with an optimum at about pH 8.3 which is parallel to the formation of the dinuclear species [Ni₂L(μ-OH)](2+), according to the increase of the peak at 510 nm in the UV-vis absorption spectrum . These studies reveal that the di-Ni(II) system shows the highest catalytic activity reported so far, with an acceleration rate 1.28 × 10⁷ times faster than the uncatalyzed reaction. The bridging hydroxyl group in [Ni₂L(μ-OH)](2+) is responsible for the hydrolysis reaction. The possible mechanism for the BNPP cleavage promoted by di-Ni(II) system is proposed on the basis of kinetic and spectral analyses. This study provides a less common example of the asymmetric phosphodiesterase model, which is like the active sites of most native metallohydrolases. PMID:21180701

  1. Influence of Friction Resistance on Expression of Superelastic Properties of Initial NiTi Wires in "Reduced Friction" and Conventional Bracket Systems.

    PubMed

    Reznikov, Natalie; Har-Zion, Gilad; Barkana, Idit; Abed, Yosef; Redlich, Meir

    2010-01-01

    Objectives. The aim of this study was to assess the influence of resistance to sliding on expression of superelastic properties of NiTi wires. Methods and Materials. A three-point bending test was performed for 0.014 NiTi wire engaged in self-ligating (Damon, SmartClip, In-Ovation) and conventional brackets (Victory) ligated with regular and reduced friction modules (Slide). The wire was deflected in the buccal direction and allowed to straighten. The maximum load, unloading plateau and unloading capacity were registered. Results. The lowest activation load was required in the active self-ligating group (In-Ovation 2.2 ± 0.4 N) and reduced friction module group (Victory/Slide 2.9 ± 0.4 N), followed by the passive self-ligating systems (Damon 3.6 ± 0.7 N, SmartClip 3.7 ± 0.4 N). Higher activation load was obtained in the conventionally ligated group (Victory/module 4.5 ± 0.4 N). Unloading plateau phase with the load magnitude ranging from 1.27 ± 0.4 N (In-Ovation) to 1.627 ± 0.4 N (Slide) was distinct in all groups but one (Victory). Conclusions. Higher friction at flanking points reduces the net force delivered by the wire. Unloading plateau phase of NiTi load-deflection curve disappears in the conventionally ligated group thus indicating to an incomplete expression of NiTi superelastic properties. A rigid passive bracket clip amplifies resistance to sliding in an active configuration and produces a permanent deflection of the wire. PMID:20981153

  2. Phase Equilibria of the Sn-Ni-V System: The 980°C Isothermal Section and the Sn-Rich Corner at 600°C and 300°C

    NASA Astrophysics Data System (ADS)

    Wu, Changjun; Su, Xuping; Peng, Haoping; Liu, Ya; Tu, Hao; Wang, Jianhua

    2015-10-01

    Ternary Sn-Ni-V alloys were prepared and annealed at 980°C, 600°C, and 300°C for 15, 60 and 60 days, respectively. The annealed alloys were metallographically examined and the equilibrium phases formed were identified on the basis of determination of composition and x-ray diffraction analysis. The isothermal region of the ternary Sn-Ni-V system at 980°C was studied. Nine three-phase regions and more than 20 conjugate lines were detected at 980°C. The range of composition of VNi2Sn at 980°C spans 24.5-59.2 at.% V, 52.1-25.5 at.% Ni, and 15.3-23.4 at.% Sn. Its lattice constant increases with increasing V content. A sharp increase near 40.4 at.% V is indicative of a second-order transition. It is believed that atomic site occupation changed when the V content was >40.4 at.%. The maximum solubility of V in Ni3Sn2 can reach 23.3 at.%; that in Ni3Sn is below 0.6 at.%. Up to 3.4 at.% Ni dissolves in V3Sn. The Sn-rich corner of the Sn-Ni-V system at 600°C and 300°C was also investigated experimentally. The solubility of Ni in VSn2 and V in Ni3Sn4 at 600°C and 300°C are both less than 0.5 at.%.

  3. Effect of pressure on magnetic properties of the fluctuating-valence system Ce(Ni1-xCux)5

    NASA Astrophysics Data System (ADS)

    Grechnev, G. E.; Logosha, A. V.; Panfilov, A. S.; Svechkarev, I. V.; Musil, O.; Svoboda, P.

    2011-10-01

    The magnetic susceptibility χ of isostructural Ce(Ni1-xCux)5 alloys (0 ≤ x ≤ 0.9) is studied as a function of hydrostatic pressure up to 2 kbar for fixed temperatures of 77.3 and 300 K. The pronounced effect of pressure on the susceptibility is negative in sign and depends nonmonotonically on the Cu content, with a sharp maximum at x ˜ 0.4. The experimental results are discussed in terms of a valence instability of Ce ions in these alloys. The major contributions to χ and their volume dependences are calculated ab initio in a local spin density approximation for the reference compound CeNi5, and appear to be in close agreement with experimental data.

  4. Assessing the Effects of Radiation Damage on Ni-base Alloys for the Prometheus Space Reactor System

    SciTech Connect

    T Angeliu; J Ward; J Witter

    2006-04-04

    Ni-base alloys were considered for the Prometheus space reactor pressure vessel with operational parameters of {approx}900 K for 15 years and fluences up to 160 x 10{sup 20} n/cm{sup 2} (E > 0.1 MeV). This paper reviews the effects of irradiation on the behavior of Ni-base alloys and shows that radiation-induced swelling and creep are minor considerations compared to significant embrittlement with neutron exposure. While the mechanism responsible for radiation-induced embrittlement is not fully understood, it is likely a combination of helium embrittlement and solute segregation that can be highly dependent on the alloy composition and exposure conditions. Transmutation calculations show that detrimental helium levels would be expected at the end of life for the inner safety rod vessel (thimble) and possibly the outer pressure vessel, primarily from high energy (E > 1 MeV) n,{alpha} reactions with {sup 58}Ni. Helium from {sup 10}B is significant only for the outer vessel due to the proximity of the outer vessel to the BeO control elements. Recommendations for further assessments of the material behavior and methods to minimize the effects of radiation damage through alloy design are provided.

  5. Assessing the Effects of Radiation Damage on Ni-base Alloys for the Prometheus Space Reactor System

    SciTech Connect

    T. Angeliu

    2006-01-19

    Ni-base alloys were considered for the Prometheus space reactor pressure vessel with operational parameters of {approx}900 K for 15 years and fluences up to 160 x 10{sup 20} n/cm{sup 2} (E > 0.1 MeV). This paper reviews the effects of irradiation on the behavior of Ni-base alloys and shows that radiation-induced swelling and creep are minor considerations compared to significant embrittlement with neutron ,exposure. While the mechanism responsible for radiation-induced embrittlement is not fully understood, it is likely a combination of helium embrittlement and solute segregation that can be highly dependent on the alloy composition and exposure conditions. Transmutation calculations show that detrimental helium levels would be expected at the end of life for the inner safety rod vessel (thimble) and possibly the outer pressure vessel, primarily from high energy (E > 1 MeV) n,{alpha} reactions with {sup 58}Ni. Helium from {sup 10}B is significant only for the outer vessel due to the proximity of the outer vessel to the Be0 control elements. Recommendations for further assessments of the material behavior and methods to minimize the effects of radiation damage through alloy design are provided.

  6. CEMS and SEM studies of the ion-beam mixed Ni-Sn and Al-Sn systems

    NASA Astrophysics Data System (ADS)

    Czako-Nagy, I.; Fedrizzi, L.; Gratton, L. M.; Principi, G.; Vertes, A.

    1986-02-01

    Metallic119Sn was vapour deposited on Al and Ni substrates to form layers about 40nm thick and subsequently irradiated with 100keV Xe+ at fluences 1, 5 and 10·1015 Xe+/cm2. Irradiation with 100keV N+ at 5·1016N+/cm2 fluence was also accomplished on an Al sample on which a layer of 100nm119Sn was previously electrodeposited. Surface evolution of the deposited layers due to irradiation has been observed by SEM and loss of Tin due to sputtering has been evidenced by EDX microanalysis. Changes of chemical structure at the irradiated surfaces have been followed by CEMS: β-Sn, SnO, SnAl2O4, SnO2 and SnAl2O5 or β-Sn, dissolved Tin in Nickel, SnO2, Ni3Sn and Ni3Sn2 phases were recognized on the surface of Aluminium and Nickel substrates respectively.

  7. Joining of Ni-TiC FGM and Ni-Al Intermetallics by Centrifugal Combustion Synthesis

    NASA Astrophysics Data System (ADS)

    Ohmi, Tatsuya; Mizuma, Kiminori; Matsuura, Kiyotaka; Iguchi, Manabu

    2008-02-01

    A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermet and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.

  8. Joining of Ni-TiC FGM and Ni-Al Intermetallics by Centrifugal Combustion Synthesis

    SciTech Connect

    Ohmi, Tatsuya; Matsuura, Kiyotaka; Iguchi, Manabu; Mizuma, Kiminori

    2008-02-15

    A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermet and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.

  9. The initial errors that induce a significant "spring predictability barrier" for El Niño events and their implications for target observation: results from an earth system model

    NASA Astrophysics Data System (ADS)

    Duan, Wansuo; Hu, Junya

    2015-08-01

    The National Center for Atmospheric Research Community Earth System Model is used to study the "spring predictability barrier" (SPB) problem for El Niño events from the perspective of initial error growth. By conducting perfect model predictability experiments, we obtain two types of initial sea temperature errors, which often exhibit obvious season-dependent evolution and cause a significant SPB when predicting the onset of El Niño events bestriding spring. One type of initial errors possesses a sea surface temperature anomaly (SSTA) pattern with negative anomalies in the central-eastern equatorial Pacific, plus a basin-wide dipolar subsurface temperature anomaly pattern with negative anomalies in the upper layers of the eastern equatorial Pacific and positive anomalies in the lower layers of the western equatorial Pacific. The other type consists of an SSTA component with positive anomalies over the southeastern equatorial Pacific, plus a large-scale zonal dipole pattern of the subsurface temperature anomaly with positive anomalies in the upper layers of the eastern equatorial Pacific and negative anomalies in the lower layers of the central-western equatorial Pacific. Both exhibit a La Niña-like evolving mode and cause an under-prediction for Niño-3 SSTA of El Niño events. For the former initial error type, the resultant prediction errors grow in a manner similar to the behavior of the growth phase of La Niña; while for the latter initial error type, they experience a process that is similar to El Niño decay and transition to a La Niña growth phase. Both two types of initial errors cause negative prediction errors of Niño-3 SSTA for El Niño events. The prediction errors for Niño-3 SSTA are mainly due to the contribution of initial sea temperature errors in the large-error-related regions in the upper layers of the eastern tropical Pacific and/or in the lower layers of the western tropical Pacific. These regions may represent ``sensitive areas'' for El

  10. The initial errors that induce a significant "spring predictability barrier" for El Niño events and their implications for target observation: results from an earth system model

    NASA Astrophysics Data System (ADS)

    Duan, Wansuo; Hu, Junya

    2016-06-01

    The National Center for Atmospheric Research Community Earth System Model is used to study the "spring predictability barrier" (SPB) problem for El Niño events from the perspective of initial error growth. By conducting perfect model predictability experiments, we obtain two types of initial sea temperature errors, which often exhibit obvious season-dependent evolution and cause a significant SPB when predicting the onset of El Niño events bestriding spring. One type of initial errors possesses a sea surface temperature anomaly (SSTA) pattern with negative anomalies in the central-eastern equatorial Pacific, plus a basin-wide dipolar subsurface temperature anomaly pattern with negative anomalies in the upper layers of the eastern equatorial Pacific and positive anomalies in the lower layers of the western equatorial Pacific. The other type consists of an SSTA component with positive anomalies over the southeastern equatorial Pacific, plus a large-scale zonal dipole pattern of the subsurface temperature anomaly with positive anomalies in the upper layers of the eastern equatorial Pacific and negative anomalies in the lower layers of the central-western equatorial Pacific. Both exhibit a La Niña-like evolving mode and cause an under-prediction for Niño-3 SSTA of El Niño events. For the former initial error type, the resultant prediction errors grow in a manner similar to the behavior of the growth phase of La Niña; while for the latter initial error type, they experience a process that is similar to El Niño decay and transition to a La Niña growth phase. Both two types of initial errors cause negative prediction errors of Niño-3 SSTA for El Niño events. The prediction errors for Niño-3 SSTA are mainly due to the contribution of initial sea temperature errors in the large-error-related regions in the upper layers of the eastern tropical Pacific and/or in the lower layers of the western tropical Pacific. These regions may represent ``sensitive areas'' for El

  11. The initial errors that induce a significant "spring predictability barrier" for El Niño events and their implications for target observation: results from an earth system model

    NASA Astrophysics Data System (ADS)

    Hu, Junya; Duan, Wansuo

    2016-04-01

    The National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM) is used to study the "spring predictability barrier" (SPB) problem for El Niño events from the perspective of initial error growth. By conducting perfect model predictability experiments, we obtain two types of initial sea temperature errors, which often exhibit obvious season-dependent evolution and cause a significant SPB when predicting the onset of El Niño events bestriding spring. One type of initial errors possesses a sea surface temperature anomaly (SSTA) pattern with negative anomalies in the central-eastern equatorial Pacific, plus a basin-wide dipolar subsurface temperature anomaly pattern with negative anomalies in the upper layers of the eastern equatorial Pacific and positive anomalies in the lower layers of the western equatorial Pacific. The other type consists of an SSTA component with positive anomalies over the southeastern equatorial Pacific, plus a large-scale zonal dipole pattern of the subsurface temperature anomaly with positive anomalies in the upper layers of the eastern equatorial Pacific and negative anomalies in the lower layers of the central-western equatorial Pacific. Both exhibit a La Niña-like evolving mode and cause an under-prediction for Niño-3 SSTA of El Niño events. For the former initial error type, the resultant prediction errors grow in a manner similar to the behavior of the growth phase of La Niña; while for the latter initial error type, they experience a process that is similar to El Niño decay and transition to a La Niña growth phase. Both two types of initial errors cause negative prediction errors of Niño-3 SSTA for El Niño events. The prediction errors for Niño-3 SSTA are mainly due to the contribution of initial sea temperature errors in the large-error-related regions in the upper layers of the eastern tropical Pacific and/or in the lower layers of the western tropical Pacific. These regions may represent ''sensitive

  12. Effects of alloying and local order in AuNi contacts for Ohmic radio frequency micro electro mechanical systems switches via multi-scale simulation

    NASA Astrophysics Data System (ADS)

    Gaddy, Benjamin E.; Kingon, Angus I.; Irving, Douglas L.

    2013-05-01

    Ohmic RF-MEMS switches hold much promise for low power wireless communication, but long-term degradation currently plagues their reliable use. Failure in these devices occurs at the contact and is complicated by the fact that the same asperities that bear the mechanical load are also important to the flow of electrical current needed for signal processing. Materials selection holds the key to overcoming the barriers that prevent widespread use. Current efforts in materials selection have been based on the material's (or alloy's) ability to resist oxidation as well as its room-temperature properties, such as hardness and electrical conductivity. No ideal solution has yet been found via this route. This may be due, in part, to the fact that the in-use changes to the local environment of the asperity are not included in the selection criteria. For example, Joule heating would be expected to raise the local temperature of the asperity and impose a non-equilibrium thermal gradient in the same region expected to respond to mechanical actuation. We propose that these conditions should be considered in the selection process, as they would be expected to alter mechanical, electrical, and chemical mechanisms in the vicinity of the surface. To this end, we simulate the actuation of an Ohmic radio frequency micro electro mechanical systems switch by using a multi-scale method to model a current-carrying asperity in contact with a polycrystalline substrate. Our method couples continuum solutions of electrical and thermal transport equations to an underlying molecular dynamics simulation. We present simulations of gold-nickel asperities and substrates in order to evaluate the influence of alloying and local order on the early stages of contact actuation. The room temperature response of these materials is compared to the response of the material when a voltage is applied. Au-Ni interactions are accounted for through modification of the existing Zhou embedded atom method

  13. Predictability of the Ningaloo Niño/Niña.

    PubMed

    Doi, Takeshi; Behera, Swadhin K; Yamagata, Toshio

    2013-01-01

    The seasonal prediction of the coastal oceanic warm event off West Australia, recently named the Ningaloo Niño, is explored by use of a state-of-the-art ocean-atmosphere coupled general circulation model. The Ningaloo Niño/Niña, which generally matures in austral summer, is found to be predictable two seasons ahead. In particular, the unprecedented extreme warm event in February 2011 was successfully predicted 9 months in advance. The successful prediction of the Ningaloo Niño is mainly due to the high prediction skill of La Niña in the Pacific. However, the model deficiency to underestimate its early evolution and peak amplitude needs to be improved. Since the Ningaloo Niño/Niña has potential impacts on regional societies and industries through extreme events, the present success of its prediction may encourage development of its early warning system. PMID:24100593

  14. The evaluation of chemical wear on single crystal diamond tools while diamond turning a binary Cu-Ni alloy system

    NASA Astrophysics Data System (ADS)

    Browy, Eric Calmer

    The current work describes the evaluation of chemical wear on diamond tools while diamond turning copper nickel alloys of varying composition. The primary goal of my project is to quantify the chemical wear of single crystal diamond tools while diamond turning Cu-Ni alloys of different compositions. Pure copper is commonly understood to give negligible tool wear, while pure nickel is reported to give rapid wear. The Cu-Ni equilibrium phase diagram shows a single phase at all compositions. The development and testing of a method to evaluate and quantify diamond tool wear is also described within the current work. The method chosen for development is the metrology of the progressive edge recession of the diamond. A procedure of progressive plunge cuts into an ultra-bright acid copper before and after diamond turning of the workpiece takes a snapshot of the edge of the diamond tool as the cutting distance increases. An algorithm executed in MatLabRTM displays the residual tool wear after removal of the initial diamond tool geometry. A theoretical model has been developed to predict the chemical diamond tool wear and the results will be shown within the body of work.

  15. Thermodynamic evaluation of small-scale systems with biomass gasifiers, solid oxide fuel cells with Ni/GDC anodes and gas turbines

    NASA Astrophysics Data System (ADS)

    Aravind, P. V.; Woudstra, T.; Woudstra, N.; Spliethoff, H.

    Thermodynamic calculations were carried out to evaluate the performance of small-scale gasifier-SOFC-GT systems of the order of 100 kW. Solid Oxide Fuel Cells (SOFCs) with Nickel/Gadolinia Doped Ceria (Ni/GDC) anodes were considered. High system electrical efficiencies above 50% are achievable with these systems. The results obtained indicate that when gas cleaning is carried out at temperatures lower than gasification temperature, additional steam may have to be added to biosyngas in order to avoid carbon deposition. To analyze the influence of gas cleaning at lower temperatures and steam addition on system efficiency, additional system calculations were carried out. It is observed that steam addition does not have significant impact on system electrical efficiency. However, generation of additional steam using heat from gas turbine outlet decreases the thermal energy and exergy available at the system outlet thereby decreasing total system efficiency. With the gas cleaning at atmospheric temperature, there is a decrease in the electrical efficiency of the order of 4-5% when compared to the efficiency of the systems working with intermediate to high gas-cleaning temperatures.

  16. The Ni-rich part of the Al–Ge–Ni phase diagram

    PubMed Central

    Jandl, Isabella; Reichmann, Thomas L.; Richter, Klaus W.

    2013-01-01

    The Ni-rich part of the ternary system Al–Ge–Ni (xNi > 50 at.%) was investigated by means of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). The two isothermal sections at 550 °C and 700 °C were determined. Within these two sections a new ternary phase, designated as τ4, AlyGe9−yNi13±x (hP66, Ga3Ge6Ni13-type) was detected and investigated by single crystal X-ray diffraction. Another ternary low temperature phase, τ5, was found only in the isothermal section at 550 °C around the composition AlGeNi4. This compound was found to crystallise in the Co2Si type structure (oP12, Pnma). The structure was identified by Rietveld refinement of powder data. The NiAs type (B8) phase based on binary Ge3Ni5 revealed an extended solid solubility of Al and the two isotypic compounds AlNi3 and GeNi3 form a complete solid solution. Based on DTA results, six vertical sections at 55, 60, 70, 75 and 80 at.% Ni and at a constant Al:Ni ratio of 1:3 were constructed. Furthermore, the liquidus surface projection and the reaction scheme (Scheil diagram) were completed by combining our results with previous results from the Ni-poor part of the phase diagram. Six invariant ternary reactions were identified in the Ni-rich part of the system. PMID:27087754

  17. Formation of dioxins on NiO and NiCl2 at different oxygen concentrations.

    PubMed

    Yang, Jie; Yan, Mi; Li, Xiaodong; Lu, Shengyong; Chen, Tong; Yan, Jianhua; Olie, Kees; Buekens, Alfons

    2015-08-01

    Model fly ash (MFA) containing activated carbon (AC) as source of carbon, NaCl as source of chlorine and either NiO or NiCl2 as de novo catalyst, was heated for 1h at 350 °C in a carrier gas flow composed of N2 containing 0, 6, 10, and 21 vol.% O2, to study the formation of PCDD/Fs (dioxins) and its dependence on oxygen. The formation of PCDD/Fs with NiCl2 was stronger by about two orders of magnitude than with NiO and the difference augmented with rising oxygen concentration. The thermodynamics of the NiO-NiCl2 system were represented, X-ray absorption near edge structural (XANES) spectroscopy allowed to probe the state of oxidation of the nickel catalyst in the MFA and individual metal species were distinguished using the LCF (Linear combination fitting) technique: thus three supplemental nickel compounds (Ni2O3, Ni(OH)2, and Ni) were found in the fly ash. Principal Component Analysis (PCA) indicates that both Ni2O3 and NiCl2 probably played an important role in the formation of PCDD/Fs. PMID:25951618

  18. Corrosion performance of bi-layer Ni/Cr2C3-NiCr HVAF thermal spray coating

    NASA Astrophysics Data System (ADS)

    Sadeghimeresht, E.; Markocsan, N.; Nylén, P.; Björklund, S.

    2016-04-01

    The corrosion behavior of three HVAF thermal spray coating systems (A: single-layer Ni, B: single-layer Cr2C3-NiCr coatings, and C: bi-layer Ni/Cr2C3-NiCr coating) was comparatively studied using immersion, salt spray, and electrochemical tests. Polarization and EIS results showed that the corrosion behavior of Cr2C3-NiCr coatings in 3.5 wt.% NaCl solution was significantly improved by adding the intermediate layer of Ni. It was illustrated that the polarization resistance of the bi-layer Ni/Cr2C3-NiCr and single-layer Cr2C3-NiCr coatings were around 194 and 38 kΩ cm2, respectively. Microstructure analysis revealed that the bond coating successfully prevented the corrosion propagation toward the coating.

  19. Effects of PEG-Induced Water Deficit in Solanum nigrum on Zn and Ni Uptake and Translocation in Split Root Systems.

    PubMed

    Feller, Urs; Anders, Iwona; Wei, Shuhe

    2015-01-01

    Drought strongly influences root activities in crop plants and weeds. This paper is focused on the performance of the heavy metal accumulator Solanum nigrum, a plant which might be helpful for phytoremediation. The water potential in a split root system was decreased by the addition of polyethylene glycol (PEG 6000). Rubidium, strontium and radionuclides of heavy metals were used as markers to investigate the uptake into roots, the release to the shoot via the xylem, and finally the basipetal transport via the phloem to unlabeled roots. The uptake into the roots (total contents in the plant) was for most makers more severely decreased than the transport to the shoot or the export from the shoot to the unlabeled roots via the phloem. Regardless of the water potential in the labeling solution, (63)Ni and (65)Zn were selectively redistributed within the plant. From autoradiographs, it became evident that (65)Zn accumulated in root tips, in the apical shoot meristem and in axillary buds, while (63)Ni accumulated in young expanded leaves and roots but not in the meristems. Since both radionuclides are mobile in the phloem and are, therefore, well redistributed within the plant, the unequal transfer to shoot and root apical meristems is most likely caused by differences in the cell-to-cell transport in differentiation zones without functional phloem (immature sieve tubes). PMID:27135329

  20. LDA-Prediction of New Stable Crystal Structures within=0A= the Cu-Au and Ni-Pt Alloy Systems.^*

    NASA Astrophysics Data System (ADS)

    Sanati, M.; Wang, L.; Zunger, Alex

    2002-03-01

    Cu-Au and Ni-Pt are among the best studied fcc alloy systems, exhibiting the famous L10 (AB) and L12 (A_3B) phases. We were wondering if a complete configurational search of the T=3D0 LDA total energies would reveal any unexpected phases. Total-energy calculations of ~ 30 arbitrarily chosen structures were used to construct a generalized (momentum-space) Ising Hamiltonian containing ~ 20 pair-interactions, ~ 5-10 many-body terms, as well as the long-range strain term. This Hamiltonian was tested carefully as to its ability to predict the LDA energies of other structures. Once accuracy is established, we searched the energies of all fcc configurations with 20 or less atoms per primitive cell ( ~ 2,700,000 structures), finding the known L1_0, L12 plus new, unsuspected structures. The new ground state structures are NiPt_7, Cu_2Au, and Cu_2Au_3. We find that LDA calculations of these structures confirm that they are ground states. We describe the band structure and other properties of these new structures. ^* Supported by DOE, SC-BES-DMS. abstract.

  1. Effects of PEG-Induced Water Deficit in Solanum nigrum on Zn and Ni Uptake and Translocation in Split Root Systems

    PubMed Central

    Feller, Urs; Anders, Iwona; Wei, Shuhe

    2015-01-01

    Drought strongly influences root activities in crop plants and weeds. This paper is focused on the performance of the heavy metal accumulator Solanum nigrum, a plant which might be helpful for phytoremediation. The water potential in a split root system was decreased by the addition of polyethylene glycol (PEG 6000). Rubidium, strontium and radionuclides of heavy metals were used as markers to investigate the uptake into roots, the release to the shoot via the xylem, and finally the basipetal transport via the phloem to unlabeled roots. The uptake into the roots (total contents in the plant) was for most makers more severely decreased than the transport to the shoot or the export from the shoot to the unlabeled roots via the phloem. Regardless of the water potential in the labeling solution, 63Ni and 65Zn were selectively redistributed within the plant. From autoradiographs, it became evident that 65Zn accumulated in root tips, in the apical shoot meristem and in axillary buds, while 63Ni accumulated in young expanded leaves and roots but not in the meristems. Since both radionuclides are mobile in the phloem and are, therefore, well redistributed within the plant, the unequal transfer to shoot and root apical meristems is most likely caused by differences in the cell-to-cell transport in differentiation zones without functional phloem (immature sieve tubes). PMID:27135329

  2. New complex bismuth oxides in the Bi{sub 2}O{sub 3}–NiO–Sb{sub 2}O{sub 5} system and their properties

    SciTech Connect

    Egorysheva, A.V.; Ellert, O.G.; Zubavichus, Y.V.; Gajtko, O.M.; Efimov, N.N.; Svetogorov, R.D.; Murzin, V.Yu.

    2015-05-15

    Phase equilibria in the Bi{sub 2}O{sub 3}–NiO–Sb{sub 2}O{sub 5} system have been investigated. The isothermal section of the system (650°) has been constructed. For the first time the existence of the pyrochlore structure solid solution, (Bi{sub 2−x}Ni{sub x})Ni{sub 2/3−y}Sb{sub 4/3+y}O{sub 7±δ}, x=0.1−0.35, y=0−0.1, and a new compound Bi{sub 3}Ni{sub 2/3}Sb{sub 7/3}O{sub 11} of KSbO{sub 3} structure type have been discovered. The structures and properties of these compounds were studied by XRD, XAFS, diffuse reflection spectroscopy and magnetic methods. Rietveld refinement of synchrotron radiation-based powder XRD data for pyrochlore sample of 38.43Bi{sub 2}O{sub 3}–33.0NiO–28.57Sb{sub 2}O{sub 5} composition and Bi{sub 3}Ni{sub 2/3}Sb{sub 7/3}O{sub 11} compound was performed. The best possible refinement of the positional parameters for both pyrochlore and Bi{sub 3}Ni{sub 2/3}Sb{sub 7/3}O{sub 11} structures was achieved for disordered models. Magnetic, diffuse reflection and an X-ray absorption spectroscopy study confirmed that in both compounds nickel ions are mainly in a 2+ oxidation state. According to magnetic data, Bi{sub 1.84}Ni{sub 0.16}(Ni{sub 0.63}Sb{sub 1.37})O{sub 7} pyrochlore and Bi{sub 3}Ni{sub 2/3}Sb{sub 7/3}O{sub 11} are overall paramagnetic in nature. - Graphical abstract: Isothermal section of the Bi{sub 2}O{sub 3}–NiO–Sb{sub 2}O{sub 5} system at 650 °C in air and variation of magnetic susceptibility and inverse susceptibility with temperature for Bi{sub 1.84}Ni{sub 0.79}Sb{sub 1.37}O{sub 7} pyrochlore. - Highlights: • We have constructed the isothermal section of the system Bi{sub 2}O{sub 3}–NiO–Sb{sub 2}O{sub 5}. • The boundaries of pyrochlore structure solid solution have been determined. • New Bi{sub 3}Ni{sub 2/3}Sb{sub 7/3}O{sub 11} compound of KSbO{sub 3} structure type have been discovered. • The structures were studied by means of synchrotron X-ray diffraction and XAFS. • Magnetic measurements

  3. Magnetic, structural and dc electrical resistivity studies on the divalent cobalt substituted Ni-Zn ferrite system

    NASA Astrophysics Data System (ADS)

    Siva Ram Prasad, M.; Prasad, B. B. V. S. V.; Rajesh Babu, B.

    2015-02-01

    Polycrystalline cobalt substituted Ni-Zn ferrite with composition Ni0.65-xCox Zn0.35Fe2O4(x = 0.00-0.25 insteps of 0.05) have been prepared through the conventional solid state ceramic method. Calcination and sintering have been performed in air atmosphere at 950°C and 1250°C for 4 h and 2 h, respectively followed by natural cooling to room temperature. X-ray diffraction patterns of all samples indicated the formation of the single spinel structure and the accurate lattice parameter for each composition has been determined using the Nelson-Riley error function. The increase in lattice constant on cobalt substitution is attributed to the ionic radius difference between the displaced and the substituted ion. The variation in lattice constant on incorporation of Co2+ ion indicates its solubility into the spinel lattice and noticeable modification in structural properties have been observed. The observed increase in the saturation magnetization and Curie temperature with the increase in the Co2+ substitution is due to its higher magnetic moment compared to that of Ni2+, improvement in the A-B exchange interaction mechanism and large positive contribution to magnetic anisotropy due to presence of Co2+ when they are at the octahedral sites. The observed variation in the initial magnetic permeability and the magnetic loss factor with cobalt substitution measured at a low frequency of 1 KHz have been attributed to the modification in the density, porosity, grain size and anisotropy contributions. A nearly comparable variation is observed in the room temperature dc electrical resistivity and activation energy for conduction and is attributed to the modification in structure, role and nature of cobalt ions and the microstructure aspects like grain size and pore concentration. The activation energy values in the range of 0.28 to 0.36 eV suggest a possible electron hopping. The observed changes in the structural and the magnetic and electrical properties have all been

  4. Complex band structure with ultrasoft pseudopotentials: fcc Ni and Ni nanowire

    NASA Astrophysics Data System (ADS)

    Smogunov, Alexander; Dal Corso, Andrea; Tosatti, Erio

    2003-06-01

    We generalize to magnetic transition metals the approach proposed by Choi and Ihm for calculating the complex band structure of periodic systems, a key ingredient for future calculations of conductivity of an open quantum system within the Landauer-Buttiker theory. The method is implemented with ultrasoft pseudopotentials and plane wave basis set in a DFT-LSDA ab initio scheme. As a first example, we present the complex band structure of bulk fcc Ni (which constitutes the tips of a Ni nanocontact) and monatomic Ni wire (the junction between two tips). Based on our results, we anticipate some features of the spin-dependent conductance in a Ni nanocontact.

  5. Enthalpy of mixing of liquid Ni-Zr and Cu-Ni-Zr alloys

    SciTech Connect

    Witusiewicz, V.T.; Sommer, F.

    2000-04-01

    Since the Al-Cu-Ni-Zr system is a basis for the production of bulk amorphous materials by rapid solidification techniques from the liquid state, it is of great scientific interest to determine the partial and the integral thermodynamic functions of liquid and undercooled liquid alloys. Such data, as was pointed out previously, are important in order to understand their extremely good glass-forming ability in multicomponent metallic systems as well as for processing improvements. In order to measure the thermodynamic properties of the Al-Cu-Ni-Zr quaternary, it is necessary to have reliable thermochemical data for its constituent canaries and ternaries first. In a series of articles, the authors have reported in detail the thermodynamic properties of liquid Al-Cu, Al-Ni, Cu-Ni, Cu-Zr, Al-Zr, Al-Cu-Ni, and Al-Cu-Zr alloys. This article deals with the direct calorimetric measurements of the partial and the integral enthalpies of mixing of liquid Ni-Zr and Cu-Ni-Zr alloys and the heat capacity of liquid Ni{sub 26}Zr{sub 74}. In a subsequent article, the authors will present similar data for the liquid ternary Al-Ni-Zr and for the liquid quaternary Al-Cu-Ni-Zr alloys.

  6. Change of the kinetics of solidification and microstructure formation induced by convection in the Ni-Al system

    NASA Astrophysics Data System (ADS)

    Reutzel, S.; Hartmann, H.; Galenko, P. K.; Schneider, S.; Herlach, D. M.

    2007-07-01

    The purpose of the present work was to measure the velocity of dendrite growth in undercooled Ni-Al alloy melts as a function of undercooling. The experiments were performed both by containerless electromagnetic levitation on Earth and under reduced gravity conditions during parabolic flight campaigns. While under terrestrial conditions, strong magnetic fields are required to compensate the gravitational force, the forces to compensate disturbing accelerations are decreased by orders of magnitude in reduced gravity. In turn, the alternating electromagnetic fields induce convection, which is strong under terrestrial conditions while much weaker in reduced gravity. The heat and mass transport in front of the solid-liquid interface during solidification controls the dynamics of dendrite growth. By comparing results obtained on Earth and in reduced gravity, it was demonstrated that the change of transport conditions by convection significantly alters the kinetics of solidification and the evolution of grain refined microstructures at undercoolings less than 100K.

  7. Magnetic and magnetodielectric coupling anomalies in the Haldane spin-chain system Nd2BaNiO5

    NASA Astrophysics Data System (ADS)

    Basu, Tathamay; Mohapatra, Niharika; Singh, Kiran; Sampathkumaran, E. V.

    2015-03-01

    We report the magnetic, heat-capacity, dielectric and magnetodielectric (MDE) behaviour of a Haldane spin-chain compound containing light rare-earth ion, Nd2BaNiO5, in detail, as a function of temperature (T) and magnetic field (H) down to 2 K. In addition to the well-known long range antiferromagnetic order setting in at (TN = ) 48 K as indicated in dc magnetization (M), we have observed another magnetic transition near 10 K; this transition appears to be of a glassy-type which vanishes with a marginal application of external magnetic field (even H = 100 Oe). There are corresponding anomalies in dielectric constant (ɛ') as well with variation of T. The isothermal M(H) curves at 2 and 5 K reveal the existence of a magnetic-field induced transition around 90 kOe; the isothermal ɛ'(H) also tracks such a metamagnetic transition. These results illustrate the MDE coupling in this compound. Additionally, we observe a strong frequency dependence of a step in ɛ'(T) with this feature appearing around 25-30 K for the lowest frequency of 1 kHz, far below TN. This is attributed to interplay between crystal-field effect and exchange interaction between Nd and Ni, which establishes the sensitivity of dielectric measurements to detect such effects. Interestingly enough, the observed dispersions of the ɛ'(T) curves is essentially H-independent in the entire T-range of measurement, despite the existence of MDE coupling, which is in sharp contrast with other heavy rare-earth members in this series.

  8. Optimization of the interface polarization of the La 2NiO 4-based cathode working with the Ce 1- xSm xO 2- δ electrolyte system

    NASA Astrophysics Data System (ADS)

    Pérez-Coll, D.; Aguadero, A.; Escudero, M. J.; Núñez, P.; Daza, L.

    The performance of La 2NiO 4 cathode material and Ce 1- xSm xO 2- δ (x = 0.1, 0.2, 0.3, 0.4) electrolyte system was analyzed. Ceria-based materials were prepared by the freeze-drying precursor route whereas La 2NiO 4 was prepared by the nitrate-citrate procedure. Electrolyte pellets were obtained after sintering the powders at 1600 °C for 10 h. Also dense ceria-based electrolytes samples were obtained by calcining the powders at 1150 °C after the addition of 2 mol%-Co. Interface polarization measurements were performed by impedance spectroscopy in air at open circuit voltage, using symmetrical cells prepared after the deposition of porous La 2NiO 4-electrodes on the Ce 1- xSm xO 2- δ system. X-ray diffraction (XRD) of cathode materials after using in symmetrical cells confirmed no significant reaction between La 2NiO 4 and ceria-based electrolytes. The efficiency of the cathode material is highly dependent on the composition of the electrolyte, and low-content Sm-doped ceria samples revealed an important decrease in the performance of the system. Differences in electrochemical behaviour were attributed principally to the oxide ion transference between cathode and electrolyte, and were correlated to the conductivity of the electrolyte. In this way cobalt-doped electrolytes with a Sm-content ≤30% perform better than free-cobalt samples due to the increase in grain boundary conductivity. Finally, composites of the ceria-based materials and La 2NiO 4 to use as cathode were prepared and an important increase of the interface performance was observed compared to La 2NiO 4 pure cathode. Predictions of maximun power density were obtained by the mixed transport properties of the electrolytes and by the interface polarization results. The use of composite materials could allow to increase the performance of the cell from 170 mW cm -2 for pure La 2NiO 4 cathode, to 370 mW cm -2 for La 2NiO 4-Ce 0.8Sm 0.2O 2- δ cathode, both working with Ce 0.8Sm 0.2O 2- δ electrolyte

  9. The Influence of Cooling Rate During Crystallization on the Effective Partitioning Coefficient in High-Entropy Alloys from Al-Ti-Co-Ni-Fe System

    NASA Astrophysics Data System (ADS)

    Górecki, Kamil; Bala, Piotr; Cios, Grzegorz; Koziel, Tomasz; Stępień, Milena; Wieczerzak, Krzysztof

    2016-07-01

    An influence of two different cooling rates on the microstructure and dispersion of the components of high-entropy alloy from Al-Ti-Co-Ni-Fe system has been examined. For investigated alloys, the effective partitioning coefficient has been calculated. This factor indicates the degree of segregation of elements and allows for the specification of the differences between dendrites and interdendritic regions. The obtained results allow for the conclusion that the cooling rate substantially affect the growth of dendrites and the volume fraction of interdendritic regions as well as the partitioning of elements in the alloy. Furthermore, the obtained results made it possible to compare the influence of the cooling rate and the chemical composition on the dispersion of the alloying elements.

  10. The Influence of Cooling Rate During Crystallization on the Effective Partitioning Coefficient in High-Entropy Alloys from Al-Ti-Co-Ni-Fe System

    NASA Astrophysics Data System (ADS)

    Górecki, Kamil; Bala, Piotr; Cios, Grzegorz; Koziel, Tomasz; Stępień, Milena; Wieczerzak, Krzysztof

    2016-04-01

    An influence of two different cooling rates on the microstructure and dispersion of the components of high-entropy alloy from Al-Ti-Co-Ni-Fe system has been examined. For investigated alloys, the effective partitioning coefficient has been calculated. This factor indicates the degree of segregation of elements and allows for the specification of the differences between dendrites and interdendritic regions. The obtained results allow for the conclusion that the cooling rate substantially affect the growth of dendrites and the volume fraction of interdendritic regions as well as the partitioning of elements in the alloy. Furthermore, the obtained results made it possible to compare the influence of the cooling rate and the chemical composition on the dispersion of the alloying elements.

  11. Dynamical multi-breakup processes in the {sup 124}Sn+{sup 64}Ni system at 35 MeV/nucleon

    SciTech Connect

    Papa, M.; Cardella, G.; De Filippo, E.; Giuliani, G.; Lanzano, G.; Pagano, A.; Pirrone, S.; Politi, G.; Porto, F.; Verde, G.; Amorini, F.; Anzalone, A.; Bonasera, A.; Cavallaro, S.; Colonna, M.; Di Toro, M.; Giustolisi, F.; Iacono-Manno, M.; La Guidara, E.; Lanzalone, G.

    2007-05-15

    Multi-breakup processes for the {sup 124}Sn+{sup 64}Ni system at 35 MeV/nucleon have been studied with the forward part of the CHIMERA detector. An extensive comparison between experimental data corresponding to almost complete ternary events and constrained molecular dynamics (CoMD-II) calculations suggests different characteristic times in the selected processes. This is in agreement with previous studies of the same reaction already published concerning the prompt intermediate-mass-fragment emission. Stimulated by CoMD-II calculations, we investigate the existence of more complex dynamical multi-breakup processes occurring on the same time scale. A detailed study of the rotational dynamics leading to slower dynamical fission processes is also presented.

  12. Large Scale DD Simulation Results for Crystal Plasticity Parameters in Fe-Cr And Fe-Ni Systems

    SciTech Connect

    Zbib, Hussein M.; Li, Dongsheng; Sun, Xin; Khaleel, Mohammad A.

    2012-04-30

    The development of viable nuclear energy source depends on ensuring structural materials integrity. Structural materials in nuclear reactors will operate in harsh radiation conditions coupled with high level hydrogen and helium production, as well as formation of high density of point defects and defect clusters, and thus will experience severe degradation of mechanical properties. Therefore, the main objective of this work is to develop a capability that predicts aging behavior and in-service lifetime of nuclear reactor components and, thus provide an instrumental tool for tailoring materials design and development for application in future nuclear reactor technologies. Towards this end goal, the long term effort is to develop a physically based multiscale modeling hierarchy, validated and verified, to address outstanding questions regarding the effects of irradiation on materials microstructure and mechanical properties during extended service in the fission and fusion environments. The focus of the current investigation is on modern steels for use in nuclear reactors including high strength ferritic-martensitic steels (Fe-Cr-Ni alloys). The effort is to develop a predicative capability for the influence of irradiation on mechanical behavior. Irradiation hardening is related to structural information crossing different length scales, such as composition, dislocation, and crystal orientation distribution. To predict effective hardening, the influence factors along different length scales should be considered. Therefore, a hierarchical upscaling methodology is implemented in this work in which relevant information is passed between models at three scales, namely, from molecular dynamics to dislocation dynamics to dislocation-based crystal plasticity. The molecular dynamics (MD) was used to predict the dislocation mobility in body centered cubic (bcc) Fe and its Ni and Cr alloys. The results are then passed on to dislocation dynamics to predict the critical resolved

  13. Scattering process for the system 7Be + 58Ni at 23.2 MeV beam energy

    NASA Astrophysics Data System (ADS)

    Mazzocco, M.; Torresi, D.; Fierro, N.; Acosta, L.; Boiano, A.; Boiano, C.; Glodariu, T.; Guglielmetti, A.; La Commara, M.; Martel, I.; Mazzocchi, C.; Molini, P.; Pakou, A.; Parascandolo, C.; Parker, V. V.; Patronis, N.; Pierroutsakou, D.; Romoli, M.; Sanchez-Benitez, A. M.; Sandoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Stiliaris, E.; Strano, E.; Stroe, L.; Zerva, K.

    2013-03-01

    We measured for the first time the scattering process of 7Be nuclei from a 58Ni target at 23.2 MeV beam energy. The experiment was performed at the Laboratori Nazionali di Legnaro (LNL, Italy), where the 7Be Radioactive Ion Beam was in-flight produced with the facility EXOTIC. Charged reaction products were detected by means of the detector array DINEX, arranged in a cylindrical configuration around the target to ensure a polar angle coverage in the ranges θcm = 40°-80° and 110°-150°. The scattering differential cross section was analyzed within the optical model formalism with the coupled-channel code FRESCO to extract the total reaction cross section. The result was compared with those obtained at lower beam energies in an earlier experiment performed at the University of Notre Dame (USA). At the present stage of our analysis, the two data sets were found to be not fully consistent each other.

  14. Process Control and Characterization of NiCr Coatings by HVOF-DJ2700 System: A Process Map Approach

    NASA Astrophysics Data System (ADS)

    Valarezo, Alfredo; Choi, Wanhuk B.; Chi, Weiguang; Gouldstone, Andrew; Sampath, Sanjay

    2010-09-01

    The concept of ‘process maps’ has been utilized to study the fundamentals of process-structure-property relationships in high velocity oxygen fuel (HVOF) sprayed coatings. Ni-20%Cr was chosen as a representative material for metallic alloys. In this paper, integrated experiments including diagnostic studies, splat collection, coating deposition, and property characterization were carried out in an effort to investigate the effects of fuel gas chemistry (fuel/oxygen ratio), total gas flow, and energy input on particle states: particle temperature ( T) and velocity ( V), coating formation dynamics, and properties. Coatings were deposited on an in situ curvature sensor to study residual stress evolution. The results were reconciled within the framework of process maps linking torch parameters with particle states (1st order map) and relating particle state with deposit properties (2nd order map). A strong influence of particle velocity on induced compressive stresses through peening effect is discussed. The complete tracking of the coating buildup history including particle state, residual stress evolution and deposition temperature, in addition to single splat analysis, allows the interpretation of resultant coating microstructures and properties and enables coating design with desired properties.

  15. Capture of Hydrogen Using ZrNi

    NASA Technical Reports Server (NTRS)

    Patton, Lisa; Wales, Joshua; Lynch, David; Parrish, Clyde

    2005-01-01

    Water, as ice, is thought to reside in craters at the lunar poles along with CH4 and H2 . A proposed robotic mission for 2012 will utilize metal/metal hydrides for H2 recovery. Specifications are 99% capture of H2 initially at 5 bar and 100C (or greater), and degassing completely at 300C. Of 47-systems examined using the van't Hoff equation, 4 systems, Mg/MgH2, Mg2Ni/Mg2NiH4, ZrNi/ZrNiH2.8, and Pd/PdH0.77, were considered likely candidates for further examination. It is essential, when selecting a system, to also examine questions regarding activation, kinetics, cyclic stability, and gas impurity effects. After considering those issues, ZrN1 was selected as the most promising candidate, as it is easily activated and rapidly forms ZrNiH 2.8 . In addition, it resists oxide poisoning by CO2, and H2O, while some oxidation by O2 is recommended for improved activation . The presence of hydrogen in the as received Zr-Ni alloy from Alfa Aesar posed additional technical problems. X-ray diffraction of the Zr-Ni powder (-325 mesh), with a Zr:Ni wt% ratio of 70:30, was found to consist of ZrH2, ZrNiH2.8, and ZrNi. ZrH2 in the alloy presented the risk that after degassing that both Zr and ZrNi would be present, and thus lead to erroneous results regarding the reactivity of ZrNi with H2 . Fortunately, ZrH2 is a highly stable hydride that does not degas H2 to any significant extent at temperatures below 300C. Based on equilibrium calculations for the decomposition of ZrH2, only 1 millionth of the hydride decomposed at 300C under a N2 atmosphere flowing at 25 ccm for 64 hours, the longest time for pretreatment employed in the investigation. It was possible, from the X-ray results and knowledge of the Zr:Ni ratio, to compute the composition of a pretreated specimen as being 76 wt% ZrNi and the balance ZrH2.

  16. Geochemical roots of autotrophic carbon fixation: hydrothermal experiments in the system citric acid, H 2O-(±FeS)-(±NiS)

    NASA Astrophysics Data System (ADS)

    Cody, G. D.; Boctor, N. Z.; Hazen, R. M.; Brandes, J. A.; Morowitz, Harold J.; Yoder, H. S.

    2001-10-01

    Recent theories have proposed that life arose from primitive hydrothermal environments employing chemical reactions analogous to the reductive citrate cycle (RCC) as the primary pathway for carbon fixation. This chemistry is presumed to have developed as a natural consequence of the intrinsic geochemistry of the young, prebiotic, Earth. There has been no experimental evidence, however, demonstrating that there exists a natural pathway into such a cycle. Toward this end, the results of hydrothermal experiments involving citric acid are used as a method of deducing such a pathway. Homocatalytic reactions observed in the citric acid-H 2O experiments encompass many of the reactions found in modern metabolic systems, i.e., hydration-dehydration, retro-Aldol, decarboxylation, hydrogenation, and isomerization reactions. Three principal decomposition pathways operate to degrade citric acid under thermal and aquathermal conditions. It is concluded that the acid catalyzed βγ decarboxylation pathway, leading ultimately to propene and CO 2, may provide the most promise for reaction network reversal under natural hydrothermal conditions. Increased pressure is shown to accelerate the principal decarboxylation reactions under strictly hydrothermal conditions. The effect of forcing the pH via the addition of NaOH reveals that the βγ decarboxylation pathway operates even up to intermediate pH levels. The potential for network reversal (the conversion of propene and CO 2 up to a tricarboxylic acid) is demonstrated via the Koch (hydrocarboxylation) reaction promoted heterocatalytically with NiS in the presence of a source of CO. Specifically, an olefin (1-nonene) is converted to a monocarboxylic acid; methacrylic acid is converted to the dicarboxylic acid, methylsuccinic acid; and the dicarboxylic acid, itaconic acid, is converted into the tricarboxylic acid, hydroaconitic acid. A number of interesting sulfur-containing products are also formed that may provide for additional

  17. Comparison of working length control consistency between hand K-files and Mtwo NiTi rotary system

    PubMed Central

    Krajczár, Károly; Varga, Enikő; Jeges, Sára; Tóth, Vilmos

    2016-01-01

    Background The purpose of this study was to investigate the consistency of working length control between hand instrumentation in comparison to engine driven Mtwo nickel-titanium rotary files. Material and Methods Forty extracted maxillary molars were selected and divided onto two parallel groups. The working lengths of the mesiobuccal root canals were estimated. The teeth were fixed in a phantom head. The root canal preparation was carried out group 1 (n=20) with hand K-files, (VDW, Munich, Germany) and group 2 (n=20) with Mtwo instruments (VDW, Munich, Germany). Vestibulo-oral and mesio-distal directional x-ray images were taken before the preparation with #10 K-file, inserted into the mesiobuccal root canal to the working length, and after preparation with #25, #30 and #40 files. Working lenght changes were detected with measurements between the radiological apex and the instrument tips. Results In the Mtwo group a difference in the working competency (p<0.05) could be noticed only in the vestibulo-oral direction from #10 to #40 file. The hand instrument group showed a significant difference in working length competency for each larger file size (p<0.05) (ANOVA). Regression analysis in the hand instrumentation group indicated a working length decrease with a mean of 0,2 mm after each consecutive file size (p<0.01). Conclusions The outcome of our trial indicated a high consistency in working length control for root canal preparation under simulated clinical condition using Mtwo rotary files. Mtwo NiTi rotary file did therefore proved to be more accurate in comparison to the conventional hand instrumentation. Key words:Working length, Mtwo, nickel-titanium, hand preparation, engine driven preparation. PMID:27034752

  18. Composition Dependence of Phase Stability, Deformation Mechanisms, and Mechanical Properties of the CoCrFeMnNi High-Entropy Alloy System

    NASA Astrophysics Data System (ADS)

    Tasan, C. C.; Deng, Y.; Pradeep, K. G.; Yao, M. J.; Springer, H.; Raabe, D.

    2014-10-01

    The proposal of configurational entropy maximization to produce massive solid-solution (SS)-strengthened, single-phase high-entropy alloy (HEA) systems has gained much scientific interest. Although most of this interest focuses on the basic role of configurational entropy in SS formability, setting future research directions also requires the overall property benefits of massive SS strengthening to be carefully investigated. To this end, taking the most promising CoCrFeMnNi HEA system as the starting point, we investigate SS formability, deformation mechanisms, and the achievable mechanical property ranges of different compositions and microstructural states. A comparative assessment of the results with respect to room temperature behavior of binary Fe-Mn alloys reveals only limited benefits of massive SS formation. Nevertheless, the results also clarify that the compositional requirements in this alloy system to stabilize the face-centered cubic (fcc) SS are sufficiently relaxed to allow considering nonequiatomic compositions and exploring improved strength-ductility combinations at reduced alloying costs.

  19. Composition Dependence of Phase Stability, Deformation Mechanisms, and Mechanical Properties of the CoCrFeMnNi High-Entropy Alloy System

    NASA Astrophysics Data System (ADS)

    Tasan, C. C.; Deng, Y.; Pradeep, K. G.; Yao, M. J.; Springer, H.; Raabe, D.

    2014-09-01

    The proposal of configurational entropy maximization to produce massive solid-solution (SS)-strengthened, single-phase high-entropy alloy (HEA) systems has gained much scientific interest. Although most of this interest focuses on the basic role of configurational entropy in SS formability, setting future research directions also requires the overall property benefits of massive SS strengthening to be carefully investigated. To this end, taking the most promising CoCrFeMnNi HEA system as the starting point, we investigate SS formability, deformation mechanisms, and the achievable mechanical property ranges of different compositions and microstructural states. A comparative assessment of the results with respect to room temperature behavior of binary Fe-Mn alloys reveals only limited benefits of massive SS formation. Nevertheless, the results also clarify that the compositional requirements in this alloy system to stabilize the face-centered cubic (fcc) SS are sufficiently relaxed to allow considering nonequiatomic compositions and exploring improved strength-ductility combinations at reduced alloying costs.

  20. PRINCEPS: A computer-based approach to the structural description and recognition of trends within structural databases, and its application to the Ce-Ni-Si System

    DOE PAGESBeta

    Guo, Yiming; Fredrickson, Daniel C.

    2016-04-01

    Intermetallic crystal structures offer an enormous structural diversity, with an endless array of structural motifs whose connection to stability and physical properties are often mysterious. Making sense of the often complex crystal structures that arise here, developing a clear structural description, and identifying connections to other phases can be laborious and require an encyclopedic knowledge of structure types. In this Article, we present PRINCEPS, an algorithm based on a new coordination environment projection scheme that facilitates the structural analysis and comparison of such crystal structures. We demonstrate the potential of this approach by applying it to the complex Ce-Ni-Si ternarymore » system, whose 17 binary and 21 ternary phases would present a daunting challenge to one seeking to understand the system by manual inspection (but has nonetheless been well-described through the heroic efforts of previous researchers). With the help of PRINCEPS, most of the ternary phases in this system can be rationalized as intergrowths of simple structural fragments, and grouped into a handful of structural series (with some outliers). Lastly, these results illustrate how the PRINCEPS approach can be used to organize a vast collection of crystal structures into structurally meaningful families, and guide the description of complex atomic arrangements.« less

  1. Comparative study of the performance of alumina-supported Ni-Mo, Ni-W and Ni-Mo-W catalysts in hydrotreating vacuum residue

    SciTech Connect

    Absi-Halabi, M.; Stanislaus, A.; Al-Dolama, K.

    1996-12-31

    The performance of a NiMoW/Al{sub 2}O{sub 3} catalyst for promoting various reactions during residual oil hydroprocessing is reported. Catalyst performance and properties are compared to that of conventional NiMo and NiW catalysts. Performance evaluation tests were conducted in a high pressure fixed bed reactor system using Kuwait vacuum residue as feed. Hydrodesulfurization, hydrodenitrogenation, hydrodemetalization, hydroconversion to distillates, asphaltene removal and CCR reduction reactions were monitored. The NiMoW catalyst was more active for various conversions than the NiMo and NiW catalysts. The addition of W to NiMo/Al{sub 2}O{sub 3} enhanced the hydrogenation function of the catalyst. 11 refs., 3 figs., 2 tabs.

  2. Electroslag surfacing of steel shafting with Ni alloy 625 and 70Cu-30Ni strip

    SciTech Connect

    Devletian, J.H.; Gao, Y.P.; Wood, W.E.

    1996-12-31

    A comprehensive study of electroslag surfacing (ESS) of steel with Ni Alloy 625 and 70Cu-30Ni strip electrodes was conducted to establish the feasibility of replacing forged bearing sleeves on propulsion shafting with integral weld surfacing. The base material was MIL-S-23284, Class 1 steel in the form of 41--66 cm (16--26 in.) diameter shafting and 76 mm (3 in.) thick flat plate. All ESS was carried out at a heat input level of approximately 5.9kJ/mm (150 kJ/in.) using 30 x 0.5 mm (1.2 x 0.02 in.) strip electrodes. Assessments of mechanical properties and microstructure of Ni Alloy 625 surfacing and 70Cu-30Ni surfacing were conducted to establish the structure-property relationships in these complex alloy systems. In addition, a solidification cracking test was developed to determine the relative cracking susceptibilities of these strip surfacing alloys. Although the Ni Alloy 625 surfacing contained small islands of interdendritic MC type carbides and Laves phase, the mechanical properties of this surfacing were satisfactory. The 70Cu-30Ni surfacing required a buttering layer of 30Cu-70Ni or pure Ni to prevent solidification cracking. The inherent ductility-dip sensitivity of 70Cu-30Ni surfacing was overcome by the development of a suitable ESS procedure.

  3. Preparation of magnetic Ni/wollastonite and zeolite P/Ni/wollastonite composite fibers

    NASA Astrophysics Data System (ADS)

    Jiang, Jinlong; Lu, Xinyuan; Huang, Huan; Duanmu, Chuansong; Zhou, Sumin; Gu, Xu; Chen, Jing

    2012-08-01

    Magnetic composite fibers with wollastonite (WO) core and Ni shell were prepared by electroless plating using natural mineral WO fibers as supporters. Zeolite P layers were then loaded on the surface of Ni/WO fibers by in situ hydrothermal method. The sample structure and properties were characterized via SEM, XRD, SQUID, EDX, and N2 adsorption. The compact Ni-P coatings on the surface of WO fibers resulted in good magnetic properties of the Ni/WO fibers and zeolite P/Ni/WO fibers. After two crystallization cycles, a continuous zeolite P layer could be formed on the surface of Ni-P coating. The zeolite loading improved the stability of Ni-P coating in the acid solution, resulting in that the zeolite P/Ni/WO fibers can be used at a wide pH range of 3-7. Zeolite P/Ni/WO fiber exhibited a good sorption property for Cu2+ in the aqueous solution (12.48 mg/g) and could be reused after regeneration, indicating that it could be an effective and reusable adsorbent for metal ions from a liquid system.

  4. Layer-Resolved Magnetic Moments in Ni/Pt Multilayers

    NASA Astrophysics Data System (ADS)

    Wilhelm, F.; Poulopoulos, P.; Ceballos, G.; Wende, H.; Baberschke, K.; Srivastava, P.; Benea, D.; Ebert, H.; Angelakeris, M.; Flevaris, N. K.; Niarchos, D.; Rogalev, A.; Brookes, N. B.

    2000-07-01

    The magnetic moments in Ni/Pt multilayers are thoroughly studied by combining experimental and ab initio theoretical techniques. SQUID magnetometry probes the samples' magnetizations. X-ray magnetic circular dichroism separates the contribution of Ni and Pt and provides a layer-resolved magnetic moment profile for the whole system. The results are compared to band-structure calculations. Induced Pt magnetic moments localized mostly at the interface are revealed. No magnetically ``dead'' Ni layers are found. The magnetization per Ni volume is slightly enhanced compared to bulk NiPt alloys.

  5. The near-infrared spectrum of NiCl: Analysis of vibrational components of system G and system H between 12,500 cm-1 and 13,750 cm-1

    NASA Astrophysics Data System (ADS)

    Harms, Jack C.; Gipson, Courtney N.; Grames, Ethan M.; O'Brien, James J.; O'Brien, Leah C.

    2016-03-01

    The near-infrared spectrum of nickel chloride, NiCl, has been recorded at high resolution from 12,400-12,600 cm-1, 13,200-13,500 cm-1, and 13,600-13,750 cm-1 using intracavity laser absorption spectroscopy, ILS. The NiCl molecules were produced in the plasma discharge of a nickel-lined, copper hollow cathode with ∼1.8 torr of Ar as the sputter gas and a trace amount of CCl4 as the chloride source. Several transitions were observed and analyzed, including the (2, 0), (1, 0), and (0, 1) bands of the [13.0] 2Π3/2-X2Π3/2 transition, System G, and the (1, 0) band of the [12.3] 2Σ--X2Π3/2 transition, System H. The transitions were analyzed using PGOPHER and obtained molecular parameters are reported. A potential energy curve for the [13.0] 2Π3/2 state has been constructed using the vibrational information from the analyzed transitions.

  6. Crystal chemistry of the G-phases in the {l_brace}Ti, Zr, Hf{r_brace}-Ni-Si systems

    SciTech Connect

    Grytsiv, A.; Chen Xingqiu; Rogl, P. Podloucky, R.; Schmidt, H.; Giester, G.; Pomjakushin, V.

    2007-02-15

    Ternary compounds M{sub 6}Ni{sub 16}Si{sub 7} (M=Ti, Zr, Hf) have been investigated by X-ray powder/single crystal and neutron powder diffraction. Compounds with Zr and Hf crystallize in the ordered Th{sub 6}Mn{sub 23} type (Mg{sub 6}Cu{sub 16}Si{sub 7}-type, space group Fm3-bar m), whereas Ti{sub 6}Ni{sub 16.7}Si{sub 7} contains an additional Ni atom partially occupying the 24e site (M2 site, x=0.4637,0,0; occ.=0.119) inside a Ti octahedron; Ti atoms occupy a split position. Ti{sub 6}Ni{sub 16.7}Si{sub 7} represents a new variant of the filled Th{sub 6}Mn{sub 23} type structure. Ab initio calculations confirm the structural difference: additional Ni atoms favour the 24e site for Ti{sub 6}Ni{sub 16.7}Si{sub 7}, however, for the Zr and Hf-based compounds the unoccupied site renders an energetically lower ground state. Enthalpies of formation of Ti{sub 6}Ni{sub 17}Si{sub 7}, Zr{sub 6}Ni{sub 16}Si{sub 7}, and Hf{sub 6}Ni{sub 16}Si{sub 7} were calculated to be -68.65, -74.78, and -78.59kJ/(mol of atoms), respectively.

  7. Giant magnetoresistance in evaporated NiFe/Cu and NiFeCo/Cu multilayers (abstract)

    NASA Astrophysics Data System (ADS)

    Zeltser, A. M.; Smith, Neil

    1996-04-01

    increases with annealing temperature. This suggests that lattice interdiffusion is more prominent in the NiFe- system, consistent with a greater equilibrium compared solubility of Cu in the NiFe matrix compared to that of Ag. It is believed that Cu diffusion along the NiFe grain boundaries creates intra-layer magnetic discontinuity in NiFe and promotes inter-layer antiferromagnetic coupling between adjacent NiFe layers, which then gives rise to the observed GMR. Evaporated NiFe/Cu ML showed very small hysteresis and uniform GMR properties throughout the thickness, which makes them good candidates for GMR-DMR heads.

  8. In situ NiTi/Nb(Ti) composite

    SciTech Connect

    Jiang, Daqiang Cui, Lishan; Jiang, Jiang; Zheng, Yanjun

    2013-12-15

    Graphical abstract: - Highlights: • In situ NiTi/Nb(Ti) composites were fabricated. • The transformation temperature was affected by the mixing Ti:Ni atomic ratios. • The NiTi component became micron-scale lamella after forging and rolling. • The composite exhibited high strength and high damping capacity. - Abstract: This paper reports on the creation of a series of in situ NiTi/Nb(Ti) composites with controllable transformation temperatures based on the pseudo-binary hypereutectic transformation of NiTi–Nb system. The composite constituent morphology was controlled by forging and rolling. It is found that the thickness of the NiTi lamella in the composite reached micron level after the hot-forging and cold-rolling. The NiTi/Nb(Ti) composite exhibited high damping capacity as well as high yield strength.

  9. Paramagnetic intermediates in reactions of the components of catalytic systems of the Ziegler type. Reactions of azo and azomethine complexes of Ni(II) with diethylaluminum chloride

    SciTech Connect

    Abbasov, Ya.A.; Ismailov, E.G.; Medzhidov, A.A.

    1988-04-01

    The intermediate paramagnetic particles, i.e., radical particles, complexes of Ni(I), and Ni/sub n/(O) aggregates, formed as a result of the reaction of azo and azomethine complexes of Ni(II) with Et/sub 2/AlCl in solvent media (toluene, THF, heptane) have been identified with the aid of ESR. The possibility of the stabilization of reactive intermediate complexes of Ni(I) by organophosphorus ligands (DPPE and TPP) has been demonstrated, and the magnetic-resonance parameters of their adducts have been determined. It has been postulated that the formation of radical particles occurs as a result of the coordination of the nitrogen atoms of the azo or azomethine ligands by the organoaluminum compound followed by splitting of the -N=N or -CH=N bonds.

  10. B-Ni-Ti (164)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 2 http://dx.doi.org/10.1007/97.etType="URL"/> 'Systems from B-Be-Fe to Co-W-Zr' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'B-Ni-Ti (164)' with the content:

  11. Calorimetric and magnetic study for Ni{sub 50}Mn{sub 36}In{sub 14} and relative cooling power in paramagnetic inverse magnetocaloric systems

    SciTech Connect

    Chen, Jing-Han; Bruno, Nickolaus M.; Karaman, Ibrahim; Huang, Yujin; Li, Jianguo; Ross, Joseph H.

    2014-11-28

    The non-stoichiometric Heusler alloy Ni{sub 50}Mn{sub 36}In{sub 14} undergoes a martensitic phase transformation in the vicinity of 345 K, with the high temperature austenite phase exhibiting paramagnetic rather than ferromagnetic behavior, as shown in similar alloys with lower-temperature transformations. Suitably prepared samples are shown to exhibit a sharp transformation, a relatively small thermal hysteresis, and a large field-induced entropy change. We analyzed the magnetocaloric behavior both through magnetization and direct field-dependent calorimetry measurements. For measurements passing through the first-order transformation, an improved method for heat-pulse relaxation calorimetry was designed. The results provide a firm basis for the analytic evaluation of field-induced entropy changes in related materials. An analysis of the relative cooling power (RCP), based on the integrated field-induced entropy change and magnetizing behavior of the Mn spin system with ferromagnetic correlations, shows that a significant RCP may be obtained in these materials by tuning the magnetic and structural transformation temperatures through minor compositional changes or local order changes.

  12. Phase Equilibrium Experiments on Potential Lunar Core Compositions: Extension of Current Knowledge to Multi-Component (Fe-Ni-Si-S-C) Systems

    NASA Technical Reports Server (NTRS)

    Righter, K.; Pando, K.; Danielson, L.

    2014-01-01

    Numerous geophysical and geochemical studies have suggested the existence of a small metallic lunar core, but the composition of that core is not known. Knowledge of the composition can have a large impact on the thermal evolution of the core, its possible early dynamo creation, and its overall size and fraction of solid and liquid. Thermal models predict that the current temperature at the core-mantle boundary of the Moon is near 1650 K. Re-evaluation of Apollo seismic data has highlighted the need for new data in a broader range of bulk core compositions in the PT range of the lunar core. Geochemical measurements have suggested a more volatile-rich Moon than previously thought. And GRAIL mission data may allow much better constraints on the physical nature of the lunar core. All of these factors have led us to determine new phase equilibria experimental studies in the Fe-Ni-S-C-Si system in the relevant PT range of the lunar core that will help constrain the composition of Moon's core.

  13. Os, Nd, O and S isotope constraints on country rock contamination in the conduit-related Eagle Cu-Ni-(PGE) deposit, Midcontinent Rift System, Upper Michigan

    NASA Astrophysics Data System (ADS)

    Ding, Xin; Ripley, Edward M.; Shirey, Steven B.; Li, Chusi

    2012-07-01

    The Eagle Cu-Ni-(PGE) deposit is hosted by mafic to ultramafic intrusive rocks associated with the Marquette-Baraga dike swarm in northern Michigan. Sulfide mineralization formed in a conduit system during early stages in the development of the ∼1.1 Ga Midcontinent Rift System. The conduit environment represents a prime location for melt-rock interaction. In order to better assess the extent of country rock contamination in the Eagle system, a combined trace element, Nd, Os, O and S isotope study of country rocks, sulfide-bearing igneous rocks and massive sulfide was undertaken. Both the Eagle and the weakly mineralized East Eagle intrusion show trace element patterns that are similar to those of picritic basalts that formed during early stages of rift development. The trace element, Os, Nd, and O isotopic values of the igneous rocks are consistent with <5% of bulk contamination by Paleoproterozoic and Archean country rocks. Both the Re-Os and Sm-Nd system provide isochrons that are in agreement with the 1107 Ma U-Pb baddeleyite age of the intrusive rocks. Calculated γOs(1100) and εNd(1100) values for the magmas are +34 and -2. δ18O values of pyroxene in feldspathic pyroxenite range from 6.5‰ to 6.6‰ and provide the only indication that bulk contamination may locally have exceeded 20%. Sulfur isotopic values of disseminated and massive sulfide in the Eagle intrusion range from 0.3‰ to 4.6‰. The δ34S values are much lower than those that characterize most of the country rocks, but could still be indicative of a contribution of S from country rocks of up to ∼50%. Δ33S values of the disseminated and massive sulfides range from -0.10‰ to 0.09‰ indicating a source in Paleoproterozoic country rocks. Semi-massive sulfide in the Eagle deposit has δ34S values between 2.2‰ and 5.3‰, and Δ33S values show a broad range between -0.86‰ and 0.86‰ indicating a major contribution from an Archean source. Isotopic data from the Eagle deposit strongly

  14. Role of natural nanoparticles on the speciation of Ni in andosols of la Reunion

    NASA Astrophysics Data System (ADS)

    Levard, Clément; Doelsch, Emmanuel; Rose, Jérôme; Masion, Armand; Basile-Doelsch, Isabelle; Proux, Olivier; Hazemann, Jean-Louis; Borschneck, Daniel; Bottero, Jean-Yves

    2009-08-01

    Andosols on the island of Réunion have high nickel (Ni) concentrations due to the natural pedo-geochemical background. Enhanced knowledge of Ni speciation is necessary to predict the bioavailability and potential toxicity of this element. Ni speciation in these andosols, marked by the presence of high amounts of natural aluminosilicate nanoparticles, was investigated in two complementary systems: (i) In a soil sample—densimetric fractionation was first performed in order to separate the potential bearing phases, prior to Ni speciation characterization. (ii) In a synthetic sample—Ni reactivity with synthetic aluminosilicate nanoparticle analogs were studied. In both cases, Ni speciation was determined using X-ray absorption spectroscopy (XAS). The results revealed that Ni had the same local environment in both systems (natural and synthetic systems), and Ni was chemically linked to natural short-range ordered aluminosilicates or analogs. This complex represented about 75% of the total Ni in the studied soil.

  15. Voids in fast-neutron-irradiated Cu, Ni and Cu-Ni concentrated alloys studied by TEM and positron annihilation methods

    NASA Astrophysics Data System (ADS)

    Fukushima, H.; Ochiai, K.; Shimomura, Y.

    The effect of concentrated Ni and Cu solute atoms in the Cu-Ni system on the formation of voids has been examined using Cu, Cu-8 at.% Ni, Ni-8 at.% Cu and Ni irradiated with fast-neutrons in the FFTF-MOTA. Both solute atoms introduced smaller voids in the grains of the concentrated alloys than voids in the normal grains of pure-Cu and pure-Ni. Slight increase of irradiation temperature and the higher dose of fast-neutrons induced coalescence of voids in the grains of Ni-8 at.% Cu, but it resulted in the abrupt decrease of the concentration of small voids in the grains and the formation of heterogeneously distributed larger voids near grain boundaries in Cu-8 at.% Ni. Heterogeneous distribution of larger voids was also observed in other materials. Annealing at higher temperatures induced segregation of impurity atoms at a void surface in Ni-8 at.% Cu.

  16. Determination of 63Ni and 59Ni in spent ion-exchange resin and activated charcoal from the IEA-R1 nuclear research reactor.

    PubMed

    Taddei, M H T; Macacini, J F; Vicente, R; Marumo, J T; Sakata, S K; Terremoto, L A A

    2013-07-01

    A radiochemical method has been adapted to determine (59)Ni and (63)Ni in samples of radioactive wastes from the water cleanup system of the IEA-R1 nuclear research reactor. The process includes extraction chromatographic resin with dimethylglyoxime (DMG) as a functional group. Activity concentrations of (59)Ni and (63)Ni were measured, respectively, by X-ray spectrometry and liquid scintillation counting, whereas the chemical yield was determined by ICP-OES. The average ratio of measured activity concentrations of (63)Ni and (59)Ni agree well with theory. PMID:23524230

  17. The Effect of Metal Composition on Fe-Ni Partition Behavior between Olivine and FeNi-Metal, FeNi-Carbide, FeNi-Sulfide at Elevated Pressure

    NASA Technical Reports Server (NTRS)

    Holzheid, Astrid; Grove, Timothy L.

    2005-01-01

    Metal-olivine Fe-Ni exchange distribution coefficients were determined at 1500 C over the pressure range of 1 to 9 GPa for solid and liquid alloy compositions. The metal alloy composition was varied with respect to the Fe/Ni ratio and the amount of dissolved carbon and sulfur. The Fe/Ni ratio of the metal phase exercises an important control on the abundance of Ni in the olivine. The Ni abundance in the olivine decreases as the Fe/Ni ratio of the coexisting metal increases. The presence of carbon (up to approx. 3.5 wt.%) and sulfur (up to approx. 7.5 wt.%) in solution in the liquid Fe-Ni-metal phase has a minor effect on the partitioning of Fe and Ni between metal and olivine phases. No pressure dependence of the Fe-Ni-metal-olivine exchange behavior in carbon- and sulfur-free and carbon- and sulfur-containing systems was found within the investigated pressure range. To match the Ni abundance in terrestrial mantle olivine, assuming an equilibrium metal-olivine distribution, a sub-chondritic Fe/Ni-metal ratio that is a factor of 17 to 27 lower than the Fe/Ni ratios in estimated Earth core compositions would be required, implying higher Fe concentrations in the core forming metal phase. A simple metal-olivine equilibrium distribution does not seem to be feasible to explain the Ni abundances in the Earth's mantle. An equilibrium between metal and olivine does not exercise a control on the problem of Ni overabundance in the Earth's mantle. The experimental results do not contradict the presence of a magma ocean at the time of terrestrial core formation, if olivine was present in only minor amounts at the time of metal segregation.

  18. Shear bond strength to dentin and Ni-Cr-Be alloy with the All-Bond universal adhesive system.

    PubMed

    Barkmeier, W W; Suh, B I; Cooley, R L

    1991-01-01

    The shear bond strength of the All-Bond system to dentin and a nonprecious alloy was evaluated. Eighty human molar teeth (10 per group) were used in the dentin bonding phase of the study. A bond site was prepared in dentin, and both the succinic anhydride modified HEMA and 10 percent phosphoric acid dentin conditioning techniques were evaluated under both wet and dry conditions. Eighty Rexillium III specimens were used in the metal bonding phase of the study. All-Bond primer and opaquer were applied to the metal surface, followed by a visible light-cured composite restorative material. Dentin bond strengths were determined at 24 hours, while metal bond strengths were evaluated both at 24 hours and after thermocycling (2,500 cycles). Separate groups were established for adhesion to both dentin and metal with the composite placed in a plastic matrix or a gelatin capsule. The highest mean shear bond values to dentin were obtained in the groups with the gelatin capsule bonding procedure, where the dentin was treated with 10 percent phosphoric acid and then blotted dry (wet technique) before the bonding procedure (39.99 MPa). These values were higher than the succinic anhydride modified HEMA-treated group with gentle air drying (wet technique-29.56 MPa). There was essentially no difference in mean shear bond strengths to dentin when a succinic anhydride modified HEMA dentin conditioner was used with aggressive (dry technique) or gentle air drying (wet technique) [29.56 versus 29.08 MPa]. High bond strengths to Rexillium III were obtained when the All-Bond adhesive system was used in combination with a dual-care opaquer and a composite restorative material.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1817584

  19. Processing and Mechanical Properties of NiAl-Based In-Situ Composites. Ph.D. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Johnson, David Ray

    1994-01-01

    In-situ composites based on the NiAl-Cr eutectic system were successfully produced by containerless processing and evaluated. The NiAl-Cr alloys had a fibrous microstructure while the NiAl-(Cr,Mo) alloys containing 1 at. percent or more molybdenum exhibited a lamellar structure. The NiAl-28Cr-6Mo eutectic displays promising high temperature strength while still maintaining a reasonable room temperature fracture toughness when compared to other NiAl-based materials. The Laves phase NiAlTa was used to strengthen NiAl and very promising creep strengths were found for the directionally solidified NiAl-NiAlTa eutectic. The eutectic composition was found to be near NiAl-15.5Ta (at. percent) and well aligned microstructures were produced at this composition. An off-eutectic composition of NiAl-14.5Ta was also processed, consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of these two phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Polyphase in-situ composites were generated by directional solidification of ternary eutectics. The systems investigated were the Ni-Al-Ta-X (X=Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and both the eutectic composition and temperature were determined. Of these ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr,Al)NiTa-Cr eutectic was intermediate between those of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  20. Numerical Prediction of the Thermodynamic Properties of Ternary Al-Ni-Pd Alloys

    NASA Astrophysics Data System (ADS)

    Zagula-Yavorska, Maryana; Romanowska, Jolanta; Kotowski, Sławomir; Sieniawski, Jan

    2016-01-01

    Thermodynamic properties of ternary Al-Ni-Pd system, such as exGAlNPd, µAl(AlNiPd), µNi(AlNiPd) and µPd(AlNiPd) at 1,373 K, were predicted on the basis of thermodynamic properties of binary systems included in the investigated ternary system. The idea of predicting exGAlNiPd values was regarded as calculation of values of the exG function inside a certain area (a Gibbs triangle) unless all boundary conditions, that is values of exG on all legs of the triangle are known (exGAlNi, exGAlPd, exGNiPd). This approach is contrary to finding a function value outside a certain area, if the function value inside this area is known. exG and LAl,Ni,Pd ternary interaction parameters in the Muggianu extension of the Redlich-Kister formalism were calculated numerically using the Excel program and Solver. The accepted values of the third component xx differed from 0.01 to 0.1 mole fraction. Values of LAlNiPd parameters in the Redlich-Kister formula are different for different xx values, but values of thermodynamic functions: exGAlNiPd, µAl(AlNiPd), µNi(AlNiPd) and µPd(AlNiPd) do not differ significantly for different xx values. The choice of xx value does not influence the accuracy of calculations.

  1. A new phase in Ni-Sn-P system and its property as an anode material for lithium-ion batteries

    SciTech Connect

    Xia, Z.P.; Lin, Y.; Li, Z.Q.

    2008-09-15

    A new metastable phase was synthesized by ball milling. The new phase is tetragonal with lattice parameters a = 3.671 A and c = 4.033 A. It was found that the new phase transformed into equilibrium orthorhombic Ni{sub 2}SnP phase at 973 K. The initial capacity of the lithium battery with the tetragonal Ni{sub 2}SnP phase as anode material reaches 500.4 mAh/g, but decreases to 181.8 mAh/g after 25 cycles. However, its initial irreversible capacity is 102 mAh/g, which makes it a promising anode material.

  2. Laser ablation of Al-Ni alloys and multilayers

    NASA Astrophysics Data System (ADS)

    Roth, Johannes; Trebin, Hans-Rainer; Kiselev, Alexander; Rapp, Dennis-Michael

    2016-05-01

    Laser ablation of Al-Ni alloys and multilayers has been studied by molecular dynamics simulations. The method was combined with a two-temperature model to describe the interaction between the laser beam, the electrons, and the atoms. As a first step, electronic parameters for the alloys had to be found and the model developed originally for pure metals had to be generalized to multilayers. The modifications were verified by computing melting depths and ablation thresholds for pure Al and Ni. Here known data could be reproduced. The improved model was applied to the alloys Al_3Ni, AlNi and AlNi_3. While melting depths and ablation thresholds for AlNi behave unspectacular, sharp drops at high fluences are observed for Al_3Ni and AlNi_3. In both cases, the reason is a change in ablation mechanism from phase explosion to vaporization. Furthermore, a phase transition occurs in Al_3Ni. Finally, Al layers of various thicknesses on a Ni substrate have been simulated. Above threshold, 8 nm Al films are ablated as a whole while 24 nm Al films are only partially removed. Below threshold, alloying with a mixture gradient has been observed in the thin layer system.

  3. Euhedral metallic-Fe-Ni grains in extraterrestrial samples

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1993-01-01

    Metallic Fe-Ni is rare in terrestrial rocks, being largely restricted to serpentinized peridotites and volcanic rocks that assimilated carbonaceous material. In contrast, metallic Fe-Ni is nearly ubiquitous among extraterrestrial samples (i.e., meteorites, lunar rocks, and interplanetary dust particles). Anhedral grains are common. For example, in eucrites and lunar basalts, most of the metallic Fe-Ni occurs interstitially between silicate grains and thus tends to have irregular morphologies. In many porphyritic chondrules, metallic Fe-Ni and troilite form rounded blebs in the mesostasis because their precursors were immiscible droplets. In metamorphosed ordinary chondrites, metallic Fe-Ni and troilite form coarse anhedral grains. Some of the metallic Fe-Ni and troilite grains has also been mobilized and injected into fractures in adjacent silicate grains where local shock-reheating temperatures reached the Fe-FeS eutectic (988 C). In interplanetary dust particles metallic Fe-Ni most commonly occurs along with sulfide as spheroids and fragments. Euhedral metallic Fe-Ni grains are extremely rare. Several conditions must be met before such grains can form: (1) grain growth must occur at free surfaces, restricting euhedral metallic Fe-Ni grains to systems that are igneous or undergoing vapor-deposition; (2) the metal (+/-) sulfide assemblage must have an appropriate bulk composition so that taenite is the liquidus phase in igneous systems or the stable condensate phase in vapor-deposition systems; and (3) metallic Fe-Ni grains must remain underformed during subsequent compaction, thermal metamorphism, and shock. Because of these restrictions, the occurrence of euhedral metallic Fe-Ni grains in an object can potentially provide important petrogenetic information. Despite its rarity, euhedral metallic Fe-Ni occurs in a wide variety of extraterrestrial materials. Some of these materials formed in the solar nebula; others formed on parent body surfaces by meteoroid

  4. Fabrication and catalytic activity of FeNi@Ni nanocables for the reduction of p-nitrophenol.

    PubMed

    Zhou, Linyi; Wen, Ming; Wu, Qingsheng; Wu, Dandan

    2014-06-01

    Magnetic FeNi@Ni nanocables were prepared as a superior recyclable catalyst towards the hydrogenation reduction of p-nitrophenol to p-aminophenol through a two-step tunable assembly process in a solvothermal system. The proposed fabrication mechanism was verified through characterization by SEM, TEM, XRD, XPS, and UV-Vis. The as-prepared FeNi@Ni nanocomposites are core-shell-structured nanocables with Ni nanoparticles (NPs) attached on FeNi nanorods (NRs) surface loosely. The catalytic reactivity monitored by means of a UV-vis dynamic process shows FeNi@Ni nanocables can catalyse the transformation of p-nitrophenol to p-aminophenol completely under an ambient atmosphere at room temperature, and enable the catalysis to be more efficient than its counterparts FeNi NRs and Ni NPs due to the interfacial synergistic effect. Additionally, the resultant hierarchical metal-alloy nanocomposites possess ferromagnetic behaviour, and can be easily separated and recycled by an external magnet field for application. PMID:24714959

  5. Resistance Switching Behavior in Epitaxially Grown NiO

    NASA Astrophysics Data System (ADS)

    Lee, S. R.; Bak, J. H.; Park, Y. D.; Char, K.; Kim, D. C.; Jung, R.; Seo, S.; Li, X. S.; Park, G.-S.; Yoo, I. K.

    2008-03-01

    Reproducible resistance switching behavior has been found in NiO films prepared by a pulsed laser deposition system. The I-V measurements of epitaixally grown NiO on SrRuO3 electrode show a bipolar resistive memory switching behavior, in contrast with a unipolar switching behavior of polycrystalline NiO on Pt electrode. In order to understand the resistive memory switching mechanism in NiO, the I-V characteristics and memory switching property of epitaxial NiO prepared under various synthesis conditions and electrodes has been investigated. The IV measurements at room temperature suggest that the interface between NiO and the electrode plays an important role on the resistive switching phenomena. To analyze the role of the interface, our efforts to control the interfaces and to measure the I-V characteristics at low temperature will be presented.

  6. Giant magnetoresistance in evaporated Ni-Fe/Cu and Ni-Fe-Co/Cu multilayers

    NASA Astrophysics Data System (ADS)

    Zeltser, Alexander M.; Smith, Neil

    1996-06-01

    The magnetic and transport properties of electron-beam evaporated (Ni83Fe17/Cu)10 and (Ni66Fe16Co18/Cu)10 multilayers were studied as a function of the Cu spacer, magnetic layer and Ta buffer layer thicknesses, as well as annealing conditions. All multilayers exhibited very small giant magnetoresistance (GMR) effect (<0.3%) in the as-deposited state, however, after magnetic post-annealing at 300-325 °C, GMR increased up to 4.5%-7%, depending on the multilayer type. In contrast to sputtered Ni-Fe-(Co)/Cu multilayers, GMR showed no oscillatory behavior as a function of Cu thickness. Similar to that reported in sputtered ``discontinuous'' Ni-Fe/Ag multilayers, it is believed that Cu diffusion along the Ni-Fe-(Co) grain boundaries creates intra-layer magnetic discontinuities in Ni-Fe-(Co) layers which promote inter-layer antiferromagnetic coupling. The evaporated Ni-Fe/Cu multilayers exhibited very low remanence, exceptionally low hysteresis, and quite uniform GMR properties through the thickness of the multilayer. All of these makes them potentially attractive for application to future magnetoresistive reproduce heads for very high areal density magnetic storage systems.

  7. The El Niño Southern Oscillation and the historic malaria epidemics on the Indian subcontinent and Sri Lanka: an early warning system for future epidemics?

    PubMed

    Bouma, M J; van der Kaay, H J

    1996-02-01

    The recurrent great malaria epidemics which occurred in the Punjab province of former British India and Ceylon before the introduction of residual insecticides have been related to excessive and failing monsoon rains respectively. In the arid Punjab, rainfall facilitated breeding and increased the lifespan of the mosquito vector and, in the wet part of Ceylon, failing monsoon rains caused rivers to pool, creating more favourable breeding conditions. The periodic fluctuations in monsoon rainfall and epidemic malaria are here explained in relation to the El Niño Southern Oscillation. In the Punjab, epidemic malaria between 1868 and 1943 correlates significantly (r = 0.34, P < 0.005) with the sea surface temperature anomalies in the Eastern Equatorial Pacific, a parameter of the oscillation, and epidemics were significantly more prevalent in a year with a wet monsoon following a dry El Niño year than in other years. In Ceylon, epidemics were significantly more prevalent during El Niño years, when the same south-west monsoon tends to fail. With the reduced reliance on residual insecticides and the recurrence of epidemic malaria on the Indian subcontinent, advances made in predicting El Niño events may be used to forecast high and low risk years for future malaria epidemics. PMID:8673827

  8. NiW and NiRu Bimetallic Catalysts for Ethylene Steam Reforming: Alternative Mechanisms for Sulfur Resistance

    SciTech Connect

    Rangan, M.; Yung, M. M.; Medlin, J. W.

    2012-06-01

    Previous investigations of Ni-based catalysts for the steam reforming of hydrocarbons have indicated that the addition of a second metal can reduce the effects of sulfur poisoning. Two systems that have previously shown promise for such applications, NiW and NiRu, are considered here for the steam reforming of ethylene, a key component of biomass derived tars. Monometallic and bimetallic Al{sub 2}O{sub 3}-supported Ni and W catalysts were employed for ethylene steam reforming in the presence and absence of sulfur. The NiW catalysts were less active than Ni in the absence of sulfur, but were more active in the presence of 50 ppm H{sub 2}S. The mechanism for the W-induced improvements in sulfur resistance appears to be different from that for Ru in NiRu. To probe reasons for the sulfur resistance of NiRu, the adsorption of S and C{sub 2}H{sub 4} on several bimetallic NiRu alloy surfaces ranging from 11 to 33 % Ru was studied using density functional theory (DFT). The DFT studies reveal that sulfur adsorption is generally favored on hollow sites containing Ru. Ethylene preferentially adsorbs atop the Ru atom in all the NiRu (111) alloys investigated. By comparing trends across the various bimetallic models considered, sulfur adsorption was observed to be correlated with the density of occupied states near the Fermi level while C{sub 2}H{sub 4} adsorption was correlated with the number of unoccupied states in the d-band. The diverging mechanisms for S and C{sub 2}H{sub 4} adsorption allow for bimetallic surfaces such as NiRu that enhance ethylene binding without accompanying increases in sulfur binding energy. In contrast, bimetallics such as NiSn and NiW appear to decrease the affinity of the surface for both the reagent and the poison.

  9. Measurement of 63Ni and 59Ni by accelerator mass spectrometry using characteristic projectile X-rays

    NASA Astrophysics Data System (ADS)

    McAninch, J. E.; Hainsworth, L. J.; Marchetti, A. A.; Leivers, M. R.; Jones, P. R.; Dunlop, A. E.; Mauthe, R.; Vogel, J. S.; Proctor, I. D.; Straume, T.

    1997-03-01

    The long-lived isotopes of nickel (59Ni, 63Ni) have current and potential use in a number of applications including cosmic radiation studies, biomedical tracing, characterization of low-level radioactive wastes, and neutron dosimetry. Methods are being developed at LLNL for the routine detection of these isotopes by AMS. One intended application is in Hiroshima dosimetry. The reaction 63Cu(n,p)63Ni has been identified as one of a small number of reactions which might be used for the direct determination of the fast neutron fluence emitted by the Hiroshima bomb. AMS measurement of 63Ni (t{1}/{2} = 100 y) requires the chemical removal of 63Cu, which is a stable isobar of 63Ni. Following the electrochemical separation of Ni from gram-sized copper samples, the Cu concentration is further lowered to < 2 × 10-8 ({Cu}/{Ni}) using the reaction of Ni with carbon monoxide to form the gas Ni(CO)4. The Ni(CO)4 is thermally decomposed directly in sample holders for measurement by AMS. After analysis in the AMS spectrometer, the ions are identified using characteristic projectile X-rays, allowing further rejection of remaining 63Cu. In a demonstration experiment, 63Ni was measured in Cu wires (2-20 g) which had been exposed to neutrons from a 252Cf source. We successfully measured 63Ni at levels necessary for the measurement of Cu samples exposed near the Hiroshima hypocenter. For the demonstration samples, the Cu content was chemically reduced by a factor of 1012 with quantitative retention of 63Ni. Detection sensitivity (3σ) was ˜ 20 fg 63Ni in 1 mg Ni carrier ({63Ni}/{Ni} ≈ 2 × 10-11). Significant improvements in sensitivity are expected with planned incremental changes in the methods. Preliminary results indicate that a similar sensitivity is achievable for 59Ni (t{1}/{2} = 105 y). Initial work has been undertaken on the application of this isotope as a biomedical tracer in living systems.

  10. Decomposition and multiphase reactions in the system UO 2(NO 3) 2·6H 2O-Ni(NO 3) 2·6H 2O at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Kalekar, Bhupesh B.; Rajagopalan, K. V.; Ravindran, P. V.

    2009-09-01

    Solid state reactions between uranyl nitrate hexahydrate and nickel nitrate hexahydrate in mixtures of various ratios have been studied at elevated temperatures. The binary system of uranyl nitrate hexahydrate and nickel nitrate hexahydrate was found to form a eutectic of composition 53 mol% uranyl nitrate hexahydrate and 47 mol% nickel nitrate hexahydrate at 40 °C. The overlap of evolution of nitric oxide (NO) and water vapour above 230 °C confirmed the presence of hydroxynitrates of uranium and nickel as intermediate products. These hydroxynitrates began to react above 280 °C to form nickel uranate, NiU 3O 10, in the case of mixtures containing 75 mol% uranyl nitrate hexahydrate. When the proportion of uranyl nitrate hexahydrate in the mixture was higher than 75 mol%, U 3O 8 formed along with nickel uranate. For the mixtures containing uranyl nitrate hexahydrate lower than 75 mol%, NiO was observed to form along with NiU 3O 10.