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Sample records for al fe ni

  1. Rapidly solidified NiAl and FeAl

    NASA Technical Reports Server (NTRS)

    Gaydosh, D. J.; Crimp, M. A.

    1984-01-01

    Melt spinning was used to produce rapidly solidified ribbons of the B2 intermetallics NiAl and FeAl. Both Fe-40Al and Fe-45Al possessed some bend ductility in the as spun condition. The bend ductility of Fe-40Al, Fe-45Al, and equiatomic NiAl increased with subsequent heat treatment. Heat treatment at approximately 0.85 T (sub m) resulted in significant grain growth in equiatomic FeAl and in all the NiAl compositions. Low bend ductility in both FeAl and NiAl generally coincided with intergranular failure, while increased bend ductility was characterized by increasing amounts of transgranular cleavage fracture.

  2. Modulus measurements in ordered Co-Al, Fe-Al, and Ni-Al alloys

    NASA Technical Reports Server (NTRS)

    Harmouche, M. R.; Wolfenden, A.

    1985-01-01

    The composition and/or temperature dependence of the dynamic Young's modulus for the ordered B2 Co-Al, Fe-Al, and Ni-Al aluminides has been investigated using the piezoelectric ultrasonic composite oscillator technique (PUCOT). The modulus has been measured in the composition interval 48.49 to 52.58 at. pct Co, 50.87 to 60.2 at. pct Fe, and 49.22 to 55.95 at. pct Ni for Co-Al, Fe-Al, and Ni-Al, respectively. The measured values for Co-Al are in the temperature interval 300 to 1300 K, while those for the other systems are for ambient temperature only. The data points show that Co-Al is stiffer than Fe-Al, which is stiffer than Ni-Al. The data points for Fe-Al and Ni-Al are slightly higher than those reported in the literature.

  3. 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.

  4. On the crack growth resistance and strength of the B2 iron aluminides Fe-40Al, Fe-45Al, and Fe-10Ni-40Al (at. %)

    SciTech Connect

    Schneibel, J.H.; Maziasz, P.J.

    1994-09-01

    The crack growth resistance and yield strength of the B2 iron aluminides Fe-40Al, Fe-45Al, are Fe-10Ni-40Al (at. %) have been investigated at room temperature laboratory air. After fast cooling from 1273 K, Fe-45Al and Fe-10Ni-40Al are much stronger than Fe-40Al, and exhibit considerably lower crack growth resistance. The crack growth resistance decreases with decreasing crack propagation velocity. Low crack propagation velocities favor intergranular fracture, whereas high velocities can lead to significant contributions from transgranular fracture. Boron additions to Fe-40Al and Fe-10Ni-40Al improve the crack growth resistance, reduce its dependence on the crack propagation velocity, and cause the path to be predominantly transgranular. In a plot of fracture toughness versus yield strength, the properties of the iron aluminides are similar to those of typical aluminum alloys.

  5. Modeling of the solubilities of NiO/NiAl2O4 and FeO/FeAl2O4 in cryolite melts at 1300 K

    NASA Astrophysics Data System (ADS)

    Zhang, Yunshu; Wu, Xiaoxia; Rapp, Robert A.

    2004-02-01

    Experiments to measure the solubilities of NiO/NiAl2O4 and FeO/FeAl2O4 were performed, and the results confirmed existing literature values. The solubilities of NiAl2O4 and FeAl2O4 in Al2O3-saturated cryolite melts at 1300 K were modeled thermodynamically in terms of the Ni-containing complexes Na2NiF4 and Na4NiF6, and the Fe-containing solutes FeF2, Na2FeF4, and Na4FeF6. The experimental solubility data were fitted to multiple simultaneous equilibria. Equilibrium constants and ΔG f 0 values for the formation reactions of the these solutes were thereby estimated. The solubilities of NiO/NiAl2O4 and FeO/FeAl2O4 and solute distributions in Al2O3-undersaturated cryolite melts were calculated for a number of melt compositions from the present model. The existence of several competitive solute species is inherent to highly buffered ionic cryolite solutions where the traditional log-log methodology had previously failed to identify dominant single solutes. In such solutions, individual solutes of oxides are not likely to dominate over a wide composition range so that a more global modeling is required. The principal solute species identified in the present study exhibit reasonable three-dimensional (3-D) anion geometries.

  6. Equilibrium point defects in intermetallics with the [ital B]2 structure: NiAl and FeAl

    SciTech Connect

    Fu, C.L.; Ye, Y.; Yoo, M.H. ); Ho, K.M. )

    1993-09-01

    Equilibrium point defects and their relation to the contrasting mechanical behavior of NiAl and FeAl are investigated. For NiAl, the defect structure is dominated by two types of defects---monovacancies on the Ni sites and substitutional antisite defects on the Al sites. The defect structure of FeAl differs from that of NiAl in the occurrence of antisite defects at the transition-metal sites for Al-rich alloys and the tendency for vacancy clustering. The strong ordering (and brittleness) of NiAl is attributed mainly to the difference in atomic size between constituent atoms.

  7. Local structure study of Fe dopants in Ni-deficit Ni3Al alloys

    DOE PAGESBeta

    V. N. Ivanovski; Umicevic, A.; Belosevic-Cavor, J.; Lei, Hechang; Li, Lijun; Cekic, B.; Koteski, V.; Petrovic, C.

    2015-08-24

    We found that the local electronic and magnetic structure, hyperfine interactions, and phase composition of polycrystalline Ni–deficient Ni 3-x FexAl (x = 0.18 and 0.36) were investigated by means of 57 Fe Mössbauer spectroscopy. The samples were characterized by X–ray diffraction and magnetization measurements. The ab initio calculations performed with the projector augmented wave method and the calculations of the energies of iron point defects were done to elucidate the electronic structure and site preference of Fe doped Ni 3 Al. Moreover, the value of calculated electric field gradient tensor Vzz=1.6 1021Vm-2 matches well with the results of Mössbauer spectroscopymore » and indicates that the Fe atoms occupy Ni sites.« less

  8. Point defect concentrations and solid solution hardening in NiAl with Fe additions

    SciTech Connect

    Pike, L.M.; Chang, Y.A.; Liu, C.T.

    1997-08-01

    The solid solution hardening behavior exhibited when Fe is added to NiAl is investigated. This is an interesting problem to consider since the ternary Fe additions may choose to occupy either the Ni or the Al sublattice, affecting the hardness at differing rates. Moreover, the addition of Fe may affect the concentrations of other point defects such as vacancies and Ni anti-sites. As a result, unusual effects ranging from rapid hardening to solid solution softening are observed. Alloys with varying amounts of Fe were prepared in Ni-rich (40 at. % Al) and stoichiometric (50 at. % Al) compositions. Vacancy concentrations were measured using lattice parameter and density measurements. The site occupancy of Fe was determined using ALCHEMI. Using these two techniques the site occupancies of all species could be uniquely determined. Significant differences in the defect concentrations as well as the hardening behavior were encountered between the Ni-rich and stoichiometric regimes.

  9. Precipitation and fracture behaviour of Fe-Mn-Ni-Al alloys

    NASA Astrophysics Data System (ADS)

    Heo, Yoon-Uk; Lee, Hu-Chul

    2013-12-01

    The effects of Al addition on the precipitation and fracture behaviour of Fe-Mn-Ni alloys were investigated. With the increasing of Al concentration, the matrix and grain boundary precipitates changed from L10 θ-MnNi to B2 Ni2MnAl phase, which is coherent and in cube-to-cube orientation relationship with the α‧-matrix. Due to the suppression of the θ-MnNi precipitates at prior austenite grain boundaries (PAGBs), the fracture mode changed from intergranular to transgranular cleavage fracture. Further addition of Al resulted in the discontinuous growth of Ni2MnAl precipitates in the alloy containing 4.2 wt.% Al and fracture occurred by void growth and coalescence, i.e. by ductile dimple rupture. The transition of the fracture behaviour of the Fe-Mn-Ni-Al alloys is discussed in relation to the conversion of the precipitates and their discontinuous precipitation behaviour at PAGBs.

  10. A systematic ALCHEMI study of Fe-doped NiAl alloys

    SciTech Connect

    Anderson, I.M.; Bentley, J.; Duncan, A.J.

    1995-06-01

    ALCHEMI site-occupation studies of alloying additions to ordered aluminide intermetallic alloys have been performed with varying degrees of success, depending on the ionization delocalization correction. This study examines the variation in the site-occupancy of Fe in B2-ordered NiAl vs solute concentration and alloy stoichiometry. The fraction of Fe on the `Ni` site is plotted vs Fe concentration. The good separation among the data from alloys of the three stoichiometries shows that the site occupancy of iron depends on the relative concentrations of the Ni and Al host elements; however a preference for the `Ni` site is clearly indicated.

  11. Microstructure and mechanical behavior of Fe30Ni 20Mn35Al15 and modified Fe30Ni 20Mn35Al15 alloys

    NASA Astrophysics Data System (ADS)

    Meng, Fanling

    A novel alloy with nominal composition Fe30Ni 20Mn35Al15 has been found to show good room-temperature strength and significant ductility. The current project is to study the wear properties of as-cast Fe30Ni20Mn35Al 15 and discuss the possibility of further improving the mechanical properties of this alloy. The dry sliding wear of as-cast Fe30Ni20Mn 35Al15 was studied in in four different environments, i.e. air, dry oxygen, dry argon and a 4% hydrogen/nitrogen mixture. Two-body and three-body abrasive wear mechanism was found for tests in oxygen-containing environments, while plastic flow mechanisms dominated the wear behavior for tests in argon. Hydrogen embrittlement led to 1000% increase of wear loss by causing more rapid crack nucleation of the asperities. The effects of different additions of chromium (≤ 8 at. %) on both microstructure and fracture behavior of Fe30Ni20Mn 35Al15 were investigated. All alloys consisted of (Ni, Al)-rich B2 and (Fe, Mn)-rich f.c.c. phases with most of the Cr residing in the f.c.c. phase. The addition of 6 at. % Cr not only increased the room temperature ductility, but also completely suppressed the environmental embrittlement observed in the Cr-free alloy at low strain rates. The effects of varying the Al concentration on the microstructures and tensile properties of six two-phase FeNiMnAl alloys with a composition close to Fe30Ni20Mn35Al15 were studied. The increase in f.c.c. volume fraction and f.c.c. lamellar width led to an increase in ductility and a decrease in yield strength. The correlation between the yield stress and f.c.c. lamellar spacing lambda obeyed a Hall-Petch-type relationship, i.e. sigmay=252+0.00027lambda-1, where the units for sigmay and lambda are MPa and meter, respectively. FeNiMnAl alloy with B2 and f.c.c. phases aligned along was reported to show high strength at room temperature. The mechanical properties of Fe 28Ni18Mn33Al21, consisting of (Ni, Al)-enriched B2 and (Fe, Mn)-enriched f.c.c. phases with

  12. Formation and Yield of Multi-Walled Carbon Nanotubes Synthesized via Chemical Vapour Deposition Routes Using Different Metal-Based Catalysts of FeCoNiAl, CoNiAl and FeNiAl-LDH

    PubMed Central

    Hussein, Mohd Zobir; Mohamad Jaafar, Adila; Hj. Yahaya, Asmah; Masarudin, Mas Jaffri; Zainal, Zulkarnain

    2014-01-01

    Multi-walled carbon nanotubes (MWCNTs) were prepared via chemical vapor deposition (CVD) using a series of different catalysts, derived from FeCoNiAl, CoNiAl and FeNiAl layered double hydroxides (LDHs). Catalyst-active particles were obtained by calcination of LDHs at 800 °C for 5 h. Nitrogen and hexane were used as the carrier gas and carbon source respectively, for preparation of MWCNTs using CVD methods at 800 °C. MWCNTs were allowed to grow for 30 min on the catalyst spread on an alumina boat in a quartz tube. The materials were subsequently characterized through X-ray diffraction, Fourier transform infrared spectroscopy, surface area analysis, field emission scanning electron microscopy and transmission electron microscopy. It was determined that size and yield of MWCNTs varied depending on the type of LDH catalyst precursor that is used during synthesis. MWCNTs obtained using CoNiAl-LDH as the catalyst precursor showed smaller diameter and higher yield compared to FeCoNiAl and FeNiAl LDHs. PMID:25380526

  13. Formation and yield of multi-walled carbon nanotubes synthesized via chemical vapour deposition routes using different metal-based catalysts of FeCoNiAl, CoNiAl and FeNiAl-LDH.

    PubMed

    Hussein, Mohd Zobir; Jaafar, Adila Mohamad; Yahaya, Asmah Hj; Masarudin, Mas Jaffri; Zainal, Zulkarnain

    2014-01-01

    Multi-walled carbon nanotubes (MWCNTs) were prepared via chemical vapor deposition (CVD) using a series of different catalysts, derived from FeCoNiAl, CoNiAl and FeNiAl layered double hydroxides (LDHs). Catalyst-active particles were obtained by calcination of LDHs at 800 °C for 5 h. Nitrogen and hexane were used as the carrier gas and carbon source respectively, for preparation of MWCNTs using CVD methods at 800 °C. MWCNTs were allowed to grow for 30 min on the catalyst spread on an alumina boat in a quartz tube. The materials were subsequently characterized through X-ray diffraction, Fourier transform infrared spectroscopy, surface area analysis, field emission scanning electron microscopy and transmission electron microscopy. It was determined that size and yield of MWCNTs varied depending on the type of LDH catalyst precursor that is used during synthesis. MWCNTs obtained using CoNiAl-LDH as the catalyst precursor showed smaller diameter and higher yield compared to FeCoNiAl and FeNiAl LDHs. PMID:25380526

  14. Glycerol Steam Reforming Over Ni-Fe-Ce/Al2O3 Catalyst: Effect of Cerium.

    PubMed

    Go, Gwang-Sub; Go, Yoo-Jin; Lee, Hong-Joo; Moon, Dong-Ju; Park, Nam-Cook; Kim, Young-Chul

    2016-02-01

    In this work, hydrogen production from glycerol by steam reforming was studied using Ni-metal oxide catalysts. Ni-based catalyst becomes deactivated during steam reforming reactions because of coke deposits and sintering. Therefore, the aim of this study was to reduce carbon deposits and sintering on the catalyst surface by adding a promoter. Ni-metal oxide catalysts supported on Al2O3 were prepared via impregnation method, and the calcined catalyst was reduced under H2 flow for 2 h prior to the reaction. The characteristics of the catalysts were examined by XRD, TPR, TGA, and SEM. The Ni-Fe-Ce/Al2O3 catalyst, which contained less than 2 wt% Ce, showed the highest hydrogen selectivity and glycerol conversion. Further analysis of the catalysts revealed that the Ni-Fe-Ce/Al2O3 catalyst required a lower reduction temperature and produced minimum carbon deposit. PMID:27433687

  15. Weldability of high toughness Fe-12% Ni alloys containing Ti, Al or Nb

    NASA Technical Reports Server (NTRS)

    Devletian, J. H.; Stephens, J. R.; Witzke, W. R.

    1977-01-01

    Three exceptionally high-toughness Fe-12%Ni alloys designed for cryogenic service were welded using the GTA welding process. Evaluation of weldability included equivalent energy (KIed) fracture toughness tests, transverse-weld tensile tests at -196 and 25 C and weld crack sensitivity tests. The Fe-12%Ni-0.25%Ti alloy proved extremely weldable for cryogenic applications, having weld and HAZ properties comparable with those of the wrought base alloy. The Fe-12%Ni-0.5%Al had good weld properties only after the weld joint was heat treated. The Fe-12%Ni-0.25%Nb alloy was not considered weldable for cryogenic use because of its poor weld joint properties at -196 C and its susceptibility to hot cracking.

  16. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel by Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Pereloma, E. V.; Stohr, R. A.; Miller, M. K.; Ringer, S. P.

    2009-12-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 °C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe)3Ti and (Ni,Fe)3(Al,Mn) precipitates eventually form after isothermal aging for ~60 seconds. The morphology of the (Ni,Fe)3Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe)3(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe)3Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  17. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel using Atom Probe Tomography

    SciTech Connect

    Pereloma, E. V.; Stohr, R A; Miller, Michael K; Ringer, S. P.

    2009-01-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe){sub 3}Ti and (Ni,Fe){sub 3}(Al,Mn) precipitates eventually form after isothermal aging for {approx}60 seconds. The morphology of the (Ni,Fe){sub 3}Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe){sub 3}(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe){sub 3}Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

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

    PubMed

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

    2010-08-01

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

  19. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO3 Fe3Al, Co3Al, and Ni3Al based intermetallic phases

    DOE PAGESBeta

    Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

    2014-11-07

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO3 Fe3Al, Co3Al and Ni3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe3Al and Co3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.« less

  20. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  1. ALCHEMI of Fe-doped B2-ordered NiAl alloys with different doping levels

    SciTech Connect

    Anderson, I.M.; Bentley, J.; Duncan, A.J.

    1994-09-01

    The ALCHEMI technique yields exact expressions for best-fit parameters in terms of ionization localization constants and site distributions of 3 elements distributed over two sublattices. In this paper, a graphical plotting technique is applied to Fe-doped NiAl B2-ordered alloys Ni{sub 0.5-x}Fe{sub x}Al{sub 0.5}, with x=0.02 or 0.10. The thin foil samples were examined in an electron microscope with an x-ray spectrometer.

  2. Local structure study of Fe dopants in Ni-deficit Ni3Al alloys

    SciTech Connect

    V. N. Ivanovski; Umicevic, A.; Belosevic-Cavor, J.; Lei, Hechang; Li, Lijun; Cekic, B.; Koteski, V.; Petrovic, C.

    2015-08-24

    We found that the local electronic and magnetic structure, hyperfine interactions, and phase composition of polycrystalline Ni–deficient Ni 3-x FexAl (x = 0.18 and 0.36) were investigated by means of 57 Fe Mössbauer spectroscopy. The samples were characterized by X–ray diffraction and magnetization measurements. The ab initio calculations performed with the projector augmented wave method and the calculations of the energies of iron point defects were done to elucidate the electronic structure and site preference of Fe doped Ni 3 Al. Moreover, the value of calculated electric field gradient tensor Vzz=1.6 1021Vm-2 matches well with the results of Mössbauer spectroscopy and indicates that the Fe atoms occupy Ni sites.

  3. Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

    NASA Astrophysics Data System (ADS)

    Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

    2015-02-01

    High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

  4. Exchange bias effects in Heusler alloy Ni2MnAl/Fe bilayers

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Tomoki; Kubota, Takahide; Sugiyama, Tomoko; Huminiuc, Teodor; Hirohata, Atsufumi; Takanashi, Koki

    2016-06-01

    Ni2MnAl Heusler alloy thin films were epitaxially grown on MgO(1 0 0) single crystal substrates by ultra-high-vacuum magnetron sputtering technique. X-ray diffraction and transmission electron microscopy observation revealed that the structures of all the Ni2MnAl thin films were B2-ordered regardless of the deposition temperature ranging from room temperature to 600 °C. The temperature dependence of electrical resistivity showed a kink about 280 K, which was consistent with a reported value of the Néel temperature for antiferromagnetic B2-Ni2MnAl. The magnetization curves of Ni2MnAl/Fe bilayer samples showed a shift caused by the interfacial exchange interaction at 10 K. The maximum value of the exchange bias field H ex was 55 Oe corresponding to the exchange coupling energy J k of 0.03 erg cm‑2.

  5. The microstructure of near-equiatomic B2/f.c.c. FeNiMnAl alloys

    SciTech Connect

    Baker, I.; Wu, H.; Wu, X.; Miller, M.K.; Munroe, P.R.

    2011-10-15

    A microstructural analysis of two FeNiMnAl alloys, Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20}, was performed by a combination of atom probe tomography and transmission electron microscopy techniques. Although the microstructures of both alloys, which consist of alternating platelets aligned along < 100> of the B2-ordered phase, are similar to B2/b.c.c. two-phase alloys previously observed in the FeNiMnAl system, the two phases present in the current alloys are B2-ordered and f.c.c., with the latter phase being heavily twinned. Very fine ({approx} 5 nm) precipitates, whose chemistry was similar to that of the f.c.c. (Fe, Mn)-rich phase, were found within the B2 (Ni, Al)-rich phase in both alloys. - Highlights: {yields} The microstructures of the novel alloys Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20} were characterized. {yields} Atom probe tomography and transmission electron microscopy were used in the study. {yields} A < 100>-aligned B2-ordered phase and heavily-twinned f.c.c. phase were present. {yields} Very fine (Fe, Mn)-rich precipitates were found within the B2 (Ni, Al)-rich phase.

  6. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    DOE PAGESBeta

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; Gao, Michael C.; Tang, Zhi; Poplawsky, Jonathan D.; Liaw, Peter K.

    2016-07-19

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

  7. Spark plasma sintering of a nanocrystalline Al-Cu-Mg-Fe-Ni-Sc alloy

    NASA Astrophysics Data System (ADS)

    Zúñiga, Alejandro; Ajdelsztajn, Leonardo; Lavernia, Enrique J.

    2006-04-01

    The microstructure and aging behavior of a nanocrystalline Al-Cu-Mg-Fe-Ni-Sc alloy was studied. The nanocrystalline powders were produced by milling at liquid nitrogen temperature and then consolidated using spark plasma sintering (SPS). The microstructure after SPS consisted of a bimodal aluminum grain structure (coarse-grained and fine-grained regions), along with Al9FeNi and Al2CuMg particles dispersed throughout. The microstructure observed in the as-consolidated sample is rationalized on the basis of high current densities that are generated during sintering. Solution treatment and aging of the SPS Al-Cu-Mg-Fe-Ni-Sc sample resulted in softening instead of hardening. This observation can be explained by the reduced amount of Cu, Mg, and Si in solid solution available to form S' Al2CuMg due to the precipitation of Al7FeCu2 and Si-rich particles, and by the fact that rodlike S' Al2CuMg particles could only precipitate out in the coarse-grained regions, greatly decreasing their influence on the hardness. This lack of precipitation in the fine-grained region is argued to represent a new physical observation and is rationalized on the basis of physical and thermodynamic effects. The nanocrystalline SPS Al-Cu-Mg-Fe-Ni-Sc sample was also extremely thermally stable, retaining a fine-grained structure even after solution treatment at 530°C for 5 h. The observed thermal stability is rationalized on the basis of solute drag and Zener pinning caused by the impurities introduced during the cryomilling process.

  8. The Microstructure of Near-Equiatomic B2/f.c.c. FeNiMnAl Alloys

    SciTech Connect

    Baker, Ian; Wu, H; Wu, Xiaolan; Miller, Michael K; Munroe, P R

    2011-01-01

    A microstructural analysis of two FeNiMnAl alloys, Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20}, was performed by a combination of atom probe tomography and transmission electron microscopy techniques. Although the microstructures of both alloys, which consist of alternating platelets aligned along <100> of the B2-ordered phase, are similar to B2/b.c.c. two-phase alloys previously observed in the FeNiMnAl system, the two phases present in the current alloys are B2-ordered and f.c.c., with the latter phase being heavily twinned. Very fine ({approx} 5 nm) precipitates, whose chemistry was similar to that of the f.c.c. (Fe, Mn)-rich phase, were found within the B2 (Ni, Al)-rich phase in both alloys.

  9. Theoretical analysis of compatibility of several reinforcement materials with NiAl and FeAl matrices

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1989-01-01

    Several potential reinforcement materials were assessed for their chemical, coefficient of thermal expansion (CTE), and mechanical compatibility with the intermetallic matrices based on NiAl and FeAl. Among the ceramic reinforcement materials, Al2O3, TiC, and TiB2, appear to be the optimum choices for NiAl and FeAl matrices. However, the problem of CTE mismatch with the matrix needs to be solved for these three reinforcement materials. Beryllium-rich intermetallic compounds can be considered as potential reinforcement materials provided suitable reaction barrier coatings can be developed for these. Based on preliminary thermodynamic calculations, Sc2O3 and TiC appear to be suitable as reaction barrier coatings for the beryllides. Several reaction barrier coatings are also suggested for the currently available SiC fibers.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  11. An overview of the welding of Ni{sub 3}Al and Fe{sub 3}Al alloys

    SciTech Connect

    Santella, M.L.

    1996-12-31

    Weldability (degree to which defect formation is resisted when an alloy is welded) is an issue in fabrication of Ni{sub 3}Al and Fe{sub 3}Al. Work to define and improve welding of Ni{sub 3}Al and Fe{sub 3}Al alloys is reviewed and progress illustrated by examples of current activities. The cast Ni{sub 3}Al alloys currently under development, IC221M and IC396M, have low resistance to solidification cracking and hence difficult to weld. Modifications to the composition of both base alloys and weld deposits,however, increase their resistance to cracking. Crack-free, full-penetration welds were made in centrifugally cast tubes of IC221M. Tensile and stress- rupture properties of the weldments compare favorably with base metal properties. Weldability issues have limited the use of Fe{sub 3}Al alloys to weld overlay applications. Filler metal compositions suitable for weld overlay cladding were developed, and the preheat and postweld heat treatment needed to avoid cracking, were determined experimentally.

  12. Analysis of the microstructure of Cr-Ni surface layers deposited on Fe{sub 3}Al by TIG

    SciTech Connect

    Ma Haijun . E-mail: hjma123@mail.sdu.edu.cn; Li Yajiang; Wang Juan

    2006-12-15

    A series of Cr-Ni alloys were overlaid on a Fe{sub 3}Al surface by tungsten inert gas arc welding (TIG) technology. The microstructure of the Cr-Ni surface layers were analysed by means of optical metallography, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that when the appropriate TIG parameters were used and Cr25-Ni13 and Cr25-Ni20 alloys were used for the overlaid materials, the Cr-Ni surface layers were crack-free. The matrix of the surface layer was austenite (A), pro-eutectoid ferrite (PF), acicular ferrite (AF), carbide-free bainite (CFB) and lath martensite (LM), distributed on the austenitic grain boundaries as well as inside the grains. The phase constituents of the Cr25-Ni13 surface layer were {gamma}-Fe, Fe{sub 3}Al, FeAl, NiAl, an Fe-C compound and an Fe-C-Cr compound. The microhardness of the fusion zone was lower than that of the Fe{sub 3}Al base metal and Cr25-Ni13 surface layer.

  13. Structure and energetics of high index Fe, Al, Cu and Ni surfaces using equivalent crystal theory

    NASA Technical Reports Server (NTRS)

    Rodriguez, Agustin M.; Bozzolo, Guillermo; Ferrante, John

    1993-01-01

    Equivalent crystal theory (ECT) is applied to the study of multilayer relaxations and surface energies of high-index faces of Fe, Al, Ni, and Cu. Changes in interplanar spacing as well as registry of planes close to the surface and the ensuing surface energies changes are discussed in reference to available experimental data and other theoretical calculations. Since ECT is a semiempirical method, the dependence of the results on the variation of the input used was investigated.

  14. Thermoelastic Martensitic Transformations in Single Crystals of FeNiCoAlX(B) Alloys

    NASA Astrophysics Data System (ADS)

    Chumlyakov, Yu. I.; Kireeva, I. V.; Kuts, O. A.; Platonova, Yu. N.; Poklonov, V. V.; Kukshauzen, I. V.; Kukshauzen, D. A.; Panchenko, M. Yu.; Reunova, K. A.

    2016-03-01

    Using single crystals of Fe-based disordered alloys (Fe - 28% Ni - 17% Co - 11.5% Al - 2.5% X (0.05% B) (at.%) (X = Ti, Nb(B), (Ti + Nb)B), undergoing thermoelastic γ-α '-martensitic transformations (MTs), it is shown that precipitation of particles of the ordered γ'-phase in the course of aging at T = 973 K for 5 h results in the development of shape memory (SME) and superelasticity (SE) effects. It is experimentally found that variation in chemical composition and size of disperse particles of the γ'-phase allows controlling both mechanical and functional properties - SME and SE.

  15. 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)

  16. Effect of minor Fe substitution for Ni on the magnetic properties of a Gd55Al20Ni25 bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Ding, Ding; Li, Zheng; Wang, Zheng Wen; Wu, Cheng; Zhang, Yi Qing

    2016-03-01

    In this work, we studied the effect of micro-alloying on the glass-forming ability (GFA) and magnetic properties of Gd55Al20Ni25 bulk metallic glass (BMG). By minor Fe substitution for Ni, we obtained Gd55Al20Ni23Fe2 BMG with enhanced magneto-caloric effect (MCE) and GFA similar to Gd55Al20Ni25 BMG. The maximum magnetic entropy change (-ΔSmpeak) and the magnetic refrigerant capacity (Rc) of Gd55Al20Ni23Fe2 BMG within the field range of 5 T are about 9.05 J kg-1 K-1 and 850J ṡkg-1, respectively, both of which are larger than the values of Gd55Ni25Al20 BMG. The mechanism for the improved MCE of the Gd55Al20Ni23Fe2 BMG was investigated and the magneto-caloric behaviors were studied by constructing the field dependence of - ΔSmpeak of Gd55Al20Ni23Fe2 BMG.

  17. Negative permittivity behavior in Fe50Ni50/Al2O3 magnetic composite near percolation threshold

    NASA Astrophysics Data System (ADS)

    Chen, Min; Fan, Run-hua; Gao, Meng; Pan, Shi-bing; Yu, Ming-xun; Zhang, Zi-dong

    2015-05-01

    The physical properties of conductor-insulator composites often take dramatic changes near the percolation threshold (fc), leading to interesting applications, such as double negative material. This phenomenon also will be enlarged by increasing the differences between the properties of the constitutive phases. In this paper, the Fe50Ni50/Al2O3 magnetic cermets with different Fe50Ni50 volume contents (10%, 20%, 30%, 40%) were prepared via hot-pressing sintering. The permittivity of Fe50Ni50/Al2O3 composites has been studied in the radio frequency range. The results indicate that when the Fe50Ni50 content is below fc, the reactance of the composites takes a negative value, which indicates a capacitive character. The metallic Fe50Ni50 grains are isolated in the insulating ceramic matrix, leading to an insulator-like dielectric property. When the volume fraction of Fe50Ni50 reaches 40% which is above fc, the composites manifest an inductive character. In this case, the negative permittivity has been obtained over the whole test frequency range due to the percolation phenomenon, which makes Fe50Ni50/Al2O3 composites as promising candidates for double negative materials.

  18. Cyclic Deformation Behavior of Aged FeNiCoAlTa Single Crystals

    NASA Astrophysics Data System (ADS)

    Krooß, P.; Niendorf, T.; Karaman, I.; Chumlyakov, Y.; Maier, H. J.

    2012-11-01

    The cyclic deformation behavior of [001] oriented Fe-28Ni-17Co-11.5Al-2.5Ta (at.%) shape memory single crystals was investigated under tension. Dog-bone shaped specimens were tested up to 100 cycles after different aging heat treatments in order to characterize the cyclic stress-strain response and functional degradation. The smaller particles formed as a consequence of short aging for 1 h at 700°C, as compared to longer aging for 7 h, resulted in significantly enhanced resistance to cyclic degradation.

  19. CVD Diamond Coating on Al-Interlayered FeCoNi Alloy Substrate: An Interfacial Study

    NASA Astrophysics Data System (ADS)

    Li, Y. S.; Sun, X. Y.; Yang, L. Z.; Kurmaev, E. Z.; Yang, Q.

    2015-12-01

    In this study, an Al thin film interlayer of 80 nm thick has been applied on FeCoNi alloy substrate which possesses a low coefficient of thermal expansion, to enhance the interfacial adhesion of diamond films produced by microwave plasma-enhanced chemical vapor deposition. Characterization of the top deposit, interlayer and the underlying substrate was performed by Raman spectroscopy, energy dispersive X-ray analysis, X-ray photoelectronic spectroscopy, X-scanning electron microscopy and X-ray diffraction. The Al interlayer has effectively inhibited the formation of graphitic carbon and markedly enhanced the nucleation, growth and adhesion of diamond films. The beneficial role Al plays is primarily attributed to the formation of an alumina barrier layer on the substrate surface, as verified by interfacial analysis.

  20. Nucleation of ordered Fe islands on Al 2O 3/Ni 3Al(1 1 1)

    NASA Astrophysics Data System (ADS)

    Lehnert, A.; Krupski, A.; Degen, S.; Franke, K.; Decker, R.; Rusponi, S.; Kralj, M.; Becker, C.; Brune, H.; Wandelt, K.

    2006-05-01

    Scanning tunneling microscopy (STM) has been used to investigate the nucleation and stability of iron clusters on the Al 2O 3/Ni 3Al(1 1 1) surface as a function of coverage and annealing temperature. We show that atomic beam deposition of iron leads to hexagonally ordered cluster arrangements with a distance of 24 Å between the clusters evidencing the template effect of the alumina film. The shape of the iron clusters is two-dimensional (2D) at deposition temperatures from 130 K to 160 K and three-dimensional (3D) at 300 K. However, the 2D iron clusters grown between 130 K and 160 K are stable up to 350 K.

  1. Microstructural and magnetic characterization of iron precipitation in Ni-Fe-Al alloys

    SciTech Connect

    Duman, Nagehan; Mekhrabov, Amdulla O.; Akdeniz, M. Vedat

    2011-06-15

    The influence of annealing on the microstructural evolution and magnetic properties of Ni{sub 50}Fe{sub x}Al{sub 50-x} alloys for x = 20, 25, and 30 has been investigated. Solidification microstructures of as-cast alloys reveal coarse grains of a single B2 type {beta}-phase and typical off eutectic microstructure consisting of proeutectic B2 type {beta} dendrites and interdendritic eutectic for x = 20 and x > 20 at.% Fe respectively. However, annealing at 1073 K results in the formation of FCC {gamma}-phase particles along the grain boundaries as well as grain interior in x = 20 at.% Fe alloy. The volume fraction of interdentritic eutectic regions tend to decrease and their morphologies start to degenerate by forming FCC {gamma}-phase for x > 20 at.% Fe alloys with increasing annealing temperatures. Increasing Fe content of alloys induce an enhancement in magnetization and a rise in the Curie transition temperature (T{sub C}). Temperature scan magnetic measurements and transmission electron microscopy reveal that a transient rise in the magnetization at temperatures well above the T{sub C} of the alloys would be attributed to the precipitation of a nano-scale ferromagnetic BCC {alpha}-Fe phase. Retained magnetization above the Curie transition temperature of alloy matrix, together with enhanced room temperature saturation magnetization of alloys annealed at favorable temperatures support the presence of ferromagnetic precipitates. These nano-scale precipitates are shown to induce significant precipitation hardening of the {beta}-phase in conjunction with enhanced room temperature saturation magnetization in particular when an annealing temperature of 673 K is used. - Research Highlights: {yields} Evolution of microstructure and magnetic properties with varying Fe content. {yields} Transient rise in magnetization via the formation of ferromagnetic phase. {yields} Enhancements in saturation magnetization owing to precipitated ferromagnetic phase. {yields} Nanoscale

  2. Study of the effects of implantation on the high Fe-Ni-Cr and Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Ribarsky, M. W.

    1985-01-01

    A theoretical study of the effects of implantation on the corrosion resistance of Fe-Ni-Cr and Ni-Cr-Al alloys was undertaken. The purpose was to elucidate the process by which corrosion scales form on alloy surfaces. The experiments dealt with Ni implanted with Al, exposed to S at high temperatures, and then analyzed using scanning electron microscopy, scanning Auger spectroscopy and X-ray fluorescence spectroscopy. Pair bonding and tight-binding models were developed to study the compositions of the alloys and as a result, a new surface ordering effect was found which may exist in certain real alloys. With these models, the behavior of alloy constituents in the presence of surface concentrations of O or S was also studied. Improvements of the models to take into account the important effects of long- and short-range ordering were considered. The diffusion kinetics of implant profiles at various temperatures were investigated, and it was found that significant non-equilibrium changes in the profiles can take place which may affect the implants' performance in the presence of surface contaminants.

  3. High temperature sulfidation of Fe{sub 3}Al and NiCr thermal spray coatings at 600 C

    SciTech Connect

    Luer, K.; DuPont, J.; Marder, A.

    1999-11-01

    Three Fe{sub 3}Al and two Ni45Cr thermal spray coatings were tested in Ar-3.5H{sub 2}-0.1H{sub 2}S for 500h at 600 C and compared to AISI 1008 steel. The three Fe{sub 3}Al-type coatings were processed from the same lot of gas atomized Fe{sub 3}Al powder using a high velocity oxygen fuel (HVOF) thermal spray process and an air plasma spray (APS) process. In general, the Fe{sub 3}Al-type composition displayed excellent resistance to sulfidation corrosion at 600 C which correlated with the reported literature on wrought Fe{sub 3}Al alloys. HVOF processing did not significantly degrade the composition of the consumable and produced coatings with low porosity, low oxide content, high sulfidation resistance, and high resistance to sulfur penetration. In contrast, APS processing caused significant degradation to the particles which reduced the sulfidation resistance of the coating and enabled local sulfidation attack at alloy depleted regions. The APS processed Fe{sub 3}Al coating also contained high porosity which enabled sulfur to fully penetrate the splat boundaries of the coating to the substrate. The two Ni45Cr-type coatings were produced using different processes and different consumables. One of the Ni45Cr coatings was processed using a proprietary wire combustion arc-spray (CAS) process. The second Ni45Cr coating was processed using a HVOF spray process. Both NiCr-type coatings reacted moderately with the sulfidizing gas at 600 C to form a mixed chromium oxide-sulfide scale despite marked differences in coating structure and composition. CAS processing caused significant degradation of the Ni45Cr consumable and produced a coating with low porosity and high oxide content. In contrast, HVOF processing caused negligible degradation of the Ni45Cr consumable and produced a coating with low porosity and moderate oxide content.

  4. Galvanomagnetic properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-01

    The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3 d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit ( H > 10 kOe), the value and the sign of the normal ( R 0) and anomalous ( R s ) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R s in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio ( R s ∝ ρ 0 3.1 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  5. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-15

    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  6. Effect of Strain Rate on Deformation Behavior of AlCoCrFeNi High-Entropy Alloy by Nanoindentation

    NASA Astrophysics Data System (ADS)

    Tian, L.; Jiao, Z. M.; Yuan, G. Z.; Ma, S. G.; Wang, Z. H.; Yang, H. J.; Zhang, Y.; Qiao, J. W.

    2016-05-01

    In this study, nanoindentation tests with continuous stiffness measurement technique were measured to investigate the deformation behavior of a high-entropy alloy AlCoCrFeNi under different indentation strain rates at room temperature. Results suggest that the creep behavior exhibits remarkable strain rate dependence. In-situ scanning images showed a conspicuous pileup around the indents, indicating that an extremely localized plastic deformation occurred during the nanoindentation. Under different strain rates, elastic modulus basically remains unchanged, while the hardness decreases with increasing indentation depth due to the indentation size effect. Furthermore, the modulus and hardness of AlCoCrFeNi HEAs are greater than that of the Al x CoCrFeNi (x = 0.3,0.5) at the strain rate of 0.2 s-1 due to its higher negative enthalpy of mixing related to the atomic binding force, and the solid solution strengthening induced by the lattice distortion, respectively.

  7. Effect of Strain Rate on Deformation Behavior of AlCoCrFeNi High-Entropy Alloy by Nanoindentation

    NASA Astrophysics Data System (ADS)

    Tian, L.; Jiao, Z. M.; Yuan, G. Z.; Ma, S. G.; Wang, Z. H.; Yang, H. J.; Zhang, Y.; Qiao, J. W.

    2016-06-01

    In this study, nanoindentation tests with continuous stiffness measurement technique were measured to investigate the deformation behavior of a high-entropy alloy AlCoCrFeNi under different indentation strain rates at room temperature. Results suggest that the creep behavior exhibits remarkable strain rate dependence. In-situ scanning images showed a conspicuous pileup around the indents, indicating that an extremely localized plastic deformation occurred during the nanoindentation. Under different strain rates, elastic modulus basically remains unchanged, while the hardness decreases with increasing indentation depth due to the indentation size effect. Furthermore, the modulus and hardness of AlCoCrFeNi HEAs are greater than that of the Al x CoCrFeNi ( x = 0.3,0.5) at the strain rate of 0.2 s-1 due to its higher negative enthalpy of mixing related to the atomic binding force, and the solid solution strengthening induced by the lattice distortion, respectively.

  8. Calculations of structural, elastic, electronic, magnetic and phonon properties of FeNiMnAl by the first principles

    SciTech Connect

    Uğur, Şule; İyigör, Ahmet

    2014-10-06

    The electronic, elastic and dynamical properties of the quaternary alloy FeNiMnAl have been investigated using a pseudopotential plane wave method within the generalized gradient approximation (GGA). We determined the lattice parameters and the bulk modulus B. In addition, the elastic properties such as elastic constans (C{sub 11}, C{sub 12} and C{sub 44}), the shear modulus G, the young modulus E, the poisson's ratio σ and the B/G ratio are also given. The FeNiMnAl Heusler alloy exhibit a ferromagnetic half-metallic behavior with the total magnetic moment of 4.02 μ{sub B}. The phonon dispersion of FeNiMnAl has been performed using the density functional theory and the direct method with 2×2×2 supercell.

  9. Microstructural Evolution and Functional Properties of Fe-Mn-Al-Ni Shape Memory Alloy Processed by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Niendorf, Thomas; Brenne, Florian; Krooß, Philipp; Vollmer, Malte; Günther, Johannes; Schwarze, Dieter; Biermann, Horst

    2016-06-01

    In the current study, a Fe-Mn-Al-Ni shape memory alloy is processed by additive manufacturing for the first time. Microstructural evolution upon processing is strongly affected by thermal gradients and solidification velocity and, thus, by processing parameters and the actual specimen geometry. By single-step solutionizing heat treatment pronounced grain growth is initiated leading to microstructures showing good reversibility. The compressive stress-strain response revealed maximum reversible pseudo-elastic strain of about 7.5 pct. Critical steps toward further optimization of additively manufactured Fe-Mn-Al-Ni shape memory alloys are discussed.

  10. Microstructural Evolution and Functional Properties of Fe-Mn-Al-Ni Shape Memory Alloy Processed by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Niendorf, Thomas; Brenne, Florian; Krooß, Philipp; Vollmer, Malte; Günther, Johannes; Schwarze, Dieter; Biermann, Horst

    2016-03-01

    In the current study, a Fe-Mn-Al-Ni shape memory alloy is processed by additive manufacturing for the first time. Microstructural evolution upon processing is strongly affected by thermal gradients and solidification velocity and, thus, by processing parameters and the actual specimen geometry. By single-step solutionizing heat treatment pronounced grain growth is initiated leading to microstructures showing good reversibility. The compressive stress-strain response revealed maximum reversible pseudo-elastic strain of about 7.5 pct. Critical steps toward further optimization of additively manufactured Fe-Mn-Al-Ni shape memory alloys are discussed.

  11. New Fe-Co-Ni-Cu-Al-Ti Alloy for Single-Crystal Permanent Magnets

    NASA Astrophysics Data System (ADS)

    Belyaev, I. V.; Bazhenov, V. E.; Moiseev, A. V.; Kireev, A. V.

    2016-03-01

    A new alloy intended for single-crystal permanent magnets has been suggested. The new alloy has been designed based on the well-known Fe-Co-Ni-Cu-Al-Ti system and contains to 1 wt % Hf. The alloy demonstrates an enhanced potential ability for single-crystal forming in the course of unidirectional solidification of ingot. Single-crystal permanent magnets manufactured from this alloy are characterized by a high level of magnetic properties. When designing the new alloy, computer simulation of the phase composition and calculations of solidification parameters of complex metallic systems have been performed using the Thermo-Calc software and calculation and experimental procedures based on quantitative metallographic analysis of quenched structures. After the corresponding heat treatment, the content of high-magnetic phase in the alloy is 10% higher than that in available analogous alloys.

  12. Microstructure and Properties of FeAlCrNiMo x High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Li, X. C.; Dou, D.; Zheng, Z. Y.; Li, J. C.

    2016-06-01

    FeAlCrNiMo x high-entropy alloys were prepared. The effect of Mo content on the microstructure and the properties of the alloys were investigated. When the Mo content was 0.1, the alloys were composed of single BCC solid solution; when Mo content reaches 0.25, the alloys were composed of BCC solid solution and ordered B2 solid solution. When Mo content is more than 0.75, some σ phases emerged. The volume fraction of the second phase increases with the increasing Mo content, and the crystal grains became coarsening. The yield strength, fracture strength, and hardness increase with the increasing Mo content and reach 2252, 2612 MPa, and 1006 Hv, respectively. The magnetic transformation undergoes from the ferromagnetism to paramagnetism with the increasing Mo content. The saturation intensity and remnant magnetism are decreased with the increasing Mo content.

  13. The cyclic oxidation resistance at 1200 C of beta-NiAl, FeAl, and CoAl alloys with selected third element additions

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Titran, R. H.

    1992-01-01

    The intermetallic compounds Beta-NiAl, FeAl, and CoAl were tested in cyclic oxidation with selected third element alloy additions. Tests in static air for 200 1-hr cycles at 1200 C indicated by specific weight change/time data and x-ray diffraction analysis that the 5 at percent alloy additions did not significantly improve the oxidation resistance over the alumina forming baseline alloys without the additions. Many of the alloy additions were actually deleterious. Ta and Nb were the only alloy additions that actually altered the nature of the oxide(s) formed and still maintained the oxidation resistance of the protective alumina scale.

  14. Rocking-beam spectrum images and ALCHEMI of Ni{sub 50}Al{sub 40}Fe{sub 10}

    SciTech Connect

    Anderson, I.M.; Bentley, J.

    1997-04-01

    A rocking-beam energy-dispersive X-ray (EDX) spectrum image was acquired near the [035] zone axis of a B2-ordered alloy of composition Ni{sub 50}Al{sub 40}Fe{sub 10}. Images comparable to those acquired by Rossouw et al. were formed a posteriori by integrating the X-ray intensities in windows enclosing the Al-K, Fe-K{sub {alpha}}, and Ni-K{sub {alpha}} characteristic X-ray peaks for each pixel of the spectrum image. These images are shown along with a bright-field transmission channeling pattern (TCP), which records the signal from the bright-field STEM detector as the incident beam direction is varied with the beam-tilt coils, and an EDX spectrum from one pixel of the image. The range of orientations from which the spectrum image was acquired is indicated by the square superimposed on the TCP. ALCHEMI (atom-location by channeling-enhanced microanalysis) was performed on a subset of the spectrum image using standard methods. Spectra from a series of {approximately}30 pixels along lines parallel to the (200) band were summed at each of 31 orientations relative to the band in the range 0 {le} {theta}/{theta}{sub 200} {le} 2.3. Characteristic X-ray intensities of the K-shell X-rays of Ni, Fe, and Al were extracted from the 31 summed spectra with the simplex fitting procedure of the DTSA spectral analysis software. The fraction of Fe on the `Ni`-site from this analysis, p{sub Fe`Ni`} = 23.8 {+-} 2.1%, is in excellent agreement with p{sub Fe`Ni`} = 23.7 {+-} 0.9%, which was determined by an analysis of a series of ten spectra acquired at orientations of the crystal carefully chosen so that the contributions of nonsystematic reflections are negligible.

  15. EFFECTS OF AQUEOUS AL, CD, CU, FE(II), NI, AND ZN ON PB IMMOBILIZATION BY HYDROXYAPATITE

    EPA Science Inventory

    The effects of aqueous Al, Cd, Cu, Fe(II), Ni, or Zn on Pb immobilization by hydroxyapatite (Ca10(PO4),(OH)2) were studied. ead was removed mainly via hydroxyapatite dissolution and hydroxypyromorphite (Pb10(PO4)6(OH)2) precipitation in the presence of these metals with a Pb remo...

  16. Strain rate sensitivity of nanoindentation creep in an AlCoCrFeNi high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Wang, Z. H.; Wu, R. F.; Qiao, J. W.

    2016-09-01

    Creep behaviors of an AlCoCrFeNi high-entropy alloy with the body-centered cubic structure were investigated by nanoindentation. The enhanced strain gradient induced by higher strain rate leads to decreased strain rate sensitivity during creep process. The present alloy exhibits excellent creep resistance, mainly due to its large entropy of mixing and highly distorted lattice structure.

  17. Effect of Heat Treatment on Morphology of Fe-Rich Intermetallics in Hypereutectic Al-Si-Cu-Ni Alloy with 1.26 pct Fe

    NASA Astrophysics Data System (ADS)

    Sha, Meng; Wu, Shusen; Wan, Li; Lü, Shulin

    2013-12-01

    Cobalt is generally considered as the element that can neutralize the negative effects of iron in Al alloys, such as inducing fracture and failure for stress concentration. Nevertheless, Fe-rich intermetallics would be inclined to form coarse plate-like δ-Al4(Fe, Co, Ni)Si2 particles when the content of Fe was high, which could also cause inferior mechanical properties. The dissolution and transformation of δ-Al4(Fe, Co, Ni)Si2 phase in solution heat-treated samples of Al-20Si-1.85Cu-1.05Ni-1.26Fe-1.35Co alloy were studied using optical microscopy, image analysis, and scanning electron microscopy. The effects of solution heat treatment time ranging from 0 to 9 hours at 783.15 K (510 °C) on mechanical properties were also investigated. The coarse plate-like δ-Al4(Fe, Co, Ni)Si2 particles varied slowly through concurrent dissolution along widths and at the plate tips as solution treatment time increased, which could be explained from diffusion-induced grain boundary migration. Solution heat treatment also has an important influence on mechanical properties. The maximum ultimate tensile strength and yield strength after T6 treatment were 258 and 132 MPa, respectively, while the maximum hardness was 131 HB. Compared with those of the samples in the as-cast state, they increased by 53, 42, and 28 pct, respectively. Moreover, δ-Al4(Fe, Co, Ni)Si2 phase, which appears as a coarse plate-like particle in two dimensions, is actually a cuboid in three dimensions. The length of this cuboid is close to the width, while the height is much smaller.

  18. Anodic Corrosion Behavior of NiFe2O4-Based Cermet in Na3AlF6-K3AlF6-AlF3 for Aluminum Electrolysis

    NASA Astrophysics Data System (ADS)

    Tian, Zhongliang; Lai, Yanqing; Yang, Shu; Li, Jie; Hwang, Jiann-Yang; Liu, Yexiang

    2015-03-01

    A (Cu,Ni)/(10NiO-NiFe2O4) cermet was tested as an inert anode for aluminum electrolysis in Na3AlF6-K3AlF6-AlF3 melt at 1173 K (900 °C), and its corrosion behavior was studied. The results show that the low-temperature Na3AlF6-K3AlF6-AlF3 bath is beneficial, improving the service conditions. With the combined effects of the electrolyte composition and the nascent oxygen during electrolysis, the metal phase (Cu,Ni) at the surface of anode will not be leached preferentially, but be transferred into the aluminates including FeAl2O4, NiAl2O4 and CuAl2O4. This is helpful for the anode to improve its corrosion resistance.

  19. High-field magnetic properties of Ho 2Fe 15M 2 compounds (M  Al, Ga, Ni and Si)

    NASA Astrophysics Data System (ADS)

    Wang, J. L.; Tang, N.; Li, W. Z.; Qin, W. D.; Pan, H. Y.; Nasunjilegal, B.; Yang, F. M.; de Boer, F. R.

    1996-07-01

    The crystalline structure and magnetic properties of the Ho 2Fe 15M 2 compounds with M  Al, Si, Ni, and Ga have been investigated. X-ray diffraction patterns on powder samples show that all compounds crystallize in the Th 2Ni 17-type structure. The substitution of Al and Ga for Fe leads to an increase in the lattice constants a and c, but a decrease for Si substitution. Substitution of all the M elements for Fe leads to an increase in the Curie temperature and to a decrease in the saturation magnetization. The exchange coupling constants JHoT between Ho and transition metal spins are found to be almost independent of the substituting atom.

  20. Aluminium Electrolysis with Fe-Ni-Al2O3 Inert Anodes at 850 °C

    NASA Astrophysics Data System (ADS)

    Shi, Zhongning; Junli, Junli; Gao, Bingliang; Hu, Xianwei; Wang, Zhaowen

    2011-06-01

    Fe-Ni-Al2O3 cermet materials were prepared, and the electrolysis with these anodes were performed in cryolite-based electrolyte consisted of 44NaF-40AlF3-8NaCl-5CaF2-3Al2O3(wt%) at 850 °C. The purity of produced aluminium is 97-98%, while the calculated anodic corrosion rate is 18.2 mm/a-24.0 mm/a. The EPMA analysis showed that there is an oxide scale consisting of Fe2O3 and FeAl2O4 on the anode working surface. The homeostasis of dissolution and formation of oxide scale makes the thickness of the oxide scale and the cell voltage stable within a certain range. The dissolution of oxide scale results in the presence of FeF3 in the electrolyte. By analysis of the corrosion process, it shows that low temperature, high alumina concentration and low CR electrolysis is preferred for using Fe-Ni-Al2O3 inert anodes for aluminium electrolysis.

  1. High-field magnetization of heusler alloys Fe2 XY ( X = Ti, V, Cr, Mn, Fe, Co, Ni; Y = Al, Si)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Belozerova, K. A.; Weber, H. W.

    2015-10-01

    The magnetization curves of ferromagnetic Heusler alloys Fe2 XY (where X = Ti, V, Cr, Mn, Fe, Co, Ni are transition 3 d elements and Y = Al, Si are the s and p elements of the third period of the Periodic Table) have been measured at T = 4.2 K in the field range H ≤ 70 kOe. It has been shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  2. Influence cobalt on microstructural and hardness property of Al-Zn-Mg-Cu-Fe-Cr-Ni P/ M alloys

    NASA Astrophysics Data System (ADS)

    Naeem, Haider T.; Mohammad, Kahtan S.; Hussin, Kamarudin; Rahmat, Azim; Bashirom, Nurhuda

    2015-05-01

    In this study, influence cobalt additives on the microstructural and hardness properties of an Al-Zn-Mg-Cu-Fe-Cr-Ni PM alloy undergone the retrogression and re-aging treatment were carried out. Green compacts pressed at 370 MPa were then sintered at temperature 650°C in argon atmosphere for two hours. The sintered compacts subjected to a homogenizing treated at 470°C for 1.5 hours then aged at 120°C for 24 hours and retrogressed at 180°C for 30 minutes, and then re-aged at 120°C for 24 hours. Microstructural results of the Al-Zn-Mg-Cu-Fe-Cr-Ni-Co alloys introduced an intermetallics compound in the matrix of alloy, identified as the Al5Co2, Al70Co20Ni10 and Al4Ni3 phases besides to the MgZn2 and Mg2Zn11 phases which produced of the precipitation hardening during heat treatment. These compounds with precipitates provided strengthening of dispersion that led to improved Vickers's hardness and dinsifications properties of the alloy. The highest Vickers hardness of aluminum alloy containing cobalt was gotten after applying the retrogression and re-aging treatment.

  3. Influence of Detonation Gun Spraying Conditions on the Quality of Fe-Al Intermetallic Protective Coatings in the Presence of NiAl and NiCr Interlayers

    NASA Astrophysics Data System (ADS)

    Senderowski, Cezary; Bojar, Zbigniew

    2009-09-01

    The paper presents results of detailed research of the application of detonation gun (D-gun) spraying process for deposition of Fe-Al intermetallic coatings in the presence of NiAl and NiCr interlayers. A number of D-gun experiments have been carried out with significant changes in spraying parameters which define the process energy levels (changes in volumes of the working and fuel gases, and the distance and frequency of spraying). These changes directly influenced the quality of the coatings. The initial results underlay the choice of the process parameters with the view to obtain the most advantageous of geometric and physical-mechanical properties of the coating material, interlayer and substrate. The metallurgical quality of the coatings was considered by taking into account grain morphology, the inhomogeneity of chemical content and phase structure, the cohesive porosity in the coating volume, and adhesive porosity in the substrate/interlayer/coating boundaries. The surface roughness level was also considered. It was found that the D-gun sprayed coatings are in all cases built with flat lamellar splats. The splats develop from powder particles which are D-gun transformed in their plasticity and geometry. A significant result of the optimization of D-gun spraying parameters is the lack of signs of melting of the material (even in microareas) while the geometry of the subsequently deposited grains is considerably changed and the adhesivity and cohesion of the layers proves to be high. This is considered as an undeniable proof of high plasticity of the D-gun formed Fe-Al intermetallic coating.

  4. Phase Evolution and Properties of Al2CrFeNiMo x High-Entropy Alloys Coatings by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Jiang, Li; Jiang, Hui; Pan, Xuemin; Cao, Zhiqiang; Deng, Dewei; Wang, Tongmin; Li, Tingju

    2015-10-01

    A series of Al2CrFeNiMo x ( x = 0 to 2.0 at.%) high-entropy alloys coatings was synthesized on stainless steel by laser cladding. The effect of Mo content on the microstructures and mechanical properties of Al2CrFeNiMo x coatings was studied. The results show that the laser clad layer consists of the cladding zone, bonding zone, and heat-affected zone. The Al2CrFeNiMo x coatings are composed of two simple body-center cubic phases and the cladding zone is mainly composed of equiaxed grains. When the content of Mo reaches 2 at.%, a eutectic structure is found in the interdendritic regions. The surface microhardness of the Al2CrFeNiMo2 coating is 678 HV, which is about three times higher than that of the substrate (243 HV). Compared with stainless steel, the wear resistance of the coatings has been improved greatly. The wear mass loss of the Al2CrFeNiMo alloy is 9.8 mg, which is much less than that of the substrate (18.9 mg) and its wear scar width is the lowest among the Al2CrFeNiMo x coatings, indicating that the wear resistance of the Al2CrFeNiMo is the best.

  5. Room-temperature deformation behavior of a directionally solidified {beta} (B2)-(Ni-Fe-Al) intermetallic alloy

    SciTech Connect

    Misra, A.; Kim, J.T.; Gibala, R.

    1997-01-01

    The room-temperature mechanical behavior of a directionally solidified columnar-grained, single-phase {beta} (B2)-(Ni-20 at. pct Fe-30 At. pct Al) intermetallic alloy deformed along the hard {l_angle}001{r_angle} direction has been characterized. The 0.2 pct offset compressive yield stress was found to be comparable to that of {l_angle}001{r_angle} single crystals of stoichiometric NiAl. The dislocation substructure consisted of a preponderance of long, straight a{l_angle}111{r_angle} screw dislocations on {l_brace}112{r_brace} planes, with cross-slip on {l_brace}123{r_brace} and {l_brace}110{r_brace} planes. The superpartials were not resolved by weak-beam imaging conditions, indicating that the antiphase boundary (APB) energy of NiAl is not reduced significantly by the Fe addition. The dislocation substructure was analyzed as a function of strain and compared to the dislocation substructure in {l_angle}001{r_angle} NiAl and body-centered cubic (bcc) metals deformed at low homologous temperatures. The debris left behind by a{l_angle}111{r_angle} screw dislocations consisted of prismatic edge dipole loops 5 to 25 nm in diameter.

  6. Superior Mechanical Properties of AlCoCrFeNiTi x High-Entropy Alloys upon Dynamic Loading

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Ma, S. G.; Chu, M. Y.; Yang, H. J.; Wang, Z. H.; Zhang, Y.; Qiao, J. W.

    2016-02-01

    High-entropy alloys with composition of AlCoCrFeNiTi x ( x: molar ratio; x = 0, 0.2, 0.4) under quasi-static and dynamic compression exhibit excellent mechanical properties. A positive strain-rate sensitivity of yield strength and the strong work-hardening behavior during plastic flows dominate upon dynamic loading in the present alloy system. The constitutive relationships are extracted to model flow behaviors by employing the Johnson-Cook constitutive model. Upon dynamic loading, the ultimate strength and fracture strain of AlCoCrFeNiTi x alloys are superior to most of bulk metallic glasses and in situ metallic glass matrix composites.

  7. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO3 Fe3Al, Co3Al, and Ni3Al based intermetallic phases

    SciTech Connect

    Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

    2014-11-07

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternary alloying additions in DO3 Fe3Al, Co3Al and Ni3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe3Al and Co3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.

  8. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al based intermetallic phases

    SciTech Connect

    Samolyuk, G. D.; Stocks, G. M.; Újfalussy, B.

    2014-11-07

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co, and Ti within the AlNi-based matrix phase. In this paper, we report the results of first-principles calculations of the site preference of ternary alloying additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which correspond to experimental situation, Ti and Fe are found to occupy the α sites, while Co and Ni prefer the γ sites of the DO{sub 3} lattice. An important finding is that the magnetic moments of transition metals in Fe{sub 3}Al and Co{sub 3}Al are ordered ferromagnetically, whereas the Ni{sub 3}Al were found to be nonmagnetic unless the Fe or Co is added as a ternary element.

  9. Site occupations in Li/sub 2/ ordered alloys by axial electron channeling microanalysis. [Ni/sub 3/AlX (X = Co, Hf, Fe)

    SciTech Connect

    Bentley, J.

    1986-01-01

    Experiments using analytical electron microscopes were performed on Ni/sub 3/Al alloys with additions of Fe, Co, or Hf. Corrections had to be made for delocalization effects. Results agree with atom probe field-ion microscopy. (DLC)

  10. Shape Memory Effect and Superelasticity in [001] Single Crystals of Fe-Ni-Co-Al-Nb(B) Ferromagnetic Alloy

    NASA Astrophysics Data System (ADS)

    Chumlyakov, Yu. I.; Kireeva, I. V.; Kuts, O. A.; Panchenko, M. Yu.; Karaka, É.; Maier, H. J.

    2015-11-01

    Shape memory effect (SME) and superelasticity (SE) during thermoelastic martensitic transformation (MT) from the FCC high-temperature γ-phase to the BCT α'-martensite are investigated in Fe - 28% Ni - 17% Co - 11.5% Al - 2.5% Nb (Nb) and Fe - 28% Ni - 17% Co - 11.5% Al - 2.5% Nb - 0.05% B (NbB) (at.%) single crystals oriented for tension along the [001] direction after aging at 973 K for 10 h. Non-equiaxial (NiAl) β-phase particles with thickness d and length l equal to 60-80 and 340-500 nm, respectively, and volume fraction f ≥ 3-5% are precipitated in Nb crystals during aging simultaneously with the (FeNiCo)3(AlNb) γ´-phase with sizes d = 12.5-16.5 nm. It is shown that precipitation of the β-phase with f ≤ 3-5% in the crystal volume does not reduce the crystal plasticity, and SME of 4.2% and SE up to 6.5% under loading are observed during thermoelastic γ-α' MT in single crystals in a wide range of temperatures from 77 to 293 K. The β-phase is not detected in NbB crystals during aging. It is established that boron in NbB crystals slows down the aging processes: the γ'-phase particles have sizes 6.5-8 nm. The SME of 4.2% and SE up to 4.0% are observed in NbB crystals at temperatures from 77 to 243 K.

  11. Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Rong; Wang, Zhao-Qin; Lin, Tie-Song; He, Peng; Sekulic, Dusan P.

    2016-05-01

    Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe- x ( x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang's proposition, the two alloys form simple solid solutions. The electronegativity difference (Δ χ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe- x ( x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

  12. Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Rong; Wang, Zhao-Qin; Lin, Tie-Song; He, Peng; Sekulic, Dusan P.

    2016-03-01

    Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe-x (x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang's proposition, the two alloys form simple solid solutions. The electronegativity difference (Δχ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe-x (x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

  13. Effect of Cr on Microstructure and Properties of a Series of AlTiCr x FeCoNiCu High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Li, Anmin; Ma, Ding; Zheng, Qifeng

    2014-04-01

    A series of AlTiCr x FeCoNiCu ( x: molar ratio, x = 0.5, 1.0, 1.5, 2.0, 2.5) high-entropy alloys (HEAs) were prepared by vacuum arc furnace. These alloys consist of α-phase, β-phase, and γ-phase. These phases are solid solutions. The structure of α-phase and γ-phase is face-centered cubic structure and that of β-phase is body-centered cubic (BCC) structure. There are four typical cast organizations in these alloys such as petal organization (α-phase), chrysanthemum organization (α-phase + β-phase), dendrite (β-phase), and inter-dendrite (γ-phase). The solidification mode of these alloys is affected by Chromium. If γ-phase is not considered, AlTiCr0.5FeCoNiCu and AlTiCrFeCoNiCu belong to hypoeutectic alloys; AlTiCr1.5FeCoNiCu, AlTiCr2.0FeCoNiCu, and AlTiCr2.5FeCoNiCu belong to hypereutectic alloys. The cast organizations of these alloys consist of pro-eutectic phase and eutectic structure (α + β). Compact eutectic structure and a certain amount of fine β-phase with uniform distribution are useful to improve the microhardness of the HEAs. More γ-phase and the microstructure with similar volume ratio values of α-phase and β-phase improve the compressive strength and toughness of these alloys. The compressive fracture of the series of AlTiCr x FeCoNiCu HEAs shows brittle characteristics, suggesting that these HEAs are brittle materials.

  14. Site preference of ternary alloying additions to NiTi: Fe, Pt, Pd, Au, Al, Cu, Zr and Hf

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Mosca, Hugo O.

    2004-01-01

    Atomistic modeling of the site substitution behavior of Pd in NiTi (J. Alloys and Comp. (2004), in press) has been extended to examine the behavior of several other alloying additions, namely, Fe, Pt, Au, Al, Cu, Zr and Hf in this important shape memory alloy. It was found that all elements, to a varying degree, displayed absolute preference for available sites in the deficient sublattice. How- ever, the energetics of the different substitutional schemes, coupled with large scale simulations indicate that the general trend in all cases is for the ternary addition to want to form stronger ordered structures with Ti.

  15. Site preferences and effects of X (X = Mn, Fe, Co, Cu) on the properties of NiAl: A first-principles study

    NASA Astrophysics Data System (ADS)

    Li, Hongshan; Cao, Yong; Zhou, Shenggang; Zhu, Peixian; Zhu, Jingchuan

    2016-03-01

    The site preference of X (X = Mn, Fe, Co, Cu) in NiAl and its effects on structural, electronic and elastic properties were investigated by performing first-principles calculations using density functional theory (DFT). Formation enthalpy calculations show that adding X increases the formation enthalpy of NiAl, indicating that X addition reduces the stability of system. The site preference was investigated by calculating the transfer energy of NiAl alloys with X. The results further exhibit that Mn, Fe and Cu show no site preference, but Co tends to occupy Ni site. By analyzing electronic density of states, Mulliken population, overlap population and valence charge density, the electronic property and bond characters were discussed. The elastic property calculation shows that only substitution of Ni by Cu increased the plasticity of alloy, while in the other cases the plasticity was decreased.

  16. The effects of annealing on the microstructure and mechanical properties of Fe28Ni18Mn33Al21

    DOE PAGESBeta

    Meng, Fanling; Qiu, Jingwen; Baker, Ian; Bei, Hongbin

    2015-08-20

    In this paper, As-cast Fe28Ni18Mn33Al21, which consists of aligned, 50 nm, (Ni, Al)-rich B2, and (Fe, Mn)-rich f.c.c. phases, was annealed at a variety of temperatures up to 1423 K and the microstructure and mechanical properties were examined. It was shown that the as-cast microstructure arises from a eutectoid transformation at ~1300 K. Annealing at temperatures ≤1073 K produces β-Mn-structured precipitates and hardness values up to 816 HV, while annealing at temperatures >1073 K leads to dramatic coarsening of the two-phase B2/f.c.c. microstructure (up to 5.5 µm after 50 h at 1273 K), but does not lead to β-Mn precipitation.more » Interestingly, annealing at temperatures >1073 K delays the onset of β-Mn precipitation during subsequent anneals at lower temperatures. Coarsening the B2/f.c.c. lamellar structure by annealing at higher temperatures softens it and leads to increases in ductility from fracture before yield to ~8 % elongation. Finally, the presence of β-Mn precipitates makes the very fine, brittle B2/f.c.c. microstructures even more brittle, but significant ductility (8.4 % elongation) is possible even with β-Mn precipitates present if the B2/f.c.c. matrix is coarse and, hence, more ductile.« less

  17. Tribological Properties of AlCrCuFeNi2 High-Entropy Alloy in Different Conditions

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Ma, Shengguo; Gao, Michael C.; Zhang, Chuan; Zhang, Teng; Yang, Huijun; Wang, Zhihua; Qiao, Junwei

    2016-07-01

    In order to understand the environmental effect on the mechanical behavior of high-entropy alloys, the tribological properties of AlCrCuFeNi2 are studied systematically in dry, simulated rainwater, and deionized water conditions against the Si3N4 ceramic ball at a series of different normal loads. The present study shows that both the friction and wear rate in simulated rainwater are the lowest. The simulated rainwater plays a significant role in the tribological behavior with the effect of forming passive film, lubricating, cooling, cleaning, and corrosion. The wear mechanism in simulated rainwater is mainly adhesive wear accompanied by abrasive wear as well as corrosive wear. In contrast, those in dry condition and deionized water are abrasive wear, adhesive wear, and surface plastic deformation. Oxidation contributes to the wear behavior in dry condition but is prevented in liquid condition. In addition, the phase diagram of Al x CrCuFeNi2 is predicted using CALPHAD modeling, which is in good agreement with the literature report and the present study.

  18. Evaluation of tribological behavior of Al-Co-Cr-Fe-Ni high entropy alloy using molecular dynamics simulation.

    PubMed

    Huang, Jen-Ching

    2012-01-01

    High-entropy alloys have been studied extensively for their excellent properties and performance, including outstanding strength and resistance to oxidation at high temperatures. This study employed molecular dynamics simulation to produce a high-entropy alloy containing an equal molar ratio of Al, Co, Cr, Fe, and Ni and investigated the tribological behavior of the material using a diamond tool in a vacuum environment. We also simulated a AlCoCrFeNi high-entropy alloy cooled from a high temperature molten state to 300 K in a high-speed quenching process to produce an amorphous microstructure. In a simulation of nanoscratching, the cutting force-distance curve of high-entropy alloys was used to evaluate work hardening and stick-slip. An increase in temperature was shown to reduce the scratching force and scratching resistance. Nanoscratching the high-entropy alloy at elevated temperatures provided evidence of work hardening; however, the degree of work hardening decreased with an increase in temperature. And it can also be found that when the temperature is higher, the fluctuation of the cutting force curve is greater. PMID:22549875

  19. Tribological Properties of AlCrCuFeNi2 High-Entropy Alloy in Different Conditions

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Ma, Shengguo; Gao, Michael C.; Zhang, Chuan; Zhang, Teng; Yang, Huijun; Wang, Zhihua; Qiao, Junwei

    2016-02-01

    In order to understand the environmental effect on the mechanical behavior of high-entropy alloys, the tribological properties of AlCrCuFeNi2 are studied systematically in dry, simulated rainwater, and deionized water conditions against the Si3N4 ceramic ball at a series of different normal loads. The present study shows that both the friction and wear rate in simulated rainwater are the lowest. The simulated rainwater plays a significant role in the tribological behavior with the effect of forming passive film, lubricating, cooling, cleaning, and corrosion. The wear mechanism in simulated rainwater is mainly adhesive wear accompanied by abrasive wear as well as corrosive wear. In contrast, those in dry condition and deionized water are abrasive wear, adhesive wear, and surface plastic deformation. Oxidation contributes to the wear behavior in dry condition but is prevented in liquid condition. In addition, the phase diagram of Al x CrCuFeNi2 is predicted using CALPHAD modeling, which is in good agreement with the literature report and the present study.

  20. Phase Transformation and Aging Behavior of Al0.5CoCrFeNiSi0.2 High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Wu, G. F.; Dai, P. Q.

    2015-05-01

    An Al0.5CoCrFeNiSi0.2 high-entropy alloy was prepared by vacuum arc melting. The alloy was aged from 700 to 1100 °C. The effects of aging on the phase transformation and mechanical performances were explored. The as-cast alloy showed a dendritic (DR) microstructure. The DR region was an Fe,Cr-rich FCC phase, while the interdendritic (ID) region was a spinodal structure composed of Fe,Cr-rich BCC (A2) and Ni,Al-rich BCC (B2) phases. At aging temperatures between 700 and 900 °C, the Fe,Cr-rich BCC (A2) phase in the ID region transformed into σ and Fe,Cr-rich FCC phases. Meanwhile, some Ni,Al-rich FCC phase particles precipitated from the DR region. During aging at 1100 °C, the DR microstructure disappeared, and a microstructure composed of Fe,Cr-rich FCC and Ni,Al-rich BCC (B2) phases both possessing a lamellar shape was developed. The alloy exhibited evident hardening and lower tensile strain when the aging temperature was lower than 1000 °C, which was mainly attributed to the generation of the σ phase in the ID region. However, a contrasting behavior was observed when the aging temperature was higher than 1000 °C, which was attributed to the redissolution of the σ phase and the microstructure coarsening.

  1. Influence of transition metals (Cr, Mn, Fe, Co and Ni) on the methane combustion over Pd/Ce-Zr/Al 2O 3 catalyst

    NASA Astrophysics Data System (ADS)

    Yue, Baohua; Zhou, Renxian; Wang, Yuejuan; Zheng, Xiaoming

    2006-06-01

    The effects of transition metals (Cr, Mn, Fe, Co and Ni) on the catalytic properties of Pd/Ce-Zr/Al 2O 3 catalyst for methane combustion have been investigated. The supported Pd catalysts are characterized by BET, XRD, TEM, TPR, TPO and TPSR measurements. Activity tests in methane combustion show that Pd/Ce-Zr-Ni/Al 2O 3 has the highest catalytic activity and thermal stability among all catalysts. The results of TEM show that the addition of Ni to Pd/Ce-Zr/Al 2O 3 increases the dispersion of Pd component and inhibits the site growth. The results of TPO and TPSR show that the addition of Ni inhibits the decomposition of PdO particles and improves the reduction-reoxidation properties of the active PdO species, which increases the catalytic activity and thermal stability of the Pd/Ce-Zr/Al 2O 3 catalyst.

  2. Microstructural evolution and mechanical properties of an Fe-18Ni-16Cr-4Al base alloy during aging at 950°C

    NASA Astrophysics Data System (ADS)

    Wang, Man; Sun, Yong-duo; Feng, Jing-kai; Zhang, Rui-qian; Tang, Rui; Zhou, Zhang-jian

    2016-03-01

    The development of Gen-IV nuclear systems and ultra-supercritical power plants proposes greater demands on structural materials used for key components. An Fe-18Ni-16Cr-4Al (316-base) alumina-forming austenitic steel was developed in our laboratory. Its microstructural evolution and mechanical properties during aging at 950°C were investigated subsequently. Micro-structural changes were characterized by scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. Needle-shaped NiAl particles begin to precipitate in austenite after ageing for 10 h, whereas round NiAl particles in ferrite are coarsened during aging. Precipitates of NiAl with different shapes in different matrices result from differences in lattice misfits. The tensile plasticity increases by 32.4% after aging because of the improvement in the percentage of coincidence site lattice grain boundaries, whereas the tensile strength remains relatively high at approximately 790 MPa.

  3. Nanoindentation Creep Behavior of an Al0.3CoCrFeNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Lijun; Yu, Pengfei; Cheng, Hu; Zhang, Huan; Diao, Haoyan; Shi, Yunzhu; Chen, Bilin; Chen, Peiyong; Feng, Rui; Bai, Jie; Jing, Qin; Ma, Mingzhen; Liaw, P. K.; Li, Gong; Liu, Riping

    2016-03-01

    Nanoindentation creep behavior was studied on a coarse-grained Al0.3CoCrFeNi high-entropy alloy with a single face-centered cubic structure. The effects of the indentation size and loading rate on creep behavior were investigated. The experimental results show that the hardness, creep depth, creep strain rate, and stress exponent are all dependent on the holding load and loading rate. The creep behavior shows a remarkable indentation size effect at different maximum indentation loads. The dominant creep mechanism is dislocation creep at high indentation loads and self-diffusion at low indentation loads. An obvious loading rate sensitivity of creep behavior is found under different loading rates for the alloy. A high loading rate can lead to a high strain gradient, and numerous dislocations emerge and entangle together. Then during the holding time, a large creep deformation characteristic with a high stress exponent will happen.

  4. Structure and magnetic properties of a Ni3(Al, Fe, Cr) single crystal subjected to high-temperature deformation

    NASA Astrophysics Data System (ADS)

    Kazantseva, N. V.; Rigmant, M. B.; Stepanova, N. N.; Davydov, D. I.; Shishkin, D. A.; Terent'ev, P. B.; Vinogradova, N. I.

    2016-05-01

    The structure and magnetic properties of the Ni3(Al, Fe, Cr) single crystal subjected to high-temperature tensile deformation to failure at 850-900°C have been studied. No recrystallized grains and metastable phases were found. The rupture zone of the alloy subjected to deformation (at 900°C) to the highest degree demonstrates the fragmentation accompanied by rotation of atomic layers and changes of the chemical composition in the nickel and aluminum sublattices. Magnetic studies of the alloy have shown the existence of two Curie temperatures for samples cut from the rupture zone. Samples cut away from the rupture zone exhibit no additional magnetic transitions; twines and planar stacking faults in the alloy structure. The alloy deformed to the lower degree of deformation (at 850°C) also demonstrates twins; no ferromagnetic state was found to form.

  5. Atomistic clustering-ordering and high-strain deformation of an Al0.1CrCoFeNi high-entropy alloy

    DOE PAGESBeta

    Sharma, Aayush; Singh, Prashant; Johnson, Duane D.; Liaw, Peter K.; Balasubramanian, Ganesh

    2016-08-08

    Here, computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived propertiesmore » are in quantitative agreement with KKR-CPA calculations (first-principles) and experiments. We study AlxCrCoFeNi for Al ranging from 0 ≤ x ≤2 mole fractions, and find that the HEA shows large chemical clustering over a wide temperature range for x < 0.5. At various temperatures high-strain compression promotes atomistic rearrangements in Al0.1CrCoFeNi, resulting in a clustering-to-ordering transition that is absent for tensile loading. Large fluctuations under stress, and at higher temperatures, are attributed to the thermo-plastic instability in Al0.1CrCoFeNi.« less

  6. Atomistic clustering-ordering and high-strain deformation of an Al0.1CrCoFeNi high-entropy alloy

    PubMed Central

    Sharma, Aayush; Singh, Prashant; Johnson, Duane D.; Liaw, Peter K.; Balasubramanian, Ganesh

    2016-01-01

    Computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived properties are in quantitative agreement with KKR-CPA calculations (first-principles) and experiments. We study AlxCrCoFeNi for Al ranging from 0 ≤ x ≤2 mole fractions, and find that the HEA shows large chemical clustering over a wide temperature range for x < 0.5. At various temperatures high-strain compression promotes atomistic rearrangements in Al0.1CrCoFeNi, resulting in a clustering-to-ordering transition that is absent for tensile loading. Large fluctuations under stress, and at higher temperatures, are attributed to the thermo-plastic instability in Al0.1CrCoFeNi. PMID:27498807

  7. Atomistic clustering-ordering and high-strain deformation of an Al0.1CrCoFeNi high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Sharma, Aayush; Singh, Prashant; Johnson, Duane D.; Liaw, Peter K.; Balasubramanian, Ganesh

    2016-08-01

    Computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived properties are in quantitative agreement with KKR-CPA calculations (first-principles) and experiments. We study AlxCrCoFeNi for Al ranging from 0 ≤ x ≤2 mole fractions, and find that the HEA shows large chemical clustering over a wide temperature range for x < 0.5. At various temperatures high-strain compression promotes atomistic rearrangements in Al0.1CrCoFeNi, resulting in a clustering-to-ordering transition that is absent for tensile loading. Large fluctuations under stress, and at higher temperatures, are attributed to the thermo-plastic instability in Al0.1CrCoFeNi.

  8. Atomistic clustering-ordering and high-strain deformation of an Al0.1CrCoFeNi high-entropy alloy.

    PubMed

    Sharma, Aayush; Singh, Prashant; Johnson, Duane D; Liaw, Peter K; Balasubramanian, Ganesh

    2016-01-01

    Computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived properties are in quantitative agreement with KKR-CPA calculations (first-principles) and experiments. We study AlxCrCoFeNi for Al ranging from 0 ≤ x ≤2 mole fractions, and find that the HEA shows large chemical clustering over a wide temperature range for x < 0.5. At various temperatures high-strain compression promotes atomistic rearrangements in Al0.1CrCoFeNi, resulting in a clustering-to-ordering transition that is absent for tensile loading. Large fluctuations under stress, and at higher temperatures, are attributed to the thermo-plastic instability in Al0.1CrCoFeNi. PMID:27498807

  9. NiAl alloys for structural uses

    NASA Technical Reports Server (NTRS)

    Koss, D. A.

    1991-01-01

    Alloys based on the intermetallic compound NiAl are of technological interest as high temperature structural alloys. These alloys possess a relatively low density, high melting temperature, good thermal conductivity, and (usually) good oxidation resistance. However, NiAl and NiAl-base alloys suffer from poor fracture resistance at low temperatures as well as inadequate creep strength at elevated temperatures. This research program explored macroalloying additions to NiAl-base alloys in order to identify possible alloying and processing routes which promote both low temperature fracture toughness and high temperature strength. Initial results from the study examined the additions of Fe, Co, and Hf on the microstructure, deformation, and fracture resistance of NiAl-based alloys. Of significance were the observations that the presence of the gamma-prime phase, based on Ni3Al, could enhance the fracture resistance if the gamma-prime were present as a continuous grain boundary film or 'necklace'; and the Ni-35Al-20Fe alloy was ductile in ribbon form despite a microstructure consisting solely of the B2 beta phase based on NiAl. The ductility inherent in the Ni-35Al-20Fe alloy was explored further in subsequent studies. Those results confirm the presence of ductility in the Ni-35Al-20Fe alloy after rapid cooling from 750 - 1000 C. However exposure at 550 C caused embrittlement; this was associated with an age-hardening reaction caused by the formation of Fe-rich precipitates. In contrast, to the Ni-35Al-20Fe alloy, exploratory research indicated that compositions in the range of Ni-35Al-12Fe retain the ordered B2 structure of NiAl, are ductile, and do not age-harden or embrittle after thermal exposure. Thus, our recent efforts have focused on the behavior of the Ni-35Al-12Fe alloy. A second parallel effort initiated in this program was to use an alternate processing technique, mechanical alloying, to improve the properties of NiAl-alloys. Mechanical alloying in the

  10. Microstructure and mechanical properties of Fe-Ni-Cr-Al steel wires produced by in-rotating-water spinning method

    NASA Astrophysics Data System (ADS)

    Inoue, A.; Tomioka, H.; Masumoto, T.

    1985-02-01

    Nonequilibrium austenite, γ, or duplex austenite + lath martensite,γ + α' L, phase wires with high strengths and large elongation have been produced in Fe-Ni-Cr-Al-C alloy system by the in-rotating-water spinning method in which a melt stream is ejected into a rotating water layer. These wires have a circular cross section and a white luster, and the wire diameter is in the range of 80 to 180 µm. The γ phase has a grain size as small as about 1 to 4 µm. The yield strength, Σy, tensile fracture strength, ay, and elongation, ɛp, are about 340 to 655 MPa, 440 to 975 MPa, and 12 to 22 pct for the γ single phase wires and about 465 to 865 MPa, 640 to 1350 MPa, and 2 to 18 pct for the α'L+ γ duplex phase wires. A cold drawing causes significant increases in Σy and Σf, and the attained values are about 3200 MPa and 4030 MPa for Fe-8Ni-12.5Cr-2.5Al-3C wire drawn to about 95 pct reduction in area owing to the formation of a strain-induced α'L phase and a remarkable work-hardening ability of γ and α'L phases. On the subsequent low-temperature annealing around 673 K, the Σy and Σf increase further to 4000 MPa and 4240 MPa, respectively, probably because of the enhancement of the interaction between dislocations and interstitial carbon atoms. Around the temperature (≃800 K) where the γ phase decomposes into a stable mixed structure of α + ordered bec compound + M7C3 on annealing, the ɛp decreases drastically and the fracture surface morphology changes from a dimple pattern to a cleavage pattern. It has been therefore inferred that the high strengths and good ductility of the melt-quenched y and γ + α'L wires are due to the suppression of the phase transformation of y to a mixed structure of γ + ordered bec compound + M7C3 carbide by the melt-quenching technique.

  11. Tailoring the magnetic properties of new Fe-Ni-Co-Al-(Ta,Nb)-B superelastic rapidly quenched microwires

    SciTech Connect

    Borza, F. Lupu, N.; Dobrea, V.; Chiriac, H.

    2015-05-07

    Ferromagnetic Fe-Ni-Co-Al-(Ta,Nb)-B microwires with diameters from 170 μm to 50 μm, which possess both superelastic and good magnetic properties, have been prepared by rapid quenching from the melt using the in rotating water spinning technique followed by cold-drawing and ageing. The cold-drawing and annealing processes lead to the initialization of premartensitic phases as confirmed by the X-ray diffraction and scanning transmission electron microscopic investigations, more significantly in the 50 μm cold-drawn microwires. An increase in the coercive field and in the saturation magnetization has been obtained by annealing, more importantly in the case of Nb-containing alloy. Ageing by thermal or current annealing led to the initialization of the superelastic effect. High values of strain of up to 1.8%, very good repeatability under successive loading, and values of superelastic effect of up to 1.2% have been achieved. The structural analysis coupled with the stress-strain data suggests that these materials annealed at 800 °C have superelastic potential at reduced ageing times. The magnetic behavior was found to be easily tailored through both thermal and thermomagnetic treatments with changes in the magnetic parameters which can be contactless detected. The results are important for future applications where both mechanical and magnetic properties matter, i.e., sensing/actuating systems.

  12. Laser surface forming of AlCoCrCuFeNi particle reinforced AZ91D matrix composites

    NASA Astrophysics Data System (ADS)

    Meng, Guanghui; Yue, T. M.; Lin, Xin; Yang, Haiou; Xie, Hui; Ding, Xu

    2015-07-01

    Traditionally, the laser melt injection (LMI) technique can only be used for forming ceramic particles reinforced metal matrix composites (MMCs) for enhancing surface properties of lightweight engineering materials. In this research, the LMI method was employed to form metal particles reinforced MMCs on AZ91D instead. This was viable because of the unique properties of the AlCoCrCuFeNi high-entropy alloy (HEA) metal particles used. The large difference in melting point between the HEA and the substrate material (AZ91D), and the limited reaction and the lack of fusion between the HEA and Mg have made it possible that a metal particles reinforced AZ91D composite material was produced. The reason of limited reaction was considered mainly due to the relatively high mixing enthalpy between the HEA constituent elements and Mg. Although there was some melting occurred at the particles surface with some solute segregation found in the vicinity close to the surface, intermetallic compounds were not observed. With regard to the wear resistance of the MMCs, it was found that when the volume fraction of the reinforcement phase, i.e. the HEA particles, reached about 0.4, the wear volume loss of the coating was only one-seventh of that of the substrate material.

  13. Gradient Distribution of Martensite Phase in Melt-Spun Ribbons of a Fe-Ni-Ti-Al Alloy.

    PubMed

    Bondar, Volodymyr; Danilchenko, Vitalij; Dzevin, Ievgenij

    2016-12-01

    Metallographic, X-ray diffraction and magnetometric analysis were used to study the regularities of martensitic transformation in melt-spun ribbons of a Fe - 28 wt. % Ni - 2.1 wt. % Ti - 2 wt. % Al - 0.05 wt. % C alloy. The substantial differences in volume fractions of the martensite phase in local regions of thin melt-spun ribbons of the alloy are related to the size effect of the transformation and structural inhomogeneity of the ribbons. The distribution of austenitic grain size in different local areas of melt-spun ribbons is significantly different. The principal factor for changing the completeness of the martensitic transformation is the size effect of transformation. Difference in the martensite volume fraction in local regions of a ribbon is mainly determined by the different volume fractions of ultrafine-grained (500-1000 nm) and nanosized (80-100 nm and less) initial austenite grains, in which the transformation was slowed down or completely suppressed. Other factors almost do not affect the completeness of the martensitic transformation. The strong stabilizing effect of the reverse α-γ transformation with respect to the subsequent direct γ-α transformation in the melt-spun ribbons is also related to the grain size effect. PMID:26897002

  14. Gradient Distribution of Martensite Phase in Melt-Spun Ribbons of a Fe-Ni-Ti-Al Alloy

    NASA Astrophysics Data System (ADS)

    Bondar, Volodymyr; Danilchenko, Vitalij; Dzevin, Ievgenij

    2016-02-01

    Metallographic, X-ray diffraction and magnetometric analysis were used to study the regularities of martensitic transformation in melt-spun ribbons of a Fe - 28 wt. % Ni - 2.1 wt. % Ti - 2 wt. % Al - 0.05 wt. % C alloy. The substantial differences in volume fractions of the martensite phase in local regions of thin melt-spun ribbons of the alloy are related to the size effect of the transformation and structural inhomogeneity of the ribbons. The distribution of austenitic grain size in different local areas of melt-spun ribbons is significantly different. The principal factor for changing the completeness of the martensitic transformation is the size effect of transformation. Difference in the martensite volume fraction in local regions of a ribbon is mainly determined by the different volume fractions of ultrafine-grained (500-1000 nm) and nanosized (80-100 nm and less) initial austenite grains, in which the transformation was slowed down or completely suppressed. Other factors almost do not affect the completeness of the martensitic transformation. The strong stabilizing effect of the reverse α-γ transformation with respect to the subsequent direct γ-α transformation in the melt-spun ribbons is also related to the grain size effect.

  15. Ductility enhancement from interface dislocation sources in a directionally solidified beta + gamma + gamma-prime Ni-Fe-Al composite alloy

    NASA Technical Reports Server (NTRS)

    Larsen, M.; Misra, A.; Hartfield-Wunsch, S.; Noebe, R.; Gibala, R.

    1990-01-01

    A directionally solidified beta + gamma + gamma-prime Ni-Fe-Al in situ composite alloy of composition Ni50Fe30Al20 has been used to investigate the effect of a plastically soft second phase on the mechanical behavior of a B2 ordered intermetallic alloy. This material exhibits extensive plasticity during compressive deformation at room temperature and fails in shear with extensive gamma + gamma-prime lamellar or rod pullout. The material also exhibits about 10 percent tensile elongation to fracture at room temperature, with final fracture that includes substantial necking of the gamma + gamma-prime lamellae or rods. Observation of slip lines and dislocation substructures discloses that the normally brittle beta matrix undergoes extensive plasticity in order to deform compatibly with the more ductile gamma phase. The plasticity of the beta matrix is accomplished by the generation of glissile dislocations into the beta matrix from the beta/gamma interface region and is enhanced because of a favorable beta-gamma orientation relationship for slip transfer. Ductility enhancement from interface-generated mobile dislocations generated from beta-gamma interfaces is compared to that observed in film-coated beta-NiAl single crystals and FeAl polycrystals.

  16. Magnetic core-shell nano-TiO2/Al2O3/NiFe2O4 microparticles with enhanced photocatalytic activity.

    PubMed

    Jing, Mao-Xiang; Han, Chong; Wang, Zhou; Shen, Xiang-Qian

    2013-07-01

    The core-shell nano-TiO2/Al2O3/NiFe2O4 microparticles of 5-8 microm were prepared by the heterogeneous precipitation followed by calcination treatment. The morphologies, structure, crystalline phase, and magnetic property were characterized by optical biomicroscopy (OBM), scanning electron microscopy (SEM), X-ray diffractometry (XRD) and vibrating sample magnetometer (VSM) respectively. The photocatalytic activity was evaluated by degrading methyl orange solution either under UV light and sunlight. The results indicate that the nano-TiO2 layer consists of needle-like nanoparticles and the intermediate layer of Al2O3 avoids the nano-TiO2 agglomeration, shedding and uneven loading. The nano-TiO2/Al2O3/NiFe2O4 composite particles show high magnetization of 31.5 emu/g and enhanced photocatalytic activity to completely degrade 50 mg/L methyl orange solution either under UV light and sun light. The enhanced activity of the composite is attributed to the unique structure, insulation effect of Al2O3 intermediate layer and the hybrid effect of anatase TiO2 and NiFe2O4. The obtained catalyst may be magnetically separable and useful for many practical applications due to the improved photocatalytic properties under sunlight. PMID:23901515

  17. Shape Memory effect and Superelasticity in the [001] Single crystals of a FeNiCoAlTa Alloy with γ-α'-Thermoelastic Martensitic Transformations

    NASA Astrophysics Data System (ADS)

    Chumlyakov, Yu. I.; Kireeva, I. V.; Kretinina, I. V.; Keinikh, K. S.; Kuts, O. A.; Kirillov, V. A.; Karaman, I.; Maier, H.

    2013-12-01

    Using single crystals of a Fe - 28% Ni - 17% Co - 11.5% Al - 25% Ta (аt.%) alloy, oriented for tensile loading along the [001] direction, the shape-memory (SME) and superelasticity (SE) effects caused by reversible thermoelastic martensitic transformations (MTs) from a high-temperature fcc-phase into a bctmartensite are investigated. It is demonstrated that the conditions necessary for the thermoelastic MTs to occur are achieved by aging at 973 K within the time interval (t) from 0.5 to 7.0 hours, which is accompanied by precipitation of the γ'-phase particles, (FeNiCo)3(AlTa), whose d < 8-12 nm. When the size of the γ'-precipitates becomes as large as d ≥ 8-12 nm, the MT becomes partially reversible. The physical causes underlying the kinetics of thermoelstic reversible fcc-bct MTs are discussed.

  18. Fabrication and Wear Behavior Analysis on AlCrFeNi High Entropy Alloy Coating Under Dry Sliding and Oil Lubrication Test Conditions

    NASA Astrophysics Data System (ADS)

    Tang, Yipin; Wang, Shouren; Sun, Bin; Wang, Yan; Qiao, Yang

    2016-03-01

    In this paper, AlCrFeNi high entropy alloy coating was fabricated on the surface of Q235 steel using hot pressing sintering process. The coating has the controlled thickness size and excellent mechanical properties. Scanning electron microscopy (SEM), XRD and hardness testing method were used to study the morphology, phase structure and hardness of high entropy alloys coating. The lattice distortion plays a significant role in increasing the hardness. Coating formation mechanism caused by the element diffusion under the hot pressing effect is also discussed in the paper. Simultaneously, the dry sliding and oil lubrication wear tests, wear morphology observation and wear mechanism discussion were completed. As the result shows, AlCrFeNi high entropy alloys coating exhibits superior wear resistance either at dry sliding or oil lubrication tests owing to its hard high entropy solid solution structure.

  19. High-Strength Low-Carbon Ferritic Steel Containing Cu-Fe-Ni-Al-Mn Precipitates

    NASA Astrophysics Data System (ADS)

    Vaynman, Semyon; Isheim, Dieter; Prakash Kolli, R.; Bhat, Shrikant P.; Seidman, David N.; Fine, Morris E.

    2008-02-01

    An investigation of a low-carbon, Fe-Cu-based steel, for Naval ship hull applications, with a yield strength of 965 MPa, Charpy V-notch absorbed impact-energy values as high as 74 J at -40 °C, and an elongation-to-failure greater than 15 pct, is presented. The increase in strength is derived from a large number density (approximately 1023 to 1024 m-3) of copper-iron-nickel-aluminum-manganese precipitates. The effect on the mechanical properties of varying the thermal treatment was studied. The nanostructure of the precipitates found within the steel was characterized by atom-probe tomography. Additionally, initial welding studies show that a brittle heat-affected zone is not formed adjacent to the welds.

  20. Nanocrystalline NiFe2O4 and nanocomposites of (NiFe2O4)(1-x)(Al2O3)x (x = 0.25, 0.40): superparamagnetic behavior and Mössbauer spectroscopy.

    PubMed

    Mukherjee, S; Acharya, S; Das, D; Chakrabarti, P K

    2010-09-01

    Nanocrystalline NiFe2O4 with different particle sizes and nanocomposites of (NiFe2O4)(1-x)(Al2O3)x (x = 0.25, 0.40) were prepared by using co-precipitation method. In this method two techniques viz., 'ultrasonication' and 'magnetic stirring' during co-precipitation were used. The as prepared samples were annealed at different temperatures to obtain samples with different particle sizes. The formation of the nanocrystalline spinel phases of all the samples were confirmed by X-ray diffraction (XRD) patterns. The sizes of the nanoparticles of all the samples were calculated from the broadening of the (311) line in the XRD pattern. The distribution of sizes are remarkably less in samples obtained from 'ultrasonication' technique compared to those obtained in 'magnetic stirring' technique. The different soft magnetic quantities viz., coercive field, magnetization, remanance, hysteresis losses etc. were extracted from the ac hysteresis loops observed at different frequencies. The variations of coercive field and hysteresis loss as functions of frequency and particle sizes have been studied. Mössbauer spectra of the samples along with the hysteresis loops recorded at room temperature indicate the presence of superparamagnetic (SPM) relaxations of the nanoparticles. Also, SPM relaxations have been introduced in the samples annealed at higher temperature by encapsulating the nanoparticles in non-magnetic matrix of Al2O3 with 40% coating. PMID:21133083

  1. The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.

  2. Effects of Cu, Fe and Co addition on the glass-forming ability and mechanical properties of Zr-Al-Ni bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Li, YanHui; Zhang, Wei; Dong, Chuang; Makino, Akihiro

    2012-12-01

    The thermal stability, glass-forming ability (GFA) and mechanical properties of Zr60Al15Ni25- x TM x (TM = Cu, Fe and Co, x = 0-10) bulk metallic glasses (BMGs) were systematically investigated. Additional 5-10 at.% Cu greatly enhances the thermal stability and GFA of the base alloy. Zr60Al15Ni15Cu10 BMG exhibits the largest supercooled liquid region of 104 K and critical diameter of 18 mm. However, addition of 5-10 at.% Fe or Co decrease the thermal stability and GFA. In addition, the plasticity of the BMG can be improved by adding of Cu, while the strength is decreased slightly. Zr60Al15Ni20Cu5 BMG has the largest plastic strain of 5.5% with a yield stress of 1755 MPa and Young's modulus of 83 GPa. Addition of Co brings an increase of strength but a lower of plasticity, and additional Fe reduces the strength and plasticity simultaneously.

  3. A Successful Synthesis of the CoCrFeNiAl0.3 Single-Crystal, High-Entropy Alloy by Bridgman Solidification

    SciTech Connect

    Ma, S. G.; Zhang, S. F.; Gao, M. C.; Liaw, P. K.; Zhang, Y.

    2013-08-22

    For the first time, a face-centered-cubic, single-crystal CoCrFeNiAl{sub 0.3} (designated as Al0.3), high-entropy alloy (HEA) was successfully synthesized by the Bridgman solidification (BS) method, at an extremely low withdrawal velocity through a constant temperature gradient, for which it underwent two BS steps. Specially, at the first BS step, the alloy sample underwent several morphological transitions accompanying the crystal growth from the melt. This microstructure evolves from as-cast dendrites, to equiaxed grains, and then to columnar crystals, and last to the single crystal. In particular, at the equiaxed-grain region, some visible annealing twins were observed, which indicates a low stacking fault energy of the Al0.3 alloy. Although a body-centered- cubic CoCrFeNiAl (Al1) HEA was also prepared under the same conditions, only a single columnar-crystal structure with instinctively preferential crystallographic orientations was obtained by the same procedure. A similar morphological transition from dendrites to equiaxed grains occurred at the equiaxed-grain region in Al1 alloy, but the annealing twins were not observed probably because a higher Al addition leads to a higher stacking fault energy for this alloy.

  4. Fracture behavior of a B2 Ni-30Al-20Fe-0.05Zr intermetallic alloy in the temperature range 300 to 1300 K

    NASA Technical Reports Server (NTRS)

    Raj, S. V.

    1992-01-01

    The fracture behavior of a B2 Ni-30Al-20Fe-0.05Zr (at. pct) alloy was investigated using results of tensile tests conducted in the temperature range 300-1300 K under initial strain rates that varied between 10 exp -6 and 10 exp -3/sec, together with results of deformation measurements reported by Raj et al. (1992). Microstructural observations revealed that the alloy had failed by transgranular cleavage fracture below 873 K and by ductile fracture, power-law cavitation, triple point cracking, and rupture above this temperautre. The fracture map constructed using fracture results is compared with those for other classes of materials, showing that the atomic bonding plays a significant role in the low-temperature ductility of NiAl-based alloys.

  5. Evolution of Microstructure and Mechanical Properties of the Ni-25Al-27.5Fe-1.0Nb Intermetallic Alloy after Thermal Mechanical Treatment

    NASA Astrophysics Data System (ADS)

    Fu, Chih-Chiang; Jang, Jason Shian-Ching; Tsai, Han-Chang; Li, Tsung-Hsiung

    The evolution of microstructure and mechanical properties of the Ni-25Al-27.5Fe-1.0Nb intermetallic alloy after thermal mechanical treatment (TMT) was systematically investigated by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM) with electron dispersive spectrum (EDS) capability, and atmosphere-controlled tensile test at room temperature with different strain rate. The results of XRD reveals that a matrix of β' phase [(Ni, Fe) Al type ordered bcc structure] and a precipitated γ phase (Ni3Fe fcc solid solution) co-exist in this alloy after TMT. The dendritic microstructure of the as-cast alloy was eliminated after TMT process. In parallel, a refined and homogeneous distributed lath precipitates can be obtained after annealing at 820 for 4 hr. Additionally, this alloy presents a relative high strength as well as ductile mechanical behavior (UTS~1320 MPa and ɛ~8%, respectively) at room temperature in air. A 30% improvement in yield strength is suggested to be contributed by the refined microstructure from the TMT. Moreover, the tensile strength and ductility of this alloy exhibit insensitive response with respect to the loading strain rate at room temperature.

  6. Cantilever detected ferromagnetic resonance in thin Fe50Ni50, Co2FeAl0.5Si0.5 and Sr2FeMoO6 films using a double modulation technique

    NASA Astrophysics Data System (ADS)

    Alfonsov, Alexey; Ohmichi, Eiji; Leksin, Pavel; Omar, Ahmad; Wang, Hailong; Wurmehl, Sabine; Yang, Fengyuan; Ohta, Hitoshi

    2016-09-01

    In this work we introduce a new method, which employs commercial piezo-cantilevers, for a ferromagnetic resonance (FMR) detection from thin, nm-size, films. Our setup has an option to rotate the sample in the magnetic field and it operates up to the high microwave frequencies of 160 GHz. Using our cantilever based FMR spectrometer we have investigated a set of samples, namely quasi-bulk and 84 nm film Co2FeAl0.5Si0.5 samples, 16 nm Fe50Ni50 film and 150 nm Sr2FeMoO6 film. Low frequency and room temperature test of our setup using 84 nm Co2FeAl0.5Si0.5 film yielded a result identical to a standard X-Band spectrometer, namely a single line with quite small linewidth. Our measurements at low temperatures and high frequencies revealed a quite strong FMR response detected in all samples. The FMR spectra share common features, such as the emergence of the second line with an opposite angular dependence, and a drastic increase of the linewidths with increasing microwave frequency. We believe that these findings are results of the complicated dynamics of the magnetization at low temperatures and high frequencies, which we were able to probe using our cantilever based FMR setup.

  7. Cantilever detected ferromagnetic resonance in thin Fe50Ni50, Co2FeAl0.5Si0.5 and Sr2FeMoO6 films using a double modulation technique.

    PubMed

    Alfonsov, Alexey; Ohmichi, Eiji; Leksin, Pavel; Omar, Ahmad; Wang, Hailong; Wurmehl, Sabine; Yang, Fengyuan; Ohta, Hitoshi

    2016-09-01

    In this work we introduce a new method, which employs commercial piezo-cantilevers, for a ferromagnetic resonance (FMR) detection from thin, nm-size, films. Our setup has an option to rotate the sample in the magnetic field and it operates up to the high microwave frequencies of 160GHz. Using our cantilever based FMR spectrometer we have investigated a set of samples, namely quasi-bulk and 84nm film Co2FeAl0.5Si0.5 samples, 16nm Fe50Ni50 film and 150nm Sr2FeMoO6 film. Low frequency and room temperature test of our setup using 84nm Co2FeAl0.5Si0.5 film yielded a result identical to a standard X-Band spectrometer, namely a single line with quite small linewidth. Our measurements at low temperatures and high frequencies revealed a quite strong FMR response detected in all samples. The FMR spectra share common features, such as the emergence of the second line with an opposite angular dependence, and a drastic increase of the linewidths with increasing microwave frequency. We believe that these findings are results of the complicated dynamics of the magnetization at low temperatures and high frequencies, which we were able to probe using our cantilever based FMR setup. PMID:27498338

  8. Microstructures and Mechanical Performance of Plasma-Nitrided Al0.3CrFe1.5MnNi0.5 High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Tang, Wei-Yeh; Chuang, Ming-Hao; Lin, Su-Jien; Yeh, Jien-Wei

    2012-07-01

    This study investigates the effect of plasma nitriding at 798 K (525 °C) on microstructures and the mechanical performance of Al0.3CrFe1.5MnNi0.5 high-entropy alloys (HEAs) obtained using different cast and wrought processing. All the alloys can be well nitride, with a thickness of around 80 μm, and attain a peak hardness level around Hv 1300 near the surface. The main nitride phases are CrN, AlN, and (Mn, Fe)4N. Those of the substrates are bcc, fcc, Al-, and Ni-rich B2 precipitates, and ρ phase. Their relative amounts depend on the prior processing and also change under the heat treatment during nitriding. The formation of ρ phase during nitriding could in-situ harden the substrate to attain the suitable level required for wear applications. This gives the advantage in simplifying the processing for making a wear-resistance component or a mold since austenitizing, quench hardening, and tempering required for steels such as SACM and SKD steels are no longer required and final finishing can be accomplished before nitriding. Nitrided Al0.3CrFe1.5MnNi0.5 samples have much better wear resistance than un-nitrided ones by 49 to 80 times and also exhibit superior adhesive wear resistance to conventional nitrided alloys: nitriding steel SACM-645 (AISI 7140), 316 stainless steel, and hot-mold steel SKD-61 (AISI H13) by 22 to 55 times depending on prior processing. The superiority is due to the fact that the present nitrided alloys possess a much thicker highly hardened layer than the conventional alloys.

  9. Deformation behavior of a Ni-30Al-20Fe-0.05Zr intermetallic alloy in the temperature range 300 to 1300 K

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Locci, I. E.; Noebe, R. D.

    1992-01-01

    The deformation properties of an extruded Ni-30Al-20Fe-0.05Zr (at. pct) alloy in the temperature range 300-1300 K were investigated under initial tensile strain rates that varied between 10 exp -6 and 10 exp -3/sec and in constant load compression creep between 1073 and 1300 K. Three deformation regimes were observed: region I, occurring between 400 and 673 K, which consisted of an athermal regime of less than 0.3 percent tensile ductility; region II, between 673 and 1073, where exponential creep was dominant; and region III, between 1073 and 1300 K, where a significant improvement in tensile ductility was observed.

  10. NiAl-base composite containing high volume fraction of AlN for advanced engines

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan (Inventor); Whittenbeger, John D. (Inventor); Lowell, Carl F. (Inventor)

    1994-01-01

    A particulate reinforced NiAl-AlN composite alloy has a NiAl matrix and greater than about 13 volume percent fine particles of AlN within the matrix. The particles preferably have a diameter from about 15 nanometers to about 50 nanometers. The particulate reinforced NiAl-AlN composite alloy may be prepared by cryomilling prealloyed NiAl in liquid nitrogen using grinding media having a diameter of from about 2 to 6 mm at an impeller speed of from about 450 RPM to about 800 RPM. The cryomilling may be done for a duration of from about 4 hours to about 20 hours to obtain a cryomilled powder. The cryomilled powder may be consolidated to form the particulate reinforced NiAl-AlN composite alloy. The particulate reinforced alloy can further include a toughening alloy. The toughening alloy may include NiCrAlY, FeCrAlY, and FeAl.

  11. Electrolyte loss in corrosion of 30Cr-45Ni-1Al-0.03 Y-Fe alloy for MCFC separator

    SciTech Connect

    Masamura, Katsumi; Ohe, Koichiro; Takemura, Masahiro

    1996-12-31

    To establish high performance of MCFC, a new high corrosion resistant alloy (30%Cr-45%Ni-1 %Al-0.03%Y-Fe) for MCFC separator has been developed. The developed alloy has good corrosion resistance for both anode and cathode environments. On the other hand, one of the main factors to determine the life time of MCFC stack is electrolyte loss. A potential danger of electrolyte loss cased by corrosion of metal components is pointed out. Basic mechanism of electrolyte loss is proposed according to following reactions. High Cr content alloy such as type 310S(25%Cr-20%Ni) has disadvantages in view of electrolyte loss in spite of high corrosion resistance. It is said that the dissolution of Cr ion into electrolyte is detrimental for electrolyte loss, because a mole of CrO{sub 4}{sup 2+} ion combines 2 moles of K{sup +} ions as K{sub 2}CrO{sub 4}, while a mole of Fe{sup 3+} ion combine a mole of Li{sup +} ion as LiFeO{sub 2}. To understand the mechanism of electrolyte loss due to corrosion of metal component, the distribution of metal ions in oxide and molten salt were studied.

  12. The Influence of Hydrogen on Shape Memory Effect and Superelasticity in [001]-Oriented FeNiCoAlTi Single Crystals

    NASA Astrophysics Data System (ADS)

    Chumlyakov, Yu. I.; Kireeva, I. V.; Platonova, Yu. N.

    2016-04-01

    Using [001]-oriented single crystals of an iron-based alloy (Fe - 28% Ni - 17% Co - 11.5% Al - 2.5% Ti at.%), which were aged at 973 K for 7 h, the influence of hydrogen on the axial-stress temperature response σ0.1(T), the values of shape-memory effect (SME) and superelasticity (SE) is investigated during thermoelastic γ-α'-martensitic transformation (MT) (γ-FCC - face centered lattice, α'-BCT - body centered tetragonal lattice) under tensile conditions. It is found that saturation of [001]-oriented single crystals of the Fe - 28% Ni - 17% Co - 11.5% Al - 2.5% Ti alloy with hydrogen within 2 h at T = 300 K and current density j = 50 mA/cm2 results in lower starting temperature, Ms, of a forward MT during cooling and Md temperature, increased strength properties of the high-temperature phase at Md temperature and wider temperature range of SE observation compared to hydrogen-free crystals. It is shown that hydrogen affects but only slightly the SME and SE values, the temperature and stress hysteresis under the above saturation mode. In [001]-oriented crystals aged at 973 K for 7 h, which are saturated with hydrogen and hydrogen-free, the SME and SE values are found to be equal to 7.8-8 and 6.5-6.9%, respectively.

  13. Structural and magnetic study of Al{sup 3+} doped Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4} nanoferrites

    SciTech Connect

    Wang, L.; Rai, B.K.; Mishra, S.R.

    2015-05-15

    Graphical abstract: Hyperfine field of individual sites (inset) and weighted average hyperfine field as a function of Al{sup 3+} content for Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4}. - Highlights: • Grain size reduction with Al{sup 3+} substitution. • Preferred occupancy of Al{sup 3+} at B site for higher Al{sup 3+} content. • Reduction in Ms, Tc, and hyperfine field with increasing Al{sup 3+} content. • Size dependent variation in coercivity. • Changes in isomer shift due to competing effect of volume and substitution. - Abstract: Nanostructured Al{sup 3+} doped Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) ferrites were synthesized via the wet chemical method. X-ray diffraction, transmission electron microscopy, and magnetization measurements have been used to investigate the structural and magnetic properties of spinel ferrites calcined at 950 °C. With the doping of Al{sup 3+}, the particle size of Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4} first increased to 47 nm at x = 0.4 and then decreased down to 37 nm at x = 1. The main two absorption bands in IR spectra were observed around 600 cm{sup −1} and 400 cm{sup −1} corresponding to stretching vibration of tetrahedral and octahedral group Fe{sup 3+}–O{sup 2−}. Saturation magnetization and hyperfine field values decreased linearly with Al{sup 3+} due to magnetic dilution and the relative strengths of Fe–O–Me (Me = Fe, Ni, Zn, and Al) superexchanges. The coercive field showed an inverse dependence on ferrite particle size with minimum value of 82 Oe for x = 0.4. A continuous drop in Curie temperature was observed with the Al{sup 3+} substitution. From the Moessbauer spectral analysis and X-ray diffraction analysis, it is deduced that Al{sup 3+} for x < 0.4 has no obvious preference for either tetrahedral or octahedral site but has a greater preference for the B site for x > 0.4. In nutshell the study presents detailed

  14. Ageing behaviour of an Fe-20Ni-1.8Mn-1.6Ti-0.59Al (wt%) maraging alloy: clustering, precipitation and hardening

    SciTech Connect

    Pereloma, E.V. . E-mail: elena.pereloma@spme.monash.edu.au; Shekhter, A.; Miller, M.K.; Ringer, S.P.

    2004-11-08

    Changes in the solute distribution as well as the evolution of precipitation, microstructure and mechanical properties have been studied in an experimental maraging Fe-20Ni-1.8Mn-1.5Ti-0.59Al (wt%) alloy during ageing at 550 deg C. An initial hardening reaction within 5 s is reported, which is remarkable in terms of extent and rapidity. This strengthening was caused by the formation of complex multi-component atomic co-clusters containing primarily Ni-Ti-Al as well as some Mn. This cluster strengthened condition produced the optimum toughness observed throughout the ageing sequence. After 60 s ageing, the appearance of discrete precipitation of needle-shaped {eta}-Ni{sub 3}Ti particles was associated with a second rise in hardness towards an eventual peak at 600 s. This precipitation hardening was accompanied by an increase in tensile strength and a decrease in ductility. A reverse transformation of martensite to austenite occurs progressively during ageing and this contributes to the initial and secondary softening.

  15. Magnetic Properties of FeNi-Based Thin Film Materials with Different Additives.

    PubMed

    Liang, Cai; Gooneratne, Chinthaka P; Wang, Qing Xiao; Liu, Yang; Gianchandani, Yogesh; Kosel, Jurgen

    2014-09-01

    This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B. PMID:25587418

  16. Effects of pH, surface finish and thermal treatment on the corrosion of AlFeNi aluminum alloy. Characterization of oxide layers

    NASA Astrophysics Data System (ADS)

    Nabhan, D.; Kapusta, B.; Billaud, P.; Colas, K.; Hamon, D.; Dacheux, N.

    2015-02-01

    The aluminum alloy AlFeNi used as fuel cladding for the Jules Horowitz Reactor (JHR) may undergo corrosion in the reactor environment. In order to qualify the corrosion behavior of the fuel elements of the JHR in accidental conditions, several specimens of AlFeNi have been corroded at 250 °C for different durations (9-34 days) in distilled water at various pH (4.9, 5.2 and 5.6) chosen to simulate that currently considered for the JHR. On all specimens, the only crystalline corrosion product formed is boehmite (AlOOH). The corrosion film is composed of three oxide layers which show through thickness chemical composition variations. The iron-nickel precipitates pre-existing in the metal matrix are present in the inner and intermediate oxide layers though oxidized. For long corrosion times, some of the iron and nickel particles are released in the water and some precipitation is observed at the surface of the oxide layer. The effect of surface finish (as received or polished) and thermal treatment (annealed and not annealed) on the oxide growth rate has also been investigated. For durations over 25 days, pH = 5.6 appears to be more favorable than pH = 5.2 and 4.9 in terms of oxide thickness and weight gain limitation. This effect of pH is however reduced on unpolished specimens. The effect of surface finish on the corrosion behavior as measured by optical microscopy appears to be strong, especially for pH = 4.9 where polished samples exhibited an accelerated evolution of the oxide thickness and of the mass gain. This could be due to the combined effect of a strong acid solution (pH = 4.9) and of the local microstructural changes formed at the interface through polishing. The effect of thermal treatment on the behavior of unpolished AlFeNi specimens during corrosion tests in the conditions investigated was found to be small. In this study, microstructural and chemical analyses were performed on the corroded specimens in order to get a better understanding of the

  17. Magnetic properties of the mixed spinel NiAl 2 xCr xFe 2-3 xO 4

    NASA Astrophysics Data System (ADS)

    Chhaya, Urvi V.; Trivedi, Bimal S.; Kulkarni, R. G.

    1999-01-01

    The crystal and magnetic properties of the Al and Cr co-substituted disordered spinel series NiAl 2 xCr xFe 2-3 xO 4 ( x=0.1-0.6) are investigated by means of X-ray diffraction, magnetization, Mössbauer effect and AC susceptibility measurements. The lattice constants are determined and the applicability of Vegards law has been tested. The variation of the saturation magnetic moment per formula unit measured at 77 K with the Al-Cr content is satisfactorily explained on the basis of Néel's collinear spin ordering model for x=0.1-0.2. The Mössbauer spectra at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe 3+ at tetrahedral (A) and octahedral (B) sites for x⩽0.4. Mössbauer results confirm a collinear ferrimagnetic structure for x=0.1-0.2. The nB values obtained from magnetization and Mössbauer data for x=0.3-0.6 display a discrepancy between them, thus exhibiting a significant canting on the B-site which is explained satisfactorily on the basis of the non-collinear spin ordering model of random canting.The Curie temperature obtained from AC susceptibility decreases nearly linear with x from x=0.1-0.4 and it shows a sudden change near x⩾0.4 indicating a change in magnetic structure.

  18. Elevated-Temperature Corrosion of CoCrCuFeNiAl0.5Bx High-Entropy Alloys in Simulated Syngas Containing H2S

    SciTech Connect

    Dogan, Omer N; Nielsen, Benjamin C; Hawk, Jeffrey A

    2013-08-01

    High-entropy alloys are formed by synthesizing five or more principal elements in equimolar or near equimolar concentrations. Microstructure of the CoCrCuFeNiAl{sub 0.5}B{sub x} (x = 0, 0.2, 0.6, 1) high-entropy alloys under investigation is composed of a mixture of disordered bcc and fcc phases and borides. These alloys were tested gravimetrically for their corrosion resistance in simulated syngas containing 0, 0.01, 0.1, and 1 % H{sub 2}S at 500 °C. The exposed coupons were characterized using XRD and SEM. No significant corrosion was detected at 500 °C in syngas containing 0 and 0.01 % H{sub 2}S while significant corrosion was observed in syngas containing 0.1 and 1 % H{sub 2}S. Cu{sub 1.96}S was the primary sulfide in the external corrosion scale on the low-boron high-entropy alloys, whereas FeCo{sub 4}Ni{sub 4}S{sub 8} on the high-boron high-entropy alloys. Multi-phase Cu-rich regions in the low-B high-entropy alloys were vulnerable to corrosive attack.

  19. 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.

  20. High-Temperature Tensile Strength of Al10Co25Cr8Fe15Ni36Ti6 Compositionally Complex Alloy (High-Entropy Alloy)

    NASA Astrophysics Data System (ADS)

    Daoud, H. M.; Manzoni, A. M.; Wanderka, N.; Glatzel, U.

    2015-06-01

    Homogenizing at 1220°C for 20 h and subsequent aging at 900°C for 5 h and 50 h of a novel Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy (high-entropy alloy) produces a microstructure consisting of an L12 ordered γ' phase embedded in a face-centered cubic solid-solution γ matrix together with needle-like B2 precipitates (NiAl). The volume fraction of γ' phase is ~46% and of needle-like B2 precipitates <5%, which is in accordance with the prediction of calculation of phase diagram method (CALPHAD using Thermo-Calc software with TTNi7 database; Thermo-Calc Software, Stockholm, Sweden). The high-temperature tensile tests were carried out at room temperature, 600°C, 700°C, 800°C, and 1000°C. The tensile strength as well as the elongation to failure of both heat-treated specimens is very high at all tested temperatures. The values of tensile strength has been compared with literature data of well-known Alloy 800H and Inconel 617, and is discussed in terms of the observed microstructure.

  1. The Mechanical and Corrosion Behaviors of As-cast and Re-melted AlCrCuFeMnNi Multi-Component High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Soare, Vasile; Mitrica, Dumitru; Constantin, Ionut; Popescu, Gabriela; Csaki, Ioana; Tarcolea, Mihai; Carcea, Ioan

    2015-04-01

    A multi-component AlCrCuFeMnNi high-entropy alloy, prepared by vacuum induction melting, was investigated for structural, mechanical, and corrosion characteristics, before and after the re-melting process. Optical microscopy analysis revealed a dendritic solidification behavior. The interdendritic area contains two main phases and occasionally small hard phases. The re-melting process produced a finer dendritic structure, with rounded dendrites and reduced interdendritic hard phases. The SEM-EDAX analysis showed that the dendrite region contains a Widmanstatten type of structure and are composed of Cr-Fe rich phases, whereas the interdendrite region contains Cu and Mn rich phases. XRD analysis revealed two disordered BCC type A2 structures with high Cr and Fe content and an FCC A12 type of structure for the Cu and Mn rich interdendritic phase. The lattice constants, determined by X-ray diffraction, are 2.87 and 2.91 Å for the A2 phases and 3.67 Å for A1 phase. The Vickers micro hardness increased with the homogeneity of the alloy, having a maximum value of 4370 MPa for the re-melted sample. Corrosion tests carried out in 3.5 wt pct sodium chloride aerated solution indicated that the corrosion resistance improved with the re-melting process, being 1.5 to 2 times better than that of 304 stainless steel.

  2. Influence of deformation on the structure and the mechanical properties of a high-entropy Fe25Cr20Ni20Co10Mn15Al10 alloy

    NASA Astrophysics Data System (ADS)

    Gorban', B. F.; Nazarenko, V. A.; Danilenko, N. I.; Karpets, M. V.; Krapivka, N. A.; Firstov, S. A.; Makarenko, E. S.

    2014-10-01

    The phase composition, the hardness, and the elasticity modulus of a high-entropy Fe25Cr20Ni20Co10Mn15Al10 alloy have been studied in the as-cast state, after rolling deformation, and after subsequent high-temperature annealing. The alloy consists of the following two phases: solid substitutional solutions with bcc and fcc crystal lattices; in the as-cast state and after annealing the bcc solid solution is ordered according to B2 type (CsCl). The mixture rule is applied for the calculation of the electron density, the atomic radius, and the melting point at grain boundaries and in the grain volume of the alloy after deformation and annealing. The obtained data demonstrate that the alloy is thermally stable.

  3. Modeling of circular piezoelectric micro ultrasonic transducer using CuAl10Ni5Fe4 on ZnO film for sonar applications

    NASA Astrophysics Data System (ADS)

    Yaacob, M. I. H.; Arshad, M. R.; Manaf, A. Abd.

    2011-03-01

    Modeling and theoretical characterization of piezoelectric micro ultrasonic transducer ( pMUT) using ZnO film sandwiched between nickel aluminum bronze (CuAl10Ni5Fe4) electrodes was reported in this paper. The transducer is targeted to be utilized in sonar applications. Analyses on the model were carried out using finite element method. Model's dimensional parameters were optimized for desired performance. Simplified technique was proposed to determine transmit and receive sensitivities of the model. As the result, micro ultrasonic transducer model with resonance frequency of 40 kHz was proposed with estimated receive and transmit sensitivities of -93 dB re 1 V/μPa and 137 dB re 1 μPa/V, respectively. Further model validations require actual device fabrication and this will be included in our future works.

  4. Influence of Bridgman solidification on microstructures and magnetic behaviors of a non-equiatomic FeCoNiAlSi high-entropy alloy

    SciTech Connect

    Zuo, Tingting; Yang, Xiao; Liaw, Peter K.; Zhang, Yong

    2015-09-07

    The non-equiatomic FeCoNiAlSi alloy is prepared by the Bridgman solidification (BS) technique at different withdrawal velocities (V = 30, 100, and 200 μm/s). Various characterization techniques have been used to study the microstructure and crystal orientation. The morphological evolutions accompanying the crystal growth of the alloy prepared at different withdrawal velocities are nearly the same, from equiaxed grains to columnar crystals. The transition of coercivity is closely related to the local microstructure, while the saturation magnetization changes little at different sites. The coercivity can be significantly reduced from the equiaxed grain area to the columnar crystal area when the applied magnetic field direction is parallel to the crystal growth direction, no matter what is the withdrawal velocity. As a result, the alloy possesses magnetic anisotropy when the applied magnetic field is in different directions.

  5. Influence of Bridgman solidification on microstructures and magnetic behaviors of a non-equiatomic FeCoNiAlSi high-entropy alloy

    DOE PAGESBeta

    Zuo, Tingting; Yang, Xiao; Liaw, Peter K.; Zhang, Yong

    2015-09-07

    The non-equiatomic FeCoNiAlSi alloy is prepared by the Bridgman solidification (BS) technique at different withdrawal velocities (V = 30, 100, and 200 μm/s). Various characterization techniques have been used to study the microstructure and crystal orientation. The morphological evolutions accompanying the crystal growth of the alloy prepared at different withdrawal velocities are nearly the same, from equiaxed grains to columnar crystals. The transition of coercivity is closely related to the local microstructure, while the saturation magnetization changes little at different sites. The coercivity can be significantly reduced from the equiaxed grain area to the columnar crystal area when the appliedmore » magnetic field direction is parallel to the crystal growth direction, no matter what is the withdrawal velocity. As a result, the alloy possesses magnetic anisotropy when the applied magnetic field is in different directions.« less

  6. Microstructure and Tensile Behavior of Al8Co17Cr17Cu8Fe17Ni33 (at.%) High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Daoud, H. M.; Manzoni, A.; Völkl, R.; Wanderka, N.; Glatzel, U.

    2013-12-01

    Microstructure evolution and tensile behavior of the high-entropy alloy Al8Co17Cr17Cu8Fe17Ni33 (at.%) are investigated at room temperature and at 500°C in the as-cast state and under different heat-treatment conditions. Detailed microstructural characterizations are carried out using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The equilibrium phase evolution as a function of temperature was calculated using the Thermo-Calc software (Thermo-Calc Software, Stockholm, Sweden) integrated with TTNi-7 database. The observed majority phase is a face-centered cubic solid solution for all tested specimens. Tensile ductility at room temperature and at elevated temperature is enhanced by heat treatment at 1150°C. An embrittlement phenomenon has been observed after a heat treatment at 700°C resulting in significant degradation in tensile properties.

  7. Effects of temperature on serrated flows of Al0.5CoCrCuFeNi high-entropy alloy

    DOE PAGESBeta

    Chen, Shuying; Xie, Xie; Chen, Bilin; Qiao, Junwei; Zhang, Yong; Ren, Yang; Dahmen, Karin A.; Liaw, Peter K.

    2015-08-14

    Compression behavior of the Al0.5CoCrCuFeNi high-entropy alloy (HEA) was studied at different temperatures from 673K to 873K at a low strain rate of 5 x 10-5/s to investigate the temperature effect on the mechanical properties and serration behavior. The face-centered cubic (FCC) structure is confirmed at the lower temperature of 673 K and 773 K, and a structure of mixed FCC and body-centered cubic (BCC) is identified at a higher temperature of 873 K after compression tests using high-energy synchrotron X-ray diffraction. As a result, by comparing the stress-strain curves at different temperatures, two opposite directions of serrations types weremore » found, named upward serrations appearing at 673 K and 773 K and downward serrations at 873 K, which may be due to dynamic strain aging.« less

  8. 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.

  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

    2016-04-01

    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.

  10. Effects of temperature on serrated flows of Al0.5CoCrCuFeNi high-entropy alloy

    SciTech Connect

    Chen, Shuying; Xie, Xie; Chen, Bilin; Qiao, Junwei; Zhang, Yong; Ren, Yang; Dahmen, Karin A.; Liaw, Peter K.

    2015-08-14

    Compression behavior of the Al0.5CoCrCuFeNi high-entropy alloy (HEA) was studied at different temperatures from 673K to 873K at a low strain rate of 5 x 10-5/s to investigate the temperature effect on the mechanical properties and serration behavior. The face-centered cubic (FCC) structure is confirmed at the lower temperature of 673 K and 773 K, and a structure of mixed FCC and body-centered cubic (BCC) is identified at a higher temperature of 873 K after compression tests using high-energy synchrotron X-ray diffraction. As a result, by comparing the stress-strain curves at different temperatures, two opposite directions of serrations types were found, named upward serrations appearing at 673 K and 773 K and downward serrations at 873 K, which may be due to dynamic strain aging.

  11. Microstructure and martensitic transformation in the Fe-Mn-Al-Ni shape memory alloy with B2-type coherent fine particles

    NASA Astrophysics Data System (ADS)

    Omori, T.; Nagasako, M.; Okano, M.; Endo, K.; Kainuma, R.

    2012-12-01

    Microstructure and martensitic transformation yielding a magnetic change were investigated for Fe43.5Mn34Al15Ni7.5 alloy with B2-type fine precipitates. Thermoelastic martensitic transformation from the ferromagnetic parent phase to the weak magnetic martensite with a nano-twinned fcc structure was confirmed. High-angle annular dark-field scanning transmission electron microscopic observation revealed that a β particle of about 10 nm maintains coherency with the matrix martensite phase, even though distorted due to the martensitic transformation. The martensitic transformation temperatures decreased about 75 K by application of a magnetic field of 70 kOe and magnetic field-induced reverse martensitic transformation was confirmed.

  12. The elastic, electronic and magnetism structure of the MAl and M3Al (M=Fe and Ni) alloy with and without hydrogen atoms

    NASA Astrophysics Data System (ADS)

    Mubarak, A. A.

    2016-03-01

    The energetic stability, electronic and magnetism of the MAl, M3Al alloy (M=Fe, Ni) and variant surfaces of MAl (001) with and without hydrogen atoms are investigated by utilizing DFT and GGA as the exchange-correlation potential. All presented alloys with and without the H atom absorption is found elastically and thermodynamically stable. The calculated absorption energy shows that H is more energetically stable in the bridge and octahedral site in MAl and M3Al alloys, respectively. Hydrogen atoms absorption is expanded and brittle the studied host alloys. The ability of absorption of H atom at more than one site in the MAl alloy is found energetically and thermodynamically stable. The H adsorption on the variant surfaces of MAl (001) is predicted too. Fourfold and top sites are found more energetically stable to adsorbed the H atom on the above surface layer of H/MAl-M and H/MAl-Al, respectively. The obvious changes are observed in the interlayer spacing for studied surfaces which yields to decrease the LDOS and magnetic moments of the surface and subsurface layers.

  13. On the Production of He, Ne, and AR Isotopes from Mg, Al, Si, Ca, Fe, and NI in an Artificially Irradiated Meteoroid

    NASA Astrophysics Data System (ADS)

    Wieler, R.; Signet, P.; Rosel, R.; Herpers, U.; Lupke, M.; Lange, H.-J.; Michel, R.

    1992-07-01

    The production of He, Ne, and Ar isotopes from their main target elements was investigated in an experiment (1) by irradiating a 50-cm-diameter gabbro sphere isotropically with 1.6 GeV protons. The model meteoroid contained, among a large number of other targets, pure element foils of Mg, Al, Si, Fe, and Ni at 10 different depths and wollastonite targets at 3 different depths in central bores. After the irradiation, radionuclide production in these targets was measured by gamma spectrometry. Stable He, Ne, and Ar isotopes were measured in statically operated mass spectrometers. Here, we report the results for stable He, Ne, and Ar isotopes and for ^22Na. The production depth profiles vary widely, ranging from profiles with near-surface production 15% higher than in the center (^22Na from Fe) to such profiles with production in the center 45% higher than near the surface (^20Ne from Mg). The isotope ratios ^3He/^4He and ^3He/^21Ne in Mg, Al, Si and ^22Ne/^21Ne in Mg all decrease significantly with increasing shielding. The production rates of He, Ne, and ^22Na from Mg, Al, and Si in the 1600-MeV simulation experiment are 1.5 to 3 times higher than in the model meteoroid of similar size but irradiated earlier with 600 MeV protons (2). This increase is attributed to the increase of the production of secondary neutrons with primary energies rising from 600 to 1600 MeV. This effect also causes the depth dependences of isotope ratios observed in the 1600-MeV simulation that was not seen in the 600-MeV experiment. Model calculations of the production of He, Ne, and Ar isotopes and of ^22Na were performed for the artificial meteorites of the 600- and 1600 MeV-exposures as well as for real meteoroids. Production rates were calculated from depth-dependent p- and n- spectra, which were derived by Monte Carlo techniques using the HERMES code system (3), and from cross sections for the relevant nuclear reactions as described earlier (4). The cross section database for p

  14. Synthesis and magnetic properties of hard-soft SRFe10Al2O19/NiZnFe2O4 ferrite nanocomposites.

    PubMed

    Rai, B K; Wang, L; Mishra, S R; Nguyen, V V; Liu, J P

    2014-07-01

    Pure phase exchange-coupled nanocomposites of hard-soft magnetic oxides, (hard) SrFe10Al2O19(-) (soft) Ni0.75Zn0.25Fe2O4 were prepared via autocombution method. Magnetic properties of the nanocomposites were assessed as a function of soft-phase content in the nanocomposite. A 40% increase in M(s) value was observed for nanocomposite with 30 Wt.% of the soft phase. A linear increase in M(r)/M(s) with soft-phase content indicates the presence of enhanced exchange-coupling between hard and soft phases of the nanocomposite. The highest M(r)/M(s) ratio of 0.68 was obtained for nanocomposite containing 30 Wt.% of the soft-phase. The observed reduction in coercieve field values of the nanocomposite with increase in soft-phase content is explained on the basis of competition between exchange and dipolar interaction between hard-soft and soft-soft phases of the nanocomposite. PMID:24758015

  15. Proton induced K X-ray production cross sections of the elements Al, Si, Ti, Fe, and Ni in the 0.7-2.0 MeV energy range

    NASA Astrophysics Data System (ADS)

    Bertol, Ana Paula Lamberti; Hinrichs, Ruth; Vasconcellos, Marcos A. Z.

    2015-12-01

    Proton induced K-shell ionization cross sections were obtained for the elements Al, Si, Ti, Fe, and Ni in the 0.7-2.0 MeV energy range. The accuracy of these fundamental parameters is essential for PIXE analysis and the data in the literature present a considerable spread, mainly for Al and Si. The values obtained for Ti, Fe and Ni are compatible with the current theories and the experimental results reported in the literature. However, Al and Si cross sections present important differences from theoretical and experimental data. We propose values for the fluorescent yields of Al and Si that are compatible with recent results and can be incorporated in the computations of K X-ray production cross sections.

  16. Domain Structures and Anisotropy in Exchange-coupled [Co/Pd]-NiFe and [Co/Ni]-NiFe Multilayers

    NASA Astrophysics Data System (ADS)

    Tryputen, Larysa; Chung, Sunjae; Mohseni, Majid; Nguyen, T. N. Anh; Åkerman, Johan; Guo, Feng; McMichael, Robert D.; Ross, Caroline A.

    2014-03-01

    Exchange-coupled multilayers [Co/Pd]5-/NiFe and [Co/Ni]4-NiFe with strong perpendicular magnetic anisotropy have been proposed to use in spin-torque switching and oscillators devices with tilted fixed and free layer to improve their functional performance. We present an experimental study of the magnetization behavior of [Co/Pd]5-/NiFe and [Co/Ni]4-NiFe multilayers measured using magnetometry, magnetic force microscopy (MFM) and ferromagnetic resonance (FMR) as a function of the thickness of the top NiFe layer. We varied the thickness of the NiFe layer in [Co/Pd]5-NiFe (t), t = 0 - 80 nm and [Co/Ni]4-NiFe (t), t = 0.5 - 2.5 nm in order to study the interplay between perpendicular magnetization of the Co/Pd or Co/Ni multilayers and in-plane magnetization of the NiFe. Our magnetometry and FMR data suggest that the [Co/Ni]4/NiFe multilayer behaves like a homogeneous ferromagnetic film with anisotropy that reorients towards in-plane as the NiFe thickness increases, whereas the [Co/Pd]5/NiFe multilayer reveals more complex behavior in which the [Co/Pd] layer retains out-of-plane anisotropy while the magnetization of NiFe layer tilts in-plane with increasing thickness. MFM showed that domains with ~0.1 +/-m size were visible in [Co/Pd]-/NiFe with NiFe thickness of 20-80 nm. Multilayers were patterned into sub-100 nm dots using ion beam etching and their magnetization behavior are compared with unpatterned films.

  17. Evolution of the microstructure and magnetic properties of as-cast and melt spun Fe2NiAl alloy during aging

    NASA Astrophysics Data System (ADS)

    Menushenkov, V. P.; Gorshenkov, M. V.; Shchetinin, I. V.; Savchenko, A. G.; Savchenko, E. S.; Zhukov, D. G.

    2015-09-01

    Fe2NiAl-based alloy with the nominal composition Fe51.1Ni23.5Al23.7Si1.7 was prepared by casting and melt-spinning. Comparison of the phase composition, microstructure and magnetic properties of water-quenched bulk samples and melt spun ribbons after isothermal aging in the 500-900 °C range were carried out. TEM investigations of the decomposition of the solid solution into β- and β2 phases during cooling or quenching and subsequent aging have revealed different types of decomposition products. The optimal periodic modulated structure with coercive force Hc~700 Oe was observed after cooling of as-cast alloy at a critical rate. In this structure the paramagnetic β2 phase forms a continuous network that isolates elongated single domain ferromagnetic β particles. The water-quenched bulk samples and melt spun ribbons were characterized by zone structure with zones about 10 nm and 4 nm in size. The isothermal aging of quenched samples resulted in the formation of modulated microstructure dissimilar to those of the optimal state. The coarsening of ferromagnetic β particles as well as deterioration of the magnetic insulation of β particles occur in bulk samples after aging at Tag>700 °C that decreases Hc≤350 Oe. The dependence δM(H) was measured and negative values of δM(H) in the H=0-2000 Oe range indicate that magnetostatic interactions between the β particles are dominant. The melt spun ribbons were characterized by the presence of antiphase domain boundaries (APD) and discontinuous precipitation (DP) products at grain boundaries (GB). The cellular areas at GBs consisting of alternating lamellas of β‧- and β2‧ type phases were formed after aging the ribbons at Tag>500 °C. At Tag>700 °C the modulated structure formed inside grains and the wide intergranular double-layer of β and β2 phases develops by the coalescence of the primary DP products that decrease Hc≤250 Oe. MFM image of the magnetic structure correlated with the microstructure of the

  18. The oxidation of Ni-rich Ni-Al intermetallics

    NASA Technical Reports Server (NTRS)

    Doychak, J.; Smialek, J. L.; Barrett, C. A.

    1989-01-01

    The oxidation of Ni-Al intermetallic alloys in the beta-NiAl phase field and in the two phase beta-NiAl/gamma'-Ni3Al phase field has been studied between 1000 and 1400 C. The stoichiometric beta-NiAl alloy doped with Zr was superior to other alloy compositions under cyclic and isothermal oxidation. The isothermal growth rates did not increase monotonically as the alloy Al content was decreased. The characteristically ridged alpha-Al203 scale morphology, consisting of cells of thin, textured oxide with thick growth ridges at cell boundaries, forms on oxidized beta-NiAl alloys. The correlation of scale features with isothermal growth rates indicates a predominant grain boundary diffusion growth mechanism. The 1200 C cyclic oxidation resistance decreases near the lower end of the beta-NiAl phase field.

  19. The oxidation of Ni-rich Ni-Al intermetallics

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

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

    PubMed Central

    Feuerbacher, Michael

    2016-01-01

    High-entropy alloys are multicomponent metallic materials currently attracting high research interest. They display a unique combination of chemical disorder and crystalline long-range order, and due to their attractive properties are promising candidates for technological application. Many high-entropy alloys possess surprisingly high strength, occasionally in combination with high ductility and low density. The mechanisms effecting these attractive mechanical properties are not understood. This study addresses the deformation mechanism of a Al28Co20Cr11Fe15Ni26 high-entropy alloy, which is a two-phase material, consisting of a B2-ordered matrix and disordered body-centred inclusions. We quantitatively analyse the microstructure and dislocations in deformed samples by transmission-electron-microscopic methods including weak-beam imaging and convergent-beam electron diffraction. We find that the deformation process in the B2 phase is dominated by heterogeneous slip of screw dislocations gliding on planes. The dislocations are perfect superdislocations of the B2 lattice and show no dissociation. This indicates that the antiphase-boundary energy in the structure is very high, inhibiting spread of the dislocation core. Along with the observation of a widely extending strain field associated to the dislocations, our results provide a possible explanation for the high strength of this high-entropy alloy as a direct consequence of its dislocation structure. PMID:27430993

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

    PubMed

    Feuerbacher, Michael

    2016-01-01

    High-entropy alloys are multicomponent metallic materials currently attracting high research interest. They display a unique combination of chemical disorder and crystalline long-range order, and due to their attractive properties are promising candidates for technological application. Many high-entropy alloys possess surprisingly high strength, occasionally in combination with high ductility and low density. The mechanisms effecting these attractive mechanical properties are not understood. This study addresses the deformation mechanism of a Al28Co20Cr11Fe15Ni26 high-entropy alloy, which is a two-phase material, consisting of a B2-ordered matrix and disordered body-centred inclusions. We quantitatively analyse the microstructure and dislocations in deformed samples by transmission-electron-microscopic methods including weak-beam imaging and convergent-beam electron diffraction. We find that the deformation process in the B2 phase is dominated by heterogeneous slip of screw dislocations gliding on planes. The dislocations are perfect superdislocations of the B2 lattice and show no dissociation. This indicates that the antiphase-boundary energy in the structure is very high, inhibiting spread of the dislocation core. Along with the observation of a widely extending strain field associated to the dislocations, our results provide a possible explanation for the high strength of this high-entropy alloy as a direct consequence of its dislocation structure. PMID:27430993

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

    NASA Astrophysics Data System (ADS)

    Feuerbacher, Michael

    2016-07-01

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

  3. Photosensitivity of the Ni-A state of [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F with visible light

    SciTech Connect

    Osuka, Hisao; Shomura, Yasuhito; Komori, Hirofumi; Shibata, Naoki; Nagao, Satoshi; Higuchi, Yoshiki; Hirota, Shun

    2013-01-04

    Highlights: Black-Right-Pointing-Pointer Ni-A state of [NiFe] hydrogenase showed light sensitivity. Black-Right-Pointing-Pointer New FT-IR bands were observed with light irradiation of the Ni-A state. Black-Right-Pointing-Pointer EPR g-values of the Ni-A state shifted upon light irradiation. Black-Right-Pointing-Pointer The light-induced state converted back to the Ni-A state under the dark condition. -- Abstract: [NiFe] hydrogenase catalyzes reversible oxidation of molecular hydrogen. Its active site is constructed of a hetero dinuclear Ni-Fe complex, and the oxidation state of the Ni ion changes according to the redox state of the enzyme. We found that the Ni-A state (an inactive unready, oxidized state) of [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F (DvMF) is light sensitive and forms a new state (Ni-AL) with irradiation of visible light. The Fourier transform infrared (FT-IR) bands at 1956, 2084 and 2094 cm{sup -1} of the Ni-A state shifted to 1971, 2086 and 2098 cm{sup -1} in the Ni-AL state. The g-values of g{sub x} = 2.30, g{sub y} = 2.23 and g{sub z} = 2.01 for the signals in the electron paramagnetic resonance (EPR) spectrum of the Ni-A state at room temperature varied for -0.009, +0.012 and +0.010, respectively, upon light irradiation. The light-induced Ni-AL state converted back immediately to the Ni-A state under dark condition at room temperature. These results show that the coordination structure of the Fe site of the Ni-A state of [NiFe] hydrogenase is perturbed significantly by light irradiation with relatively small coordination change at the Ni site.

  4. Effect of cold rolling on the microstructure and mechanical properties of Al0.25CoCrFe1.25Ni1.25 high-entropy alloy

    SciTech Connect

    Wang, Z.; Gao, M. C.; Ma, S. G.; Yang, H. J.; Wang, Z. H.; Ziomek-Moroz, M.; Qiao, J. W.

    2015-08-05

    Cold rolling can break down the as-cast dendrite microstructure and thus may have pronounced impact on the mechanical behavior of the alloy. In the present study, the effect of cold rolling on the microstructure and mechanical properties of Al0.25CoCrFe1.25Ni1.25 high-entropy alloy in the face-centered cubic structure was investigated. With increasing the thickness reduction from cold rolling, the hardness, the yield strength, and the fracture strength increased at the cost of reducing ductility. At the thickness reduction of 80%, the tensile strength (hardness) was 702 MPa (406 MPa), 1.62 (2.43) times that in the as-cast condition. Compared to traditional alloys, Al0.25CoCrFe1.25Ni1.25 has the highest hardening rate with respect to CR thickness reduction. Lastly, the phase relation and the mixing properties of Gibbs free energy, enthalpy and entropy of AlxCoCrFe1.25Ni1.25 were predicted using the CALPHAD method.

  5. Enhancement of magnetoresistance by inserting thin NiAl layers at the interfaces in Co2FeGa0.5Ge0.5/Ag/Co2FeGa0.5Ge0.5 current-perpendicular-to-plane pseudo spin valves

    NASA Astrophysics Data System (ADS)

    Jung, J. W.; Sakuraba, Y.; Sasaki, T. T.; Miura, Y.; Hono, K.

    2016-03-01

    We have investigated the effects of insertion of a thin NiAl layer (≤0.63 nm) into a Co2FeGa0.5Ge0.5 (CFGG)/Ag interface on the magnetoresistive properties in CFGG/Ag/CFGG current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo spin valves (PSVs). First-principles calculations of ballistic transmittance clarified that the interfacial band matching at the (001)-oriented NiAl/CFGG interface is better than that at the (001)-Ag/CFGG interface. The insertion of 0.21-nm-thick NiAl layers at the Co2FeGa0.5Ge0.5/Ag interfaces effectively improved the magnetoresistance (MR) output; the observed average and the highest MR ratio (ΔRA) are 62% (25 mΩ μm2) and 77% (31 mΩ μm2) at room temperature, respectively, which are much higher than those without NiAl insertion. Microstructural analysis using scanning transmission electron microscopy confirmed the existence of thin NiAl layers at the Ag interfaces with only modest interdiffusion even after annealing at 550 °C. The improvement of the interfacial spin-dependent scattering by very thin NiAl insertion can be a predominant reason for the enhancement of the MR output.

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

    NASA Astrophysics Data System (ADS)

    Zeltser, A. M.; Smith, Neil

    1996-04-01

    The magnetic and transport properties of electron beam evaporated (Ni83Fe17/Cu)10 and (Ni66Fe16Co18/Cu)10 multilayers (ML) were studied as a function of the Cu spacer and magnetic layer thicknesses (tCu and tNiFe), annealing conditions and Ta buffer layer thickness. The ML were evaporated in a magnetic field at deposition rates ˜ 2 Å/s and background pressure <5×10-8 mbar on Si/SiO2 substrates at Ts=200 °C. These ML exhibited two unique features: (1) ΔR/R and the interlayer coupling did not show oscillatory behavior as a function of tCu; and (2) after magnetic post annealing, ΔR/R increased from <0.3% in the as-deposited state, to up to ˜6% and 7% in Ta/(NiFe/Cu) and (NiFeCo/Cu), respectively. The coupling between the NiFe layers changed from ferromagnetic in the as-deposited state Mr/Ms˜0.9k;20 to essentially antiferromagnetic Mr/Ms<0.2) after appropriate annealing, and the ML became virtually isotropic in-plane. This is quite different from strong oscillatory behavior of giant magnetoresistance (GMR) previously reported in (NiFe/Cu) as-deposited ML made by ion-beam sputtering. After annealing at 300° and 325 °C for 2 h, the ΔR/R became ˜4.5% and ˜6.5% in (NiFe/Cu) and (NiFeCo/Cu) ML, respectively, and remained approximately constant for tCu=20 to 40 Å. The coupling field generally decreased with an increase in Cu and NiFe and after annealing at 300 °C dropped to as low as ˜25 and 45 Oe in (NiFe/Cu) and (NiFeCo/Cu) ML, respectively. The of ΔR/R Ta/(NiFe/Cu) ML increased with the thickness of Ta buffer layer from 30 to 70 Å. The high-angle θ-2θ x-ray scans of (NiFe/Cu) ML showed (111) texture, essentially independent of annealing temperature. The low-angle x-ray diffraction did not reveal roughening of the Cu-NiFe interfaces as a result of annealing. In many respects the GMR behavior of these ML is similar to that reported in sputtered ``discontinuous'' NiFe/Ag. However, in contrast to the latter, the resistivity of NiFe/Cu monotonically

  7. Influence of W, Mo and Ti trace elements on the phase separation in Al8Co17Cr17Cu8Fe17Ni33 based high entropy alloy.

    PubMed

    Manzoni, Anna M; Daoud, Haneen M; Voelkl, Rainer; Glatzel, Uwe; Wanderka, Nelia

    2015-12-01

    Compositionally complex alloys, also called high entropy alloys, have been investigated for over a decade in view of different applications, but so far only a small number of alloys can be considered as presenting good enough properties for industrial application. The most common family of elements is Al-Co-Cr-Cu-Fe-Ni. The equiatomic alloy having 5 phases and being too brittle, the composition has been modified in order to improve the mechanical properties. Different compositions have been tested and as a first result ductile Al8Co17Cr17Cu8Fe17Ni33 has been chosen for deeper investigation. It shows a dendritic segregation into Co-Cr-Fe rich cores and Al-Cu-Ni rich interdendritic sites. The as-cast state is characterized mainly by two phases, namely Al-Cu-Ni rich precipitates of L12 structure inside a solid solution matrix. After homogenization both alloys consists of a single solid solution phase. Results are compared to calculations by ThermoCalc. In order to further improve the properties of the alloy the Cr content has been decreased and replaced by trace elements W, Mo and Ti, which, according to ThermoCalc, increase the melting point and the phase transition temperature which leads to the formation of the L12 phase. As-cast and heat treated samples of the base and the modified alloy have been investigated by transmission electron microscopy and three dimensional atom probe. Results of the investigations will be discussed in terms of microstructure, hardness and coherence with Thermo Calc predictions. PMID:26159736

  8. Melting of Fe and Fe0.9Ni0.1 alloy at high pressures

    NASA Astrophysics Data System (ADS)

    Zhang, D.; Jackson, J. M.; Zhao, J.; Sturhahn, W.; Alp, E. E.; Hu, M. Y.; Toellner, T.

    2014-12-01

    Cosmochemical studies suggest that the cores of terrestrial planets are primarily composed of Fe alloyed with about 5 to 10 wt% Ni, plus some light elements (e.g., McDonough and Sun 1995). Thus, the high pressure melting curve of Fe0.9Ni0.1 is considered to be an important reference for characterizing the cores of terrestrial planets. We have determined the melting points of fcc-structured Fe and Fe0.9Ni0.1 up to 86 GPa using an in-situ method that monitors the atomic dynamics of the Fe atoms in the sample, synchrotron Mössbauer spectroscopy (Jackson et al. 2013). A laser heated diamond anvil cell is used to provide the high pressure-high temperature environmental conditions, and in-situ X-ray diffraction is used to constrain the pressure of the sample. To eliminate the influence of temperature fluctuations experienced by the sample on the determination of melting, we develop a Fast Temperature Readout (FasTeR) spectrometer. The FasTeR spectrometer features a fast reading rate (>100 Hz), a high sensitivity, a large dynamic range and a well-constrained focus. By combining the melting curve of fcc-structured Fe0.9Ni0.1 alloy determined in our study and the fcc-hcp phase boundary from Komabayashi et al. (2012), we calculate the fcc-hcp-liquid triple point of Fe0.9Ni0.1. Using this triple point and the thermophysical parameters from a nuclear resonant inelastic X-ray scattering study on hcp-Fe (Murphy et al. 2011), we compute the melting curve of hcp-structured Fe0.9Ni0.1. We will discuss our new experimental results with implications for the cores of Venus, Earth and Mars. Select references: McDonough & Sun (1995): The composition of the Earth. Chem. Geol. 120, 223-253. Jackson et al. (2013): Melting of compressed iron by monitoring atomic dynamics, EPSL, 362, 143-150. Komabayashi et al. (2012): In situ X-ray diffraction measurements of the fcc-hcp phase transition boundary of an Fe-Ni alloy in an internally heated diamond anvil cell, PCM, 39, 329-338. Murphy et al

  9. Effect of cold rolling on the microstructure and mechanical properties of Al0.25CoCrFe1.25Ni1.25 high-entropy alloy

    DOE PAGESBeta

    Wang, Z.; Gao, M. C.; Ma, S. G.; Yang, H. J.; Wang, Z. H.; Ziomek-Moroz, M.; Qiao, J. W.

    2015-08-05

    Cold rolling can break down the as-cast dendrite microstructure and thus may have pronounced impact on the mechanical behavior of the alloy. In the present study, the effect of cold rolling on the microstructure and mechanical properties of Al0.25CoCrFe1.25Ni1.25 high-entropy alloy in the face-centered cubic structure was investigated. With increasing the thickness reduction from cold rolling, the hardness, the yield strength, and the fracture strength increased at the cost of reducing ductility. At the thickness reduction of 80%, the tensile strength (hardness) was 702 MPa (406 MPa), 1.62 (2.43) times that in the as-cast condition. Compared to traditional alloys, Al0.25CoCrFe1.25Ni1.25more » has the highest hardening rate with respect to CR thickness reduction. Lastly, the phase relation and the mixing properties of Gibbs free energy, enthalpy and entropy of AlxCoCrFe1.25Ni1.25 were predicted using the CALPHAD method.« less

  10. Processing and Mechanical Properties of Directionally Solidified NiAl/NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    Promising creep strengths were found for a directionally solidified NiAl-NiAlTa alloy when compared to other NiAl based intermetallics. The directionally solidified alloy had an off-eutectic composition that resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of the two phase alloy was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Alloying additions that may improve the room temperature toughness by producing multiphase alloys are discussed.

  11. Synthesis and electrochemical studies on Al 2O 3 coated LiNi 0.5Co 0.44Fe 0.06VO 4 for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Fey, George Ting-Kuo; Muralidharan, Pandurangan; Cho, Yung-Da

    LiNi 0.5Co 0.44Fe 0.06VO 4 cathode material has been synthesized by a citric acid:polyethylene glycol polymeric method at 723 K for 5 h in air. The surface of the LiNi 0.5Co 0.44Fe 0.06VO 4 was coated with various wt.% of Al 2O 3 by a wet chemical procedure and heat treated 873 K for 2 h in air. The samples were characterized by XRD, FTIR, SEM, and TEM techniques. XRD patterns expose that the complete crystalline phase occurred at 723 K and there was no indication of new peaks for the coated samples. FTIR spectra show that the complete removal of organic residues and the formation of LiNi 0.5Co 0.44Fe 0.06VO 4. TG/DTGA results reveal that the formation of LiNi 0.5Co 0.44Fe 0.06VO 4 occurred between 480 and 670 K and the complete crystalline occurred at 723 K. SEM micrographs show the various morphological stages of the polymeric intermediates. TEM micrographs of the pristine LiNi 0.5Co 0.44Fe 0.06VO 4 reveal that the particle size ranged from 130 to 150 nm and Al 2O 3 coating on the fine particles was compact and had an average thickness of about 15 nm. The charge-discharge experiments were carried out between 2.8 and 4.9 V (versus Li) at a current rate of 0.15 C. The 1.0 wt.% Al 2O 3 coated sample had the best electrochemical performance, with an initial capacity of 65 mAh g -1 and capacity retention of 60% after 50 cycles. The electrochemical impedance behavior suggests that the failure of pristine cathode performance is associated with an increase in the impedance growth on the surface of the cathode material upon continuous cycling.

  12. Improving the low temperature ductility of NiAl

    NASA Technical Reports Server (NTRS)

    Guha, Sumit; Munroe, Paul R.; Baker, Ian

    1989-01-01

    As part of a study aimed at developing a ductile NiAl-based alloy, ingots of Ni-Fe-Al alloys were cast and hot extruded to rods. The purpose of the iron additions was two-fold viz; to produce a change in the slip vector from 001 to 111 line and, in one alloy, to add a L1(2)-structured ductile second phase. Extruded Ni-20Al-30Fe was two-phase, containing a pro-eutectic B2 phase in a fine lamellar structure of B2+L1(2) phases. Room temperature tensile testing of both single extruded and double extruded alloys resulted in 8-percent and 22-percent plastic elongation and yield stresses of 850 and 760 MPa, respectively. Fracture in both cases occurred by ductile tearing of the eutectic and transgranular cleavage of the proeutectic phase at 1350 MPa. The ductility in double extruded condition is higher than that reported earlier in rapidly solidified wires by Inoue et al. (1984). By comparison, extruded single-phase B2-structured Ni-30Al-20Fe exhibited a fracture strength of 780 MPa, no plasticity, and a mixture of intergranular fracture and transgranular cleavage. This is contrast to earlier work by Inoue et al. where a yield stress of 400 MPa, 5 percent plastic strain, and a mixture of dimple and intergranular fracture was reported.

  13. 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.

  14. [NiFeSe]-hydrogenase chemistry.

    PubMed

    Wombwell, Claire; Caputo, Christine A; Reisner, Erwin

    2015-11-17

    The development of technology for the inexpensive generation of the renewable energy vector H2 through water splitting is of immediate economic, ecological, and humanitarian interest. Recent interest in hydrogenases has been fueled by their exceptionally high catalytic rates for H2 production at a marginal overpotential, which is presently only matched by the nonscalable noble metal platinum. The mechanistic understanding of hydrogenase function guides the design of synthetic catalysts, and selection of a suitable hydrogenase enables direct applications in electro- and photocatalysis. [FeFe]-hydrogenases display excellent H2 evolution activity, but they are irreversibly damaged upon exposure to O2, which currently prevents their use in full water splitting systems. O2-tolerant [NiFe]-hydrogenases are known, but they are typically strongly biased toward H2 oxidation, while H2 production by [NiFe]-hydrogenases is often product (H2) inhibited. [NiFeSe]-hydrogenases are a subclass of [NiFe]-hydrogenases with a selenocysteine residue coordinated to the active site nickel center in place of a cysteine. They exhibit a combination of unique properties that are highly advantageous for applications in water splitting compared with other hydrogenases. They display a high H2 evolution rate with marginal inhibition by H2 and tolerance to O2. [NiFeSe]-hydrogenases are therefore one of the most active molecular H2 evolution catalysts applicable in water splitting. Herein, we summarize our recent progress in exploring the unique chemistry of [NiFeSe]-hydrogenases through biomimetic model chemistry and the chemistry with [NiFeSe]-hydrogenases in semiartificial photosynthetic systems. We gain perspective from the structural, spectroscopic, and electrochemical properties of the [NiFeSe]-hydrogenases and compare them with the chemistry of synthetic models of this hydrogenase active site. Our synthetic models give insight into the effects on the electronic properties and reactivity of

  15. Doping effect on the structural properties of Cu1-x(Ni, Zn, Al and Fe)xO samples (0

    NASA Astrophysics Data System (ADS)

    Amaral, J. B.; Araujo, R. M.; Pedra, P. P.; Meneses, C. T.; Duque, J. G. S.; dos S. Rezende, M. V.

    2016-09-01

    In this work, the effect of insertion of transition metal, TM (=Ni, Zn, Al and Fe), ions in Cu1-xTMxO samples (0Ni and Zn-doped samples show a small amount of spurious phases for concentrations above x=0.05. Based on these results, a defect disorder study for using atomistic computational simulations which is based on the lattice energy minimization technique is employed to predict the location of the dopant ions in the structure. In agreement with XRD data, our computational results indicate that the trivalent (Al and Fe ions) are more favorable to be incorporated into CuO matrix than the divalent (Ni and Zn ions).

  16. NiAl-Based Approach For Rocket Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Nathal, Michael V. (Inventor); Gayda, John (Inventor); Noebe, Ronald D. (Inventor)

    2005-01-01

    A multi-layered component, such as a rocket engine combustion chamber, includes NiAl or NiAl-based alloy as a structural layer on the hot side of the component. A second structural layer is formed of material selected form Ni-based superalloys, Co-based alloys, Fe-based alloys, Cu, and Cu-based alloys. The second material is more ductile than the NiAl and imparts increased toughness to the component. The second material is selected to enhance one or more predetermined physical properties of the component. Additional structural layers may be included with the additional material(s) being selected for their impact on physical properties of the component.

  17. NiAl-based approach for rocket combustion chambers

    NASA Technical Reports Server (NTRS)

    Nathal, Michael V. (Inventor); Gayda, John (Inventor); Noebe, Ronald D. (Inventor)

    2005-01-01

    A multi-layered component, such as a rocket engine combustion chamber, includes NiAl or NiAl-based alloy as a structural layer on the hot side of the component. A second structural layer is formed of material selected from Ni-based superalloys, Co-based alloys, Fe-based alloys, Cu, and Cu-based alloys. The second material is more ductile than the NiAl and imparts increased toughness to the component. The second material is selected to enhance one or more predetermined physical properties of the component. Additional structural layers may be included with the additional material(s) being selected for their impact on physical properties of the component.

  18. Incorporation of Ba in Al and Fe pollucite

    NASA Astrophysics Data System (ADS)

    Vance, Eric R.; Gregg, Daniel J.; Griffiths, Grant J.; Gaugliardo, Paul R.; Grant, Charmaine

    2016-09-01

    Ba, the transmutation product of radioactive Cs, can be incorporated at levels of up to ∼0.07 formula units in Cs(1-2x)BaxAlSi2O6 aluminium pollucite formed by sol-gel methods and sintering at 1400 °C, with more Ba forming BaAl2Si2O8 phases. The effect of Ba substitution in pollucite-structured CsFeSi2O6 was also studied and no evidence of Ba substitution in the pollucite structure via cation vacancies or Fe2+ formation was obtained. The Ba entered a Fe-silicate glass structure. Charge compensation was also attempted with a Cs+ + Fe3+ ↔ Ba2+ + Ni2+ scheme but again the Ba formed a glass and NiO was evident. PCT leaching data showed CsFeSi2O6 to be very leach resistant.

  19. Oxidation behavior of FeAl+Hf,Zr,B

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Doychak, Joseph

    1988-01-01

    The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of HfO2. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.

  20. 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.

  1. Electrochemical and corrosion properties of YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Cu, Co, Mn) hybride-forming alloys

    SciTech Connect

    Korobov, I.I.; Vasina, S.Ya.; Petrii, O.A.

    1995-06-01

    Hydrogen sorption by electrode materials based on YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Co, Cu, Mn) intermetallic compounds (IMC) with Cu and PTFE binders is studied in 1 M NaOH solution. The obtained reversible electrochemical capacities correspond to YNi{sub 2.5}M{sub 0.5}H{sub 1.3-1.7} hybrides which are stable at room temperature and atmospheric pressure. The application of Cu binder allows one to more completely use the material sorption capacity and promotes both extraction and sorption of hydrogen by IMC.

  2. Compatibility of potential reinforcing ceramics with Ni and Fe aluminides

    NASA Technical Reports Server (NTRS)

    Moser, J. A.; Aindow, M.; Clark, W. A. T.; Draper, S.; Fraser, H. L.

    1990-01-01

    The compatibility of candidate ceramic reinforcement materials with intermetallic matrices for high temperature composite systems has been evaluated. Powders of FeAl and NiAl were mixed with ceramic powders and consolidated by hot isostatic pressing and subsequent heat treatment. The microstructures of these composites and the nature of the ceramic/matrix interfaces were assessed using a wide variety of electron-beam techniques. The system FeAl/TiB2 was found to be particularly promising. The matrix appears to be bonded to the ceramic particles, which may be the result of diffusion of Fe into the ceramic. The particles stabilized in a previously unreported monoclinic crystal structure, rather than the equilibrium hexagonal form exhibited by the binary compound.

  3. Fabric cutting application of FeAl-based alloys

    SciTech Connect

    Sikka, V.K.; Blue, C.A.; Sklad, S.P.; Deevi, S.C.; Shih, H.R.

    1998-11-01

    Four intermetallic-based alloys were evaluated for cutting blade applications. These alloys included Fe{sub 3}Al-based (FAS-II and FA-129), FeAl-based (PM-60), and Ni{sub 3}Al-based (IC-50). These alloys were of interest because of their much higher work-hardening rates than the conventionally used carbon and stainless steels. The FeAl-based PM-60 alloy was of further interest because of its hardening possibility through retention of vacancies. The vacancy retention treatment is much simpler than the heat treatments used for hardening of steel blades. Blades of four intermetallic alloys and commercially used M2 tool steel blades were evaluated under identical conditions to cut two-ply heavy paper. Comparative results under identical conditions revealed that the FeAl-based alloy PM-60 outperformed the other intermetallic alloys and was equal to or somewhat better than the commercially used M2 tool steel.

  4. Sonochemical preparation of nanosized amorphous Fe-Ni alloys

    NASA Astrophysics Data System (ADS)

    Shafi, K. V. P. M.; Gedanken, A.; Goldfarb, R. B.; Felner, I.

    1997-05-01

    Nanosized amorphous alloy powders of Fe20Ni80, Fe40Ni60, and Fe60Ni40 were prepared by sonochemical decomposition of solutions of volatile organic precursors, Fe(CO)5 and Ni(CO)4 in decalin, under an argon pressure of 100 to 150 kPa at 273 K. Magnetic susceptibility of Fe40Ni60 and Fe60Ni40 indicates blocking temperatures of 35 K and a magnetic particle size of about 6 nm. Thermogravimetric measurements of Fe20Ni80 give Curie temperatures of 322 °C for amorphous and 550 °C for crystallized forms. Differential scanning calorimetry exhibits an endothermic transition at 335 °C from a combination of the magnetic phase transition and alloy crystallization. The Mössbauer spectrum of crystallized Fe20Ni80 shows a sextet pattern with a hyperfine field of 25.04 T.

  5. Co2FeAl films with perpendicular magnetic anisotropy in multilayer structure

    NASA Astrophysics Data System (ADS)

    Li, X. Q.; Xu, X. G.; Yin, S. Q.; Zhang, D. L.; Miao, J.; Jiang, Y.

    2011-01-01

    We have fabricated Co2FeAl (CFA) films with perpendicular magnetic anisotropy (PMA) in a (Co2FeAl/Ni)6 multilayer structure. The effects of underlayer Cu thickness (tCu), Co2FeAl thickness (tCFA) and Ni thickness (tNi) on the magnetic properties have been studied. The PMA is realized with a large anisotropy energy density K = 3.7×106 ergs/cm3, a high squareness Mr/Ms = 1 and a small perpendicular coercivity Hc = 60 Oe, while tCu, tCFA and tNi are 9 nm, 0.2 nm and 0.6 nm respectively. The PMA remains after 300 °C annealing, which demonstrates better thermal stability of the (Co2FeAl/Ni)6 multilayer than that of (Co/Ni)n.

  6. The potential for ductility enhancement from surface and interface dislocation sources in NiAl

    NASA Technical Reports Server (NTRS)

    Noebe, R. D.; Bowman, R. R.; Kim, J. T.; Larsen, M.; Gibala, R.

    1990-01-01

    Limited ductility and toughness of NiAl and related aluminides near room temperature pose major problems in their potential application as structural materials. An analysis of these problems is presented as part of a review of the flow and fracture behavior of binary NiAl. Following this discussion is a demonstration that conditions of elastic and plastic constraint associated with phase boundaries afforded by surface films, internal lamellae, or precipitates may introduce sufficient densities of mobile dislocations to enhance the ductility of NiAl-based materials by significant amounts. Examples of this behavior are presented for several model materials, including 001- and 123-oriented single crystals of oxide-coated NiAl, directionally solidified beta-gamma-prime (Ni70Al30) and beta-gamma (Ni50Fe30Al20) in situ composites, and several NiAl/precipitate systems. The nature of the resulting dislocation substructures and the effects of several materials variables are described.

  7. The effects of annealing on the microstructure and mechanical properties of Fe28Ni18Mn33Al21

    SciTech Connect

    Meng, Fanling; Qiu, Jingwen; Baker, Ian; Bei, Hongbin

    2015-08-20

    In this paper, As-cast Fe28Ni18Mn33Al21, which consists of aligned, 50 nm, (Ni, Al)-rich B2, and (Fe, Mn)-rich f.c.c. phases, was annealed at a variety of temperatures up to 1423 K and the microstructure and mechanical properties were examined. It was shown that the as-cast microstructure arises from a eutectoid transformation at ~1300 K. Annealing at temperatures ≤1073 K produces β-Mn-structured precipitates and hardness values up to 816 HV, while annealing at temperatures >1073 K leads to dramatic coarsening of the two-phase B2/f.c.c. microstructure (up to 5.5 µm after 50 h at 1273 K), but does not lead to β-Mn precipitation. Interestingly, annealing at temperatures >1073 K delays the onset of β-Mn precipitation during subsequent anneals at lower temperatures. Coarsening the B2/f.c.c. lamellar structure by annealing at higher temperatures softens it and leads to increases in ductility from fracture before yield to ~8 % elongation. Finally, the presence of β-Mn precipitates makes the very fine, brittle B2/f.c.c. microstructures even more brittle, but significant ductility (8.4 % elongation) is possible even with β-Mn precipitates present if the B2/f.c.c. matrix is coarse and, hence, more ductile.

  8. Ni{sub 3}Al aluminide alloys

    SciTech Connect

    Liu, C.T.

    1993-10-01

    This paper provides a brief review of the recent progress in research and development of Ni{sub 3}Al and its alloys. Emphasis has been placed on understanding low ductility and brittle fracture of Ni{sub 3}Al alloys at ambient and elevated temperatures. Recent studies have resulted in identifying both intrinsic and extrinsic factors governing the fracture behavior of Ni{sub 3}Al alloys. Parallel efforts on alloy design using physical metallurgy principles have led to properties for structural use. Industrial interest in these alloys is high, and examples of industrial involvement in processing and utilization of these alloys are briefly mentioned.

  9. Fabrication of CuAl{sub 1−x}M{sub x}O{sub 2} (M = Fe, Cr)/Ni film delafossite compounds using spin coating and their microstructure and dielectric constant

    SciTech Connect

    Diantoro, Markus Yuwita, Pelangi Eka Olenka, Desyana Nasikhudin

    2014-09-25

    The discovery of delafossite compound has encouraged more rapid technological developments particularly in transparent electronic devices. Copper oxide-based transparent thin films delafossite semiconductor recently give much attention in the field of optoelectronic technology, after the discovery of p-type CuAlO{sub 2}. The potential applications of a p-type semiconductor transparent conductive oxides (TCO) have been applied in broad field of optoelectronics. To explore a broad physical properties interms of magnetic conducting subtitution is understudied. In this work we report the fabrication of delafossite film on Ni substrate and their characterization of CuAl{sub 1−x}M{sub x}O{sub 2} delafossite compounds doped with Cr{sup 3+} and Fe{sup 3+} from the raw material of Cu(NO{sub 3}){sub 2}@@‡3H{sub 2}O, Al(NO{sub 3}){sub 3}@@‡9H{sub 2}O, Fe(NO{sub 3}){sub 3}@@‡9H{sub 2}O and Cr(NO{sub 3}){sub 3}@@‡9H{sub 2}O. The films were prepared using spin coating through a sol-gel technique at various concentrations of x = 0, 0.03, 0.04, and 0.05 for chromium and x = 0, 0.02, 0.04, 0.06, and 0.08 for iron doped. Crystal and microstructure were characterized by means of Cu-Kα Bragg-Brentano X-RD followed by High Score Plus and SEM-EDAX. The dielectric constants of the films were characterized using LCR meter. It was found that the CuAl{sub 1−x}M{sub x}O{sub 2}/Ni delafossite films were successfully fabricated. The CuAl{sub 1−x}Fe{sub x}O{sub 2} compound crystallized with lattice parameters of a = b ranged from 2.8603 Å to 2.8675 Å and c ranged from 16.9576 to 17.0763 Å. The increase of the dopant give rise to the increase of the lattice parameters. Since iron has bigger ionic radius (69 pm) than original site of Al{sup 3+} with radius of 53 pm the crystal volume lattice also increase. Further analyses of increasing volume of the crystal, as expected, affected to the decreasing of its dielectric constant. The similar trends also shown by Cr{sup 3+} doped of

  10. Identification of an incommensurate FeAl{sub 2} overlayer on FeAl(110) using x-ray diffraction and reflectivity

    SciTech Connect

    Baddorf, A.P.; Chandavarkar, S.S.

    1995-06-30

    FeAl, like NiAl, crystallizes in the CsCl structure. Consequently the (110) planes contain equal amounts of Fe and Al distributed as interlocking rectangles. Unlike the NiAI(110) surface, which retains the (1{times}l) in-plane symmetry of the bulk, FeAl(l10) reconstructs to form an ordered, incommensurate overlayer. The reconstructed layer introduces x-ray diffraction rods at half-order positions along the [1{bar 1}0] direction, and displaced {plus_minus}0.2905 from integer positions along the [001] direction. Peak widths reveal excellent long range order. Specular reflectivity measurements above and below the Fe K{alpha} edge can be reproduced using a model containing a single reconstructed overlayer with an Fe:Al ratio of 1:2, consistent with FeA{sub I}2.

  11. Microstructure of Ni-Al powder and Ni-Al composite coatings prepared by twin-wire arc spraying

    NASA Astrophysics Data System (ADS)

    Wang, Ji-xiao; Wang, Gui-xian; Liu, Jing-shun; Zhang, Lun-yong; Wang, Wei; Li, Ze; Wang, Qi-xiang; Sun, Jian-fei

    2016-07-01

    Ni-Al powder and Ni-Al composite coatings were fabricated by twin-wire arc spraying (TWAS). The microstructures of Ni-5wt%Al powder and Ni-20wt%Al powder were characterized by scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the obtained particle size ranged from 5 to 50 μm. The morphology of the Ni-Al powder showed that molten particles were composed of Ni solid solution, NiAl, Ni3Al, Al2O3, and NiO. The Ni-Al phase and a small amount of Al2O3 particles changed the composition of the coating. The microstructures of the twin-wire-arc-sprayed Ni-Al composite coatings were characterized by SEM, EDS, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results showed that the main phase of the Ni-5wt%Al coating consisted of Ni solid solution and NiAl in addition to a small amount of Al2O3. The main phase of the Ni-20wt%Al coating mainly consisted of Ni solid solution, NiAl, and Ni3Al in addition to a small amount of Al and Al2O3, and NiAl and Ni3Al intermetallic compounds effectively further improved the final wear property of the coatings. TEM analysis indicated that fine spherical NiAl3 precipitates and a Ni-Al-O amorphous phase formed in the matrix of the Ni solid solution in the original state.

  12. Mechanisms of Formation and Transformation of Ni-Fe Hydroxycarbonates

    SciTech Connect

    Refait, Ph.; Jeannin, M.; Reffass, M.; Drissi, S.H.; Abdelmoula, M.; Genin, J.-M.R.

    2005-04-26

    The mechanisms of the transformation of (Ni,Fe)(OH)2 precipitates in carbonated aqueous solutions were studied. The reactions were monitored by measuring the redox potential of the aqueous suspension, and end products were studied by Moessbauer spectroscopy, X-ray diffraction and Raman spectroscopy. The oxidation processes were compared to those occurring without Ni, that is when the initial hydroxide is Fe(OH)2. Schematically, the oxidation of Fe(OH)2 involves two intermediate compounds, the carbonated GR of formula Fe{sup II}{sub 4}Fe{sup III}{sub 2}(OH){sub 12}CO{sub 3} {center_dot} 2H{sub 2}O, and ferrihydrite, before to lead finally to goethite {alpha}-FeOOH. It proved possible to prepare Ni(II)-Fe(III) hydroxycarbonates with ratios Fe/Ni from 1/6 to 1/3. When the Fe/Ni ratio is larger than 1/3, a two stage oxidation process takes place. The first stage leads to a Ni(II)-Fe(II)-Fe(III) hydroxycarbonate. The second stage corresponds to the oxidation of the Fe(II) remaining inside the hydroxycarbonate and leads to a mixture of Ni(II)-Fe(III) hydroxycarbonate with ferrihydrite. The main effect of Ni is then to stop the reaction at an intermediate stage, as Ni(II) is not oxidised by O2, leaving unchanged the main features of the mechanisms of transformation.

  13. 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.

  14. Fe-Ni composition dependence of magnetic anisotropy in artificially fabricated L1 0-ordered FeNi films.

    PubMed

    Kojima, Takayuki; Ogiwara, Misako; Mizuguchi, Masaki; Kotsugi, Masato; Koganezawa, Tomoyuki; Ohtsuki, Takumi; Tashiro, Taka-Yuki; Takanashi, Koki

    2014-02-12

    We prepared L10-ordered FeNi alloy films by alternate deposition of Fe and Ni monatomic layers, and investigated their magnetic anisotropy. We employed a non-ferromagnetic Au-Cu-Ni buffer layer with a flat surface and good lattice matching to L10-FeNi. An L10-FeNi film grown on Au6Cu51Ni43 showed a large uniaxial magnetic anisotropy energy (Ku = 7.0 × 10(6) erg cm(-)3). Ku monotonically increased with the long-range order parameter (S) of the L10 phase. We investigated the Fe-Ni composition dependence by alternating the deposition of Fe 1 − x and Ni 1 + x monatomic layers (− 0.4 < x < 0.4). Saturation magnetization (Ms) and Ku showed maxima (Ms = 1470 emu cm(-3), Ku = 9.3 × 10(6) erg cm(-3)) for Fe60Ni40 (x = -0.2) while S showed a maximum at the stoichiometric composition (x = 0). The change in the ratio of lattice parameters (c/a) was small for all compositions. We found that enrichment of Fe is very effective to enhance Ku. The large Ms and Ku of Fe60Ni40 indicate that Fe-rich L10-FeNi is promising as a rare-earth-free permanent magnet. PMID:24469082

  15. High-frequency permeability of electroplated CoNiFe and CoNiFe-C alloys

    NASA Astrophysics Data System (ADS)

    Rhen, Fernando M. F.; McCloskey, Paul; O'Donnell, Terence; Roy, Saibal

    We have investigated CoNiFe and CoNiFe-C electrodeposited by pulse reverse plating (PRP) and direct current (DC) techniques. CoNiFe(PRP) films with composition Co 59.4Fe 27.7Ni 12.8 show coercivity of 95 A m -1 (1.2 Oe) and magnetization saturation flux ( μ0Ms) of 1.8 T. Resistivity of CoNiFe (PRP) is about 24 μΩ cm and permeability remains almost constant μr' ˜475 up to 30 MHz with a quality factor ( Q) larger than 10. Additionally, the permeability spectra analysis shows that CoNiFe exhibits a classical eddy current loss at zero bias field and ferromagnetic resonance (FMR) when biased with 0.05 T. Furthermore, a crossover between eddy current and FMR loss is observed for CoNiFe-PRP when baised with 0.05 T. DC and PRP plated CoNiFe-C, which have resistivity and permeability of 85, 38 μΩ cm, μr'=165 and 35 with Q>10 up to 320 MHz, respectively, showed only ferromagnetic resonance losses. The ferromagnetic resonance peaks in CoNiFe and CoNiFe-C are broad and resembles a Gaussian distribution of FMR frequencies. The incorporation of C to CoNiFe reduces eddy current loss, but also reduces the FMR frequency.

  16. The new structure type Gd3Ni7Al14.

    PubMed

    Pukas, Svitlana; Gladyshevskii, Roman

    2015-11-01

    The crystal structure of Gd3Ni7Al14 (trigadolinium heptanickel tetradecaaluminide) belongs to a family of two-layer structures and can be described as an assembly of interpenetrating centred straight prisms. For the Ni atoms, trigonal prisms (Al4Gd2 and Al6) are observed, the Al atoms are inside tetragonal (Ni2Al2Gd4, Ni2Al4Gd2, Al4Gd4, Ni4Al4 and Al8) and pentagonal (Ni4Al6 and Al10) prisms, while the Gd atoms are at the centres of pentagonal (Ni4Al6) and hexagonal (Ni4Al8) prisms. In each case, the true coordination polyhedron is a capped prism, also including atoms from the same layer. The structural features of Gd3Ni7Al14 are similar to those of the intermetallides PrNi2Al3 and ZrNiAl. In all these structures, Ni-centred trigonal prisms form infinite columns via common triangular faces. The columns share prism edges and form a three-dimensional framework with six-membered rings in the (001) plane in the case of the PrNi2Al3 and ZrNiAl types. In the case of Gd3Ni7Al14, six-membered rings are also observed, but only two-thirds of the rings are interconnected via prism edges. PMID:26524174

  17. Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. 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.

  18. Orientation relationship of eutectoid FeAl and FeAl2

    PubMed Central

    Scherf, A.; Kauffmann, A.; Kauffmann-Weiss, S.; Scherer, T.; Li, X.; Stein, F.; Heilmaier, M.

    2016-01-01

    Fe–Al alloys in the aluminium range of 55–65 at.% exhibit a lamellar microstructure of B2-ordered FeAl and triclinic FeAl2, which is caused by a eutectoid decomposition of the high-temperature Fe5Al8 phase, the so-called ∊ phase. The orientation relationship of FeAl and FeAl2 has previously been studied by Bastin et al. [J. Cryst. Growth (1978 ▸), 43, 745] and Hirata et al. [Philos. Mag. Lett. (2008 ▸), 88, 491]. Since both results are based on different crystallographic data regarding FeAl2, the data are re-evaluated with respect to a recent re-determination of the FeAl2 phase provided by Chumak et al. [Acta Cryst. (2010 ▸), C66, i87]. It is found that both orientation relationships match subsequent to a rotation operation of 180° about a 〈112〉 crystallographic axis of FeAl or by applying the inversion symmetry of the FeAl2 crystal structure as suggested by the Chumak data set. Experimental evidence for the validity of the previously determined orientation relationships was found in as-cast fully lamellar material (random texture) as well as directionally solidified material (∼〈110〉FeAl || solidification direction) by means of orientation imaging microscopy and global texture measurements. In addition, a preferential interface between FeAl and FeAl2 was identified by means of trace analyses using cross sectioning with a focused ion beam. On the basis of these habit planes the orientation relationship between the two phases can be described by (01)FeAl || (114) and [111]FeAl || [10]. There is no evidence for twinning within FeAl lamellae or alternating orientations of FeAl lamellae. Based on the determined orientation and interface data, an atomistic model of the structure relationship of Fe5Al8, FeAl and FeAl2 in the vicinity of the eutectoid decomposition is derived. This model is analysed with respect to the strain which has to be accommodated at the interface of FeAl and FeAl2. PMID:27047304

  19. 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

  20. Electronic circuits having NiAl and Ni.sub.3 Al substrates

    DOEpatents

    Deevi, Seetharama C.; Sikka, Vinod K.

    1999-01-01

    An electronic circuit component having improved mechanical properties and thermal conductivity comprises NiAl and/or Ni.sub.3 Al, upon which an alumina layer is formed prior to applying the conductive elements. Additional layers of copper-aluminum alloy or copper further improve mechanical strength and thermal conductivity.

  1. Using granular C0-AI2O3 spacer for optimization of functional parameters of the FeMn/Fe20Ni80 magnetoresistive films

    NASA Astrophysics Data System (ADS)

    Gorkovenko, A. N.; Lepalovskij, V. N.; Adanakova, O. A.; Vas'kovskiy, V. O.

    2016-03-01

    In this paper we studied the possibility of tailoring the functional properties of the multilayer magnetoresistive medium with unidirectional anisotropy and the anisotropic magnetoresistance effect (AMR). Objects of the research were composite Co-Al2O3 films and Ta/Fe20Ni80/Fe50Mn50/Fe20Ni80/Co-Al2O3/Fe20Ni80/Ta multilayers structures obtained by magnetron sputtering and selectively subjected vacuum annealing. Structure, magnetic and magnetoresistive properties of the films in the temperature range 77÷440 K were investigated.

  2. Martensitic transformation of FeNi nanofilm induced by interfacial stress generated in FeNi/V nanomultilayered structure

    PubMed Central

    2014-01-01

    FeNi/V nanomultilayered films with different V layer thicknesses were synthesized by magnetron sputtering. By adjusting the thickness of the V layer, different interfacial compressive stress were imposed on FeNi layers and the effect of interfacial stress on martensitic transformation of the FeNi film was investigated. Without insertion of V layers, the FeNi film exhibits a face-centered cubic (fcc) structure. With the thickness of V inserted layers up to 1.5 nm, under the coherent growth structure in FeNi/V nanomultilayered films, FeNi layers bear interfacial compressive stress due to the larger lattice parameter relative to V, which induces the martensitic transformation of the FeNi film. As the V layer thickness increases to 2.0 nm, V layers cannot keep the coherent growth structure with FeNi layers, leading to the disappearance of interfacial compressive stress and termination of the martensitic transformation in the FeNi film. The interfacial compressive stress-induced martensitic transformation of the FeNi nanofilm is verified through experiment. The method of imposing and modulating the interfacial stress through the epitaxial growth structure in the nanomultilayered films should be noticed and utilized. PMID:25232296

  3. [FeFe]- and [NiFe]-hydrogenase diversity, mechanism, and maturation.

    PubMed

    Peters, John W; Schut, Gerrit J; Boyd, Eric S; Mulder, David W; Shepard, Eric M; Broderick, Joan B; King, Paul W; Adams, Michael W W

    2015-06-01

    The [FeFe]- and [NiFe]-hydrogenases catalyze the formal interconversion between hydrogen and protons and electrons, possess characteristic non-protein ligands at their catalytic sites and thus share common mechanistic features. Despite the similarities between these two types of hydrogenases, they clearly have distinct evolutionary origins and likely emerged from different selective pressures. [FeFe]-hydrogenases are widely distributed in fermentative anaerobic microorganisms and likely evolved under selective pressure to couple hydrogen production to the recycling of electron carriers that accumulate during anaerobic metabolism. In contrast, many [NiFe]-hydrogenases catalyze hydrogen oxidation as part of energy metabolism and were likely key enzymes in early life and arguably represent the predecessors of modern respiratory metabolism. Although the reversible combination of protons and electrons to generate hydrogen gas is the simplest of chemical reactions, the [FeFe]- and [NiFe]-hydrogenases have distinct mechanisms and differ in the fundamental chemistry associated with proton transfer and control of electron flow that also help to define catalytic bias. A unifying feature of these enzymes is that hydrogen activation itself has been restricted to one solution involving diatomic ligands (carbon monoxide and cyanide) bound to an Fe ion. On the other hand, and quite remarkably, the biosynthetic mechanisms to produce these ligands are exclusive to each type of enzyme. Furthermore, these mechanisms represent two independent solutions to the formation of complex bioinorganic active sites for catalyzing the simplest of chemical reactions, reversible hydrogen oxidation. As such, the [FeFe]- and [NiFe]-hydrogenases are arguably the most profound case of convergent evolution. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases. PMID:25461840

  4. 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.

  5. Influence of M-B (M = Fe, Co, Ni) on aluminum-water reaction

    NASA Astrophysics Data System (ADS)

    Meng, H. X.; Wang, N.; Dong, Y. M.; Jia, Z. L.; Gao, L. J.; Chai, Y. J.

    2014-12-01

    In this work, the aluminum-water reaction induced by Fe-B, Co-B and Ni-B particles was studied. The catalysts were mixtures of the metal boride and metallic particles. The chainlike Fe-B catalyst forms a network structure under the influence of an external magnetic field and has a large specific surface area. Aggregated particles of Co-B and Ni-B catalyst have small specific surface area. Catalytic activity in the initial corrosion of aluminum increases with increasing Fe-B content because of the large specific surface area and the formation of a micro galvanic cell. However, the amount of hydrogen generated slowly decreases with increasing amount of Co-B and Ni-B. The activity of Fe-B, Co-B and Ni-B in the initial Al/H2O reaction decreases in the order Fe-B > Ni-B > Co-B. The calculated apparent activation energies in the presence of Fe-B, Co-B and Ni catalysts are 38.2, 39 and 29.6 kJ mol-1, respectively. Aluminum is rapidly and completely corroded in a weakly alkaline solution (pH < 10) after consecutive additions of Al batches because of high concentrations of OH- in the local domain and an increase in the amount of Al(OH)3 precipitate.

  6. TEM studies of oxidized NiAl and Ni3Al cross sections

    NASA Technical Reports Server (NTRS)

    Doychak, J.; Ruhle, M.

    1989-01-01

    Cross sections of oxide scale/(Ni-Al) intermetallics were prepared by a new method and studied using primarily TEM. The cross sections were prepared by encasing an oxidized metal specimen sandwich in a low-melting-temperature zinc alloy. Observations of oxidized zirconium-doped beta-NiAl cross sections revealed crystallographic voids beneath an adherent Al2O3 scale. The oxide-metal interface was incoherent, but a high dislocation density in the metal near the interface suggested that a large tensile stress was induced by the attached oxide scale. A duplex Al2O3-NiAl2O4 scale formed on zirconium-doped and zirconium/boron-doped gamma-prime-Ni3Al alloys. Additional results are presented involving oxidation mechanisms and oxide-metal interface structures.

  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 eutectic to 925°C. Eutectic liquid compositions show less consistent variability with increased Ni content and have 15-16 wt% S. Subsolidus phases at 23 GPa in both Ni-free and Ni-bearing charges are consistent with those described by Fei et al (2000, American Mineralogist), with (Fe,Ni) metal, (Fe,Ni)3S and (Fe,Ni)2S commonly present. However at 38 GPa, (Fe,Ni)3S has not been observed, with pure (Fe,Ni) coexisting directly with (Fe,Ni)2S, suggesting the limited stability and importance of the Fe3S phase in planetary cores. Partitioning of nickel between the subsolidus phases shows a moderate preference for the sulfide phase over the iron-dominated metallic phase. The dP/dT slope of the eutectic in the Fe-S system is 18°C/GPa between 15 and 23 GPa, and seems to only slightly increase to 36 GPa, similar to the dP/dT slope of the Ni-bearing eutectic. Our results have important implications for planetary core chemistry, mineralogy and rheology with realistic nickel-bearing alloys showing a distinct decrease in the eutectic temperature of the system and with inner core phases having nickel partitioned into high pressure sulfides. Nickel cannot be ignored or assumed as an element equivalent to iron in this and other light alloy systems at high pressures.

  8. Research on pulse electrodeposition of Fe-Ni alloy

    SciTech Connect

    Peng, Yongsen; Zhu, Zengwei Ren, Jianhua; Chen, Jiangbo; Han, Taojie

    2014-03-15

    Fe-Ni alloys were fabricated on steel substrates by means of pulse electrodeposition in sulfate solutions. The layers were electrodeposited using different peak current densities, duty cycles and frequencies. Fe contents, microhardnesses and crystalline phases were examined systematically. The Fe content in the deposit decreased and the microhardness increased with increasing duty cycle and peak current density. The pulse frequency had little effect on Fe content but led to a slight decrease in microhardness. X-ray diffraction patterns show that the crystalline phases vary with changes in peak current density and duty cycle but are barely influenced by frequency. When the peak current density or duty cycle is relatively low, crystalline Fe-Ni alloy and pure Fe phases coexist; the pure Fe phases disappear as the peak current density or duty cycle increases. At still larger peak current densities or duty cycles, crystalline Fe-Ni alloy and pure Ni phases coexist.

  9. Exchange bias magnetism in films of NiFe/(Ni,Fe)O nanocrystallite dispersions

    SciTech Connect

    Hsiao, C.-H.; Chi, C.-C.; Wang, S.; Ouyang, H.; Desautels, R. D.; Lierop, J. van; Lin, K.-W.; Lin, T.-L.

    2014-05-07

    Ni{sub 3}Fe/(Ni,Fe)O thin films having a nanocrystallite dispersion morphology were prepared by a reactive ion beam-assisted deposition technique. The crystallite sizes of these dispersion-based films were observed to decrease from 8.4 ± 0.3 nm to 3.4 ± 0.3 nm as the deposition flow-rate increased from 2.78% to 7.89% O{sub 2}/Ar. Thin film composition was determined using selective area electron diffraction images and Multislice simulations. Through a detailed analysis of high resolution transmission electron microscopy images, the nanocrystallites were determined to be Ni{sub 3}Fe (a ferromagnet), NiO, and FeO (both antiferromagnets). It was determined that the interfacial molar Ni{sub 3}Fe ratio in the nanocrystallite dispersions increased slightly at first, then decreased as the oxygen content was increased; at 7.89% O{sub 2}/Ar, the interfacial molar ratio was essentially zero (only NiO and FeO remained). For nanocrystallite dispersion films grown with O{sub 2}/Ar flow-rate greater than 7.89%, no interfacial (intermixed) Ni{sub 3}Fe phase was detected, which resulted in no measurable exchange bias. Comparing the exchange bias field between the nanocrystallite dispersion films at 5 K, we observed a decrease in the magnitude of the exchange bias field as the nanocrystallite size decreased. The exchange bias coupling for all samples measured set in at essentially the same temperature (i.e., the exchange bias blocking temperature). Since the ferromagnetic/anti-ferromagnetic (FM/AFM) contact area in the nanocrystallite dispersion films increased as the nanocrystallite size decreased, the increase in the magnitude of the exchange bias could be attributed to larger regions of defects (vacancies and bond distortions) which occupied a significant portion of the FM/AFM interfaces in the nanocrystallite dispersion films.

  10. Bonding of WC with an iron aluminide (FeAl) intermetallic

    SciTech Connect

    Schneibel, J.H.; Subramanian, R.

    1996-08-01

    FeAl, which has high oxidation and sulfidation resistance, was shown to be thermodynamically compatible with WC. Calculations indicate that soly. of WC in liq. Fe-40at.%Al at 1450 C is about 2 at.%. Since liquid FeAl wets WC very well, the WC/FeAl system lends itself to liquid-phase sintering, resulting in close to theoretical densities. Almost fully dense cermets with 20.6 wt% FeAl binder were produced. With one-step infiltration, 98% dense cermets with only 7 wt% FeAl binder were fabricated. RT bend strengths and fracture toughness for WC-20.6 wt% FeAl reached 1680 MPa and 22 MPa{center_dot}m{sup 1/2}. Ductile binder fracture was observed on the fracture surfaces. Pores containing oxide inclusions were found, suggesting that improvements in processing are likely to further improve the mechanical properties. Insufficient process control may explain why WC/FeAlNi cermets did not show improved mechanical properties, although Ni strengthens FeAl. For WC bonded with FeAl, mechanical properties were measured at RT and 800 C. Bend strengths at 800 C in air increased with WC volume fraction, and fracture toughness were higher than at RT.

  11. Structure and Electrochemistry of LiNi1/3Co1/3-yMyMn1/3O2 (M=Ti, Al, Fe) Positive Electrode Materials

    SciTech Connect

    Wilcox, James; Patoux, Sebastien; Doeff, Marca

    2009-01-14

    A series of materials based on the LiNi1/3Co1/3-yMyMn1/3O2 (M = Ti,Al,Fe) system has been synthesized and examined structurally and electrochemically. It is found that the changes in electrochemical performance depend highly on the nature of the substituting atom and its effect on the crystal structure. Substitution with small amounts of Ti4+ (y = 1/12) leads to the formation of a high-capacity and high-rate positive electrode material. Iron substituted materials suffer from an increased antisite defect concentration and exhibit lower capacities and poor rate capabilities. Single-phase materials are found for LiNi1/3Co1/3-yAlyMn1/3O2 when y<_ 1/4 and all exhibit decreased capacities when cycled to 4.3 V. However, an increase in rate performance and cycle stability upon aluminum substitution is correlated with an improved lamellar structure.

  12. First-principles studies of Al-Ni intermetallic compounds

    SciTech Connect

    Shi Dongmin; Wen Bin; Melnik, Roderick; Yao Shan; Li Tingju

    2009-10-15

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

  13. Transformation to Ni5Al3 in a 63.0 at. pct Ni-Al alloy

    NASA Technical Reports Server (NTRS)

    Khadkikar, P. S.; Locci, I. E.; Vedula, K.; Michal, G. M.

    1993-01-01

    Microstructures of 63 at. pct P/M Ni-Al alloys with a composition close to the stoichiometry of the Ni5Al3 phase were investigated using homogenized and quenched specimens aged at low temperatures for various times. Results of analyses of XRD data and electron microscopy observations were used for quantitative phase analysis, performed to calculate the (NiAl + Ni5Al3)/Ni5Al3 phase boundary locations. The measured lattice parameters of Ni5Al3 phase formed at 823, 873, and 923 K indicated an increase in tetragonality of the phase with increasing nickel content.

  14. Substrate dependent ultrafast dynamics in thin NiFe films

    NASA Astrophysics Data System (ADS)

    Bosco, C. A. C.; Azevedo, A.; Acioli, L. H.

    2003-09-01

    We have studied the ultrafast electronic response of thin NiFe films by femtosecond transient reflectivity measurements. The experiments were performed on films with varying thicknesses, substrates, and pump fluences. It has been observed that for high excitation densities the electron cooling time depends strongly on the nature of the underlying substrate and we attribute our results to transport of hot carriers out of the excited region. In particular, we have observed that for NiFe over NiO, carrier transport should be less important than for NiFe over Si.

  15. Model study of CO inhibition of [NiFe]hydrogenase.

    PubMed

    Matsumoto, Takahiro; Kabe, Ryota; Nonaka, Kyoshiro; Ando, Tatsuya; Yoon, Ki-Seok; Nakai, Hidetaka; Ogo, Seiji

    2011-09-19

    We propose a modified mechanism for the inhibition of [NiFe]hydrogenase ([NiFe]H(2)ase) by CO. We present a model study, using a NiRu H(2)ase mimic, that demonstrates that (i) CO completely inhibits the catalytic cycle of the model compound, (ii) CO prefers to coordinate to the Ru(II) center rather than taking an axial position on the Ni(II) center, and (iii) CO is unable to displace a hydrido ligand from the NiRu center. We combine these studies with a reevaluation of previous studies to propose that, under normal circumstances, CO inhibits [NiFe]H(2)ase by complexing to the Fe(II) center. PMID:21853978

  16. The corrosion behavior of Fe-Mn-Al weld metals

    NASA Astrophysics Data System (ADS)

    Aidun, Daryush K.

    2001-02-01

    The corrosion resistance of a newly developed iron-base, Fe-Mn-Al austenitic, and duplex weld metal has been examined in the NACE solution consisting of 5 wt.% NaCl, 0.5 wt.% acetic acid, and the balance distilled water. The electrochemical techniques such as potentiodynamic polarization, Tafel plots, linear polarization, cyclic polarization, and open-circuit potential versus time were employed. The Fe-Mn-Al weld metals did not passivate and exhibited high corrosion rates. Fe-Cr-Ni (310 and 316) weld and base metals were also examined in the NACE solution at room temperature. The 310 and 316 base metals were more resistant to corrosion than the as-welded 310 and 316 weld metals. Postweld heat treatment (PWHT) improved the corrosion performance of the Fe-Mn-Al weld metals. The corrosion resistance of Fe-Mn-Al weld metals after PWHT was still inferior to that of the 310 and 316 weld and base metals.

  17. Sound velocity and elastic properties of Fe-Ni and Fe-Ni-C liquids at high pressure

    NASA Astrophysics Data System (ADS)

    Kuwabara, Soma; Terasaki, Hidenori; Nishida, Keisuke; Shimoyama, Yuta; Takubo, Yusaku; Higo, Yuji; Shibazaki, Yuki; Urakawa, Satoru; Uesugi, Kentaro; Takeuchi, Akihisa; Kondo, Tadashi

    2016-03-01

    The sound velocity ( V P) of liquid Fe-10 wt% Ni and Fe-10 wt% Ni-4 wt% C up to 6.6 GPa was studied using the ultrasonic pulse-echo method combined with synchrotron X-ray techniques. The obtained V P of liquid Fe-Ni is insensitive to temperature, whereas that of liquid Fe-Ni-C tends to decrease with increasing temperature. The V P values of both liquid Fe-Ni and Fe-Ni-C increase with pressure. Alloying with 10 wt% of Ni slightly reduces the V P of liquid Fe, whereas alloying with C is likely to increase the V P. However, a difference in V P between liquid Fe-Ni and Fe-Ni-C becomes to be smaller at higher temperature. By fitting the measured V P data with the Murnaghan equation of state, the adiabatic bulk modulus ( K S0) and its pressure derivative ( K S ' ) were obtained to be K S0 = 103 GPa and K S ' = 5.7 for liquid Fe-Ni and K S0 = 110 GPa and K S ' = 7.6 for liquid Fe-Ni-C. The calculated density of liquid Fe-Ni-C using the obtained elastic parameters was consistent with the density values measured directly using the X-ray computed tomography technique. In the relation between the density ( ρ) and sound velocity ( V P) at 5 GPa (the lunar core condition), it was found that the effect of alloying Fe with Ni was that ρ increased mildly and V P decreased, whereas the effect of C dissolution was to decrease ρ but increase V P. In contrast, alloying with S significantly reduces both ρ and V P. Therefore, the effects of light elements (C and S) and Ni on the ρ and V P of liquid Fe are quite different under the lunar core conditions, providing a clue to constrain the light element in the lunar core by comparing with lunar seismic data.

  18. 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer spin valve component investigated by polarized neutron reflectometry

    SciTech Connect

    Callori, S. J. Bertinshaw, J.; Cortie, D. L.; Cai, J. W. Zhu, T.; Le Brun, A. P.; Klose, F.

    2014-07-21

    We have observed 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer system using polarized neutron reflectometry. Magnetometry results show magnetic switching for both the biased and free NiFe layers, the latter of which reverses at low applied fields. As these measurements are only capable of providing information about the total magnetization within a sample, polarized neutron reflectometry was used to investigate the reversal behavior of the NiFe layers individually. Both the non-spin-flip and spin-flip neutron reflectometry signals were tracked around the free NiFe layer hysteresis loop and were used to detail the evolution of the magnetization during reversal. At low magnetic fields near the free NiFe coercive field, a large spin-flip signal was observed, indicating magnetization aligned perpendicular to both the applied field and pinned layer.

  19. Effect of alloying elements on <1 1 1> dislocation in NiAl: A first-principles study

    NASA Astrophysics Data System (ADS)

    Lin Lü, Bai; Qing Chen, Guo; Qu, Shen; Su, Hui; Long Zhou, Wen

    2013-05-01

    The calculation of the ductility criterion, the antiphase boundary energy and the Peierls stress indicate that compared with Cr, Au, Fe and Mn are better alloying elements improving the room-temperature ductility of polycrystalline NiAl. If the site preference behavior of Re, Os, Ir, Pt and Co can be reversed, these elements will also become better ductility elements and the Ni antisite at Al site is beneficial to the ductility of NiAl polycrystalline.

  20. Ni-Al2O3 and Ni-Al composite high-aspect-ratio microstructures

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Sorrell, Melford; Kelly, Kevin W.; Ma, Evan

    1998-09-01

    High-aspect-ratio microstructures (HARMs) have a variety of potential applications in heat transfer, fluid mechanics, catalysts and other microelectromechanical systems (MEMS). The aim of this work is to demonstrate the feasibility to fabricate high performance particulate metal-matrix composite and intermetallic micromechanical structures using the LIGA process. Well-defined functionally graded Ni-Al2O3 and Ni-Al high-aspect-ratio microposts were electroformed into lithographically patterned PMMA holes from a nickel sulfamate bath containing submicron alumina and a diluted Watts bath containing microsized aluminum particles, respectively. SEM image analysis showed that the volume fraction of the alumina reached up to around 30% in the Ni-Al2O3 deposit. The Vickers microhardness of these composites is in the range of 418 through 545, which is higher than those of nickel microstructures from a similar particle-free bath and other Ni-based electrodeposits. In the work on Ni-Al electroplating, a newly developed diluted Watts bath was used to codeposit micron-sized aluminum particles. The intermetallic compound Ni3Al was formed by the reaction of nickel matrices and aluminum particles through subsequent annealing at 630 degrees Celsius. WDS and XRD analyses confirmed that the annealed coating is a two-phase (Ni-Ni3Al) composite. The maximum aluminum volume fraction reached 19% at a cathode current density of 12 mA cm-2, and the Vickers microhardness of the as-deposited coatings is in the range 392 - 515 depending on the amount of aluminum incorporated.

  1. Characterization of NiPt, FePt, and NiFePt nanoparticles

    NASA Astrophysics Data System (ADS)

    Sutherland, Greg; Wood, Darren; Jackson, Amy; Warren, Andrew; Coffey, Kevin; Vanfleet, Richard

    2012-10-01

    Many metal alloys can form in chemically ordered structures, often resulting in significant changes in properties. The ordered structures are preferred at low temperatures and will go through an order-disorder phase transition at a critical temperature. The formation and stability of these ordered structures in alloy nanoparticles is not well understood but may give insight into the role size plays in phase transitions. To this end we are studying FePt, NiPt, and FeNiPt alloy nanoparticles. We will focus this presentation on the characterization of these nanoparticles in a Transmission Electron Microscope (TEM) for composition, size, and structure. These nanoparticles are made by co-sputtering the constituents and annealing at different temperatures in various gas mixtures. The nanoparticle samples are prepared for TEM viewing by wedge polishing. We find FePt to be ``well behaved'' meaning this alloy forms particles, retains the as deposited composition, and chemically orders as expected. However, the order-disorder temperature is too high for the desired further studies. NiPt, which has a lower order-disorder temperature, is not ``well behaved'' in that the nanoparticle compositions are not good matches to the as deposited conditions and no chemical ordering has been achieved even under conditions that should be sufficient based on bulk processing. We will discuss these results and possible implications.

  2. Ni{sub 3}Al technology transfer

    SciTech Connect

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

    1997-04-01

    Ductile Ni{sub 3}Al and Ni{sub 3}Al-based alloys have been identified for a range of applications. These applications require the use of material in a variety of product forms such as sheet, plate, bar, wire, tubing, piping, and castings. Although significant progress has been made in the melting, casting, and near-net-shape forming of nickel aluminides, some issues still remain. These include the need for: (1) high-strength castable composition for many applications that have been identified; (2) castability (mold type, fluidity, hot-shortness, porosity, etc.); (3) weld reparability of castings; and (4) workability of cast or powder metallurgy product to sheet, bar, and wire. The four issues listed above can be {open_quotes}show stoppers{close_quotes} for the commercial application of nickel aluminides. This report describes the work completed to address some of these issues during FY 1996.

  3. Ni{sub 3}Al technology transfer

    SciTech Connect

    Sikka, V.K.; Santella, M.L.; Alexander, D.J.

    1995-05-01

    Ductile Ni{sub 3}Al and Ni{sub 3}Al-based alloys have been identified for a range of applications. These applications require the use of material in a variety of product forms such as sheet, plate, bar, tubing, piping, and castings. Although significant progress has been made in the melting, casting, and near-net-shape forming of nickel aluminides, some issues still remain. These include the need for (1)high-strength castable composition for turbochargers, furnace furniture, and hot-die applications; (2) castability (fluidity, hot-shortness, porosity, etc.); (3) weld reparability of castings; and (4) hot fabricability of cast ingots. All of the issues listed above can be {open_quotes}show stoppers{close_quotes} for the commercial application of nickel aluminides. This report describes work completed to address some of these issues during the fourth quarter of FY 1994.

  4. Ni doped Fe3O4 magnetic nanoparticles.

    PubMed

    Larumbe, S; Gómez-Polo, C; Pérez-Landazábal, J I; García-Prieto, A; Alonso, J; Fdez-Gubieda, M L; Cordero, D; Gómez, J

    2012-03-01

    In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure. PMID:22755104

  5. Creep in Directionally Solidified NiAl-Mo Eutectics

    SciTech Connect

    Dudova, Marie; Kucharova, Kveta; Bartak, Tomas; Bei, Hongbin; George, Easo P; Somsen, Ch.; Dlouhy, A.

    2011-01-01

    A directionally solidified NiAl-Mo eutectic and an NiAl intermetallic, having respective nominal compositions Ni-45.5Al-9Mo and Ni-45.2Al (at.%), were loaded in compression at 1073 and 1173 K. Formidable strengthening by regularly distributed Mo fibres (average diameter 600 nm, volume fraction 14%) was observed. The fibres can support compression stresses transferred from the plastically deforming matrix up to a critical stress of the order of 2.5 GPa, at which point they yield. Microstructural evidence is provided for the dislocation-mediated stress transfer from the NiAl to the Mo phase.

  6. Effect of iron content on the structure and mechanical properties of Al25Ti25Ni25Cu25 and (AlTi)60-xNi20Cu20Fex (x=15, 20) high-entropy alloys

    NASA Astrophysics Data System (ADS)

    Fazakas, É.; Zadorozhnyy, V.; Louzguine-Luzgin, D. V.

    2015-12-01

    In this work, we investigated the microstructure and mechanical properties of Al25Ti25Ni25Cu25 Al22.5Ti22.5Ni20Cu20Fe15 and Al20Ti20Ni20Cu20Fe20 high entropy alloys, produced by arc melting and casting in an inert atmosphere. The structure of these alloys was studied by X-ray diffractometry and scanning electron microscopy. The as-cast alloys were heat treated at 773, 973 and 1173 K for 1800 s to investigate the effects of aging on the plasticity, hardness and elastic properties. Compared to the conventional high-entropy alloys the Al25Ti25Ni25Cu25, Al22.5Ti22.5Ni20Cu20Fe15 and Al20Ti20Ni20Cu20Fe20 alloys are relatively hard and ductile. Being heat treated at 973 K the Al22.5Ti22.5Ni20Cu20Fe15 alloy shows considerably high strength and relatively homogeneous deformation under compression. The plasticity, hardness and elastic properties of the studied alloys depend on the fraction and intrinsic properties of the constituent phases. Significant hardening effect by the annealing is found.

  7. K-italic-shell ionization cross sections for Al, Ti, V, Cr, Fe, Ni, Cu, and Ag by protons and oxygen ions in the energy range 0. 3--6. 4 MeV

    SciTech Connect

    Geretschlaeger, M.; Benka, O.

    1986-08-01

    Absolute K-italic-shell ionization cross sections have been measured for thin targets of Al, Ti, and Cu for protons in the energy range 0.3--2.0 MeV and for thin targets of Ti, V, Cr, Fe, Ni, Cu, and Ag for oxygen ions in the energy range 1.36--6.4 Mev. The experimental results are compared to the perturbed-stationary-state (PSS) approximation with energy-loss (E), Coulomb (C), and relativistic (R) corrections, i.e., the ECPSSR approximation (Brandt and Lapicki), to the semiclassical approximation (Laegsgaard, Andersen, and Lund), and to a theory for direct Coulomb ionization of the 1s-italicsigma molecular orbital (Montenegro and Sigaud (MS)). The proton results agree within 3% with empirical reference cross sections. Also, the ECPSSR provides best overall agreement for protons. For oxygen ions, ECPSSR and MS predict experimental results satisfactorily for scaled velocities xi> or =0.4. For lower scaled velocities, the experimental cross sections become considerably higher than theoretical predictions for Coulomb ionization. This deviation increases with increasing Z-italic/sub 1//Z/sub 2/; it cannot be explained by electron transfer to the projectile or by ionization due to target recoil atoms.

  8. AC Impedance Behavior of LaNi3.55Mn0.4Al0.3Co0.6Fe0.15 Hydrogen-Storage Alloy: Effect of Surface Area

    NASA Astrophysics Data System (ADS)

    Tliha, M.; Khaldi, C.; Lamloumi, J.

    2016-04-01

    The decrease of Cobalt content in alloy is very beneficial to reduce the production cost of the alloy, whereas the effect of Co on cycle life of the AB5-type hydrogen-storage alloys is extremely important. Therefore, it is interesting to investigate low-Co and/or Co-free AB5-type alloys in which Co was substituted by other elements. Iron is a key element in the development of low-Co AB5-type alloys. The aim of this work is to systematically investigate the effect of the real surface area on the all kinetic properties of a low-Co LaNi3.55Mn0.4Al0.3Co0.6Fe0.15 alloy under cycling using electrochemical impedance spectroscopy (EIS) technique. All kinetic properties of the electrode, such as exchange density, limiting current density, high-rate charge/discharge ability, cycle life time, electrocatalytic activity, and diffusion rate are related to the real surface area. During the EIS analysis, interestingly, we found that with increasing number of charge/discharge cycles, the metal hydride alloy powders undergo micro-cracking into smaller particles, and thus the real surface area of the alloy increases, which then influences the kinetic properties of the electrode reactions.

  9. Chitosan film loaded with silver nanoparticles-sorbent for solid phase extraction of Al(III), Cd(II), Cu(II), Co(II), Fe(III), Ni(II), Pb(II) and Zn(II).

    PubMed

    Djerahov, Lubomir; Vasileva, Penka; Karadjova, Irina; Kurakalva, Rama Mohan; Aradhi, Keshav Krishna

    2016-08-20

    The present study describes the ecofriendly method for the preparation of chitosan film loaded with silver nanoparticles (CS-AgNPs) and application of this film as efficient sorbent for separation and enrichment of Al(III), Cd(II), Cu(II), Co(II), Fe(III), Ni(II), Pb(II) and Zn(II). The stable CS-AgNPs colloid was prepared by dispersing the AgNPs sol in chitosan solution at appropriate ratio and further used to obtain a cast film with very good stability under storage and good mechanical strength for easy handling in aqueous medium. The incorporation of AgNPs in the structure of CS film and interaction between the polymer matrix and nanoparticles were confirmed by UV-vis and FTIR spectroscopy. The homogeneously embedded AgNPs (average diameter 29nm, TEM analysis) were clearly observed throughout the film by SEM. The CS-AgNPs nanocomposite film shows high sorption activity toward trace metals under optimized chemical conditions. The results suggest that the CS-AgNPs nanocomposite film can be feasibly used as a novel sorbent material for solid-phase extraction of metal pollutants from surface waters. PMID:27178907

  10. Influence of hot isostatic pressing on the structure and properties of an innovative low-alloy high-strength aluminum cast alloy based on the Al-Zn-Mg-Cu-Ni-Fe system

    NASA Astrophysics Data System (ADS)

    Akopyan, T. K.; Padalko, A. G.; Belov, N. A.

    2015-11-01

    Hot isostatic pressing (HIP) is applied for treatment of castings of innovative low-ally high-strength aluminum alloy, nikalin ATs6N0.5Zh based on the Al-Zn-Mg-Cu-Ni-Fe system. The influence of HIP on the structure and properties of castings is studied by means of three regimes of barometric treatment with different temperatures of isometric holding: t 1 = 505 ± 2°C, p 1 = 100 MPa, τ1 = 3 h (HIP1); t 2 = 525 ± 2°C, p 2 = 100 MPa, τ2 = 3 h (HIP2); and t 3 = 545 ± 2°C, p 3 = 100 MPa, τ3 = 3 h (HIP3). It is established that high-temperature HIP leads to actually complete elimination of porosity and additional improvement of the morphology of second phases. Improved structure after HIP provides improvement properties, especially of plasticity. In particular, after heat treatment according of regime HIP2 + T4 (T4 is natural aging), the alloy plasticity is improved by about two times in comparison with the initial state (from ~6 to 12%). While applying regime HIP3 + T6 (T6 is artificial aging for reaching the maximum strength), the plasticity has improved by more than three times in comparison with the initial state, as after treatment according to regimes HIP1 + T6 and HIP2 + T6 (from ~1.2 to ~5.0%), which are characterized by a lower HIP temperature.

  11. 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.

  12. Porous Alumina Template by Selective Dissolution of Ni from Sintered Al2O3-Ni Composite

    NASA Astrophysics Data System (ADS)

    Jain, M.; Moon, A. P.; Mondal, K.

    2015-07-01

    In the present study, porous alumina template was fabricated by selective dissolution of Ni from the pressureless sintered Al2O3-Ni. Alumina and Ni powders of 99.9% purity were subjected to ball milling (200 rpm, 1 h, 10:1 ball-to-powder weight ratio) in order to get homogeneous mechanical mixture. The milled powder was compacted using hydraulic press under the uniaxial pressure of 400 MPa for 1 min, and the pressureless sintering was carried out in reducing atmosphere (H2) at 1400 °C. Ni was then selectively and completely dissolved from the 1-mm-thick sintered disk of diameter 16 mm in 1 M HCl + 3 wt.% FeCl3 solution to get the porous template of alumina. The porous alumina template was found to have sufficient compressive strength. BET, x-ray diffraction, optical microscopy, and scanning electron microscopy studies along with energy dispersive spectroscopy were performed to study microstructural evolutions, bonding characteristics, and distributions of Ni before and after the dissolution of the sintered composite.

  13. Magnetic dead layers in NiFe/Ta and NiFe/Si/diamond-like carbon films

    NASA Astrophysics Data System (ADS)

    Leng, Qunwen; Han, Hua; Mao, Ming; Hiner, Craig; Ryan, Francis

    2000-05-01

    NiFe, Ta films were fabricated by ion beam deposition (IBD) and diamond-like carbon (DLC) films by ion beam chemical vapor deposition (IB-CVD) and filtered cathodic arc (FCA) process. Magnetic dead layers at interfaces of Ta/NiFe/Tn and NiFe/Si/DLC trilayer films were determined by characterizing magnetic flux loss using a B-H loop tracer. Dependence of magnetic dead layer on ion beam voltage and thicknesses of Ta, DLC, and Si layers was investigated. It is found that the thickness of magnetic dead layer increases monotonously with increasing ion beam voltage for Ta and DLC film depositions. The magnetic dead layer of 4-6 Å thick forms at Ta/NiFe and NiFe/Ta interfaces at an ion beam voltage of 1000 V, which can be attributed to the atomic intermixing of incoming energetic adatoms with atoms of grown films at interfaces. Direct ion beam deposition of the DLC film in NiFe/Si/DLC layered structure gives rise to a magnetic thickness loss of 12-18 Å. Transmission electron microscopy cross-sectional observations have confirmed the formation of an amorphous-like interfacial layer, as a result of carbonization or silicidation of NiFe at interfaces of the trilayer film.

  14. 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.

  15. Strain-rate dependence for Ni/Al hybrid foams

    NASA Astrophysics Data System (ADS)

    Jung, Anne; Larcher, Martin; Jirousek, Ondrej; Koudelka, Petr; Solomos, George

    2015-09-01

    Shock absorption often needs stiff but lightweight materials that exhibit a large kinetic energy absorption capability. Open-cell metal foams are artificial structures, which due to their plateau stress, including a strong hysteresis, can in principle absorb large amounts of energy. However, their plateau stress is too low for many applications. In this study, we use highly novel and promising Ni/Al hybrid foams which consist of standard, open-cell aluminium foams, where nanocrystalline nickel is deposited by electrodeposition as coating on the strut surface. The mechanical behaviour of cellular materials, including their behaviour under higher strain-rates, is governed by their microstructure due to the properties of the strut material, pore/strut geometry and mass distribution over the struts. Micro-inertia effects are strongly related to the microstructure. For a conclusive model, the exact real microstructure is needed. In this study a micro-focus computer tomography (μCT) system has been used for the analysis of the microstructure of the foam samples and for the development of a microstructural Finite Element (micro-FE) mesh. The microstructural FE models have been used to model the mechanical behaviour of the Ni/Al hybrid foams under dynamic loading conditions. The simulations are validated by quasi-static compression tests and dynamic split Hopkinson pressure bar tests.

  16. Uptake of Al, As, Cr, Cd, Cu, Fe, Mn, Ni, Pb, Sr, and Zn in native wheatgrasses, wildryes, and bluegrass on three metal-contaminated soils from Montana

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One of the biggest challenges to successfully phytoremediate contaminated mineland soils is the identification of native plants that possess a broad adaptation to ecological sites and either exclude or uptake heavy metals of interest. This study evaluated forage concentrations of aluminum (Al), ars...

  17. Production of Na-22 and Other Radionuclides by Neutrons in Al, SiO2, Si, Ti, Fe and Ni Targets: Implications for Cosmic Ray Studies

    NASA Technical Reports Server (NTRS)

    Sisterson, J. M.; Jones, D. T. L.; Binns, P. J.; Langen, K.; Schroeder, I.; Buthelezi, Z.; Latti, E.; Brooks, F. D.; Buffler, A.; Allie, M. S.; Herbert, M. S.; Nchodu, M. R.; Makupula, S.; Ullmann, J.; Reedy, R. C.

    2001-01-01

    Cross section measurements for neutron-induced reactions are summarized. Measured cross sections for 22 Na produced by neutrons in Al and Si are used to calculate the production rate for 22 Na in lunar rock 12002 by galactic cosmic ray particles. Additional information is contained in the original extended abstract.

  18. 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.

  19. Pressure dependence on the remanent magnetization of Fe-Ni alloys and Ni metal

    NASA Astrophysics Data System (ADS)

    Wei, Qingguo; Gilder, Stuart Alan; Maier, Bernd

    2014-10-01

    We measured the acquisition of magnetic remanence of iron-nickel alloys (Fe64Ni36, Fe58Ni42, and Fe50Ni50) and pure Ni under pressures up to 23 GPa at room temperature. Magnetization decreases markedly for Fe64Ni36 between 5 and 7 GPa yet remains ferromagnetic until at least 16 GPa. Magnetization rises by a factor of 2-3 for the other compositions during compression to the highest applied pressures. Immediately upon decompression, magnetic remanence increases for all Fe-Ni alloys while magnetic coercivity remains fairly constant at relatively low values (5-20 mT). The amount of magnetization gained upon complete decompression correlates with the maximum pressure experienced by the sample. Martensitic effects best explain the increase in remanence rather than grain-size reduction, as the creation of single domain sized grains would raise the coercivity. The magnetic remanence of low Ni Invar alloys increases faster with pressure than for other body-centered-cubic compositions due to the higher magnetostriction of the low Ni Invar metals. Thermal demagnetization spectra of Fe64Ni36 measured after pressure release broaden as a function of peak pressure, with a systematic decrease in Curie temperature. Irreversible strain accumulation from the martensitic transition likely explains the broadening of the Curie temperature spectra, consistent with our x-ray diffraction analyses.

  20. Cation distribution and mixing thermodynamics in Fe/Ni thiospinels

    NASA Astrophysics Data System (ADS)

    Haider, Saima; Grau-Crespo, Ricardo; Devey, Antony J.; de Leeuw, Nora H.

    2012-07-01

    The structural analogy between Ni-doped greigite minerals (Fe3S4) and the (Fe, Ni)S clusters present in biological enzymes has led to suggestions that these minerals could have acted as catalysts for the origin of life. However, little is known about the distribution and stability of Ni dopants in the greigite structure. We present here a theoretical investigation of mixed thiospinels (Fe1-xNix)3S4, using a combination of density functional theory (DFT) calculations and Monte Carlo simulations. We find that the equilibrium distribution of the cations deviates significantly from a random distribution: at low Ni concentrations, Ni dopants are preferably located in octahedral sites, while at higher Ni concentrations the tetrahedral sites become much more favourable. The thermodynamic mixing behaviour between greigite and polydymite (Ni3S4) is dominated by the stability field of violarite (FeNi2S4), for which the mixing enthalpy exhibits a deep negative minimum. The analysis of the free energy of mixing shows that Ni doping of greigite is very unstable with respect to the formation of a separate violarite phase. The calculated variation of the cubic cell parameter with composition is found to be non-linear, exhibiting significant deviation from Vegard’s law, but in agreement with experiment.

  1. Novel reactions of homodinuclear Ni2 complexes [Ni(RNPyS4)]2 with Fe3(CO)12 to give heterotrinuclear NiFe2 and mononuclear Fe complexes relevant to [NiFe]- and [Fe]-hydrogenases.

    PubMed

    Song, Li-Cheng; Cao, Meng; Wang, Yong-Xiang

    2015-04-21

    The homodinuclear complexes [Ni(RNPyS4)]2 (; RNPyS4 = 2,6-bis(2-mercaptophenylthiomethyl)-4-R-pyridine; R = H, MeO, Cl, Br, i-Pr) were found to be prepared by reactions of the in situ generated Li2[Ni(1,2-S2C6H4)2] with 2,6-bis[(tosyloxy)methyl]pyridine and its substituted derivatives 2,6-bis[(tosyloxy)methyl]-4-R-pyridine. Further reactions of with Fe3(CO)12 gave both heterotrinuclear complexes NiFe2(RNPyS4)(CO)5 () and mononuclear complexes Fe(RNPyS4)(CO) (), unexpectedly. Interestingly, complexes and could be regarded as models for the active sites of [NiFe]- and [Fe]-hydrogenases, respectively. All the prepared complexes were characterized by elemental analysis, spectroscopy, and particularly for some of them, by X-ray crystallography. In addition, the electrochemical properties of and as well as the electrocatalytic H2 production catalyzed by and were investigated by CV techniques. PMID:25747808

  2. The mechanical properties of FeAl

    SciTech Connect

    Baker, I.; George, E.P.

    1996-12-31

    Only in the last few years has progress been made in obtaining reproducible mechanical properties data for FeAl. Two sets of observations are the foundation of this progress. The first is that the large vacancy concentrations that exist in FeAl at high temperature are easily retained at low temperature and that these strongly affect the low-temperature mechanical properties. The second is that RT ductility is adversely affected by water vapor. Purpose of this paper is not to present a comprehensive overview of the mechanical properties of FeAl but rather to highlight our understanding of key phenomena and to show how an understanding of the factors which control the yield strength and fracture behavior has followed the discovery of the above two effects. 87 refs, 9 figs.

  3. Crystallinity of Fe-Ni Sulfides in Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Zolensky, M. E.; Ohsumi, K.; Mikouchi, T.; Hagiya, K.; Le, L.

    2008-03-01

    We examine the crystallinity and crystal structures of Fe-Ni sulfides in five carbonaceous chondrites - Acfer 094 (CM2), Tagish Lake (C2 ungrouped), Kaidun C1, Bali (CV2/3 oxidized), and Efremovka (CV3 reduced).

  4. Interdiffusion in nanometric Fe/Ni multilayer films

    SciTech Connect

    Liu, JX; Barmak, K

    2015-03-01

    Fe (3.1 nm)/Ni (3.3 nm)](20) multilayer films were prepared by DC magnetron sputtering onto oxidized Si(100) substrates. The Fe and Ni layers were shown to both be face-centered cubic by x-ray diffraction. Interdiffusion of the Fe and Ni layers in the temperature range of 300-430 degrees C was studied by x-ray reflectivity. From the decay of the integral intensity of the superlattice peak, the activation energy and the pre-exponential term for the effective interdiffusion coefficient were determined as to 1.06 +/- 0.07 eV and 5 x 10(-10) cm(2)/s, respectively. The relevance of the measured interdiffusion coefficient to the laboratory timescale synthesis of L1(0) ordered FeNi as a rare-earth free permanent magnet is discussed. (C) 2015 American Vacuum Society.

  5. Melting, Processing, and Properties of Disordered Fe-Al and Fe-Al-C Based Alloys

    NASA Astrophysics Data System (ADS)

    Satya Prasad, V. V.; Khaple, Shivkumar; Baligidad, R. G.

    2014-09-01

    This article presents a part of the research work conducted in our laboratory to develop lightweight steels based on Fe-Al alloys containing 7 wt.% and 9 wt.% aluminum for construction of advanced lightweight ground transportation systems, such as automotive vehicles and heavy-haul truck, and for civil engineering construction, such as bridges, tunnels, and buildings. The melting and casting of sound, porosity-free ingots of Fe-Al-based alloys was accomplished by a newly developed cost-effective technique. The technique consists of using a special flux cover and proprietary charging schedule during air induction melting. These alloys were also produced using a vacuum induction melting (VIM) process for comparison purposes. The effect of aluminum (7 wt.% and 9 wt.%) on melting, processing, and properties of disordered solid solution Fe-Al alloys has been studied in detail. Fe-7 wt.% Al alloy could be produced using air induction melting with a flux cover with the properties comparable to the alloy produced through the VIM route. This material could be further processed through hot and cold working to produce sheets and thin foils. The cold-rolled and annealed sheet exhibited excellent room-temperature ductility. The role of carbon in Fe-7 wt.% Al alloys has also been examined. The results indicate that Fe-Al and Fe-Al-C alloys containing about 7 wt.% Al are potential lightweight steels.

  6. Hydrogen activation by [NiFe]-hydrogenases.

    PubMed

    Carr, Stephen B; Evans, Rhiannon M; Brooke, Emily J; Wehlin, Sara A M; Nomerotskaia, Elena; Sargent, Frank; Armstrong, Fraser A; Phillips, Simon E V

    2016-06-15

    Hydrogenase-1 (Hyd-1) from Escherichia coli is a membrane-bound enzyme that catalyses the reversible oxidation of molecular H2 The active site contains one Fe and one Ni atom and several conserved amino acids including an arginine (Arg(509)), which interacts with two conserved aspartate residues (Asp(118) and Asp(574)) forming an outer shell canopy over the metals. There is also a highly conserved glutamate (Glu(28)) positioned on the opposite side of the active site to the canopy. The mechanism of hydrogen activation has been dissected by site-directed mutagenesis to identify the catalytic base responsible for splitting molecular hydrogen and possible proton transfer pathways to/from the active site. Previous reported attempts to mutate residues in the canopy were unsuccessful, leading to an assumption of a purely structural role. Recent discoveries, however, suggest a catalytic requirement, for example replacing the arginine with lysine (R509K) leaves the structure virtually unchanged, but catalytic activity falls by more than 100-fold. Variants containing amino acid substitutions at either or both, aspartates retain significant activity. We now propose a new mechanism: heterolytic H2 cleavage is via a mechanism akin to that of a frustrated Lewis pair (FLP), where H2 is polarized by simultaneous binding to the metal(s) (the acid) and a nitrogen from Arg(509) (the base). PMID:27284053

  7. Fe-30Ni-5NiO alloy as inert anode for low-temperature aluminum electrolysis

    NASA Astrophysics Data System (ADS)

    Zhu, Yuping; He, Yedong; Wang, Deren

    2011-05-01

    Fe-30Ni-5NiO alloy anodes were prepared by a spark plasma sintering process for aluminum electrolysis. NiO nano-particles with the size of ˜20 nm were dispersed in the anodes. The oxidation behaviors of the anodes were investigated at 800°C and 850°C, respectively. The electrolysis corrosion behaviors were tested in a cryolite-alumina electrolyte at a low temperature of 800°C with anodic current densities of ˜0.5 A/cm2. The results indicated that the oxidation kinetic of the anodes followed a parabolic law. A continuous Fe2O3 film selectively formed on the surface of the anode during the electrolysis process. A semi-continuous Al2O3 layer was observed at oxide film/alloy interface, probably caused by an in-situ chemical dissolution process.

  8. Creep and Toughness of Cryomilled NiAl Containing Cr

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Aikin, Beverly; Salem, Jon

    2000-01-01

    NiAl-AlN + Cr composites were produced by blending cryomilled NiAl powder with approx. 10 vol % Cr flakes. In comparison to the as-consolidated matrices, hot isostatically pressed Cr-modified materials did not demonstrate any significant improvement in toughness. Hot extruded NiAl-AlN+10.5Cr, however, possessed a toughness twice that determine for the base NiAl-AlN alloy. Measurement of the 1200 to 1400 K plastic flow properties revealed that the strength of the composites was completely controlled by the properties of the NiAl-AlN matrices. This behavior could be successfully modeled by the Rule-of-Mixtures, where load is shed from the weak Cr to the strong matrix.

  9. Anodic vacuum arc developed nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples

    SciTech Connect

    Mukherjee, S. K.; Sinha, M. K.; Pathak, B.; Rout, S. K.; Barhai, P. K.

    2009-12-01

    This paper deals with the development of nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples (TFTCs) by using ion-assisted anodic vacuum arc deposition technique. The crystallographic structure and surface morphology of individual layer films have been studied by x-ray diffraction and scanning electron microscopy, respectively. The resistivity, temperature coefficient of resistance, and thermoelectric power of as deposited and annealed films have been measured. The observed departure of these transport parameters from their respective bulk values can be understood in terms of intrinsic scattering due to enhanced crystallite boundaries. From the measured values of thermoelectric power and the corresponding temperature coefficient of resistance of annealed Cu, Ni, and Fe films, the calculated values of log derivative of the mean free path of conduction electrons at the Fermi surface with respect to energy (U) are found to be -0.51, 3.22, and -8.39, respectively. The thermoelectric response of annealed Cu-Ni and Fe-Ni TFTCs has been studied up to a maximum temperature difference of 300 deg. C. Reproducibility of TFTCs has been examined in terms of the standard deviation in thermoelectric response of 16 test samples for each pair. Cu-Ni and Fe-Ni TFTCs agree well with their wire thermocouple equivalents. The thermoelectric power values of Cu-Ni and Fe-Ni TFTCs at 300 deg. C are found to be 0.0178 and 0.0279 mV/ deg. C, respectively.

  10. The Al-Al3Ni Eutectic Reaction: Crystallography and Mechanism of Formation

    NASA Astrophysics Data System (ADS)

    Fan, Yangyang; Makhlouf, Makhlouf M.

    2015-09-01

    The characteristics of the Al-Al3Ni eutectic structure are examined with emphasis on its morphology and crystallography. Based on these examinations, the mechanism of formation of this technologically important eutectic is postulated. It is found that a thin shell of α-Al forms coherently around each Al3Ni fiber. The excellent thermal stability of the Al-Al3Ni eutectic may be attributed to the presence of this coherent layer.

  11. Comparative Study of Thermal Stability of NiFe and NiFeTa Thin Films Grown by Cosputtering Technique

    NASA Astrophysics Data System (ADS)

    Phuoc, Nguyen N.; Ong, C. K.

    2016-08-01

    A comparative study of the thermal behavior of dynamic permeability spectra for compositionally graded NiFeTa and uniform-composition NiFe thin films has been carried out. We found that the resonance frequency of the compositionally graded NiFeTa film increased with increasing temperature, while it decreased for the case of the uniform-composition NiFe thin film. This finding unambiguously suggests that the compositional gradient of the film is the only reason for the increase of the magnetic anisotropy with temperature due to its stress-induced origin, while the cosputtering technique does not play any role in this peculiar behavior. The temperature dependence of the frequency linewidth is also presented and discussed.

  12. Measurement and Modeling of the Production of He, Ne, and AR from Mg, Al, Si, Fe, and NI in an Artificial Iron Meteoroid Irradiated Isotropically with 1.6 GeV Protons

    NASA Astrophysics Data System (ADS)

    Busemann, H.; Wieler, R.; Leya, I.; Lange, H.-J.; Michel, R.; Meltzow, B.; Herpers, U.

    1995-09-01

    The production by GCR protons of He, Ne and Ar isotopes from their main target elements was investigated in a simulation experiment [1] by irradiating a 20-cm diameter iron sphere isotropically with 1.6 GeV protons. The model-meteoroid contained, among other targets, pure Mg, Al, Si, Fe, and Ni foils at various depths in central bores. Radionuclide production in these targets was measured by gamma-spectrometry. Stable He, Ne, and Ar isotopes were measured by mass spectrometry. These latter results and the ^22Na data are reported here. As in our earlier simulation with a 50-cm diameter gabbro sphere irradiated with 1.6 GeV protons [2], the present experiment simulates the exposure of meteoroids to galactic protons in space within about 20%, if normalized to the same number of particles. Some systematic deviations are attributed to differences between the monoenergetic irradiation and the exposure to the GCR spectrum and to resulting differences between the secondary particle fields. A comparison of the new production rates with those obtained in the gabbro sphere [2] clearly exhibits the influence of bulk chemical composition on production rates which was discovered earlier by Begemann and Schultz [3] in stony irons. Model calculations of the production of He, Ne, Ar, and ^22Na were performed for all artificial iron and stony meteoroids irradiated by our collaboration [2, 4, 5, this work]. Production rates were calculated from depth-dependent p- and n-spectra derived by Monte Carlo techniques using the HERMES code system [6] and from cross sections for the relevant nuclear reactions. For p-induced reactions all available experimental thin-target cross sections were used [2]. Cross sections for n-induced reactions were calculated by the new AREL code [7] which is a relativistic version of the hybrid model of preequilibrium reactions [8]. In addition to these a priori calculations a posteriori model calculations were performed. Theoretical cross sections for n

  13. A sulfur segregation study of PWA 1480, NiCrAl, and NiAl alloys

    NASA Technical Reports Server (NTRS)

    Jayne, D. T.; Smialek, J. L.

    1993-01-01

    Some nickel based superalloys show reduced oxidation resistance from the lack of an adherent oxide layer during high temperature cyclic oxidation. The segregation of sulfur to the oxide-metal interface is believed to effect oxide adhesion, since low sulfur alloys exhibit enhanced adhesion. X ray Photoelectron Spectroscopy (XPS) was combined with an in situ sample heater to measure sulfur segregation in NiCrAl, PWA 1480, and NiAl alloys. The polished samples with a 1.5 to 2.5 nm (native) oxide were heated from 650 to 1100 C with hold times up to 6 hr. The sulfur concentration was plotted as a function of temperature versus time at temperature. One NiCrAl sulfur study was performed on the same casting used by Browning to establish a base line between previous Auger Electron Spectroscopy (AES) results and the XPS results of this study. Sulfur surface segregation was similar for PWA 1480 and NiCrAl and reached a maximum of 30 at% at 800 to 850 C. Above 900 C the sulfur surface concentration decreased to about 3 at% at 1100 C. These results are contrasted to the minimal segregation observed for low sulfur hydrogen annealed materials which exhibit improved scale adhesion.

  14. Effect of NiO spin orientation on the magnetic anisotropy of the Fe film in epitaxially grown Fe/NiO/Ag(001) and Fe/NiO/MgO(001)

    SciTech Connect

    Kim, W.; Jin, E.; Wu, J.; Park, J.; Arenholz, E.; Scholl, A.; Hwang, C.; Qiu, Z.

    2010-02-10

    Single crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by Low Energy Electron Diffraction (LEED), Magneto-Optic Kerr Effect (MOKE), and X-ray Magnetic Linear Dichroism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spin orientation changes from in-plane direction in Fe/NiO/Ag(001) to out-of-plane direction in Fe/NiO/MgO(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy in Fe/NiO/Ag(001) is due to a 90{sup o}-coupling between the in-plane NiO spins and the in-plane Fe spins.

  15. Cyclic oxidation resistance of a reaction milled NiAl-AlN composite

    NASA Technical Reports Server (NTRS)

    Lowell, Carl E.; Barrett, Charles A.; Whittenberger, J. D.

    1990-01-01

    Based upon recent mechanical property tests a NiAl-AlN composite produced by cryomilling has very attractive high temperature strength. This paper focuses on the oxidation resistance of the NiAl-AlN composite at 1473 and 1573 K as compared to that of Ni-47Al-0.15Zr, one of the most oxidation resistant intermetallics. The results of cyclic oxidation tests show that the NiAl-AlN composite has excellent properties although not quite as good as those of Ni-47Al-0.15Zr. The onset of failure of the NiAl-AlN was unique in that it was not accompanied by a change in scale composition from alumina to less protective oxides. Failure in the composite appears to be related to the entrapment of AlN particles within the alumina scale.

  16. Thermal mixing of Al-Fe multilayers

    NASA Astrophysics Data System (ADS)

    Meyer, M.; Mendoza Zélis, L.; Sánchez, F. H.; Traverse, A.

    1994-12-01

    Al-Fe multilayers have been mixed by thermal treatment and their evolution followed by conversion electron Mössbauer spectroscopy. The initial and final states have been characterized by Rutherford backscattering spectrometry. The results are compared with those previously obtained in the ion beam mixing of similar systems.

  17. Ni spin switching induced by magnetic frustration in FeMn/Ni/Cu(001)

    SciTech Connect

    Wu, J.; Choi, J.; Scholl, A.; Doran, A.; Arenholz, E.; Hwang, Chanyong; Qiu, Z. Q.

    2009-03-08

    Epitaxially grown FeMn/Ni/Cu(001) films are investigated by Photoemission Electron Microscopy and Magneto-Optic Kerr Effect. We find that as the FeMn overlayer changes from paramagnetic to antiferromagnetic state, it could switch the ferromagnetic Ni spin direction from out-of-plane to in-plane direction of the film. This phenomenon reveals a new mechanism of creating magnetic anisotropy and is attributed to the out-of-plane spin frustration at the FeMn-Ni interface.

  18. Microstructure and Fracture Toughness of FeNiCr-TiC Composite Produced by Thermite Reaction

    NASA Astrophysics Data System (ADS)

    Xi, Wenjun; Shi, Chaoliang

    The microstructures of the FeNiCr-TiC composite produced by the rapid solidification thermite process were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The effects of aging treatment on the microstructure and fracture toughness of the composite were examined. Results showed that the FeNiCr-TiC composite was composed of ferrite (α-FeNiCr), TiC and NiAl (β phase). TiC particles in the matrix were in the shape of polygon and uniformly distributed, and their size was less than 3 µm. The β phase was coherent with the ferrite matrix, and its average size was about 50 nm. The fracture toughness of composite was 22 MPa·m1/2 without aging. When the aging temperature was below 600°C, the fracture toughness of the composite had higher plateau values and reached the maximum of 32 MPa·m1/2 at aging temperature 500°C due to the precipitation of NiAl phase on the nanometer scale. The fracture toughness decreased rapidly aged at 650°C, and then kept homology value in the range of 700 to 900°C, which was attributed to the precipitation of needle-shaped carbide (Cr/Fe)7C3 at the grain boundaries.

  19. Shock induced reaction of Ni/Al nanopowder mixture.

    PubMed

    Meng, C M; Wei, J J; Chen, Q Y

    2012-11-01

    Nanopowder Ni/Al mixture (mixed in Al:Ni = 2:1 stoichiometry) was shock compressed by employing single and two-stage light gas gun. The particle size of Al and Ni are 100-200 nm and 50-70 nm respectively, morphologies of Al and Ni are sphere like either. Recovered product was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. According to the XRD spectrum, the mixed powder undergo complete reaction under shock compression, reaction product consist of Ni2Al3, NiAl and corundum structure Al2O3 compound. Grain size of Ni-Al compound is less than 100 nm. With the shock pressure increasing, the ratio of Ni2Al3 decreased obviously. The corundum crystal size is 400-500 nm according to the SEM observation. The results of shock recovery experiments and analysis show that the threshold pressure for reaction of nano size powder Ni/Al mixture is much less than that of micro size powder. PMID:23421276

  20. The effect of interstitial carbon on the mechanical properties and dislocation substructure evolution in Fe40.4Ni11.3Mn34.8Al7.5Cr6 high entropy alloys

    DOE PAGESBeta

    Wang, Zhangwei; Baker, Ian; Cai, Zhonghou; Chen, Si; Poplawsky, Jonathan D.; Guo, Wei

    2016-09-01

    A systematic study of the effects of up to 1.1 at. % carbon on the mechanical properties and evolution of the dislocation substructure in a series of a high entropy alloys (HEA) based on Fe40.4Ni11.3Mn34.8Al7.5Cr6 is presented. Transmission electron microscopy (TEM), synchrotron X-ray diffraction (XRD) and atom probe tomography (APT) were used to show that all the alloys are single-phase f.c.c. random solid solutions. The lattice constant, determined from synchrotron XRD measurements, increases linearly with increasing carbon concentration, which leads to a linear relationship between the yield strength and the carbon concentration. The dislocation substructures, as determined by a TEM,more » show a transition from wavy slip to planar slip and, at higher strains, and from cell-forming structure (dislocations cells, cell blocks and dense dislocation walls) to non-cell forming structure (Taylor lattice, microbands and domain boundaries) with the addition of carbon, features related to the increase in lattice friction stress. The stacking fault energy (measured via weak-beam imaging of the separation of dislocation partials) decreases with increasing carbon content, which also contributes to the transition from wavy slip to planar slip. The formation of non-cell forming structure induced by carbon leads to a high degree of strain hardening and a substantial increase in the ultimate tensile strength. In conclusion, the consequent postponement of necking due to the high strain hardening, along with the plasticity accommodation arising from the formation of microbands and domain boundaries, result in an increase of ductility due to the carbon addition.« less

  1. Boron strengthening in FeAl

    SciTech Connect

    Baker, I.; Li, X.; Xiao, H.; Klein, O.; Nelson, C.; Carleton, R.L.; George, E.P.

    1998-11-01

    The effect of boron on the strength of B2-structured FeAl is considered as a function of composition, grain size and temperature. Boron does not affect the concentrations of antisite atoms or vacancies present, with the former increasing and the latter decreasing with increasing deviation from the stoichiometric composition. When vacancies are absent, the strength increase per at. % B per unit lattice strain, {Delta}{sigma}/({Delta}c x {epsilon}) increases with increasing aluminum concentration, but when vacancies are present (>45 at. % Al), {Delta}{sigma}/({Delta}c x {epsilon}) decreases again. Boron increases grain size strengthening in FeAl. B strengthening is roughly independent of temperature up to the yield strength peak but above the point, when diffusion-assisted deformation occurs, boron strengthening increases dramatically.

  2. Characterization of nanoscale NiAl-type precipitates in a ferritic steel by electron microscopy and atom probe tomography

    SciTech Connect

    Teng, Zhenke; Miller, Michael K; Ghosh, Gautam; Liu, Chain T; Huang, Shenyan; Russell, Kaye F; Fine, Morris E; Liaw, Peter K

    2010-01-01

    The microstructure of NiAl-type ({beta}{prime}) precipitates in an aged ferritic steel (Fe-12.7Al-9Ni-10.2Cr-1.9Mo, at.%) is characterized by transmission and analytical electron microscopy (AEM) and atom probe tomography (APT). The alloy shows a duplex precipitation of {beta}{prime} particles: primary with an average diameter of 130 nm and secondary with an average diameter of 3 nm. Based on APT, the primary and secondary {beta}{prime} have compositions of Ni{sub 41.2}Al{sub 43.6}Fe{sub 12.7}Cr{sub 0.8}Mo{sub 1.4} and Ni{sub 26.3}Al{sub 41.6}Fe{sub 26.9}Cr{sub 3.3}Mo{sub 1.7}, respectively.

  3. 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.

  4. Boron-modified Ni3Al intermetallic compound formed by spark plasma sintering of mechanically activated Ni and Al powders

    NASA Astrophysics Data System (ADS)

    Shevtsova, L. I.; Ogneva, T. S.; Mul, D. O.; Esikov, M. A.; Larichkin, A. Yu; Malikov, V. N.

    2016-04-01

    A Ni3Al intermetallic compound was obtained by spark plasma sintering of mechanically activated Ni and Al powders in atomic ratio 3:1 respectively. Samples with boron addition of 0.1 and 0.2% (wt.) and samples without boron were obtained. The maximum value of the relative density (~99 %) has been obtained for the material by sintering of mechanically activated mixture powders modified with 0.1% of boron. No differences have been found between the structure of boron-modified Ni3Al and Ni3Al without boron addition. The maximum level of bending strength (2200 MPa) has been achieved for Ni3Al with 0.1% (wt.) of boron. This value is almost 3 times the bending strength of the sample of Ni3Al sintered without boron addition.

  5. Maturation of [NiFe]-hydrogenases in Escherichia coli.

    PubMed

    Forzi, Lucia; Sawers, R Gary

    2007-06-01

    Hydrogenases catalyze the reversible oxidation of dihydrogen. Catalysis occurs at bimetallic active sites that contain either nickel and iron or only iron and the nature of these active sites forms the basis of categorizing the enzymes into three classes, the [NiFe]-hydrogenases, the [FeFe]-hydrogenases and the iron sulfur cluster-free [Fe]-hydrogenases. The [NiFe]-hydrogenases and the [FeFe]-hydrogenases are unrelated at the amino acid sequence level but the active sites share the unusual feature of having diatomic ligands associated with the Fe atoms in the these enzymes. Combined structural and spectroscopic studies of [NiFe]-hydrogenases identified these diatomic ligands as CN- and CO groups. Major advances in our understanding of the biosynthesis of these ligands have been achieved primarily through the study of the membrane-associated [NiFe]-hydrogenases of Escherichia coli. A complex biosynthetic machinery is involved in synthesis and attachment of these ligands to the iron atom, insertion of the Fe(CN)2CO group into the apo-hydrogenase, introduction of the nickel atom into the pre-formed active site and ensuring that the holoenzyme is correctly folded prior to delivery to the membrane. Although much remains to be uncovered regarding each of the individual biochemical steps on the pathway to synthesis of a fully functional enzyme, our understanding of the initial steps in CN- synthesis have revealed that it is generated from carbamoyl phosphate. What is becoming increasingly clear is that the metabolic origins of the carbonyl group may be different. PMID:17216401

  6. Magnetization reversal of uncompensated Fe moments in exchangebiased Ni/FeF2 bilayers

    SciTech Connect

    Arenholz, Elke; Liu, Kai; Li, Zhipan; Schuller, Ivan K.

    2006-01-01

    The magnetization reversal of uncompensated Fe moments in exchange biased Ni/FeF{sub 2} bilayers was determined using soft x-ray magnetic circular and linear dichroism. The hysteresis loops resulting from the Fe moments are almost identical to those of the ferromagnetic Ni layer. However, a vertical loop shift indicates that some Fe moments are pinned in the antiferromagnetically ordered FeF{sub 2}. The pinned moments are oriented antiparallel to small cooling fields leading to negative exchange bias, but parallel to large cooling fields resulting in positive exchange bias. No indication for the formation of a parallel antiferromagnetic domain wall in the FeF{sub 2} layer upon magnetization reversal in the Ni layer was found.

  7. AlN/Fe/AlN nanostructures for magnetooptic magnetometry

    SciTech Connect

    Lišková-Jakubisová, E. Višňovský, Š.; Široký, P.; Hrabovský, D.; Pištora, J.

    2014-05-07

    AlN/Fe/AlN/Cu nanostructures with ultrathin Fe grown by sputtering on Si substrates are evaluated as probes for magnetooptical (MO) mapping of weak currents. They are considered for a laser wavelength of λ = 410 nm (3.02 eV) and operate at oblique light incidence angles, φ{sup (0)}, to enable detection of both in-plane and out-of-plane magnetization. Their performance is evaluated in terms of MO reflected wave electric field amplitudes. The maximal MO amplitudes in AlN/Fe/AlN/Cu are achieved by a proper choice of layer thicknesses. The nanostructures were characterized by MO polar Kerr effect at φ{sup (0)} ≈ 5° and longitudinal Kerr effect spectra (φ{sup (0)} = 45°) at photon energies between 1 and 5 eV. The nominal profiles were refined using a model-based analysis of the spectra. Closed form analytical expressions are provided, which are useful in the search for maximal MO amplitudes.

  8. 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.

  9. 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.

  10. Evaporative segregation in 80% Ni-20% Cr and 60% Fe-40% Ni alloys

    NASA Technical Reports Server (NTRS)

    Gupta, K. P.; Mukherjee, J. L.; Li, C. H.

    1974-01-01

    An analytical approach is outlined to calculate the evaporative segregation behavior in metallic alloys. The theoretical predictions are based on a 'normal' evaporation model and have been examined for Fe-Ni and Ni-Cr alloys. A fairly good agreement has been found between the predicted values and the experimental results found in the literature.

  11. Room temperature luminescence and ferromagnetism of AlN:Fe

    NASA Astrophysics Data System (ADS)

    Li, H.; Cai, G. M.; Wang, W. J.

    2016-06-01

    AlN:Fe polycrystalline powders were synthesized by a modified solid state reaction (MSSR) method. Powder X-ray diffraction and transmission electron microscopy results reveal the single phase nature of the doped samples. In the doped AlN samples, Fe is in Fe2+ state. Room temperature ferromagnetic behavior is observed in AlN:Fe samples. Two photoluminescence peaks located at about 592 nm (2.09 eV) and 598 nm (2.07 eV) are observed in AlN:Fe samples. Our results suggest that AlN:Fe is a potential material for applications in spintronics and high power laser devices.

  12. High-performance Ni3Al synthesized from composite powders

    NASA Astrophysics Data System (ADS)

    Chiou, Wen-Chih; Hu, Chen-Ti

    1994-05-01

    Specimens of Ni3Al + B of high density (>99.3 Pct RD) and relatively large dimension have been synthesized from composite powders through processes of replacing plating and electroless Ni-B plating on Al powder, sintering, and thermal-mechanical treatment. The uniformly coated Ni layer over fine Al or Ni core particles constituting these coating/core composite powders has advantages such as better resistance to oxidation relative to pure Al powder, a greater green density as a compacted powder than prealloyed powder, the possibility of atomically added B to the material by careful choice of a suitable plating solution, and avoidance of the expensive powder metallurgy (PM) equipment such as a hot isostatic press (HIP), hot press (HP), etc. The final Ni3Al + B product is made from Ni-B-Al and Ni-B-Ni mixed composite powders by means of traditional PM processes such as compacting, sintering, rolling, and annealing, and therefore, the dimensions of the product are not constrained by the capacity of an HIP or HP. The properties of Ni3Al composite powder metallurgy (CPM) specimens tested at room temperature have been obtained, and comparison with previous reports is conducted. A tensile elongation of about 16 Pct at room temperature was attained.

  13. Point defects in the NiAl(100) surface.

    PubMed

    Lerch, D; Dössel, K; Hammer, L; Müller, S

    2009-04-01

    The stability of various point defects in NiAl(100) has been investigated by first-principles calculations. For Al-rich surfaces, Ni vacancies within the first Al layer are energetically most favourable. For Ni-rich surfaces, so-called double defects, consisting of both Ni-antisite atom in the first Al layer and a Ni vacancy within the second Ni layer, form the configuration of lowest energy, superior to singular Ni antisites. An additional and significant energy gain is found in both cases by mutual lateral interaction of the defects, when they are arranged in the diagonal direction. Respective [Formula: see text] ordered configurations were found as the most stable structures. A 50:50 mixture of both defect types turns out to be even lower in energy than the ideal Al-terminated NiAl(100) surface, proving the latter to be metastable only. This is in line with the often reported inability in experiments to prepare ideal NiAl(100) surfaces. PMID:21817482

  14. Mechanical behavior and phase stability of NiAl-based shape memory alloys

    SciTech Connect

    George, E.P.; Liu, C.T.; Horton, J.A.; Kunsmann, H.; King, T.; Kao, M.

    1993-12-31

    NiAl-based shape memory alloys (SMAs) can be made ductile by alloying with 100--300 wppm B and 14--20 at.% Fe. The addition of Fe has the undesirable effect that it lowers the temperature (A{sub p}) of the martensite {yields} austenite phase transformation. Fortunately, however, A can be raised by lowering the ``equivalent`` amount of Al in the alloy. In this way a high A{sub p} temperature of {approximately}190 C has been obtained without sacrificing ductility. Furthermore, a recoverable strain of 0.7% has been obtained in a Ni-Al-Fe alloy with A{sub p} temperature of {approximately}140 C. Iron additions do not suppress the aging-induced embrittlement that occurs in NiAl alloys at 300--500 C as a result of Ni{sub 5}Al{sub 3} precipitation. Manganese additions (up to 10 at.%) have the effect of lowering A{sub p}, degrading hot workability, and decreasing room-temperature ductility.

  15. Forging of FeAl intermetallic compounds

    SciTech Connect

    Flores, O.; Juarez, J.; Campillo, B.; Martinez, L.; Schneibel, J.H.

    1994-09-01

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

  16. Investigation of superplastic behavior of NiAl and Ni{sub 3}Al duplex alloy

    SciTech Connect

    Liu Zhenyun; Lin Dongliang; Gu Yuefeng; Shan Aidang

    1997-12-31

    The superplastic behavior of a NiAl and Ni{sub 3}Al duplex alloy was investigated. It was found that the alloy exhibits superplastic behavior over a narrow temperature range, from 975 C to 1,025 C at the strain rate of 1.52 {times} 10{sup {minus}4}s{sup {minus}1}. A maximum tensile elongation of 149% was obtained at 1,000 C with the strain rate sensitivity up to 0.375. The superplastic deformation of the duplex alloy can be approximately described by an empirical equation of the form: {dot {var_epsilon}} = Ao{sup 2.67} exp({minus}303,000/RT). Optical microstructure and TEM observation show that the superplastic behavior mechanism of the investigated alloy is a process of continuous recovery and recrystallization during deformation.

  17. 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.

  18. Deformation-induced dissolution of the intermetallics Ni3Ti and Ni3Al in austenitic steels at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Sagaradze, V. V.; Shabashov, V. A.; Kataeva, N. V.; Zavalishin, V. A.; Kozlov, K. A.; Kuznetsov, A. R.; Litvinov, A. V.; Pilyugin, V. P.

    2016-06-01

    An anomalous deformation-induced dissolution of the intermetallics Ni3Al and Ni3Ti in the matrix of austenitic Fe-Ni-Al(Ti) alloys has been revealed in experiment at cryogenic temperatures (down to 77 K) under rolling and high pressure torsion. The observed phenomenon is explained as the result of migration of deformation-stipulated interstitial atoms from a particle into the matrix in the stress field of moving dislocations. With increasing the temperature of deformation, the dissolution is replaced by the deformation-induced precipitation of the intermetallics, which is accelerated due to a sufficient amount of point defects in the matrix, gained as well in the course of deformation at lower temperatures.

  19. Irradiation-enhanced reactivity of multilayer Al/Ni nanomaterials.

    PubMed

    Manukyan, Khachatur V; Tan, Wanpeng; deBoer, Richard J; Stech, Edward J; Aprahamian, Ani; Wiescher, Michael; Rouvimov, Sergei; Overdeep, Kyle R; Shuck, Christopher E; Weihs, Timothy P; Mukasyan, Alexander S

    2015-06-01

    We have investigated the effect of accelerated ion beam irradiation on the structure and reactivity of multilayer sputter deposited Al/Ni nanomaterials. Carbon and aluminum ion beams with different charge states and intensities were used to irradiate the multilayer materials. The conditions for the irradiation-assisted self-ignition of the reactive materials and corresponding ignition thresholds for the beam intensities were determined. We discovered that relatively short (40 min or less) ion irradiations enhance the reactivity of the Al/Ni nanomaterials, that is, significantly decrease the thermal ignition temperatures (Tig) and ignition delay times (τig). We also show that irradiation leads to atomic mixing at the Al/Ni interfaces with the formation of an amorphous interlayer, in addition to the nucleation of small (2-3 nm) Al3Ni crystals within the amorphous regions. The amorphous interlayer is thought to enhance the reactivity of the multilayer energetic nanomaterial by increasing the heat of the reaction and by speeding the intermixing of the Ni and the Al. The small Al3Ni crystals may also enhance reactivity by facilitating the growth of this Al-Ni intermetallic phase. In contrast, longer irradiations decrease reactivity with higher ignition temperatures and longer ignition delay times. Such changes are also associated with growth of the Al3Ni intermetallic and decreases in the heat of reaction. Drawing on this data set, we suggest that ion irradiation can be used to fine-tune the structure and reactivity of energetic nanomaterials. PMID:25915560

  20. Lanthanide Al-Ni base Ericsson cycle magnetic refrigerants

    DOEpatents

    Gschneidner, K.A. Jr.; Takeya, Hiroyuki

    1995-10-31

    A magnetic refrigerant for a magnetic refrigerator using the Ericsson thermodynamic cycle comprises DyAlNi and (Gd{sub 0.54}Er{sub 0.46})AlNi alloys having a relatively constant {Delta}Tmc over a wide temperature range. 16 figs.

  1. 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.

  2. Lanthanide Al-Ni base Ericsson cycle magnetic refrigerants

    DOEpatents

    Gschneidner, Jr., Karl A.; Takeya, Hiroyuki

    1995-10-31

    A magnetic refrigerant for a magnetic refrigerator using the Ericsson thermodynamic cycle comprises DyAlNi and (Gd.sub.0.54 Er.sub.0.46)AlNi alloys having a relatively constant .DELTA.Tmc over a wide temperature range.

  3. Crystal orientation dependence of band matching in all-B2-trilayer current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves using Co{sub 2}Fe(Ge{sub 0.5}Ga{sub 0.5}) Heusler alloy and NiAl spacer

    SciTech Connect

    Chen, Jiamin; Hono, K.; Furubayashi, T.; Takahashi, Y. K.; Sasaki, T. T.

    2015-05-07

    We have experimentally investigated the crystal orientation dependence of band matching in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo-spin-valves using Co{sub 2}Fe(Ge{sub 0.5}Ga{sub 0.5}) (CFGG) Heusler alloy ferromagnetic layer and NiAl spacer. The high quality epitaxial CFGG/NiAl/CFGG all-B2-trilayers structure devices were fabricated on both MgO(001) and sapphire (112{sup ¯}0) single crystal substrates to create (001) and (110) crystal orientations. Same magneto-transport properties were observed from these two differently orientated devices indicating that there is no or little orientation dependence of band matching on MR output. We also found that all-B2-trilayer structure was free of lattice matching influence depending on the crystal orientation, which made it a good candidate for CPP-GMR device.

  4. Metastable γ-FeNi nanostructures with tunable Curie temperature

    NASA Astrophysics Data System (ADS)

    Miller, K. J.; Sofman, M.; McNerny, K.; McHenry, M. E.

    2010-05-01

    We report on new metastable γ-FeNi nanoparticles produced by mechanical alloying of melt-spun ribbon using a high energy ball mill followed by a solution annealing treatment in the γ-phase region and water quenching in of the face-centered cubic γ-phase. In the Fe-Ni phase diagram there is a strong compositional dependence of the Curie temperature, Tc, on composition in the γ-phase. This work studies the stabilization of γ-phase nanostructures and the compositional tuning of Tc in Fe-Ni alloys which can have important ramifications on the self-regulated heating of magnetic nanoparticles in temperature ranges of interest for applications in polymer curing and cancer thermotherapies. To date we have achieved Curie temperatures as low as 120 °C by this method.

  5. Bimetallic Fe-Ni Oxygen Carriers for Chemical Looping Combustion

    SciTech Connect

    Bhavsar, Saurabh; Veser, Goetz

    2013-11-06

    The relative abundance, low cost, and low toxicity of iron make Fe-based oxygen carriers of great interest for chemical looping combustion (CLC), an emerging technology for clean and efficient combustion of fossil and renewable fuels. However, Fe also shows much lower reactivity than other metals (such as Ni and Cu). Here, we demonstrate strong improvement of Fe-based carriers by alloying the metal phase with Ni. Through a combination of carrier synthesis and characterization with thermogravimetric and fixed-bed reactor studies, we demonstrate that the addition of Ni results in a significant enhancement in activity as well as an increase in selectivity for total oxidation. Furthermore, comparing alumina and ceria as support materials highlights the fact that reducible supports can result in a strong increase in oxygen carrier utilization.

  6. Physical and mechanical metallurgy of NiAl

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.; Bowman, Randy R.; Nathal, Michael V.

    1994-01-01

    Considerable research has been performed on NiAl over the last decade, with an exponential increase in effort occurring over the last few years. This is due to interest in this material for electronic, catalytic, coating and especially high-temperature structural applications. This report uses this wealth of new information to develop a complete description of the properties and processing of NiAl and NiAl-based materials. Emphasis is placed on the controlling fracture and deformation mechanisms of single and polycrystalline NiAl and its alloys over the entire range of temperatures for which data are available. Creep, fatigue, and environmental resistance of this material are discussed. In addition, issues surrounding alloy design, development of NiAl-based composites, and materials processing are addressed.

  7. Catalytic Methane Decomposition over Fe-Al2 O3.

    PubMed

    Zhou, Lu; Enakonda, Linga Reddy; Saih, Youssef; Loptain, Sergei; Gary, Daniel; Del-Gallo, Pascal; Basset, Jean-Marie

    2016-06-01

    The presence of a Fe-FeAl2 O4 structure over an Fe-Al2 O3 catalysts is demonstrated to be vital for the catalytic methane decomposition (CMD) activity. After H2 reduction at 750 °C, Fe-Al2 O3 prepared by means of a fusion method, containing 86.5 wt % FeAl2 O4 and 13.5 wt % Fe(0) , showed a stable CMD activity at 750 °C for as long as 10 h. PMID:27159367

  8. Hydrogen-Resistant Fe/Ni/Cr-Base Superalloy

    NASA Technical Reports Server (NTRS)

    Bhat, Biliyar N.; Chen, Po-Shou; Panda, Binayak

    1994-01-01

    Strong Fe/Ni/Cr-base hydrogen- and corrosion-resistant alloy developed. Superalloy exhibits high strength and exceptional resistance to embrittlement by hydrogen. Contains two-phase microstructure consisting of conductivity precipitated phase in conductivity matrix phase. Produced in wrought, weldable form and as castings, alloy maintains high ductility and strength in air and hydrogen. Strength exceeds previously known Fe/Cr/Ni hydrogen-, oxidation-, and corrosion-resistant alloys. Provides higher strength-to-weight ratios for lower weight in applications as storage vessels and pipes that must contain hydrogen.

  9. Bimetallic FeNi concave nanocubes and nanocages.

    PubMed

    Moghimi, Nafiseh; Abdellah, Marwa; Thomas, Joseph Palathinkal; Mohapatra, Mamata; Leung, K T

    2013-07-31

    Concave nanostructures are rare because of their thermodynamically unfavorable shapes. We prepared bimetallic FeNi concave nanocubes with high Miller index planes through controlled triggering of the different growth kinetics of Fe and Ni. Taking advantage of the higher activity of the high-index planes, we then fabricated monodispersed concave nanocages via a material-independent electroleaching process. With the high-index facets exposed, these concave nanocubes and nanocages are 10- and 100-fold more active, respectively, toward electrodetection of 4-aminophenol than cuboctahedrons, providing a label-free sensing approach for monitoring toxins in water and pharmaceutical wastes. PMID:23837524

  10. Effects of two-temperature model on cascade evolution in Ni and NiFe

    DOE PAGESBeta

    Samolyuk, German D.; Xue, Haizhou; Bei, Hongbin; Weber, William J.

    2016-07-05

    We perform molecular dynamics simulations of Ni ion cascades in Ni and equiatomic NiFe under the following conditions: (a) classical molecular dynamics (MD) simulations without consideration of electronic energy loss, (b) classical MD simulations with the electronic stopping included, and (c) using the coupled two-temperature MD (2T-MD) model that incorporates both the electronic stopping and the electron-phonon interactions. Our results indicate that the electronic e ects are more profound in the higher energy cascades and that the 2T-MD model results in a smaller amount of surviving damage and smaller defect clusters, while less damage is produced in NiFe than inmore » Ni.« less

  11. Atomistic Modeling of RuAl and (RuNi) Al Alloys

    NASA Technical Reports Server (NTRS)

    Gargano, Pablo; Mosca, Hugo; Bozzolo, Guillermo; Noebe, Ronald D.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Atomistic modeling of RuAl and RuAlNi alloys, using the BFS (Bozzolo-Ferrante-Smith) method for alloys is performed. The lattice parameter and energy of formation of B2 RuAl as a function of stoichiometry and the lattice parameter of (Ru(sub 50-x)Ni(sub x)Al(sub 50)) alloys as a function of Ni concentration are computed. BFS based Monte Carlo simulations indicate that compositions close to Ru25Ni25Al50 are single phase with no obvious evidence of a miscibility gap and separation of the individual B2 phases.

  12. Tuning of interlayer exchange coupling in Ni80Fe20/Ru/Ni80Fe20 nanowires

    NASA Astrophysics Data System (ADS)

    Liu, X. M.; Lupo, P.; Cottam, M. G.; Adeyeye, A. O.

    2015-09-01

    In this work, we demonstrate how the static and dynamic properties of Ni80Fe20/Ru/Ni80Fe20 nanowires can be tuned by varying the Ru spacer layer thickness. Specifically, changing the Ru thickness we have tuned the Ruderman-Kittel-Kasuya-Yosida exchange interaction, and thus the antiferromagnetic (AFM) strength between the Ni80Fe20 layers. We show that there is a strong correlation between the interlayer coupling and features in ferromagnetic resonance (FMR) modes. We found different mode-softening degree of the FMR curves as function of the strength of AFM coupling, together with a clear frequency gap at around zero field. These experimental results are in qualitative agreement with presented micromagnetic simulations that also include biquadratic interface exchange. Understanding these characteristics may offer insights for reconfigurable vertical magnetic logic devices and microwave filters.

  13. Stripe-to-bubble transition of magnetic domains at the spin reorientation of (Fe/Ni)/Cu/Ni/Cu(001)

    SciTech Connect

    Wu, J.; Choi, J.; Won, C.; Wu, Y. Z.; Scholl, A.; Doran, A.; Hwang, Chanyong; Qiu, Z.

    2010-06-09

    Magnetic domain evolution at the spin reorientation transition (SRT) of (Fe/Ni)/Cu/Ni/Cu(001) is investigated using photoemission electron microscopy. While the (Fe/Ni) layer exhibits the SRT, the interlayer coupling of the perpendicularly magnetized Ni layer to the (Fe/Ni) layer serves as a virtual perpendicular magnetic field exerted on the (Fe/Ni) layer. We find that the perpendicular virtual magnetic field breaks the up-down symmetry of the (Fe/Ni) stripe domains to induce a net magnetization in the normal direction of the film. Moreover, as the virtual magnetic field increases to exceed a critical field, the stripe domain phase evolves into a bubble domain phase. Although the critical field depends on the Fe film thickness, we show that the area fraction of the minority domain exhibits a universal value that determines the stripe-to-bubble phase transition.

  14. Snoek peaks of carbon in Fe-Ni meteorites.

    NASA Astrophysics Data System (ADS)

    Weller, M.; Wert, C.

    1996-12-01

    Most Fe-Ni meteorites are a two phase mixture of fcc and bcc phases. The authors secured six samples of Fe contents from 95% to 85% all of which were thought to contain small amounts of carbon. They found no Snoek peaks in the as-received condition for any of the six. After being heated and cooled, three showed pronounced Snoek peaks, three showed no Snoek peaks.

  15. A ternary Ni-Al-W EAM potential for Ni-based single crystal superalloys

    NASA Astrophysics Data System (ADS)

    Fan, Qin-Na; Wang, Chong-Yu; Yu, Tao; Du, Jun-Ping

    2015-01-01

    Based on experiments and first-principles calculations, a ternary Ni-Al-W embedded-atom-method (EAM) potential is constructed for the Ni-based single crystal superalloys. The potential predicts that W atoms do not tend to form clusters in γ(Ni), which is consistent with experiments. The impurity diffusion of W in γ(Ni) is investigated using the five-frequency model. The diffusion coefficients and the diffusion activation energy of W are in reasonable agreement with the data in literatures. By W doping, the lattice misfit between the two phases decreases and the elastic constants of γ‧(Ni3Al) increase. As for alloyed elements Co, Re and W, the pinning effect of solute atom on the γ(Ni)/γ‧(Ni3Al) misfit dislocation increases with the increasing of the atomic radius.

  16. Effect of phosphate and sulfate on Ni repartitioning during Fe(II)-catalyzed Fe(III) oxide mineral recrystallization

    NASA Astrophysics Data System (ADS)

    Hinkle, Margaret A. G.; Catalano, Jeffrey G.

    2015-09-01

    Dissolved Fe(II) activates coupled oxidative growth and reductive dissolution of Fe(III) oxide minerals, causing recrystallization and the repartitioning of structurally-compatible trace metals. Phosphate and sulfate, two ligands common to natural aquatic systems, alter Fe(II) adsorption onto Fe(III) oxides and affect Fe(III) oxide dissolution and precipitation. However, the effect of these oxoanions on trace metal repartitioning during Fe(II)-catalyzed Fe(III) oxide recrystallization is unclear. The effects of phosphate and sulfate on Ni adsorption and Ni repartitioning during Fe(II)-catalyzed Fe(III) oxide recrystallization were investigated as such repartitioning may be affected by both Fe(II)-oxoanion and metal-oxoanion interactions. In most systems examined, phosphate alters Ni repartitioning during Fe(II)-catalyzed recrystallization to a larger extent than sulfate. Phosphate substantially enhances Ni adsorption onto hematite but decreases (nearly inhibiting) Fe(II)-catalyzed Ni incorporation into and release from this mineral. In the goethite system, however, phosphate suppresses Ni release but enhances Ni incorporation in the presence of aqueous Fe(II). In contrast, sulfate has little effect on macroscopic Ni adsorption and release of Ni from Fe(III) oxides, but substantially enhances Ni incorporation into goethite. This demonstrates that phosphate and sulfate have unique, mineral-specific interactions with Ni during Fe(II)-catalyzed Fe(III) oxide recrystallization. This research suggests that micronutrient bioavailability at redox interfaces in hematite-dominated systems may be especially suppressed by phosphate, while both oxoanions likely have limited effects in goethite-rich soils or sediments. Phosphate may also exert a large control on contaminant fate at redox interfaces, increasing Ni retention on iron oxide surfaces. These results further indicate that trace metal retention by iron oxides during lithification and later repartitioning during

  17. Growth in solution of hooked Ni-Fe fibers by oriented rotation and attachment approaches

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Liu, Fang; Zhang, Wei-ze

    2016-04-01

    Inspired by the curved branches of fractal trees, hooked Ni-Fe fibers were grown in situ in Ni-Fe composite coatings on a spheroidal graphite cast iron substrate. These hooked Ni-Fe fibers exhibited inclination angles of about 39°, which was in accordance with the theoretical prediction of 37°. Ni-Fe nanostructures self-assembled to form dendrites and evolved into hooked fibers by an oriented attachment reaction. The orientation rotation of Ni-Fe nanostructures played an important role in the growth of curved hooked Ni-Fe fibers. During sliding wear tests, the volume loss of the spheroidal graphite cast iron substrate was 2.2 times as large as that of the Ni-Fe coating reinforced by hooked fibers. The good load-transferring ability of hooked Ni-Fe fibers led to an improvement in their wear properties during wear tests.

  18. Effect of boron on the fracture behavior and grain boundary chemistry of Ni3Fe

    SciTech Connect

    Liu, Y.; Liu, Chain T; Heatherly Jr, Lee; George, Easo P

    2011-01-01

    The effect of B on the fracture behavior of Ni{sub 3}Fe alloys (24 and 26 at.% Fe) was studied after cathodic charging with hydrogen. In contrast to its disordered state, ordered Ni{sub 3}Fe underwent brittle intergranular fracture at room temperature. Boron addition changed its fracture mode to predominantly ductile transgranular. The grain boundary chemistry of ordered Ni{sub 3}Fe was analyzed by Auger electron spectroscopy. Boron was found to segregate to the grain boundaries of both Ni-24Fe and Ni-26Fe and reduce the hydrogen-induced embrittlement of these alloys in the ordered state.

  19. Ferromagnetic Fe2CrAl Nanowires

    NASA Astrophysics Data System (ADS)

    Dulal, Rajendra; Dahal, Bishnu; Pegg, Ian L.; Philip, John

    Heusler alloy Fe2CrAl (FCA) nanowires were grown on silicon substrates. Nanowires have diameters in the range 50 to 200 nm and lengths up to 100 µm. They exhibit cubic L21 and A2 type structure with a space group, Pm m. Magnetic characterization reveals that they display ferromagnetic behavior and has a Curie temperature above 400 K. Magnetic behavior of FCA nanowires is different from the reported bulk behavior. Bulk FCA with L21 structure has a Curie temperature around 274 K. National Science Foundation under ECCS-0845501 and NSF-MRI, DMR-0922997.

  20. Interdiffusion in nanometric Fe/Ni multilayer films

    SciTech Connect

    Liu, Jiaxing Barmak, Katayun

    2015-03-15

    [Fe (3.1 nm)/Ni (3.3 nm)]{sub 20} multilayer films were prepared by DC magnetron sputtering onto oxidized Si(100) substrates. The Fe and Ni layers were shown to both be face-centered cubic by x-ray diffraction. Interdiffusion of the Fe and Ni layers in the temperature range of 300–430 °C was studied by x-ray reflectivity. From the decay of the integral intensity of the superlattice peak, the activation energy and the pre-exponential term for the effective interdiffusion coefficient were determined as to 1.06 ± 0.07 eV and 5 × 10{sup −10} cm{sup 2}/s, respectively. The relevance of the measured interdiffusion coefficient to the laboratory timescale synthesis of L1{sub 0} ordered FeNi as a rare-earth free permanent magnet is discussed.

  1. Synthesis, characterization and mechanical properties of nanocrystalline NiAl

    SciTech Connect

    Choudry, M. |; Eastman, J.A.; DiMelfi, R.J.; Dollar, M.

    1996-11-01

    Nanocrystalline NiAl was produced from pre-cast alloys using an electron beam inert gas condensation system. In-situ compaction was carried out at 100-300 C under vacuum conditions. Energy dispersive spectroscopy was used to determine chemical composition and homogeneity. Average grain sizes in the range 4-10 nm were found from TEM dark field analyses. A compression-cage fixture was designed to perform disk bend tests. These tests revealed substantial room temperature ductility in nanocrystalline NiAl, while coarse grained NiAl showed no measurable room temperature ductility.

  2. Powder processing of NiAl for elevated temperature strength

    SciTech Connect

    Whittenberger, J.D.; Hebsur, M.; Grahle, P.; Arzt, E.; Behr, R.; Zoeltzer, K.

    1997-12-31

    In an effort to superimpose two different elevated temperature strengthening mechanisms in NiAl, one lot of an oxide dispersion strengthened (ODS) NiAl powder has been milled in liquid nitrogen (cryomilled) to introduce AlN particles at the grain boundaries, and a second lot of ODS powder was simply roasted in gaseous nitrogen as an alternative means to produce AlN reinforced grain boundaries. Powder from both of these lots as well as the starting material have been consolidated by hot extrusion and tested at 1,300 K. Both nitrogen roasting and cryomilling produced AlN within the ODS NiAl matrix which strengthened the alloy; however, based on the AlN content, cryomilling is more effective.

  3. LPE growth of Mn, Ni- and Al-substituted copper ferrite films

    NASA Astrophysics Data System (ADS)

    van der Straten, P. J. M.; Metselaar, R.

    1980-06-01

    Single-crystalline Mn-, Ni-, and Al-substituted copper ferrite films are grown by the LPE method from a PbO-B2O3 flux on (111)-MgO substrates. Solid solutions between copper ferrite and Mn3O4, NiFe2O4, and CuAl2O4 are obtained. The segregation coefficients for Ni and Al are shown to be linearly dependent on the growth temperature. From domain-structure observations and from torque measurements it is concluded that a positive uniaxial anisotropy is present in the copper ferrite films. After stress relief at the deposition temperature a stress develops during cooling to room temperature due to a difference in thermal expansion coefficients of film and substrate. This stress is responsible for the observed anisotropy.

  4. Reaction synthesis of Ni-Al based particle composite coatings

    SciTech Connect

    SUSAN,DONALD F.; MISIOLEK,WOICECK Z.; MARDER,ARNOLD R.

    2000-02-11

    Electrodeposited metal matrix/metal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles. By optimizing the process parameters, coatings were deposited with 20 volume percent aluminum particles. Coating morphology and composition were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on coating phase formation was studied in the temperature range 415 to 1,000 C. Long-time exposure at low temperature results in the formation of several intermetallic phases at the Ni matrix/Al particle interfaces and concentrically around the original Al particles. Upon heating to the 500--600 C range, the aluminum particles react with the nickel matrix to form NiAl islands within the Ni matrix. When exposed to higher temperatures (600--1,000 C), diffusional reaction between NiAl and nickel produces ({gamma})Ni{sub 3}Al. The final equilibrium microstructure consists of blocks of ({gamma}{prime})Ni{sub 3}Al in a {gamma}(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during intermetallic phase formation and microstructural development is discussed with reference to reaction synthesis of bulk nickel aluminides.

  5. Modeling of Ternary Element Site Substitution in NiAl

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Honecy, Frank

    2000-01-01

    It is well recognized that ternary alloying additions can have a dramatic impact on the behavior of ordered intermetallic alloys such as nickel aluminides. Properties as diverse as yield strength, fracture strength, fracture mode, cyclic oxidation resistance, creep strength, and thermal and electrical diffusivity can change by orders of magnitude when a few percent or less of a ternary element is added. Yet our understanding of the resulting point defect structures and the simple site preferences of ternary alloying additions is poor because these are extremely difficult characteristics to determine. This disconnection between the understanding of the structure and properties in ordered alloys is at least in part responsible for the limited development and commercialization of these materials. Theoretical methods have provided useful but limited insight in this area, since most techniques suffer from constraints in the type of elements and the crystallographic structures that can be modeled. In an effort to overcome these limitations, the Bozzolo-Ferrante-Smith (BFS) method for alloys was designed. After a brief description of this approximate quantum mechanical approach, we use BFS to investigate the energetics of Si, Ti, V, Cr, Fe, Co, Cu, Zr, Nb, Mo, Ru, Hf, Ta and W additions to B2-ordered, stoichiometric NiAl. In addition to determining the site preference for these alloying additions over a range of compositions, we include results for the concentration dependence of the lattice parameter. In this introductory paper, we performed our analyses in the absence of constitutional and thermal vacancies for alloys of the form Ni50(Al,X)50. Where data exist, a comparison between experimental, theoretical, and BFS results is also included.

  6. Overview of the development of FeAl intermetallic alloys

    SciTech Connect

    Maziasz, P.J.; Liu, C.T.; Goodwin, G.M.

    1995-09-01

    B2-phase FeAl ordered intermetallic alloys based on an Fe-36 at.% Al composition are being developed to optimize a combination of properties that includes high-temperature strength, room-temperature ductility, and weldability. Microalloying with boron and proper processing are very important for FeAl properties optimization. These alloys also have the good to outstanding resistance to oxidation, sulfidation, and corrosion in molten salts or chlorides at elevated temperatures, characteristic of FeAl with 30--40 at.% Al. Ingot- and powder-metallurgy (IM and PM, respectively) processing both produce good properties, including strength above 400 MPa up to about 750 C. Technology development to produce FeAl components for industry testing is in progress. In parallel, weld-overlay cladding and powder coating technologies are also being developed to take immediate advantage of the high-temperature corrosion/oxidation and erosion/wear resistance of FeAl.

  7. High temperature stability, interface bonding, and mechanical behavior in (beta)-NiAl and Ni3Al matrix composites with reinforcements modified by ion beam enhanced deposition

    NASA Astrophysics Data System (ADS)

    Grummon, D. S.

    1992-01-01

    In preparation for experiments with surface modified Al2O3 reinforcements in (beta)NiAl, diffusion bonding experiments were conducted. FP alumina fibers were prepared with ion sputtered surface films (Al2O3, Al, Ni) and then composited with (beta)NiAl slabs and hot pressed. After 70 thermal cycles, interfacial shear strength was measured. A roughness mechanism is proposed for the observed increased strength of the coated fibers. Creep in Ni3Al was studied.

  8. Development of weldable, corrosion-resistant iron-aluminide (FeAl) alloys

    SciTech Connect

    Maziasz, P.J.; Goodwin, G.M.; Wang, X.L.; Alexander, D.J.

    1997-04-01

    A boron-microalloyed FeAl alloy (Fe-36Al-0.2Mo-0.05Zr-0.13C, at.%, with 100-400 appm B) with improved weldability and mechanical properties was developed in FY 1994. A new scale-up and industry technology development phase for this work began in FY 1995, pursuing two parallel paths. One path was developing monolithic FeAl component and application technology, and the other was developing coating/cladding technology for alloy steels, stainless steels and other Fe-Cr-Ni alloys. In FY 1995, it was found that cast FeAl alloys had good strength at 700-750{degrees}C, and some (2.5%) ductility in air at room-temperature. Hot-extruded FeAl with refined grain size was found to have ductility and to also have good impact-toughness at room-temperature. Further, it was discovered that powder-metallurgy (P/M) FeAl, consolidated by direct hot-extrusion at 950-1000{degrees}C to have an ultra fine-grained microstructure, had the highest ductility, strength and impact-toughness ever seen in such intermetallic alloys.

  9. Improvement of in-plane anisotropy field in FeCoB/NiFe/Si thin films by Kr sputtering

    NASA Astrophysics Data System (ADS)

    Hashimoto, A.; Ito, S.; Nakagawa, S.

    2007-03-01

    Deterioration of magnetic anisotropy field in the FeCoB/NiFe/Si trilayers deposited on glass substrates was investigated. It was found that the choice of Kr as sputtering gas instead of Ar was quite effective to improve the soft magnetic characteristics of FeCoB/NiFe/Si thin films deposited on glass substrates. Kr sputtering is effective to reduce compressive residual stress in the film. The rotatable magnetic anisotropy observed in the FeCoB/NiFe/Si films deposited by Ar sputtering disappeared in the film deposited by Kr sputtering, even though they are prepared on glass disk substrates.

  10. Microstructure and strengthening of creep-tested cryomilled NiAl-AlN

    SciTech Connect

    Garg, A.; Whittenberger, J.D.; Luton, M.J.

    1997-12-31

    The B2 intermetallic NiAl is considered to be a prime candidate material for use as very high temperature structural components in gas turbine engines. The mechanical grinding of prealloyed NiAl powder in liquid nitrogen (cryomilling) results in an intermetallic matrix composite where micron sized particle free aluminide cores (grains) are surrounded by thin mantles comprised of nanometer sized AlN particles and NiAl grains. Under high temperature, slow strain rate conditions both compressive and tensile creep testing have shown that the mechanical strength of hot extruded cryomilled NiAl approaches the levels exhibited by advanced NiAl-based single crystals and simple Ni-based superalloys. Transmission electron microscopy of cryomilled materials tested between 1,100 and 1,300 K revealed little, if any, dislocation structure within the mantle regions, while the NiAl cores contained subgrains and dislocation networks after testing at all strain rates between 10{sup {minus}4} and 10{sup {minus}8} s{sup {minus}1}. These and other microstructural observations suggest that creep strength is the result of a fine NiAl grain/subgrain size, the inability of dislocations to move through the mantle and stabilization of the microstructure by the AlN particles.

  11. Effects of hydrogen absorption in TbNiAl and UNiAl

    SciTech Connect

    Bordallo, H.N.; Nakotte, H.; Schultz, A.; Kolomiets, A.V.; Havela, L.; Andreev, A.V.

    1998-12-31

    Although hydrides of intermetallic compounds are used extensively as hydrogen-storage media, little is known about the exact nature of metal-hydrogen interactions. However, this knowledge is of essential importance for the understanding of thermodynamics and other properties. Hydrides (deuterides) of TbNiAl and UNiAl have been widely studied because of drastic increase of magnetic ordering temperature under hydrogenation. Here the authors report neutron-diffraction results of the three deuterides, TbNiAlD{sub 1.28}, TbNiAlD{sub 0.8}a nd UNiAlD{sub 2.23}.

  12. Ultrahigh strength of dislocation-free Ni3Al nanocubes.

    PubMed

    Maaß, Robert; Meza, Lucas; Gan, Bin; Tin, Sammy; Greer, Julia R

    2012-06-25

    Individual Ni(3) Al nanocubes under pressure are investigated by comparing the compressive strength of both dislocation-free and irradiated Ni(3) Al nanocubes. The results are dicussed in light of the size-dependent and size-independent strength of face-centered cubic (fcc) nanocrystals in the framework of dislocation nucleation at free surfaces. This study sheds more light on the understanding of fundamental deformation mechanisms and size-affected strength in dislocation-free metallic nanocrystals. PMID:22454244

  13. Hierachical Ni@Fe2O3 superparticles through epitaxial growth of γ-Fe2O3 nanorods on in situ formed Ni nanoplates

    NASA Astrophysics Data System (ADS)

    Tahir, Muhammad Nawaz; Herzberger, Jana; Natalio, Filipe; Köhler, Oskar; Branscheid, Robert; Mugnaioli, Enrico; Ksenofontov, Vadim; Panthöfer, Martin; Kolb, Ute; Frey, Holger; Tremel, Wolfgang

    2016-05-01

    One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@γ-Fe2O3 superparticles were dispersible in water.One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@γ-Fe2O3 superparticles were dispersible in water. Electronic supplementary

  14. Engineering of high performance supercapacitor electrode based on Fe-Ni/Fe2O3-NiO core/shell hybrid nanostructures

    NASA Astrophysics Data System (ADS)

    Singh, Ashutosh K.; Mandal, Kalyan

    2015-03-01

    The present work reports on fabrication and supercapacitor applications of a core/shell Fe-Ni/Fe2O3-NiO hybrid nanostructures (HNs) electrode. The core/shell Fe-Ni/Fe2O3-NiO hybrid nanostructures have been fabricated through a two step method (nanowire fabrication and their controlled oxidation). The 1D hybrid nanostructure consists of highly porous shell layer (redox active materials NiO and Fe2O3) and the conductive core (FeNi nanowire). Thus, the highly porous shell layer allows facile electrolyte diffusion as well as faster redox reaction kinetics; whereas the conductive FeNi nanowire core provides the proficient express way for electrons to travel to the current collector, which helps in the superior electrochemical performance. The core/shell Fe-Ni/Fe2O3-NiO hybrid nanostructures electrode based supercapacitor shows very good electrochemical performances in terms of high specific capacitance nearly 1415 F g-1 at a current density of 2.5 A g-1, excellent cycling stability and rate capability. The high quality electrochemical performance of core/shell hybrid nanostructures electrode shows its potential as an alternative electrode for forthcoming supercapacitor devices.

  15. Engineering of high performance supercapacitor electrode based on Fe-Ni/Fe{sub 2}O{sub 3}-NiO core/shell hybrid nanostructures

    SciTech Connect

    Singh, Ashutosh K. E-mail: aksingh@bose.res.in; Mandal, Kalyan

    2015-03-14

    The present work reports on fabrication and supercapacitor applications of a core/shell Fe-Ni/Fe{sub 2}O{sub 3}-NiO hybrid nanostructures (HNs) electrode. The core/shell Fe-Ni/Fe{sub 2}O{sub 3}-NiO hybrid nanostructures have been fabricated through a two step method (nanowire fabrication and their controlled oxidation). The 1D hybrid nanostructure consists of highly porous shell layer (redox active materials NiO and Fe{sub 2}O{sub 3}) and the conductive core (FeNi nanowire). Thus, the highly porous shell layer allows facile electrolyte diffusion as well as faster redox reaction kinetics; whereas the conductive FeNi nanowire core provides the proficient express way for electrons to travel to the current collector, which helps in the superior electrochemical performance. The core/shell Fe-Ni/Fe{sub 2}O{sub 3}-NiO hybrid nanostructures electrode based supercapacitor shows very good electrochemical performances in terms of high specific capacitance nearly 1415 F g{sup −1} at a current density of 2.5 A g{sup −1}, excellent cycling stability and rate capability. The high quality electrochemical performance of core/shell hybrid nanostructures electrode shows its potential as an alternative electrode for forthcoming supercapacitor devices.

  16. Crystallinity of Fe-Ni Sulfides in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Ohsumi, Kazumasa; Mikouchi, Takashi; Hagiya, Kenji; Le, Loan

    2008-01-01

    The main long-term goal of this research is to understand the physical conditions in the early solar nebula through the detailed characterization of a key class of mineral present in all primitive materials: Fe-Ni sulfides [1&2]. Fe-Ni sulfides can take dozens of structures, depending on the temperature of formation, as well as other physico-chemical factors which are imperfectly understood. Add to this the additional varying factor of Ni content, and we have a potentially sensitive cosmothermometer [3]. Unfortunately, this tool requires exact knowledge of the crystal structure of each grain being considered, and there have been few (none?) studies of the detailed structures of sulfides in chondritic materials. We report here on coordinated compositional and crystallographic investigation of Fe-Ni sulfides in diverse carbonaceous chondrites, initially Acfer 094 (the most primitive CM2 [4]) Tagish Lake (a unique type C2 [5]), a C1 lithology in Kaidun [6], Bali (oxidized CV3 [7]), and Efremovka (reduced CV3 [7]).

  17. Electrochemical sensing behaviour of Ni doped Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Suresh, R.; Giribabu, K.; Manigandan, R.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2014-01-01

    Ni doped Fe3O4 nanoparticles were synthesized by simple hydrothermal method. The prepared nanomaterials were characterized by X-ray diffraction analysis, DRS-UV-Visible spectroscopy and field emission scanning electron microscopy. The XRD confirms the phase purity of the synthesized Ni doped Fe3O4 nanoparticles. The optical property of Ni doped Fe3O4 nanoparticles were studied by DRS UV-Visible analysis. The electrochemical sensing property of pure and Ni doped Fe3O4 nanoparticles were examined using uric acid as an analyte. The obtained results indicated that the Ni doped Fe3O4 nanoparticles exhibited higher electrocatalytic activity towards uric acid.

  18. Transition-metal and metalloid substitutions in L1(0)-ordered FeNi

    SciTech Connect

    Manchanda, P; Skomski, R; Bordeaux, N; Lewis, LH; Kashyap, A

    2014-05-07

    The effect of atomic substitutions on the magnetization, exchange, and magnetocrystalline anisotropy energy of L1(0)-ordered FeNi (tetrataenite) is computationally investigated. The compound naturally occurs in meteorites but has attracted renewed attention as a potential material for permanent magnets, and elemental additives will likely be necessary to facilitate the phase formation. Our density functional theory calculations use the Vienna ab-initio simulation package, applied to 4-atom unit cells of Fe2XNi and 32-atom supercells (X = Al, P, S, Ti, V, Cr, Mn, Fe, Co). While it is found that most additives deteriorate the magnetic properties, there are exceptions: excess substitutional Fe and Co additions improve the magnetization, whereas Cr, S, and interstitial B additions improve the magnetocrystalline anisotropy. (C) 2014 AIP Publishing LLC.

  19. Transition-metal and metalloid substitutions in L1{sub 0}-ordered FeNi

    SciTech Connect

    Manchanda, Priyanka; Skomski, Ralph; Bordeaux, N.; Lewis, L. H.; Kashyap, Arti

    2014-05-07

    The effect of atomic substitutions on the magnetization, exchange, and magnetocrystalline anisotropy energy of L1{sub 0}-ordered FeNi (tetrataenite) is computationally investigated. The compound naturally occurs in meteorites but has attracted renewed attention as a potential material for permanent magnets, and elemental additives will likely be necessary to facilitate the phase formation. Our density functional theory calculations use the Vienna ab-initio simulation package, applied to 4-atom unit cells of Fe{sub 2}XNi and 32-atom supercells (X = Al, P, S, Ti, V, Cr, Mn, Fe, Co). While it is found that most additives deteriorate the magnetic properties, there are exceptions: excess substitutional Fe and Co additions improve the magnetization, whereas Cr, S, and interstitial B additions improve the magnetocrystalline anisotropy.

  20. Free energies of (Co, Fe, Ni, Zn)Fe2O4 spinels and oxides in water at high temperatures and pressure from density functional theory: results for stoichiometric NiO and NiFe2O4 surfaces

    NASA Astrophysics Data System (ADS)

    O'Brien, C. J.; Rák, Z.; Brenner, D. W.

    2013-11-01

    A set of effective chemical potentials (ECPs) are derived that connect energies of (Co, Fe, Ni, Zn)Fe2O4 spinels and oxides calculated at 0 K from density functional theory (DFT) to free energies in high temperature and pressure water. The ECPs are derived and validated by solving a system of linear equations that combine DFT and experimental free energies for NiO, ZnO, Fe2O3, Fe3O4, FeO(OH), CoFe2O4, ZnFe2O4, NiFe2O4 and H2O. To connect to solution phase chemistry, a set of ECPs are also derived for solvated Ni2+, Zn2+, Fe2+ and Fe3+ ions using an analogous set of linear equations and the solid ECPs. The ECPs are used to calculate free energies of low index stoichiometric surfaces of nickel oxide (NiO) and nickel ferrite (NiFe2O4) in water as a function of temperature from 300 to 600 K at a pressure of 155 bar. Surface denuding at high temperatures is predicted, the implications of which for the formation of oxide corrosion products on heat transfer surfaces in light-water nuclear reactors are discussed.

  1. Hydriding of TiZrNiFe nanocompounds

    NASA Astrophysics Data System (ADS)

    Żywczak, A.; Shinya, Daigo; Gondek, Ł.; Takasaki, Akito; Figiel, H.

    2010-01-01

    Ti-based quasicrystals belong to the second largest group of the stable quasicrystals, showing attractive properties as hydrogen storage materials. The Ti 45Zr 38Ni 17 intermetallic compound forms an icosahedral ( i-phase) structure, in which Ti and Zr atoms possess very good chemical affinity for hydrogen absorption. We modified the Ti 45Zr 38Ni 17 compounds by substituting 3d metals (iron) for Ni to obtain amorphous phase. The samples were produced by mechanical alloying. The 3d metal atoms are located in the same positions as nickel. The structural characterization was made by means of XRD measurements. Thermodynamic properties were studied by differential scanning calorimetry (DSC) and thermal desorption spectroscopy (TDS). The obtained amorphous phases Ti 45Zr 38Ni (9,13)Fe (8,4) transform to the i-phase at the similar temperature range as Ti 45Zr 38Ni 17. The final concentration of absorbed hydrogen depends on the amount of Fe. When increasing the amount of iron, the hydrogen release temperature becomes lower. After hydriding, the samples decompose into simple metal hydrides.

  2. Energetic ion bombarded Fe/Al multilayers

    SciTech Connect

    Al-Busaidy, M.S.; Crapper, M.D.

    2006-05-15

    The utility of ion-assisted deposition is investigated to explore the possibility of counteracting the deficiency of back-reflected current of Ar neutrals in the case of lighter elements such as Al. A range of energetically ion bombarded Fe/Al multilayers sputtered with applied surface bias of 0, -200, or -400 V were deposited onto Si(111) substrates in an argon atmosphere of 4 mTorr using a computer controlled dc magnetron sputtering system. Grazing incidence reflectivity and rocking curve scans by synchrotron x rays of wavelength of 1.38 A were used to investigate the structures of the interfaces produced. Substantial evidence has been gathered to suggest the gradual suppression of interfacial mixing and reduction in interfacial roughness with increases of applied bias. The densification of the Al microstructure was noticeable and may be a consequence of resputtering attributable to the induced ion bombardment. The average interfacial roughnesses were calculated for the 0, -200, and -400 V samples to be 7{+-}0.5, 6{+-}0.5, and 5{+-}0.5 A respectfully demonstrating a 30% improvement in interface quality. Data from rocking curve scans point to improved long-range correlated roughness in energetically deposited samples. The computational code based on the recursive algorithm developed by Parratt [Phys. Rev. 95, 359 (1954)] was successful in the simulation of the specular reflectivity curves.

  3. Alloying of cold-sprayed Al Ni composite coatings by post-annealing

    NASA Astrophysics Data System (ADS)

    Lee, Ha Yong; Jung, Se Hun; Lee, Soo Yong; Ko, Kyung Hyun

    2007-01-01

    A new cold spray coating technique for thick Al coating with finely dispersed Al-Ni intermetallic compounds was tested. For easy powder preparation and high yield, rather than using of Al/compound mixture feed stock, the spraying of pure Al and Ni powders mixture followed by post-annealing was suggested. The powder composition of Al and Ni was 75:25, and 90:10 (wt.%) to expect full consumption of pure Ni into intermetallic compounds. After Al-Ni composite coatings, the Ni particles were finely dispersed and embedded in the Al matrix with a good coating yield. Above 450 °C of post-annealing temperature, the Al 3Ni and Al 3Ni 2 phases were observed in the cold-sprayed Al-Ni coatings. The Ni particles in the Al matrix were fully consumed via compounding reaction with Al at 550 °C of the annealing temperature.

  4. Synthesis and characterization of the NiFe2O4/Ni3Fe nanocomposite powder and compacts obtained by mechanical milling and spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Marinca, T. F.; Neamţu, B. V.; Popa, F.; Tarţa, V. F.; Pascuta, P.; Takacs, A. F.; Chicinaş, I.

    2013-11-01

    Nanocomposite powder and compacts of NiFe2O4/Ni3Fe type were synthesized using mechanical milling and spark plasma sintering (SPS) techniques. The samples have been investigated by X-ray diffraction (XRD), laser particles size analysis, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The nanocomposite powder was obtained by mechanical milling in a high planetary ball mill of nanocrystalline NiFe2O4 and nanocrystalline Ni3Fe powders. The nanocomposite powder consists from Ni3Fe particles covered at the surface with a layer of NiFe2O4 fine particles and NiFe2O4 particles. The nanocomposite particles have the median diameter d50 of 1.6 μm. The sintering in 400-600 °C temperature range preserve the nanocomposite phases but lead to a high porosity. The nanocomposite compacts consist in Ni3Fe clusters surrounded by NiFe2O4. A sintering temperature of 800 °C leads to a good density for the nanocomposite compacts and to the new phase formation. The new phase is a wustite type (Fe1-xNixO) and is formed at the metal/ceramic interface. A change in the Ni/Fe ratio, in the spinel structure, was evidenced during sintering. Sintering at a temperature of 800 °C, leads to the formation of a mixed iron-nickel ferrite with a very small amount of nickel, Ni1-xFexFe2O4.

  5. Physicochemical investigation of NiAl with small molybdenum additions

    NASA Technical Reports Server (NTRS)

    Troshkina, V. A.; Kucherenko, L. A.; Fadeeva, V. I.; Aristova, N. M.

    1982-01-01

    Specimens of four cast NiAl alloys, three of them containing 0.5, 1.0 and 1.5 at. % Mo., were homogenized for 10, 10, and 140 hr at 1373, 1523 and 1273 K, respectively, then kept at 1073, 1173 and 1323 K for 60, 120 and 3 hr, respectively, and quenched in icy water. The precipitation of a metastable Ni3Mo phase was observed at temperatures between 1073 and 1523 K. Molybdenum substituted for nickel was found to inhibit the lattice disordering in NiAl at 1073 and 1523 K.

  6. Analysis of NiAlTa precipitates in beta-NiAl + 2 at. pct Ta alloy

    NASA Technical Reports Server (NTRS)

    Pathare, V.; Michal, G. M.; Vedula, K.; Nathal, M. V.

    1987-01-01

    Results are reported from experiments performed to identify the precipitates, and their orientation in the matrix, in a beta-NiAl alloy containing 2 at. pct. Ta after undergoing creep test at 1300 K. Test specimens formed by extruding hot powders were compressed at 1300 K for about 50 hr at a strain rate averaging 6/1 million per sec. The specimens were then thinned and examined under an electron microscope and by X-ray diffractometry. An intermetallic NiAlTa compound with a hexagonal Cl4 structure appeared as second phase precipitates in the samples, exhibiting plate-like shapes and a habit plane close to (012). The prism planes of the hexagonal NiAlTa precipitates paralleled the closest packed planes in the cubic beta-NiAl matrix.

  7. Synthesis and properties of A{sub 6}B{sub 2}(OH){sub 16}Cl{sub 2}.4H{sub 2}O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) materials for environmental applications

    SciTech Connect

    Dias, Anderson; Cunha, Lumena; Vieira, Andiara C.

    2011-09-15

    Highlights: {yields} A{sub 6}B{sub 2}(OH){sub 16}Cl{sub 2}.4H{sub 2}O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) materials were synthesized. {yields} Chemical synthesis produced different levels of crystallinity and ordering degree. {yields} Structural investigation by Raman scattering revealed a complex band structure. {yields} A strong correlation between band structure and ionic radius was determined. -- Abstract: Double layered hydroxide materials of composition A{sub 6}B{sub 2}(OH){sub 16}Cl{sub 2}.4H{sub 2}O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) were synthesized by chemical precipitation at 60 {sup o}C. Different levels of crystallinity and ordering degree were observed depending upon the chemical environment or the combination between divalent and trivalent cations. The results from high-resolution transmission electron microscopy revealed that nanostructured layered samples were obtained with interplanar spacing compatible with previous literature. Raman scattering was employed to investigate the complex band structure observed, particularly the lattice vibrations at lower frequencies, which is intimately correlated to the cationic radius of both divalent and trivalent ions. The results showed that strongly coordinated water and chloride ions besides highly structured hydroxide layers have a direct influence on the stability of the hydrotalcites. It was observed that transition and decomposition temperatures varied largely for different chemical compositions.

  8. A threonine stabilizes the NiC and NiR catalytic intermediates of [NiFe]-hydrogenase.

    PubMed

    Abou-Hamdan, Abbas; Ceccaldi, Pierre; Lebrette, Hugo; Gutiérrez-Sanz, Oscar; Richaud, Pierre; Cournac, Laurent; Guigliarelli, Bruno; De Lacey, Antonio L; Léger, Christophe; Volbeda, Anne; Burlat, Bénédicte; Dementin, Sébastien

    2015-03-27

    The heterodimeric [NiFe] hydrogenase from Desulfovibrio fructosovorans catalyzes the reversible oxidation of H2 into protons and electrons. The catalytic intermediates have been attributed to forms of the active site (NiSI, NiR, and NiC) detected using spectroscopic methods under potentiometric but non-catalytic conditions. Here, we produced variants by replacing the conserved Thr-18 residue in the small subunit with Ser, Val, Gln, Gly, or Asp, and we analyzed the effects of these mutations on the kinetic (H2 oxidation, H2 production, and H/D exchange), spectroscopic (IR, EPR), and structural properties of the enzyme. The mutations disrupt the H-bond network in the crystals and have a strong effect on H2 oxidation and H2 production turnover rates. However, the absence of correlation between activity and rate of H/D exchange in the series of variants suggests that the alcoholic group of Thr-18 is not necessarily a proton relay. Instead, the correlation between H2 oxidation and production activity and the detection of the NiC species in reduced samples confirms that NiC is a catalytic intermediate and suggests that Thr-18 is important to stabilize the local protein structure of the active site ensuring fast NiSI-NiC-NiR interconversions during H2 oxidation/production. PMID:25666617

  9. A Threonine Stabilizes the NiC and NiR Catalytic Intermediates of [NiFe]-hydrogenase*

    PubMed Central

    Abou-Hamdan, Abbas; Ceccaldi, Pierre; Lebrette, Hugo; Gutiérrez-Sanz, Oscar; Richaud, Pierre; Cournac, Laurent; Guigliarelli, Bruno; De Lacey, Antonio L.; Léger, Christophe; Volbeda, Anne; Burlat, Bénédicte; Dementin, Sébastien

    2015-01-01

    The heterodimeric [NiFe] hydrogenase from Desulfovibrio fructosovorans catalyzes the reversible oxidation of H2 into protons and electrons. The catalytic intermediates have been attributed to forms of the active site (NiSI, NiR, and NiC) detected using spectroscopic methods under potentiometric but non-catalytic conditions. Here, we produced variants by replacing the conserved Thr-18 residue in the small subunit with Ser, Val, Gln, Gly, or Asp, and we analyzed the effects of these mutations on the kinetic (H2 oxidation, H2 production, and H/D exchange), spectroscopic (IR, EPR), and structural properties of the enzyme. The mutations disrupt the H-bond network in the crystals and have a strong effect on H2 oxidation and H2 production turnover rates. However, the absence of correlation between activity and rate of H/D exchange in the series of variants suggests that the alcoholic group of Thr-18 is not necessarily a proton relay. Instead, the correlation between H2 oxidation and production activity and the detection of the NiC species in reduced samples confirms that NiC is a catalytic intermediate and suggests that Thr-18 is important to stabilize the local protein structure of the active site ensuring fast NiSI-NiC-NiR interconversions during H2 oxidation/production. PMID:25666617

  10. Structure, stability and magnetic properties of (NiAl)n(n≤6) clusters

    NASA Astrophysics Data System (ADS)

    Wen, Jun-Qing; Zhang, Jian-Min; Chen, Guo-Xiang; Zhang, Xiao-Zhen; Wen, Zhen-Yi

    2016-09-01

    In this paper, density functional theory with generalized gradient approximation (GGA) for the exchange-correlation potential has been used to calculate the energetically global-minimum geometries and electronic states of (NiAl)n(n≤6) clusters. Full structural optimizations, analysis of energy and frequency calculation are performed. The most stable structures of (NiAl)n clusters are all three-dimensional structures except NiAl. The average bond lengths of (NiAl)n clusters are larger than that of Ni2n, and are smaller than that of Al2n. The binding energy per atom of Ni2n and (NiAl)n has the same change trend, and that are larger than that of Al2n. Stability analysis shows that Ni8, (NiAl)2 and Al10 clusters have higher relative stability than other clusters. Mulliken analysis indicates that charges always transfer from Al atoms to Ni atoms, and the average charges of transfer from Al atoms to Ni atoms have a maximum at (NiAl)6, implying the strong interaction between Al and Ni atoms in (NiAl)6. The average atomic magnetic moments of (NiAl)n are smaller than that of true Ni2n. The analysis of the static polarizability shows that the electronic structures of (NiAl)n clusters tend to be compact with the increase of atoms.

  11. Radiation effects on interface reactions of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni)

    NASA Astrophysics Data System (ADS)

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; Rory Kennedy, J.

    2015-01-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 °C or 550 °C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reach the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick's laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.

  12. Radiation effects on interface reactions of U/Fe, U/(Fe+Cr), and U/(Fe+Cr+Ni)

    SciTech Connect

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; Rory Kennedy, J.

    2014-10-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 C or 550 C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reach the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.

  13. Radiation effects on interface reactions of U/Fe, U/(Fe+Cr), and U/(Fe+Cr+Ni)

    DOE PAGESBeta

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; et al

    2014-10-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 C or 550 C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reachmore » the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.« less

  14. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy.

    PubMed

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B; Gee, Leland B; Scott, Aubrey D; Yoda, Yoshitaka; Tanaka, Yoshihito; Lubitz, Wolfgang; Cramer, Stephen P

    2015-01-01

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the (57)Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique 'wagging' mode involving H(-) motion perpendicular to the Ni(μ-H)(57)Fe plane was studied using (57)Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)(57)Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe-CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)(57)Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)(57)Fe(CO)3](+) and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H(-) binding Ni more tightly than Fe. The present methodology is also relevant to characterizing Fe-H moieties in other important natural and synthetic catalysts. PMID:26259066

  15. The electrodeposition of FeCrNi stainless steel: microstructural changes induced by anode reactions.

    PubMed

    Hasegawa, Madoka; Yoon, Songhak; Guillonneau, Gaylord; Zhang, Yucheng; Frantz, Cédric; Niederberger, Christoph; Weidenkaff, Anke; Michler, Johann; Philippe, Laetitia

    2014-12-21

    The FeCrNi alloy, whose composition is close to that of stainless steel 304, was prepared by electrodeposition and characterized. Nanocrystalline FeCrNi (nc-FeCrNi) was obtained by employing a double-compartment cell where the anode is separated from the cathode compartment, while amorphous FeCrNi (a-FeCrNi) was deposited in a conventional single electrochemical cell. The carbon content of nc-FeCrNi was found to be significantly lower than that of a-FeCrNi, suggesting that carbon inclusion is responsible for the change in the microstructure. The major source of carbon is associated with the reaction compounds at the anode electrode, presumably decomposed glycine. Crystal structure analysis by XRD and TEM revealed that the as-deposited nc-FeCrNi deposits consist of α-Fe which transforms to γ-Fe upon thermal annealing. Nanoindentation tests showed that nc-FeCrNi exhibits higher hardness than a-FeCrNi, which is consistent with the inverse Hall-Petch behavior. PMID:25367332

  16. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    NASA Astrophysics Data System (ADS)

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; Yoda, Yoshitaka; Tanaka, Yoshihito; Lubitz, Wolfgang; Cramer, Stephen P.

    2015-08-01

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique `wagging' mode involving H- motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe-CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H- binding Ni more tightly than Fe. The present methodology is also relevant to characterizing Fe-H moieties in other important natural and synthetic catalysts.

  17. Hybrid Al + Al3Ni metallic foams synthesized in situ via laser engineered net shaping

    NASA Astrophysics Data System (ADS)

    Zheng, Baolong; Li, Ying; Smugeresky, John E.; Zhou, Yizhang; Baker, Dean; Lavernia, Enrique J.

    2011-09-01

    A hybrid, Al + Al3Ni metallic foam was synthesized in situ via laser engineered net shaping (LENS®) of Ni-coated 6061 Al powder in the absence of a foaming agent. During LENS® processing, the Ni coating reacted with the Al matrix, resulting in the simultaneous formation of a fine dispersion of Al3Ni, and a high volume fraction of porosity. As a reinforcement phase, the intermetallic compound formed particles with a size range of 1-5 µm and a volume fraction of 63%, with accompanying 35-300 µm pores with a 60% volume fraction. The microstructure of the as-deposited Al + Al3Ni composite foams was characterized using SEM, EDS, XRD and TEM/HRTEM techniques. The evolution of the microstructure was analyzed on the basis of the thermal field present during deposition, paying particular attention to the thermodynamics of the Al3Ni intermetallic compound formation as well as discussing the mechanisms that may be responsible for the observed porosity. The mechanical behavior of the as-deposited material was characterized using compression and microhardness testing, indicating that the yield strength and hardness are 190 MPa and 320 HV, respectively, which represents an increase of over three times higher than that of annealed Al6061, or similar to heat-treated Al6061 fully dense matrix, and much higher than those of traditional Al alloy foams, and with a low density of 1.64 g/m3.

  18. Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation.

    PubMed

    Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

    2016-01-01

    Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance. PMID:27562023

  19. Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation

    PubMed Central

    Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

    2016-01-01

    Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance. PMID:27562023

  20. Analysis of Fe V and Ni V Wavelength Standards in the Vacuum Ultraviolet

    NASA Astrophysics Data System (ADS)

    Ward, Jacob Wolfgang; Nave, Gillian

    2015-01-01

    The recent publication[1] by J.C. Berengut et al. tests for a potential variation in the fine-structure constant in the presence of high gravitational potentials through spectral analysis of white-dwarf stars.The spectrum of the white-dwarf star studied in the paper, G191-B2B, has prominent Fe V and Ni V lines, which were used to determine any variation in the fine-structure constant via observed shifts in the wavelengths of Fe V and Ni V in the vacuum ultraviolet region. The results of the paper indicate no such variation, but suggest that refined laboratory values for the observed wavelengths could greatly reduce the uncertainty associated with the paper's findings.An investigation of Fe V and Ni V spectra in the vacuum ultraviolet region has been conducted to reduce wavelength uncertainties currently limiting modern astrophysical studies of this nature. The analyzed spectra were produced by a sliding spark light source with electrodes made of invar, an iron nickel alloy, at peak currents of 750-2000 A. The use of invar ensures that systematic errors in the calibration are common to both species. The spectra were recorded with the NIST Normal Incidence Vacuum Spectrograph on phosphor image plate and photographic plate detectors. Calibration was done with a Pt II spectrum produced by a Platinum Neon Hollow Cathode lamp.[1] J. C. Berengut, V. V. Flambaum, A. Ong, et al Phys. Rev. Lett. 111, 010801 (2013)

  1. Hierachical Ni@Fe2O3 superparticles through epitaxial growth of γ-Fe2O3 nanorods on in situ formed Ni nanoplates.

    PubMed

    Tahir, Muhammad Nawaz; Herzberger, Jana; Natalio, Filipe; Köhler, Oskar; Branscheid, Robert; Mugnaioli, Enrico; Ksenofontov, Vadim; Panthöfer, Martin; Kolb, Ute; Frey, Holger; Tremel, Wolfgang

    2016-05-01

    One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@γ-Fe2O3 superparticles were dispersible in water. PMID:26818395

  2. Atomistic Simulations of Ti Additions to NiAl

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Garg, Anita; Ferrante, John; Amador, Carlos

    1997-01-01

    The development of more efficient engines and power plants for future supersonic transports depends on the advancement of new high-temperature materials with temperature capabilities exceeding those of Ni-based superalloys. Having theoretical modelling techniques to aid in the design of these alloys would greatly facilitate this development. The present paper discusses a successful attempt to correlate theoretical predictions of alloy properties with experimental confirmation for ternary NiAl-Ti alloys. The B.F.S. (Bozzolo-Ferrante-Smith) method for alloys is used to predict the solubility limit and site preference energies for Ti additions of 1 to 25 at.% to NiAl. The results show the solubility limit to be around 5% Ti, above which the formation of Heusler precipitates is favored. These results were confirmed by transmission electron microscopy performed on a series of NiAl-Ti alloys.

  3. Atomistic simulations of Ti additions to NiAl

    SciTech Connect

    Bozzolo, G.; Noebe, R.D.; Garg, A.; Ferrante, J.; Amador, C.

    1997-12-31

    The development of more efficient engines and power plants for future supersonic transports depend on the advancement of new high-temperature materials with temperature capabilities exceeding those of Ni-based superalloys. Having theoretical modelling techniques to aid in the design of these alloys would greatly facilitate this development. The present paper discusses a successful attempt to correlate theoretical predictions of alloy properties with experimental confirmation for ternary NiAl-Ti alloys. The B.F.S. (Bozzolo- Ferrante-Smith) method for alloys is used to predict the solubility limit and site preference energies for Ti additions of 1 to 25 at. % to NiAl. The results show the solubility limit to be around 5% Ti, above which the formation of Heusler precipitates is favored. These results were confirmed by transmission electron microscopy performed on a series of NiAl-Ti alloys.

  4. Infrared thermography videos of the elastocaloric effect for shape memory alloys NiTi and Ni2FeGa

    PubMed Central

    Pataky, Garrett J.; Ertekin, Elif; Sehitoglu, Huseyin

    2015-01-01

    Infrared thermogrpahy was utilized to record the temperature change during tensile loading cycles of two shape memory alloy single crystals with pseudoelastic behavior. During unloading, a giant temperature drop was measured in the gage section due to the elastocaloric effect. This data article provides a video of a [001] oriented Ni2FeGa single crystal, including the corresponding stress–strain curve, shows the temperature drop over one cycle. The second video of a [148] oriented NiTi single crystal depicts the repeatability of the elastocaloric effect by showing two consecutive cycles. The videos are supplied in this paper. For further analysis and enhanced discussion of large temperature change in shape memory alloys, see Pataky et al. [1] PMID:26380838

  5. Infrared thermography videos of the elastocaloric effect for shape memory alloys NiTi and Ni2FeGa.

    PubMed

    Pataky, Garrett J; Ertekin, Elif; Sehitoglu, Huseyin

    2015-12-01

    Infrared thermogrpahy was utilized to record the temperature change during tensile loading cycles of two shape memory alloy single crystals with pseudoelastic behavior. During unloading, a giant temperature drop was measured in the gage section due to the elastocaloric effect. This data article provides a video of a [001] oriented Ni2FeGa single crystal, including the corresponding stress-strain curve, shows the temperature drop over one cycle. The second video of a [148] oriented NiTi single crystal depicts the repeatability of the elastocaloric effect by showing two consecutive cycles. The videos are supplied in this paper. For further analysis and enhanced discussion of large temperature change in shape memory alloys, see Pataky et al. [1]. PMID:26380838

  6. Reliability analysis of single crystal NiAl turbine blades

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan; Noebe, Ronald; Wheeler, Donald R.; Holland, Fred; Palko, Joseph; Duffy, Stephen; Wright, P. Kennard

    1995-01-01

    As part of a co-operative agreement with General Electric Aircraft Engines (GEAE), NASA LeRC is modifying and validating the Ceramic Analysis and Reliability Evaluation of Structures algorithm for use in design of components made of high strength NiAl based intermetallic materials. NiAl single crystal alloys are being actively investigated by GEAE as a replacement for Ni-based single crystal superalloys for use in high pressure turbine blades and vanes. The driving force for this research lies in the numerous property advantages offered by NiAl alloys over their superalloy counterparts. These include a reduction of density by as much as a third without significantly sacrificing strength, higher melting point, greater thermal conductivity, better oxidation resistance, and a better response to thermal barrier coatings. The current drawback to high strength NiAl single crystals is their limited ductility. Consequently, significant efforts including the work agreement with GEAE are underway to develop testing and design methodologies for these materials. The approach to validation and component analysis involves the following steps: determination of the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; measurement of the failure strength envelope of the material; coding of statistically based reliability models; verification of the code and model; and modeling of turbine blades and vanes for rig testing.

  7. FMR spin pumping in YIG/ferromagnet bilayers (ferromagnet = Fe, Co, Ni, Py)

    NASA Astrophysics Data System (ADS)

    Yang, Fengyuan; Wang, Hailong; Du, Chunhui; Hammel, P. Chris

    2014-03-01

    Generation of pure spin currents from ferromagnets (FM) to normal metals (NM) has been extensively studied by thermal and ferromagnetic resonance (FMR) spin pumping. Recently, Miao et al. demonstrated thermal injection of spin currents from Y3Fe5O12 (YIG) into Py detected by inverse spin Hall effect (ISHE) in the FM. The ISHE in FM is in fact the inverse anomalous Hall effect (SHE), but with all the signatures of ISHE in NMs. Here we report robust FMR spin pumping in YIG/FM bilayers with FM = Fe, Co, Ni and Py using cavity FMR. The resonance fields of the FMs and YIG are clearly separated, which allows distinction of spin pumping induced ISHE voltages at the YIG resonance field and the voltage signals at the FM resonance fields. The ISHE voltages reaches 220 uV for YIG/Py(2nm) bilayer and tens of uV for all YIG/FM bilayers with 10-nm FM at an rf power of 200 mW. The sign of the ISHE voltages for Py and Ni are opposite to those for Fe and Co, which agrees with the opposite signs of AHE in Ni as compared to Fe and Co.

  8. Microstructure and magnetic properties in FeCoB/NiFe double layer

    NASA Astrophysics Data System (ADS)

    Kong, Sok-hyun; Okamoto, Takeshi; Nakagawa, Shigeki

    2004-05-01

    The origin of high anisotropy field Hk and low coercivity Hc of Fe-Co-B/Ni-Fe double layered film with high 4 πMs was investigated. In-plane and out-of-plane XRD studies clarified that the lattice spacing of planes along the easy axis direction was expanded than that along the hard axis direction. The fact was confirmed that such stress caused by the lattice expansion had significant effects on the magnetoelastic energy in this double layer.

  9. High temperature deformation of NiAl and CoAl

    NASA Technical Reports Server (NTRS)

    Nix, W. D.

    1982-01-01

    The high temperature mechanical properties of the aluminides are reviewed with respect to their potential as high temperature structural materials. It is shown that NiAl and CoAl are substantially stronger than the pure metals Ni and Co at high temperatures and approach the strength of some superalloys, particularly when those superalloys are tested in "weak" directions. The factors that limit and control the high temperature strengths of NiAl and CoAl are examined to provide a basis for the development of intermetallic alloys of this type.

  10. The effect of boron doping on the Hall-Petch slope of FeAl (40 at. % Al)

    SciTech Connect

    Pike, L.M.; Liu, C.T. )

    1991-12-01

    This paper reports on the iron aluminide, FeAl, which has good oxidation resistance, low density, and low material cost. However, this aluminide shows limited ductility when tested in air at ambient temperatures. This embrittlement involves the reaction of the moisture in air with the aluminide and the generation of hydrogen at crack tips. By testing in dry oxygen, the environmental effect can be eliminated, but an intergranular fracture mode is still seen. This suggests that the grain boundaries of FeAl are intrinsically weak. It has been shown in both air and oxygen tests of FeAl that microapplying with boron suppresses intergranular fracture and subsequently increases ductility. For Ni{sub 3}Al, in which boron also suppresses intergranular fracture, two explanations of the beneficial effect of boron have been proposed. One claims that boron increases the cohesive strength of the grain boundaries. The other claims that boron enhances slip transfer at the grain boundaries. The primary experimental evidence for increased slip transfer was based on the observation that for powder-extruded (PE) Ni{sub 3}Al, the Hall-Petch slope, k{sub y}, was lowered by the addition of boron. The Hall-Petch equation, which relates yield stress, {sigma}{sub y} = {sigma}{sub o} + k{sub y}d{sup {minus} -.5}, where the intercept stress, {sigma}{sub o}, and the Hall-Petch slope, K{sub y}, are material constants.

  11. X-ray Absorption Measurements on Nickel Cathode of Sodium-beta Alumina batteries: Fe-Ni-CI Chemical Associations

    SciTech Connect

    Bowden, Mark E.; Alvine, Kyle J.; Fulton, John L.; Lemmon, John P.; Lu, Xiaochuan; Webb-Robertson, Bobbie-Jo M.; Heald, Steve M.; Balasubramanian, Mahalingam; Mortensen, Devon R.; Seidler, Gerald T.; Hess, Nancy J.

    2014-02-01

    Sections of Na-Al-NiCl2 cathodes from sodium-beta alumina ZEBRA batteries have been characterized with X-ray fluorescence mapping, and XANES measurements to probe the microstructure, elemental correlation, and chemical speciation after voltage cycling. Cycling was performed under identical load conditions at either 240 or 280 °C operating temperature and subsequently quenched in either the charged or discharged state. X-ray fluorescence mapping and XANES measurements were made adjacent to the current collector and β"-Al2O3 solid electrolyte interfaces to detect possible gradients in chemical properties across the cathode. An FeS additive, introduced during battery synthesis, was found to be present as either Fe metal or an Fe(II) chloride in all cathode samples. X-ray fluorescence mapping reveals an operating temperature and charge-state dependent spatial correlation between Fe, Ni, and Cl concentration. XANES measurements indicate that both Ni and Fe are chemically reactive and shift between metallic and chloride phases in the charged and discharged states, respectively. However the percentage of chemically active Ni and Fe is significantly less in the cell operated at lower temperature. Additionally, the cathode appeared chemically homogeneous at the scale of our X-ray measurements.

  12. X-ray absorption measurements on nickel cathode of sodium-beta alumina batteries: Fe-Ni-Cl chemical associations

    NASA Astrophysics Data System (ADS)

    Bowden, Mark E.; Alvine, Kyle J.; Fulton, John L.; Lemmon, John P.; Lu, Xiaochuan; Webb-Robertson, Bobbie-Jo; Heald, Steve M.; Balasubramanian, Mahalingam; Mortensen, Devon. R.; Seidler, Gerald T.; Hess, Nancy J.

    2014-02-01

    Sections of Na-Al-NiCl2 cathodes from sodium-beta alumina ZEBRA batteries have been characterized with X-ray fluorescence mapping, and XANES measurements to probe the microstructure, elemental correlation, and chemical speciation after voltage cycling. Cycling was performed under identical load conditions at either 240 or 280 °C operating temperature and subsequently quenched in either the charged or discharged state. X-ray fluorescence mapping and XANES measurements were made adjacent to the current collector and β″-Al2O3 solid electrolyte interfaces to detect possible gradients in chemical properties across the cathode. An FeS additive, introduced during battery synthesis, was found to be present as either Fe metal or an Fe(II) chloride in all cathode samples. X-ray fluorescence mapping reveals an operating temperature and charge-state dependent spatial correlation between Fe, Ni, and Cl concentration. XANES measurements indicate that both Ni and Fe are chemically reactive and shift between metallic and chloride phases in the charged and discharged states, respectively. However the percentage of chemically active Ni and Fe is significantly less in the cell operated at lower temperature. Additionally, the cathode appeared chemically homogeneous at the scale of our X-ray measurements.

  13. Structural and Mössbauer spectroscopic study of Fe-Ni alloy nanoparticles

    SciTech Connect

    Kumar, Asheesh; Banerjee, S. Sudarsan, V.; Meena, S. S.

    2014-04-24

    Nano-crystalline Fe-Ni alloys have been synthesized in ethylene glycol medium. Based on XRD studies it is confirmed that, in these alloys Fe atoms are incorporated at Ni site to form Ni-Fe solid solutions. Mössbauer studies have established that for alloy particles having smaller size there is significant concentration of two different types of paramagnetic Fe species and their relative concentration decreased with increase in particle size.

  14. Giant magnetoresistance studies in evaporated Ni-Fe/Cu and Ni-Fe-Co/Cu multilayers (abstract)

    NASA Astrophysics Data System (ADS)

    Haftek, E.; Zeltser, A. M.; Smith, Neil

    1997-04-01

    Room temperature giant magnetoresistance (GMR) and magnetic properties of (Ni-Fe/Cu)n and (Ni-Fe-Co/Cu)n multilayers were investigated. Alternating layers of Ni-Fe-(Co) and Cu were electron-beam evaporated in a computer-controlled high-vacuum system at base pressure of ⩽4×10-8 Torr and deposition rates of ⩽2 Å/s. To complement and expand our previous investigation,1 GMR properties were additionally studied here as a function of cobalt content of Ni-Fe-Co films, the number (n) of bilayers, deposition temperature, and type of buffer layer. The Co content was varied from 7 to 17 at. %, and the number of bilayers ranged from n=8 to 20. No significant GMR was observed in the as-deposited multilayers. To produce tangible GMR, these multilayers were annealed between 300 and 360 °C for 2 h in a 150 Oe magnetic field in an argon atmosphere. The GMR effect (ΔR/R) was essentially independent of copper spacer thickness, which varied between 25 and 30 Å. For Co containing multilayers the highest ΔR/R=7.6% was obtained for 17 at. % Co deposited at 100 °C. The ΔR/R in all Ni-Fe-Co/Cu multilayers was sensitive to the deposition temperature, and R-H loops always showed significant hysteresis independent of the type of buffer layer. For application of these materials to very high density reproduce heads,2 the best results were obtained for (27 Å NiFe/25 Å Cu)14-18 multilayers deposited at 160 °C on 70 Å Ta buffer layer. For example, n=17 multilayers annealed at 350 °C exhibited ΔR/R=7.5%, half-width at half-maximum of ˜50 Oe, essentially no anisotropy, and virtually zero hysteresis (Fig. 1). Frequency dependent permeability measurements showed constant permeability between 10 and 200 MHz. Low- and high-angle x-ray diffraction as well as atomic force microscopy were used to investigate the effect of different geometries of multilayers on structure and roughness and to correlate them with GMR properties.

  15. Long range order and vacancy properties in Al-rich Fe{sub 3}Al and Fe{sub 3}Al(Cr) alloys

    SciTech Connect

    Kim, S.M.; Morris, D.G.

    1998-05-01

    Neutron powder diffraction measurements have been carried out in situ from room temperature to about 100 C in Fe28Al (28 at.% Al), Fe32.5Al (32.5 at.% Al) and Fe28Al15Cr (28 at.% Al, 5 at.% Cr) alloys. X-ray diffraction and TEM studies provided supporting information. The data were analyzed to obtain information about the temperature dependence of the DO{sub 3} and B2 long range order parameters, the location of the Cr atoms and their effect on the ordering energies, and on the vacancy formation and migration properties in Fe28Al and Fe32.5Al alloys. The location of the ternary alloying addition in DO{sub 3} and B2 ordered Al-rich Fe{sub 3}Al is shown to be consistent with considerations of interatomic bond energies.

  16. Corrosion Behavior of Al-Al3Ni and Al-Al2Cu Functionally Graded Materials Fabricated by a Centrifugal Method

    NASA Astrophysics Data System (ADS)

    Noda, Kazuhiko; Miyahara, Keita; Watanabe, Yoshimi

    2008-02-01

    Intermetallic compounds, such as Al3Ni and Al2Cu, are effective for enhancing the mechanical properties of an alloy. Al-Al3Ni and Al-Al2Cu functionally graded materials (FGMs) might be attractive materials for advanced materials. Al-Al3Ni and Al-Al2Cu FGMs were fabricated by a centrifugal method; the centrifugal method is an extremely effective method for fabricating FGMs. Al-Al3Ni and Al-Al2Cu FGMs that had a graded distribution of intermetallic compounds could be produced by this in-situ centrifugal method. Particle size, particle shape and the distribution of intermetallic compounds were controlled by varying the content of the alloy element (Ni, Cu) in the master alloy, the cooling rate in casting and the gravity number. The casting mechanism is explained in terms of the microstructures of the Al-Al3Ni and Al-Al2Cu FGMs fabricated by this method. The corrosion behavior of the FGMs was investigated by electrochemical analysis. Polarization curves of the FGMs in a borate solution were measured by a potentiodynamic method. The presence of Al2Cu exerted a larger effect on the corrosion behavior of the FGMs than Al3Ni. Analysis of the polarization curve parameters was effective for evaluating the corrosion resistance of the FGMs.

  17. Mechanism of hydrogen activation by [NiFe] hydrogenases.

    PubMed

    Evans, Rhiannon M; Brooke, Emily J; Wehlin, Sara A M; Nomerotskaia, Elena; Sargent, Frank; Carr, Stephen B; Phillips, Simon E V; Armstrong, Fraser A

    2016-01-01

    The active site of [NiFe] hydrogenases contains a strictly conserved arginine that suspends a guanidine nitrogen atom <4.5 Å above the nickel and iron atoms. The guanidine headgroup interacts with the side chains of two conserved aspartic acid residues to complete an outer-shell canopy that has thus far proved intractable to investigation by site-directed mutagenesis. Using hydrogenase-1 from Escherichia coli, the strictly conserved residues R509 and D574 have been replaced by lysine (R509K) and asparagine (D574N) and the highly conserved D118 has been replaced by alanine (D118A) or asparagine (D118N/D574N). Each enzyme variant is stable, and their [(RS)2Niμ(SR)2Fe(CO)(CN)2] inner coordination shells are virtually unchanged. The R509K variant had >100-fold lower activity than native enzyme. Conversely, the variants D574N, D118A and D118N/D574N, in which the position of the guanidine headgroup is retained, showed 83%, 26% and 20% activity, respectively. The special kinetic requirement for R509 implicates the suspended guanidine group as the general base in H2 activation by [NiFe] hydrogenases. PMID:26619250

  18. Charge characteristics of Ni/Fe traction cells

    SciTech Connect

    DeLuca, W.H.; Biwer, R.L.; Tummillo, A.F.; Yao, N.P.

    1983-08-01

    The specific energy and cycle life of nickel/iron (Ni/Fe) battery systems exceed those of lead-acid systems. However, in order for the Ni/Fe system to achieve full capacity, a significant overcharge must be applied. As a result, electrolyte consumption and gassing levels are increased, and cycling efficiencies (Ah and Wh) are reduced. In a series of tests performed on 6V Ni/Fe modules, a range of recharge levels and charge rates were examined for three charge methods. The results show that higher discharge capacities are achieved at higher recharge Ah levels, but at lower Ah and Wh cycling efficiencies. However, when the modules are continuously cycled at any recharge level, repeatable module performance is obtained. Consequently, the optimum combination of module discharge capacity and cycle efficiency can be obtained for any given application by proper selection of the recharge level. It was also observed that at a fixed recharge level, module charge acceptance is virtually independent of the charge method. The tested modules also exhibited a self-discharge loss in capacity that was directly related to the length of the open-circuit stand time after charging and module state-of-charge. This paper describes the test procedures used, presents the test data, and discusses the results obtained.

  19. Microstructural Investigations On Ni-Ta-Al Ternary Alloys

    SciTech Connect

    Negache, M.; Souami, N.

    2010-01-05

    The Ni-Al-Ta ternary alloys in the Ni-rich part present complex microstructures. They are composed of multiple phases that are formed according to the nominal composition of the alloy, primary Ni(gamma), Ni{sub 3}Al(gamma'), Ni{sub 6}AlTa(tau{sub 3}), Ni{sub 3}Ta(delta) or in equilibrium: two solid phases (gamma'-tau{sub 3}), (tau{sub 3}-delta), (tau{sub 3}-gamma), (gamma-delta) or three solid phases (gamma'-tau{sub 3}-delta). The nature and the volume fraction of these phases give these alloys very interesting properties at high temperature, and this makes them attractive for specific applications. We have developed a series of ternary alloys in electric arc furnace, determining their solidification sequences using Differential Thermal Analysis (DTA), characterized by SEM-EDS, X-ray diffraction and by a microhardness tests. The follow-up results made it possible to make a correlation between the nature of the formed phases and their solidifying way into the Ni{sub 75}Al{sub x}Ta{sub y} (x+y = 25at.%) system, which are varied and complex. In addition to the solid solution Ni (gamma), the formed intermetallics compounds (gamma', tau{sub 3} and delta) has been identified and correlated with a complex balance between phases.We noticed that the hardness increases with the tantalum which has a hardening effect and though the compound Ni{sub 3}Ta(delta) is the hardest. The below results provide a better understanding of the complex microstructure of these alloys.

  20. Initial evaluation of continuous fiber reinforced NiAl composites

    NASA Technical Reports Server (NTRS)

    Noebe, R. D.; Bowman, R. R.; Eldridge, J. I.

    1990-01-01

    NiAl is being evaluated as a potential matrix material as part of an overall program to develop and understand high-temperature structural composites. Currently, continuous fiber composites have been fabricated by the powder cloth technique incorporating either W(218) or single crystal Al2O3 fibers as reinforcements in both binary NiAl and a solute strengthened NiAl(.05 at. pct Zr) matrix. Initial evaluation of these composite systems have included: fiber push-out testing to measure matrix/fiber bond strengths, bend testing to determine strength as a function of temperature and composite structure, and thermal cycling to establish the effect of matrix and fiber properties on composite life. The effect of matrix/fiber bond strength and matrix strength on several composite properties will be discussed.

  1. Electronic structure and magnetic properties of LiMn{sub 1.5}M{sub 0.5}O{sub 4} (M=Al, Mg, Ni, Fe) and LiMn{sub 2}O{sub 4}/TiO{sub 2} nanocrystalline electrode materials

    SciTech Connect

    Talik, E.; Lipińska, L.; Zajdel, P.; Załóg, A.; Michalska, M.; Guzik, A.

    2013-10-15

    The process of sol–gel synthesis was applied to obtain LiMn{sub 1.5}M{sub 0.5}O{sub 4} (M=Al, Mg, Ni, Fe) and LiMn{sub 2}O{sub 4}/TiO{sub 2} nanopowders. The samples were characterized by following methods: X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), X-ray photoelectron spectroscopy (XPS) and SQUID magnetometry. XPS was used to examine the chemical composition and oxidation state of manganese, in particular the Mn{sup 3+}/Mn{sup 4+} ratio from the deconvolution of the complex Mn3p lines. The size of the grains and crystallites were independently obtained from SEM images and XRD patterns, respectively. In all the cases a critical interplay of electronic (Mn{sup 3+}/Mn{sup 4+} ratio), structural (unit cell volume) and magnetic properties was observed depending on the synthesis process. - Graphical abstract: SEM image of Li{sub 0.79}Ni{sub 0.41}Mn{sub 1.35}O{sub 4.45} sample. Display Omitted - Highlights: • LiMn{sub 1.5}M{sub 0.5}O{sub 4} (M=Al, Mg, Ni, Fe) and LiMn{sub 2}O{sub 4}/TiO{sub 2} obtained by sol–gel method. • XRD method was used to determine the crystal structure. • SEM/EDX imaging have been done. • XPS electronic structure was examined and discussed. • Experimental effective magnetic moment and the calculated one were compared.

  2. 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.

  3. A [NiFe]hydrogenase model that catalyses the release of hydrogen from formic acid.

    PubMed

    Nguyen, Nga T; Mori, Yuki; Matsumoto, Takahiro; Yatabe, Takeshi; Kabe, Ryota; Nakai, Hidetaka; Yoon, Ki-Seok; Ogo, Seiji

    2014-11-11

    We report the decomposition of formic acid to hydrogen and carbon dioxide, catalysed by a NiRu complex originally developed as a [NiFe]hydrogenase model. This is the first example of H2 evolution, catalysed by a [NiFe]hydrogenase model, which does not require additional energy. PMID:25234420

  4. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    SciTech Connect

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; Yoda, Yoshitaka; Lubitz, Wolfgang; Cramer, Stephen P.

    2015-08-10

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique ‘wagging’ mode involving H- motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe–CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H- binding Ni more tightly than Fe. Lastly, the present methodology is also relevant to characterizing Fe–H moieties in other important natural and synthetic catalysts.

  5. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    DOE PAGESBeta

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; et al

    2015-08-10

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique ‘wagging’ mode involving H- motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe–CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate amore » low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H- binding Ni more tightly than Fe. Lastly, the present methodology is also relevant to characterizing Fe–H moieties in other important natural and synthetic catalysts.« less

  6. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    PubMed Central

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; Yoda, Yoshitaka; Tanaka, Yoshihito; Lubitz, Wolfgang; Cramer, Stephen P.

    2015-01-01

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique ‘wagging' mode involving H− motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe–CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H− binding Ni more tightly than Fe. The present methodology is also relevant to characterizing Fe–H moieties in other important natural and synthetic catalysts. PMID:26259066

  7. Supercoducting property of Zr-Cu-Al-Ni-Nb alloys

    NASA Astrophysics Data System (ADS)

    Okai, D.; Motoyama, G.; Kimura, H.; Inoue, A.

    The superconducting property of Zr55Cu(30-X)Al10Ni5NbX alloys prepared by arc melting and liquid quenching methods was investigated by magnetic susceptibility measurements. The crystalline alloys with X = 0∼25 at.% prepared by arc melting method exhibited superconductivity with maximum Tc,on of 10.1 K. The alloys (X = 10∼23 at.%) with crystalline particles embedded in an amorphous structure, which were fabricated by melt spinning method, showed superconductivity with Tc,on of less than 4.0 K. The superconducting property of the Zr-Cu-Al-Ni-Nb alloys was attributed to superconducting phases of Zr2Cu, Zr2Ni, Zr65Al10Nb25 and Zr-Nb contained in the Zr-Cu-Al-Ni-Nb alloys. The melt-spun Zr55Cu(30-X)Al10Ni5NbX (X = 10∼20 at.%) alloys exhibited glass transition at 718∼743 K and were found to be superconducting metallic glasses.

  8. Electronic structure and magnetic properties of Mn, Co, and Ni substitution of Fe in Fe4N

    NASA Astrophysics Data System (ADS)

    Monachesi, Patrizia; Björkman, Torbjörn; Gasche, Thomas; Eriksson, Olle

    2013-08-01

    The magnetic properties of Mn, Co, and Ni substituted Fe4N are calculated from first principles theory. It is found that the generalized gradient approximation reproduces with good accuracy the magnetic moment and equilibrium volume for the parent Fe4N structure, with the atomic moment largest for the Fe atom furthest away from the N atom (Fe I site), approaching a value of 3 μB/atom, whereas the Fe atom closer to the N atom (Fe II site) has a moment closer to that of bcc Fe. The substitution of Fe for Mn, Co, or Ni, shows an intricate behavior in which the Mn substitution clearly favors the Fe II site, Ni favors substitution on the Fe I site, and Co shows no strong preference for either lattice site. The Ni and Co substitution results in a ferromagnetic coupling to the Fe atoms, whereas Mn couples antiferromagnetically on the Fe II site and ferromagnetically on the Fe I site. For all types of doping, the total magnetic moment is enhanced compared to Fe4N only in the energetically very unfavorable case of Mn doping at the Fe I site.

  9. Influence of Ni on the lattice stability of Fe-Ni alloys at multimegabar pressures

    NASA Astrophysics Data System (ADS)

    Vekilova, O. Yu.; Simak, S. I.; Ponomareva, A. V.; Abrikosov, I. A.

    2012-12-01

    The lattice stability trends of the primary candidate for Earth's core material, the Fe-Ni alloy, were examined from first principles. We employed the exact muffin-tin orbital method (EMTO) combined with the coherent potential approximation (CPA) for the treatment of alloying effects. It was revealed that high pressure reverses the trend in the relative stabilities of the body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal close-packed (hcp) phases observed at ambient conditions. In the low pressure region the increase of Ni concentration in the Fe-Ni alloy enhances the bcc phase destabilization relative to the more close-packed fcc and hcp phases. However, at 300 GPa (Earth's core pressure), the effect of Ni addition is opposite. The reverse of the trend is associated with the suppression of the ferromagnetism of Fe when going from ambient pressures to pressure conditions corresponding to those of Earth's core. The first-principles results are explained in the framework of the canonical band model.

  10. Hyperfine fields in Fe-Ni-X alloys and their application to a study of tempering of 9Ni steel

    SciTech Connect

    Fultz, B.; Morris, J.W. Jr.

    1984-12-01

    Hyperfine interactions due to solutes in Fe-Ni-X alloys were systematized, and interpreted with a model of linear response of hyperfine magnetic fields to magnetic moments. The effects of solutes on the /sup 57/Fe hmf were used for chemical analysis of the austenite formed in 9Ni steel during tempering. Diffusion kinetics of the Ni and X solutes were found to play an important role in the formation of the austenite particles.

  11. CVD Fiber Coatings for Al2O3/NiAl Composites

    NASA Technical Reports Server (NTRS)

    Boss, Daniel E.

    1995-01-01

    While sapphire-fiber-reinforced nickel aluminide (Al2O3/NiAl) composites are an attractive candidate for high-temperature structures, the significant difference in the coefficient of thermal expansion between the NiAl matrix and the sapphire fiber creates substantial residual stresses in the composite. This study seeks to produce two fiber-coating systems with the potential to reduce the residual stresses in the sapphire/NiAl composite system. Chemical vapor deposition (CVD) was used to produce both the compensating and compliant-fiber coatings for use in sapphire/NiAl composites. A special reactor was designed and built to produce the FGM and to handle the toxic nickel precursors. This process was successfully used to produce 500-foot lengths of fiber with coating thicknesses of approximately 3 microns, 5 microns, and 10 microns.

  12. Interlayer coupling in Ni80Fe20/Ru/Ni80Fe20 multilayer films: Ferromagnetic resonance experiments and theory

    NASA Astrophysics Data System (ADS)

    Liu, X. M.; Nguyen, Hoa T.; Ding, J.; Cottam, M. G.; Adeyeye, A. O.

    2014-08-01

    We present a systematic study of the static and dynamic magnetization behavior of interlayer-coupled Ni80Fe20(200Å)/Ru(tRu)/Ni80Fe20(100 Å) trilayers as a function of the Ru spacer layer thickness tRu. As tRu was varied in the range from 0 to 15.8 Å, we observe a strong antiferromagnetic (AFM) exchange coupling between the two ferromagnetic (FM) layers for tRu = 5 Å, which becomes weak for tRu = 10 Å. For tRu = 14.1 Å, the coupled magnetic system changes from AFM to FM ordering. Using broadband ferromagnetic resonance spectroscopy, we have probed the effects of the different coupling mechanisms on both the acoustic and optic magnetic modes. We found that the biquadratic exchange coupling has a negligible effect compared to Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange coupling, while the uniaxial anisotropy at the Ni80Fe20/Ru interfaces also plays an important role in determining the behaviors of the modes. A mode anticrossing phenomenon is observed when the RKKY exchange interaction term is above a critical value. A theoretical framework developed is in very good agreement with our experimental results.

  13. Oxidation of Al2O3 continuous fiber-reinforced/NiAl composites

    NASA Technical Reports Server (NTRS)

    Doychak, J.; Nesbitt, J. A.; Noebe, R. D.; Bowman, R. R.

    1992-01-01

    The 1200 C and 1300 C isothermal and cyclic oxidation behavior of Al2O3 continuous fiber-reinforced/NiAl composites were studied. Oxidation resulted in formation of Al2O3 external scales in a similar manner as scales formed on monolithic NiAl. The isothermal oxidation of an Al2O3/NiAl composite resulted in oxidation of the matrix along the fiber/matrix interface near the fiber ends. This oxide acted as a wedge between the fiber and the matrix, and, under cyclic oxidation conditions, led to further oxidation along the fiber lengths and eventual cracking of the composite. The oxidation behavior of composites in which the Al2O3 fibers were sputter coated with nickel prior to processing was much more severe. This was attributed to open channels around the fibers which formed during processing, most likely as a result of the diffusion of the nickel coating into the matrix.

  14. Chemical ordering and large tunnel magnetoresistance in Co2FeAl/MgAl2O4/Co2FeAl(001) junctions

    NASA Astrophysics Data System (ADS)

    Scheike, Thomas; Sukegawa, Hiroaki; Inomata, Koichiro; Ohkubo, Tadakatsu; Hono, Kazuhiro; Mitani, Seiji

    2016-05-01

    Epitaxial magnetic tunnel junctions (MTJs) with a Co2FeAl/CoFe (0.5 nm)/MgAl2O4/Co2FeAl(001) structure were fabricated by magnetron sputtering. High-temperature in situ annealing led to a high degree of B2-order in the Co2FeAl layers and cation order of the MgAl2O4 barrier. Large tunnel magnetoresistance (TMR) of up to 342% was obtained at room temperature (616% at 4 K), in contrast to the TMR ratio ( ≲ 160%) suppressed by the band-folding effect in Fe/cation-ordered MgAl2O4/Fe MTJs. The present study reveals that the high degree of B2-order and the resulting high spin polarization in the Co2FeAl electrodes enable us to bypass the band-folding problem in spinel barriers.

  15. Calculation of defect properties of NiTi and FeTi

    SciTech Connect

    Lutton, R.T.; Sabochick, M.J. . Dept. of Engineering Physics); Lam, N.Q. )

    1990-12-01

    The energies and configurations of interstitials and vacancies in the B2 ordered compounds NiTi and FeTi were calculated using atomistic simulation. The stable configuration of a vacancy after the removal of an Ni atom was a vacant Ni site; similarly, the removal of an Fe atom in FeTi resulted in a vacant Fe site. Removal of a Ti atom in both compounds, however, resulted in a vacant Ni or Fe site and an adjacent antisite defect. The effective vacancy formation energies in NiTi and FeTi were calculated to be 1.48 and 1.07 eV, respectively. Interstitials in NiTi formed split {l angle}111{r angle} configurations consisting of a Ni-Ni dumbbell oriented in the {l angle}111{r angle} direction with one or two adjacent antisite defects. The Fe interstitial in FeTi had a similar configuration, except the dumbbell contained Fe atoms. The Ti interstitial in FeTi formed an {l angle}110{r angle} Fe-Fe dumbbell. 8 refs., 2 tabs.

  16. Effects of Cr and Ni on Interdiffusion and Reaction between U and Fe-Cr-Ni Alloys

    SciTech Connect

    K. Huang; Y. Park; L. Zhou; K.R. Coffey; Y.H. Sohn; B.H. Sencer; J. R. Kennedy

    2014-08-01

    Metallic U-alloy fuel cladded in steel has been examined for high temperature fast reactor technology wherein the fuel cladding chemical interaction is a challenge that requires a fundamental and quantitative understanding. In order to study the fundamental diffusional interactions between U with Fe and the alloying effect of Cr and Ni, solid-to-solid diffusion couples were assembled between pure U and Fe, Fe–15 wt.%Cr or Fe–15 wt.%Cr–15 wt.%Ni alloy, and annealed at high temperature ranging from 580 to 700 °C. The microstructures and concentration profiles that developed from the diffusion anneal were examined by scanning electron microscopy, and X-ray energy dispersive spectroscopy (XEDS), respectively. Thick U6Fe and thin UFe2 phases were observed to develop with solubilities: up to 2.5 at.% Ni in U6(Fe,Ni), up to 20 at.%Cr in U(Fe, Cr)2, and up to 7 at.%Cr and 14 at.% Ni in U(Fe, Cr, Ni)2. The interdiffusion and reactions in the U vs. Fe and U vs. Fe–Cr–Ni exhibited a similar temperature dependence, while the U vs. Fe–Cr diffusion couples, without the presence of Ni, yielded greater activation energy for the growth of intermetallic phases – lower growth rate at lower temperature but higher growth rate at higher temperature.

  17. Investigation of the mechanical properties of FeNiCrMnSi high entropy alloy wear resistant

    NASA Astrophysics Data System (ADS)

    Buluc, G.; Florea, I.; Chelariu, R.; Popescu, G.; Carcea, I.

    2016-06-01

    In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.

  18. 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

  19. Mechanical Properties of Fe-Ni Meteorites

    NASA Astrophysics Data System (ADS)

    Roberta, Mulford; El Dasher, B.

    2010-10-01

    Iron-nickel meteorites exhibit a unique lamellar microstructure, Widmanstatten patterns, consisting of small regions with steep-iron-nickel composition gradients.1,2 The microstructure arises as a result of extremely slow cooling in a planetary core or other large mass. Mechanical properties of these structures have been investigated using microindentation, x-ray fluorescence, and EBSD. Observation of local mechanical properties in these highly structured materials supplements bulk measurements, which can exhibit large variation in dynamic properties, even within a single sample. 3 Accurate mechanical properties for meteorites may enable better modeling of planetary cores, the likely origin of these objects. Appropriate values for strength are important in impact and crater modeling and in understanding the consequences of observed impacts on planetary crusts. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens.4 This was ascribed to the extreme work-hardening evident in the EBSD measurements. This particular specimen exhibited only residual Widmanstatten structures, and may have been heated and deformed during its traverse of the atmosphere. Additional specimens from the Canyon Diablo fall (type IAB, coarse octahedrite) and examples from the Muonionalusta meteorite and Gibeon fall ( both IVA, fine octahedrite), have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon re-entry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure. 1. A. Christiansen, et.al., Physica Scripta, 29 94-96 (1984.) 2. Goldstein and Ogilvie, Geochim Cosmochim Acta, 29 893-925 (1965.) 3. M. D. Furnish, M.B. Boslough, G.T. Gray II, and J.L. Remo, Int. J. Impact Eng

  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. 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.

  2. High performance magnetoimpedance in FeNi/Ti nanostructured multilayers with opened magnetic flux.

    PubMed

    Fernández, E; Svalov, A V; García-Arribas, A; Feuchtwanger, J; Barandiaran, J M; Kurlyandskaya, G V

    2012-09-01

    Magnetic [FeNi (170 nm)/Ti (6 nm)]3/Cu (L(cu) = 250 or 500 nm)/[Ti (6 nm)/FeNi (170 nm)]3 multilayers were designed with focus on high frequency applications. They were deposited onto glass or a microfluidic system compatible flexible Ciclo Olefin Copolymer substrate and comparatively tested. A maximum sensitivity for the total impedance of 110%/Oe was obtained for a driving current frequency of 30 MHz for [FeNi/Ti]3/Cu (L(cu) = 500 nm)/[Ti/FeNi]3 multilayers deposited onto a glass substrate and 45%/Oe for a driving current frequency of 65 MHz for the same multilayers deposited onto the flexible polymer substrate, a very promising result for applications. The possibility of using flexible substrate/[FeNi/Ti],/Cu/[Ti/FeNi]3 multilayers as MI pressure-sensitive elements was also demonstrated. PMID:23035503

  3. Characterization of ion beam and magnetron sputtered thin Ta/NiFe films

    NASA Astrophysics Data System (ADS)

    Mao, M.; Leng, Q.; Huai, Y.; Johnson, P.; Miller, M.; Tong, H.-C.; Miloslavsky, L.; Qian, C.; Wang, J.; Hegde, H.

    1999-04-01

    Thin Ta/NiFe films were deposited using ion beam deposition (IBD), pulsed, and static magnetron sputtering techniques. These NiFe films show anisotropy field values ˜4 Oe, easy axis coercivities ⩽1 Oe, and hard axis coercivities ⩽0.3 Oe. IBD films exhibit higher magnetoresistance ratios (ΔR/R), while little difference is noted between different deposition techniques in the sheet resistance of NiFe films. A ΔR/R value of 1.8% has been measured for a 90 Å IBD NiFe films. X-ray diffraction measurements indicate that NiFe films of the same thickness have about the same grain size regardless of deposition technique, however, IBD films exhibit superior (111) texture and crystallinity. Our results clearly indicate that the superior magnetic properties of thin IBD Ta/NiFe films are a result of high crystallographic quality of these films.

  4. Magnetic structure and anisotropy of [Co/Pd ] 5/NiFe multilayers

    NASA Astrophysics Data System (ADS)

    Tryputen, Larysa; Guo, Feng; Liu, Frank; Nguyen, T. N. Anh; Mohseni, Majid S.; Chung, Sunjae; Fang, Yeyu; Ã kerman, Johan; McMichael, R. D.; Ross, Caroline A.

    2015-01-01

    The magnetization behavior, magnetic anisotropy, and domain configurations of Co/Pd multilayers with perpendicular magnetic anisotropy capped with permalloy is investigated using magnetometry, magnetic force microscopy, and ferromagnetic resonance. The thickness of the Ni80Fe20 layer in [Co/Pd ] 5/NiFe (t ) was varied from t =0 to 80 nm in order to study the interplay between the anisotropy and magnetization directions of Co/Pd and NiFe. By varying the thickness of the NiFe layer, the net anisotropy changes sign, but domains with plane-normal magnetization are present even for the thickest NiFe. Ferromagnetic resonance measurements show a decrease in damping with increasing NiFe thickness. The results demonstrate how the magnetic behavior of mixed-anisotropy thin films can be controlled.

  5. Ferromagnetic interactions and martensitic transformation in Fe doped Ni-Mn-In shape memory alloys

    SciTech Connect

    Lobo, D. N.; Priolkar, K. R.; Emura, S.; Nigam, A. K.

    2014-11-14

    The structure, magnetic, and martensitic properties of Fe doped Ni-Mn-In magnetic shape memory alloys have been studied by differential scanning calorimetry, magnetization, resistivity, X-ray diffraction (XRD), and EXAFS. While Ni{sub 2}MnIn{sub 1−x}Fe{sub x} (0 ≤ x ≤ 0.6) alloys are ferromagnetic and non martensitic, the martensitic transformation temperature in Ni{sub 2}Mn{sub 1.5}In{sub 1−y}Fe{sub y} and Ni{sub 2}Mn{sub 1.6}In{sub 1−y}Fe{sub y} increases for lower Fe concentrations (y ≤ 0.05) before decreasing sharply for higher Fe concentrations. XRD analysis reveals presence of cubic and tetragonal structural phases in Ni{sub 2}MnIn{sub 1−x}Fe{sub x} at room temperature with tetragonal phase content increasing with Fe doping. Even though the local structure around Mn and Ni in these Fe doped alloys is similar to martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactions and structural disorder induced by Fe affect Mn-Ni-Mn antiferromagnetic interactions resulting in suppression of martensitic transformation in these Fe doped alloys.

  6. {sup 60}Fe AND {sup 26}Al IN CHONDRULES FROM UNEQUILIBRATED CHONDRITES: IMPLICATIONS FOR EARLY SOLAR SYSTEM PROCESSES

    SciTech Connect

    Mishra, R. K.; Goswami, J. N.; Rudraswami, N. G.; Tachibana, S.; Huss, G. R.

    2010-05-10

    The presence of about a dozen short-lived nuclides in the early solar system, including {sup 60}Fe and {sup 26}Al, has been established from isotopic studies of meteorite samples. An accurate estimation of solar system initial abundance of {sup 60}Fe, a distinct product of stellar nucleosynthesis, is important to infer the stellar source of this nuclide. Previous studies in this regard suffered from the lack of exact knowledge of the time of formation of the analyzed meteorite samples. We present here results obtained from the first combined study of {sup 60}Fe and {sup 26}Al records in early solar system objects to remove this ambiguity. Chondrules from unequilibrated ordinary chondrites belonging to low petrologic grades were analyzed for their Fe-Ni and Al-Mg isotope systematics. The Al-Mg isotope data provide the time of formation of the analyzed chondrules relative to the first solar system solids, the Ca-Al-rich inclusions. The inferred initial {sup 60}Fe/{sup 56}Fe values of four chondrules, combined with their time of formation based on Al-Mg isotope data, yielded a weighted mean value of (6.3 {+-} 2) x 10{sup -7} for solar system initial {sup 60}Fe/{sup 56}Fe. This argues for a high-mass supernova as the source of {sup 60}Fe along with {sup 26}Al and several other short-lived nuclides present in the early solar system.

  7. Thermoelasticity of Al3+- and Fe3+-bearing bridgemanite

    NASA Astrophysics Data System (ADS)

    Valencia-Cardona, Juan; Shukla, Gaurav; Cococcioni, Matteo; Wentzcovitch, Renata

    2015-03-01

    We present quasi-harmonic LDA+U calculations of thermoelastic properties of Fe3+- and Al3+-bearing bridgemanite (MgSiO3), the main Earth forming phase, at relevant P,T conditions and compositions. Three charge-coupled substitutions, namely, Al3+-Al3+, Fe3+-Fe3+, and Fe3+-Al3+ have been investigated. Aggregate elastic moduli and sound velocities are successfully compared with limited experimental measurements available. The effect of the pressure induced high-spin to low-spin state change in Fe3+ in the B-site has been investigated in great detail since it has potentially dramatic effects on seismic velocities in the Earth's lower mantle. Research supported by NSF/EAR and NSF/CAREER.

  8. Decomposition of a<111> and a<101> dislocations in hard-oriented NiAl single crystals

    SciTech Connect

    Srinivasan, R.; Savage, M.F.; Mills, M.J.; Daw, M.S.; Noebe, R.D.

    1998-08-04

    The B2 intermetallic compound NiAl and its alloys have been subjects of extensive study for potential use as high temperature structural materials, particularly in the aerospace industry. The factors that make them attractive candidates are their low density (5.85 g/cm{sup 3}), excellent oxidation and corrosion resistance and high melting points. But they suffer from lack of ductility at low temperatures and poor strength at higher temperatures. There are still several issues regarding deformation behavior in NiAl and other B2 alloys (e.g., FeAl) that merit further research. Study of the deformation behavior in NiAl should provide further insight into some of the outstanding issues in B2 alloys: chiefly, the nature of slip transition and the effect of various parameters such as temperature, strain rate and stoichiometry on the deformation behavior. The preferred slip system in NiAl involves a <100> slip. But on stressing along the cube axes, also known as the hard orientation, single crystals of NiAl deform at much higher stresses through the motion of a<111> dislocations at lower temperatures. Non-a<111> slip dominates at higher temperatures, with an associated increase in ductility and dramatic decrease in strength. There is also some confusion regarding the mode of deformation beyond the slip transition temperature. The exact process of this slip transition needs to be addressed in its entirety to completely understand the mechanical response of NiAl.

  9. High Frequency Properties of Ferrite/Fe-Si-Al Alloy Soft Magnetic Composites

    NASA Astrophysics Data System (ADS)

    Stergiou, Charalampos A.; Zaspalis, Vassilios

    The inclusion of Fe-Si-Al alloy particles in NiCuZn ferrite matrix was investigated with regard to the high frequency electromagnetic properties (complex permeability and permittivity). The resultant composites of relatively low density exhibit a shift of the permeability spectra to higher frequencies and an increase of dielectric polarization, which finally favour the electromagnetic wave attenuation at microwave frequencies. Thus, wider band return loss peaks are attained at frequencies above 6 GHz by thinner composite materials.

  10. He self-pumping by tokamak pump limiter materials: Al, V, Ni, and Ni/Al alloys

    SciTech Connect

    Outten, C.A. ); Barbour, J.C.; Doyle, B.L. ); Walsh, D.S. )

    1991-01-01

    An ECR plasma and Colutron ion gun were used to study He self-pumping by several possible pump-limiter materials: Ni, V, Al, and Ni/Al multi-layers. Ni and V exhibited similar pumping capacities (6 {times} 10{sup 15} He/cm{sup 2}, 200 eV) whereas Al showed a reduced capacity (6 {times} 10{sup 14} He/cm{sup 2}, 200 eV) due to increased sputtering. A He retention model based upon ion implantation ranges and sputtering rates agreed with the experimental data. The pumping efficiency increased significantly with ion energy. A new multilayer/bilayer pumping concept showed improved pumping above that for single element films. 4 refs., 5 figs.

  11. Interdiffusion behavior of Pt-modified γ-Ni + γ'-Ni3Al alloys coupled to Ni-Al-based alloys

    NASA Astrophysics Data System (ADS)

    Hayashi, Shigenari; Wang, Wen; Sordelet, Daniel J.; Gleeson, Brian

    2005-07-01

    The effect of platinum addition on the interdiffusion behavior of γ-Ni + γ'-Ni3Al alloys was studied by using diffusion couples comprised of a Ni-Al-Pt alloy mated to a Ni-Al, Ni-Al-Cr, or Ni-based commercial alloy. The commercial alloys studied were CMSX-4 and CMSX-10. Diffusion annealing was at 1150 °C for up to 100 hours. An Al-enriched γ'-layer often formed in the interdiffusion zone of a given couple during diffusion annealing due to the uphill diffusion of Al. This uphill diffusion was ascribed to Pt addition decreasing the chemical activity of aluminum in the γ + γ' alloys. For a given diffusion couple end member, the thickening kinetics of the γ' layer that formed increased with increasing Pt content in the Ni-Al-Pt γ + γ' alloy. The γ'-layer thickening kinetics in diffusion couples with Cr showed less of a dependence on Pt concentration. Inference of a negative effect of Pt and positive effect of Cr on the Al diffusion in this system enabled explanation of the observed interdiffusion behaviors. There was no or minimal formation of detrimental topologically close-packed (TCP) phases in the interdiffusion zone of the couples with CMSX-4 or CMSX-10. An overlay Pt-modified γ + γ' coating on CMSX-4 showed excellent oxidation resistance when exposed to air for 1000 hours at 1150 °C. Moreover, the Al content in the coating was maintained at a relatively high level due to Al replenishment from the CMSX-4 substrate.

  12. Effect of prior oxidation on the creep behavior of NiAl-hardened austenitic steel

    NASA Astrophysics Data System (ADS)

    Satyanarayana, D. V. V.; Malakondaiah, G.; Sarma, D. S.

    2003-11-01

    The effect of prior oxidation at 1473 K on the creep behavior of an Fe-Ni-Cr-Al alloy, hardened by ordered NiAl precipitates, has been investigated at 873 K over a stress range of 275 to 450 MPa. The alloy in the as-electroslag remelted (ESR) as well as the ESR-plus-hot-worked conditions was considered. Prior oxidation causes creep strengthening in the Fe-Ni-Cr-Al alloy, resulting in a decrease in minimum creep rate and increase in time to rupture, in contrast to the observations reported on nickel-based superalloys. Creep strengthening is, however, accompanied by a significant reduction in creep ductility. Oxidation-induced creep strengthening in the current alloy can be attributed to the improved adherence of surface oxide caused by the presence of yttrium. An effective stress that incorporates the contributions of load transfer as well as substructural strengthening is used to account for the observed oxidation-induced creep strengthening. While creep strengthening is more pronounced in the ESR cast alloy, the loss in creep ductility is more intense in the ESR wrought alloy. Increasing the oxidation time beyond 1 hour has a minimal effect on creep strengthening of both the alloys, though it lowers significantly the creep ductility of the wrought alloy. The observed differences in creep behavior of the alloy in the two different conditions could be attributed to the differences in grain size as well as morphology and related oxidation-induced damage.

  13. Strength anomaly in B2 FeAl single crystals

    SciTech Connect

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

    1994-12-31

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

  14. Synthesis of FeNi3/(Ni0.5Zn0.5)Fe2O4 nanocomposite and its high frequency complex permeability

    NASA Astrophysics Data System (ADS)

    Lu, Xuegang; Liang, Gongying; Zhang, Yumei; Zhang, Wei

    2007-01-01

    FeNi3/(Ni0.5Zn0.5)Fe2O4 nanocomposite particles were successfully synthesized using the hydrazine reduction combined with ammonia co-precipitation ferrite coating method. The x-ray and transmission electron microscopy analysis showed that face-centred cubic-structured FeNi3 nanoparticles were coated with spinel Ni-Zn ferrite. The composite particles were nearly spherical with diameters of about 80-200 nm and exhibited typical soft magnetic properties. The saturation magnetization (Ms) of the composite was greatly improved, compared with that of traditional ferrite. With increasing ferrite content, the eddy-current loss was effectively suppressed and a notable high frequency characteristic, in which the real part μ' of the permeability was almost independent of the frequency, was observed. The imaginary part μ'' remained at an extremely low value below the frequency of 300 MHz. The cut-off frequency fr was estimated to be above 1 GHz. The highest value of μ' reached 13 when the ratio of FeNi3 to Ni0.5Zn0.5Fe2O4 was 1:1. Two peaks were observed in the permeability spectra, which may be ascribed to the ferromagnetic resonances of FeNi3 and Ni-Zn ferrite respectively.

  15. Synergism between polyurethane and polydopamine in the synthesis of Ni-Fe alloy monoliths.

    PubMed

    Naresh Kumar, Thangavel; Sivabalan, Santhana; Chandrasekaran, Naveen; Phani, Kanala Lakshminarasimha

    2015-02-01

    Herein, we report the first synthesis of a light-weight macroporous 3-D alloy monolith of Ni-Fe/C using synergism between polydopamine (pDA) and polyurethane (pU); in situ formed polyurethane (pU) enables efficient mixing of pDA (carbon source) and Ni-FeOx resulting in Ni-Fe alloy monoliths at a temperature as low as ∼600 °C. The monolithic Ni-Fe/C exhibits enhanced oxygen evolution activity. PMID:25531680

  16. Properties of Bulk Fe-Ni/CNT Nanocomposites Prepared by Mechanical Milling and Sintering

    NASA Astrophysics Data System (ADS)

    Azadehranjbar, S.; Karimzadeh, F.; Enayati, M. H.; Mahmoodi, N.

    2013-08-01

    The effects of carbon nanotubes (CNTs) on mechanical and tribiological properties of the NiFe/CNT composites prepared by high energy mechanical alloying and hot pressing, were investigated. Bulk samples were prepared by sintering of cold pressed (300 MPa) samples at 1040°C for 1 h. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and optical microscopy were employed for evaluation of the phase composition, surface morphology and porosities of the samples. The microhardness of as-milled Ni3Fe and NiFe powders reached to 720 and 650 VHN, respectively. The hardness of NiFe and Ni3Fe bulk samples reduced to 190 and 270 Vickers because of the grain growth during sintering and remaining porosity. The hardness of NiFe-CNT and Ni3Fe-CNT bulk samples reached to 360 and 400 Vickers, respectively. The friction and wear properties of the bulk samples were investigated under dry conditions using a pin-on-disk test rig under an applied load of 8 N. The wear rate, mass loss and friction coefficient of the composite samples remarkably reduced in comparison with NiFe and Ni3Fe matrix alloys which demonstrate effects of the CNTs on mechanical and tribiological behavior of the composites resulting from the excellent mechanical properties and unique topological structure of the CNTs.

  17. The Model [NiFe]-Hydrogenases of Escherichia coli.

    PubMed

    Sargent, F

    2016-01-01

    In Escherichia coli, hydrogen metabolism plays a prominent role in anaerobic physiology. The genome contains the capability to produce and assemble up to four [NiFe]-hydrogenases, each of which are known, or predicted, to contribute to different aspects of cellular metabolism. In recent years, there have been major advances in the understanding of the structure, function, and roles of the E. coli [NiFe]-hydrogenases. The membrane-bound, periplasmically oriented, respiratory Hyd-1 isoenzyme has become one of the most important paradigm systems for understanding an important class of oxygen-tolerant enzymes, as well as providing key information on the mechanism of hydrogen activation per se. The membrane-bound, periplasmically oriented, Hyd-2 isoenzyme has emerged as an unusual, bidirectional redox valve able to link hydrogen oxidation to quinone reduction during anaerobic respiration, or to allow disposal of excess reducing equivalents as hydrogen gas. The membrane-bound, cytoplasmically oriented, Hyd-3 isoenzyme is part of the formate hydrogenlyase complex, which acts to detoxify excess formic acid under anaerobic fermentative conditions and is geared towards hydrogen production under those conditions. Sequence identity between some Hyd-3 subunits and those of the respiratory NADH dehydrogenases has led to hypotheses that the activity of this isoenzyme may be tightly coupled to the formation of transmembrane ion gradients. Finally, the E. coli genome encodes a homologue of Hyd-3, termed Hyd-4, however strong evidence for a physiological role for E. coli Hyd-4 remains elusive. In this review, the versatile hydrogen metabolism of E. coli will be discussed and the roles and potential applications of the spectrum of different types of [NiFe]-hydrogenases available will be explored. PMID:27134027

  18. The 1200 C cyclic oxidation behavior of two nickel-aluminum alloys (Ni3AL and NiAl) with additions of chromium, silicon, and titanium

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.; Santoro, G. J.

    1972-01-01

    The alloys Ni3Al and NiAl with and without 1 and 3 atomic percent chromium, silicon, and titanium replacing the aluminum were cyclically oxidized at 1200 C for times to 200 hours, and the results were compared with those obtained with the alloy B-1900 subjected to the same oxidation process. The evaluation was based on metal recession, specific weight change, metallography, electron microprobe analysis, and X-ray diffraction. The oxidation resistance of Ni3Al was improved by Si, unaffected by Ti, and degraded by Cr. The oxidation resistance of NiAl was slightly improved by Ti, unaffected by Si, and degraded by Cr. The oxidation resistance of Ni3Al with 1 atomic percent Si was nearly equal to that of NiAl. Alloy B-1900 exhibited oxidation resistance comparable to that of Ni3Al + Cr compositions.

  19. Cu-Ni-Fe anodes having improved microstructure

    DOEpatents

    Bergsma, S. Craig; Brown, Craig W.

    2004-04-20

    A method of producing aluminum in a low temperature electrolytic cell containing alumina dissolved in an electrolyte. The method comprises the steps of providing a molten electrolyte having alumina dissolved therein in an electrolytic cell containing the electrolyte. A non-consumable anode and cathode is disposed in the electrolyte, the anode comprised of Cu--Ni--Fe alloys having single metallurgical phase. Electric current is passed from the anode, through the electrolyte to the cathode thereby depositing aluminum on the cathode, and molten aluminum is collected from the cathode.

  20. Fe, Ni and Zn speciation, in airborne particulate matter

    NASA Astrophysics Data System (ADS)

    Thiodjio Sendja, Bridinette; Aquilanti, Giuliana; Vassura, Ivano; Giorgetti, Marco

    2016-05-01

    The study of elemental speciation in atmospheric particulate matter is important for the assessment of the source of the particle as well for the evaluation of its toxicity. XANES data at Fe, Ni, and Zn K-edges are recorded on a sample of urban dust (from the Rimini area of Emilia Romagna region, Italy) deposited on a filter and on the NIST standard reference material 1648. Using linear combination fitting we give an indication of the chemical species of the three metals present in the samples.

  1. Generalized melting criterion for amorphization. [NiZr, NiZr[sub 2], NiTi, FeTi

    SciTech Connect

    Devanathan, R. Northwestern Univ., Evanston, IL . Dept. of Materials Science and Engineering); Lam, N.Q.; Okamoto, P.R. ); Meshii, M. . Dept. of Materials Science and Engineering)

    1992-12-01

    We present a thermodynamic model of solid-state amorphization based on a generalization of the well-known Lindemann criterion. The original Lindemann criterion proposes that melting occurs when the root-mean-square amplitude of thermal displacement exceeds a critical value. This criterion can be generalized to include solid-state amorphization by taking into account the static displacements. In an effort to verify the generalized melting criterion, we have performed molecular dynamics simulations of radiation-induced amorphization in NiZr, NiZr[sub 2], NiTi and FeTi using embedded-atom potentials. The average shear elastic constant G was calculated as a function of the total mean-square atomic displacement following random atom-exchanges and introduction of Frenkel pairs. Results provide strong support for the generalized melting criterion.

  2. Oxidation of Fe-Cr-Al and Fe-Cr-Al-Y Single Crystals

    NASA Astrophysics Data System (ADS)

    Grabke, H. J.; Siegers, M.; Tolpygo, V. K.

    1995-03-01

    Single crystal samples of the alloy Fe-20%Cr-5%Al with and without Y-doping were used to study the "reactive element" (RE) effect, which causes improved oxidation behaviour and formation of a protective Al2O3 layer on this alloy. The oxidation was followed by AES at 10-7 mbar O2 up to about 1000 °C. Most observations were peculiar for this low pO2 environment, but yttrium clearly favors the formation of Al-oxide and stabilizes it also under these conditions, probably by favoring its nucleation. The oxides formed are surface compounds of about monolayer thickness, not clearly related to bulk oxides. Furthermore, the morphologies of oxide scales were investigated by SEM, after oxidation at 1000°C for 100 h at 133 mbar O2. On Fe-Cr-Al the scale is strongly convoluted and tends to spalling, whereas the presence of Y leads to flat scales which are well adherent. This difference is explained by a change in growth mechanism. The tendency for separation of oxide and metal was highest for the samples with low energy metal surface, i.e. (100) and (110), the scale was better adherent on the (111) oriented surface and on the polycrystalline specimen, since in the latter cases the overall energy for scale/metal separation is higher. All observations, from the low and from the high pO2 experiments, are discussed in relation to the approximately ten mechanisms proposed in the literature for explanation of the RE effects.

  3. Preparation, structure and mechanical properties of RuAl and (Ru,Ni)Al alloys

    SciTech Connect

    Sabariz, A.L.R.; Taylor, G.

    1997-12-31

    The intermetallic compound, RuAl with B2 CsCl type structure, has been shown to possess room-temperature toughness and plasticity. NiAl also forms a B2 compound and it is claimed that a pseudo-binary compound, (Ru,Ni)Al, may be formed because the difference in lattice parameter between the two binary phases is slight. In this work a study has been made of the mechanical properties of some polycrystalline compounds, across the RuAl-(Ru,Ni)Al pseudo-binary, prepared from high-purity elemental powders. Compressive yield stresses were measured between room-temperature and 900 C, and the mechanisms of plastic flow are discussed in relation to the dislocation structures observed by TEM. Hot-microhardness tests were made to provide an indication of the effect of solid-solution hardening.

  4. 1300 K compressive properties of a reaction milled NiAl-AlN composites

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Arzt, Eduard; Luton, Michael J.

    1990-01-01

    When B2 crystal-structure nickel aluminide is subjected to high-intensity mechanical ball milling in a liquid nitrogen bath, or 'cryomilling', an NiAl composite is obtained which contains about 10 vol pct AlN particles. This composition arises from the incorporation of N during cryomilling; during subsequent thermomechanical processing, the N reacts with Al. While compressive testing of extruded or isostatically pressed specimens at 1300 K indicated that strength at relatively fast strain rates is slightly dependent on consolidation method, slower strain rates indicate no clear dependency on densification technique: four different consolidation methods were found to yield similar creep strengths. The creep properties of NiAl-AlN are similar to those of the single-crystal Ni-base superalloy NASAIR 100.

  5. Temperature dependence of the activity of Al in dilute Ni(Al) solid solutions

    SciTech Connect

    Jiang Yong; Smith, J. R.; Evans, A. G.

    2006-12-01

    Activities of dilute Al solid solutions in Ni are determined from a first-principles approach. Both thermal lattice vibration and electronic contributions to free energies are considered and compared. Vibrational contributions tend to dominate the temperature dependencies of the free energies, though electron thermal effects are significant. Calculations show opposing temperature trends for the formation enthalpies and entropies, leading to a partial cancellation of their role in the overall energetics. Nevertheless, their remaining temperature effects are strong. Over the temperature range, 400 KAl activity coefficient varies by 15 orders of magnitude, due to the relative strength of Al-Ni and Al-Al bonds. The Ni activity coefficient only varies less than 4% over the same range. Calculational results compare well with available experimental data. The thermodynamic principles elucidated from the calculations are used to provide a fundamental interpretation.

  6. Tensile Creep of Polycrystalline Near-Stoichiometric NiAl

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2002-01-01

    Long term tensile creep studies were conducted on binary NiAl in the temperature range 700-1200 K with the objectives of characterizing and understanding the creep mechanisms. Inverse and normal primary creep curves were observed depending on stress and temperature. It was concluded that the creep of NiAl is limited by dislocation mobility. The stress exponent for creep, n, increased from 5.5 at 1200 K to 13.9 at 700 K. The true activation energy for creep, Qc, was constant and equal to about 400 kJ per mole between 20 and 50 MPa but decreased to a constant value of 250 kJ per mole between 50 and 110 MPa. The activation energy was observed to be stress dependent above 110 MPa. The tensile creep results reported in this investigation were compared with compression creep data reported in the literature. A detailed discussion of the probable dislocation creep mechanisms governing compressive and tensile creep of NiAl is presented. It is concluded that the non-conservative motion of jogs on screw dislocations influenced the nature of the primary creep curves, where the climb of these jogs involves either the next nearest neighbor or the six-jump cycle vacancy diffusion mechanism. The probable nature of the atom vacancy exchange that occur within the core of an edge dislocation undergoing climb in NiAl are schematically examined.

  7. Directional solidification studies in Ni-Al alloys

    SciTech Connect

    Lee, Je-hyun

    1993-05-01

    Three solid phases are involved in the phase equilibria of the intermetallic compound Ni{sub 3}Al near its melting point, {beta}, {gamma}{prime}(Ni{sub 3}Al), and {gamma}. The generally-accepted phase diagram involves a eutectic reaction between {beta}{prime} and {gamma}, but some recent studies agree with an older diagram due to Schramm, which has a eutectic reaction between the {beta} and {gamma}{prime} phases. The phase equilibria near Ni{sub 3}Al compositions was evaluated using quenched directional solidification experiments, that preserve the microstructures tonned at the solidification front, and using diffusion couple experiments. These experiments show that eutectic forms between {beta} and {gamma}{prime} phases, as in the Schramm diagram. Growth and phase transformations of these three phases are also studied in the directional solidification experiments. Microstructure analysis shows that etching of Ni{sub 3}Al({gamma}{prime}) is very sensitive to small composition variations and crystallographic orientation changes. The eutectic solidification study confirms that the equilibrium eutectic is {gamma}{prime}+{beta}, and that the metastable {gamma}+{beta} eutectic might be also produced in this system according to the impurities, solidification rates, and composition variations.

  8. Ductility enhancement in NiAl (B2)-base alloys by microstructural control

    NASA Astrophysics Data System (ADS)

    Ishida, K.; Kainuma, R.; Ueno, N.; Nishizawa, T.

    1991-02-01

    An attempt to improve ductility of NiAl (B2)-base alloys has been made by the addition of alloying elements and the control of microstructure. It has been found that a small amount of fcc γ phase formed by the addition of Fe, Co, and Cr has a drastic effect not only on the hot workability but also on the tensile ductility at room temperature. The enhancement in ductility is mainly due to the modification of Β-phase grains by the coexistence of γ phase. The effect of alloying elements on the hot forming ability is strongly related to the phase equilibria and partition behavior among γ, γ' (L12 structure), and Β phases in the Ni-Al-X alloy systems. The ductility-enhancement method shows promise for expanding the practical application of nickel aluminide.

  9. High temperature stability, interface bonding, and mechanical behavior in. beta. -NiAl and Ni sub 3 Al matrix composites with reinforcements modified by ion beam enhanced deposition

    SciTech Connect

    Grummon, D.S.

    1992-01-22

    In preparation for experiments with surface modified Al{sub 2}O{sub 3} reinforcements in {beta}NiAl, diffusion bonding experiments were conducted. FP alumina fibers were prepared with ion sputtered surface films (Al{sub 2}O{sub 3}, Al, Ni) and then composited with {beta}NiAl slabs and hot pressed. After 70 thermal cycles, interfacial shear strength was measured. A roughness mechanism is proposed for the observed increased strength of the coated fibers. Creep in Ni{sub 3}Al was studied. 3 figs, 1 tab. (DLC)

  10. The Charpy impact behavior of Fe{sub 3}Al and Fe{sub 3}Al-20 at % Mn alloys

    SciTech Connect

    Liu, J.N.; Yan, W.; Ma, J.L.; Wu, K.H.

    1997-12-31

    A series of experiments were conducted to investigate the impact fracture behavior of Fe{sub 3}Al and Fe{sub 3}Al-20 Mn alloys. The results of this study indicated that: (i) The addition of Mn introduces an ordered L1{sub 2}-type phase in the Fe{sub 3}Al-based alloys. On the other hand, the addition of Mn decreases the order parameter of the DO{sub 3} {alpha} phase. (ii) The total-impact energy of an Fe{sub 3}Al alloy increases with the temperature at the low-temperature range (<600 C), then drops around 700 C, and finally increases again as the temperature further elevates. (iii) The trend of the variation of the impact energy of Fe{sub 3}Al-20 at % Mn alloy with temperature is the same as that of the Fe{sub 3}Al alloy. (iv) And the addition of Mn significantly improves the impact energy of the Fe{sub 3}Al-based alloy, and changes the variation of the crack-growth energy with the testing temperature when the temperature is above 700 C.

  11. HYDROGEN ADSORPTION ON β-TiAl (001) AND Ni/TiAl (001) SURFACES

    NASA Astrophysics Data System (ADS)

    Mubarak, A. A. Karim; Alelaimi, Mahmoud

    2014-04-01

    In this paper, we present first principles calculations of the energetic, electronic and magnetic properties of the variant termination of TiAl (001) and Ni/TiAl (001) surfaces with and without hydrogen atoms. The calculations have been performed within the density functional theory using full-potential linearized augmented plane wave method. The generalized gradient approximation (GGA) is utilized as the exchange-correlation energy. The octahedral site is the stable absorption site of H atom in the β-TiAl system. This absorption reduces the cohesive energy of β-TiAl system due to increase in the lattice constant. The surface energy for both TiAl (001) terminations is calculated. The stable adsorption site of H atoms on the variant termination of TiAl (001) surface is performed. The adsorption energy of hydrogen on Ti is more energetic than that on Al. The adsorption of H atom on both terminations of H/Ni/TiAl (001) is more preferable at the bridge site. The adsorption energies are enhanced on Ni atom due to the contraction between d-Ni bands and TiAl substrate band.

  12. 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

  13. Effects of Ni content on nanocrystalline Fe-Co-Ni ternary alloys synthesized by a chemical reduction method

    NASA Astrophysics Data System (ADS)

    Chokprasombat, Komkrich; Pinitsoontorn, Supree; Maensiri, Santi

    2016-05-01

    Magnetic properties of Fe-Co-Ni ternary alloys could be altered by changing of the particle size, elemental compositions, and crystalline structures. In this work, Fe50Co50-xNix nanoparticles (x=10, 20, 40, and 50) were prepared by the novel chemical reduction process. Hydrazine monohydrate was used as a reducing agent under the concentrated basic condition with the presence of poly(vinylpyrrolidone). We found that the nanoparticles were composed of Fe, Co and Ni with compositions according to the molar ratio of the metal sources. Interestingly, the particles were well-crystalline at the as-prepared state without post-annealing at high temperature. Increasing Ni content resulted in phase transformation from body centered cubic (bcc) to face centered cubic (fcc). For the fcc phase, the average particle size decreased when increased the Ni content; the Fe50Ni50 nanoparticles had the smallest average size with the narrowest size distribution. In additions, the particles exhibited ferromagnetic properties at room temperature with the coercivities higher than 300 Oe, and the saturation magnetiation decreased with increasing Ni content. These results suggest that the structural and magnetic properties of Fe-Co-Ni alloys could be adjusted by varying the Ni content.

  14. Microstructure Evolution of Atomized Al-0.61 wt pct Fe and Al-1.90 wt pct Fe Alloys

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Dahlborg, Ulf; Bao, Cui Min; Calvo-Dahlborg, Monique; Henein, Hani

    2011-06-01

    The microstructure evolution of impulse atomized powders of Al-0.61 wt pct and Al-1.90 wt pct Fe compositions have been investigated with a scanning electron microscope, transmission electron microscope, neutron diffraction, and backscattering electron diffraction (EBSD). Both hypoeutectic and hypereutectic compositions demonstrated similar macrostructure ( i.e., primary α-Al dendrites/cells with eutectic Al-Fe intermetallics decorated at the dendritic/cellular walls). Selected area electron diffraction (SAED) analysis and SAED pattern simulation identified the eutectic Al-Fe intermetallic as AlmFe ( m = 4.0-4.4). This is verified by neutron diffraction analysis. Cubic texture was observed by EBSD on the droplets with dendritic growth direction close to <111>. The possible reasons are discussed.

  15. [NiFe] hydrogenases: structural and spectroscopic studies of the reaction mechanism.

    PubMed

    Ogata, Hideaki; Lubitz, Wolfgang; Higuchi, Yoshiki

    2009-10-01

    [NiFe] hydrogenases catalyze the reversible oxidation of dihydrogen. For this simple reaction the molecule has developed a complex catalytic mechanism, during which the enzyme passes through various redox states. The [NiFe] hydrogenase contains several metal centres, including the bimetallic Ni-Fe active site, iron-sulfur clusters and a Mg(2+) ion. The Ni-Fe active site is located in the inner part of the protein molecule, therefore a number of pathways are involved in the catalytic reaction route. These consist of an electron transfer pathway, a proton transfer pathway and a gas-access channel. Over the last 10-15 years we have been investigating the crystal structures of the [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F, which is a sulfate-reducing anaerobic bacterium. So far the crystal structures of the oxidized, H(2)-reduced and carbon monoxide inhibited states have been determined at high resolution and have revealed a rather unique structure of the hetero-bimetallic Ni-Fe active site. Furthermore, intensive spectroscopic studies have been performed on the enzyme. Based on the crystal structure, a water-soluble Ni-Ru complex has been synthesized as a functional model for the [NiFe] hydrogenases. The present review gives an overview of the catalytic reaction mechanism of the [NiFe] hydrogenases. PMID:19759926

  16. Magnetism of NiMn2O4-Fe3O4 spinel interfaces

    SciTech Connect

    Arenholz, Elke; Nelson-Cheeseman, B. B.; Chopdekar, R. V.; Bettinger, J. S.; Arenholz, E.; Suzuki, Y.

    2007-09-13

    We investigate the magnetic properties of the isostructural spinel-spinel interface of NiMn{sub 2}O{sub 4}(NMO)-Fe{sub 3}O{sub 4}. Although the magnetic transition temperature of the NMO film is preserved, both bulk and interface sensitive measurements demonstrate that the interface exhibits strong interfacial magnetic coupling up to room temperature. While NMO thin films have a ferrimagnetic transition temperature of 60 K, both NiFe{sub 2}O{sub 4} and MnFe{sub 2}O{sub 4} are ferrimagnetic at room temperature. Our experimental results suggest that these magnetic properties arise from a thin interdiffused region of (Fe,Mn,Ni){sub 3}O{sub 4} at the interface, leading to Mn and Ni magnetic properties similar to those of MnFe{sub 2}O{sub 4} and NiFe{sub 2}O{sub 4}.

  17. Interfacial Reactions Between In-Sn Solder and Ni-Fe Platings

    NASA Astrophysics Data System (ADS)

    Daghfal, John P.; Shang, P. J.; Liu, Z. Q.; Shang, J. K.

    2009-12-01

    Interfacial interactions in a Ni- xFe-Sn-In eutectic solder ( x = 30 at.%, 55 at.%) have been examined. Transmission and scanning electron microscopy (TEM/SEM) were utilized to investigate the structure, composition, and morphology of the intermetallic compounds (IMCs). Upon reflow, Ni3Sn4 and FeSn2 phases appeared at the interface along with Cu6Sn5 in the solder. Annealing experiments revealed the formation of a bilayer IMC that was Fe-rich adjacent to the Ni-Fe metallization and Ni-rich on the solder side. Kinetic studies established the apparent activation energies for both systems to be 51.8 kJ/mol and 85.1 kJ/mol, for 30 at.% and 55 at.% Fe contents, respectively. In the Fe-rich system, globular Ni3Sn4 crystals were formed upon reflow, but were changed into a cubic/faceted structure after annealing.

  18. Thermal Stability of Intermetallic Phases in Fe-rich Fe-Cr-Ni-Mo Alloys

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-09-01

    Understanding the thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys is critical to alloy design and application of Mo-containing austenitic steels. Coupled with thermodynamic modeling, the thermal stability of intermetallic Chi and Laves phases in two Fe-Cr-Ni-Mo alloys was investigated at 1273 K, 1123 K, and 973 K (1000 °C, 850 °C, and 700 °C) for different annealing times. The morphologies, compositions, and crystal structures of the precipitates of the intermetallic phases were carefully examined by scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and transmission electron microscopy. Two key findings resulted from this study. First, the Chi phase is stable at high temperature, and with the decreasing temperature it transforms into the Laves phase that is stable at low temperature. Secondly, Cr, Mo, and Ni are soluble in both the Chi and Laves phases, with the solubility of Mo playing a major role in the relative stability of the intermetallic phases. The thermodynamic models that were developed were then applied to evaluating the effect of Mo on the thermal stability of intermetallic phases in type 316 and NF709 stainless steels.

  19. Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys

    DOE PAGESBeta

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-06-12

    Understanding the stability of precipitate phases in the Fe-rich Fe-Cr-Ni-Mo alloys is critical to the alloy design and application of Mo-containing Austenitic steels. Coupled with thermodynamic modeling, stability of the chi and Laves phases in two Fe-Cr-Ni-Mo alloys were investigated at 1000, 850 and 700 °C for different annealing time. The morphologies, compositions and crystal structures of the matrix and precipitate phases were carefully examined by Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray diffraction and Transmission Electron Microscopy. The two key findings resulted from this work. One is that the chi phase is stable at high temperature and transformed intomore » the Laves phase at low temperature. The other is that both the chi and Laves phases have large solubilites of Cr, Mo and Ni, among which the Mo solubility has a major role on the relative stability of the precipitate phases. The developed thermodynamic models were then applied to evaluating the Mo effect on the stability of precipitate phases in AISI 316 and NF709 alloys.« less

  20. Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys

    SciTech Connect

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-06-12

    Understanding the stability of precipitate phases in the Fe-rich Fe-Cr-Ni-Mo alloys is critical to the alloy design and application of Mo-containing Austenitic steels. Coupled with thermodynamic modeling, stability of the chi and Laves phases in two Fe-Cr-Ni-Mo alloys were investigated at 1000, 850 and 700 °C for different annealing time. The morphologies, compositions and crystal structures of the matrix and precipitate phases were carefully examined by Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray diffraction and Transmission Electron Microscopy. The two key findings resulted from this work. One is that the chi phase is stable at high temperature and transformed into the Laves phase at low temperature. The other is that both the chi and Laves phases have large solubilites of Cr, Mo and Ni, among which the Mo solubility has a major role on the relative stability of the precipitate phases. The developed thermodynamic models were then applied to evaluating the Mo effect on the stability of precipitate phases in AISI 316 and NF709 alloys.

  1. The evolution of phase transformation in Ni/Ni3Al laminated composite under high temperature treatments

    NASA Astrophysics Data System (ADS)

    Shmorgun, V.; Gurevich, L.; Bogdanov, A.; Trunov, M.

    2016-02-01

    In this study the impact of isothermal annealing on the phase transformation rate in laminated Ni/Ni2Al3 composite was investigated. The method of nickel-aluminide coatings of the required chemical composition fabrication was proposed.

  2. Evaluation of Binary Fe-Ni Alloys as Intermediate-Temperature SOFC Interconnect

    SciTech Connect

    Zhu, Jiahong; Geng, Shujiang; Lu, Z G; Porter, Wallace D

    2007-01-01

    Binary Fe-Ni alloys with 45-60Ni (wt %) were evaluated as an interconnect material for intermediate-temperature solid oxide fuel cells (SOFCs). The oxidation resistance of the Fe-Ni alloys in air improved with increasing Ni content. The thermally grown oxide scale on these alloys generally consisted of a Fe{sub 2}O{sub 3} top layer and a (Fe,Ni){sub 3}O{sub 4} spinel inner layer, with the thickness of the Fe{sub 2}O{sub 3} layer decreasing as the Ni content increased. No measurable weight change was observed after isothermal oxidation in Ar+4%H{sub 2}+3%H{sub 2}O at 800 C and a metallic surface was maintained. The coefficient of thermal expansion (CTE) increased with the Ni content in these alloys and the CTE values were similar to those of other cell components. The (Fe,Ni){sub 3}O{sub 4} spinel with a composition similar to that thermally grown on the Fe-50Ni alloy exhibited a CTE value close to the alloy substrate, which aids scale spallation resistance for this alloy. The scale area specific resistance of the Fe-Ni alloys was found to be comparable to that of the current interconnect alloys, as a result of high electrical conductivity of the (Fe,Ni){sub 3}O{sub 4} spinel. The promise and issue with these Fe-Ni alloys as interconnect materials are highlighted and potential approaches to address the issue are outlined.

  3. Radiation resistance of (Ni,Fe)Cr2O4 spinels by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Van Brutzel, Laurent; Alvarez, Pierre; Chartier, Alain

    2014-05-01

    Molecular dynamics simulations are carried out to study primary radiation damage in NiCr2O4 and FeCr2O4 spinels, which are part of the corrosion layer of the vapour generators used in nuclear reactors. The radiation resistance of both spinels is evaluated by studying point defect recombination processes, threshold displacement energies, and 20 keV displacement cascades initiated with different PKA masses. Results are mainly in agreement with previous studies involving MgAl2O4 showing that radiation facilitates the transition to inverse spinel structure or NaCl structure. However, we find some differences between the two studied spinels indicating that NiCr2O4 is more sensitive to radiation.

  4. Abnormal magnetization behaviors in Sm-Ni-Fe-Cu alloys

    NASA Astrophysics Data System (ADS)

    Yang, W. Y.; Zhang, Y. F.; Zhao, H.; Chen, G. F.; Zhang, Y.; Du, H. L.; Liu, S. Q.; Wang, C. S.; Han, J. Z.; Yang, Y. C.; Yang, J. B.

    2016-06-01

    The magnetization behaviors in Sm-Ni-Fe-Cu alloys at low temperatures have been investigated. It was found that the hysteresis loops show wasp-waisted character at low temperatures, which has been proved to be related to the existence of multi-phases, the Fe/Ni soft magnetic phases and the CaCu5-type hard magnetic phase. A smooth-jump behavior of the magnetization is observed at T>5 K, whereas a step-like magnetization process appears at T<5 K. The CaCu5-type phase is responsible for such abnormal magnetization behavior. The magnetic moment reversal model with thermal activation is used to explain the relation of the critical magnetic field (Hcm) to the temperature (T>5 K). The reversal of the moment direction has to cross over an energy barrier of about 6.6×10-15 erg. The step-like jumps of the magnetization below 5 K is proposed to be resulted from a sharp increase of the sample temperature under the heat released by the irreversible domain wall motion.

  5. X-ray magnetic-circular-dichroism study of Ni/Fe (001) multilayers

    SciTech Connect

    Lin, T.; Schwickert, M.M.; Tomaz, M.A.; Chen, H.; Harp, G.R.

    1999-06-01

    The structure and magnetic properties of Fe/Ni(001) multilayers are studied using x-ray diffraction, magneto-optical Kerr effect magnetometry, and x-ray magnetic circular dichroism. Multilayers are deposited with constant Fe layers (12 {Angstrom}) and wedged Ni layers (0{endash}30 {Angstrom}), repeated 20 times, to explore the magnetic moment and the structure dependence upon thickness of Ni (t{sub Ni}). Up to t{sub Ni}{approx}16 {Angstrom} (11 ML), both the Fe and the Ni have a bct structure, similar to the bulk structure of bcc Fe. The magnetic moments of Ni in the bct region are nearly constant at 0.85{mu}{sub B} for a Ni thickness t{sub Ni} in the range 3 {Angstrom}{lt}t{sub Ni}{lt}16 {Angstrom}. This represents a significant enhancement over the moment in bulk fcc Ni (0.59{mu}B). The Fe/Ni multilayer undergoes a crystalline phase transition between 16 {Angstrom}{lt}t{sub Ni}{lt}23 {Angstrom}, beyond which both the Fe and Ni have an fct structure. In the fct region, the Ni magnetic moment is close to its bulk value and the Fe magnetic moment drops to 1.5{mu}{sub B}, which is {approximately}70{percent} of its bulk value. The crystalline phase transition is also accompanied by a rotation of the magnetic easy axis by 45{degree} in the plane of the film. {copyright} {ital 1999} {ital The American Physical Society}

  6. Interface bonding of NiCrAlY coating on laser modified H13 tool steel surface

    NASA Astrophysics Data System (ADS)

    Reza, M. S.; Aqida, S. N.; Ismail, I.

    2016-06-01

    Bonding strength of thermal spray coatings depends on the interfacial adhesion between bond coat and substrate material. In this paper, NiCrAlY (Ni-164/211 Ni22 %Cr10 %Al1.0 %Y) coatings were developed on laser modified H13 tool steel surface using atmospheric plasma spray (APS). Different laser peak power, P p, and duty cycle, DC, were investigated in order to improve the mechanical properties of H13 tool steel surface. The APS spraying parameters setting for coatings were set constant. The coating microstructure near the interface was analyzed using IM7000 inverted optical microscope. Interface bonding of NiCrAlY was investigated by interfacial indentation test (IIT) method using MMT-X7 Matsuzawa Hardness Tester Machine with Vickers indenter. Diffusion of atoms along NiCrAlY coating, laser modified and substrate layers was investigated by energy-dispersive X-ray spectroscopy (EDXS) using Hitachi Tabletop Microscope TM3030 Plus. Based on IIT method results, average interfacial toughness, K avg, for reference sample was 2.15 MPa m1/2 compared to sample L1 range of K avg from 6.02 to 6.96 MPa m1/2 and sample L2 range of K avg from 2.47 to 3.46 MPa m1/2. Hence, according to K avg, sample L1 has the highest interface bonding and is being laser modified at lower laser peak power, P p, and higher duty cycle, DC, prior to coating. The EDXS analysis indicated the presence of Fe in the NiCrAlY coating layer and increased Ni and Cr composition in the laser modified layer. Atomic diffusion occurred in both coating and laser modified layers involved in Fe, Ni and Cr elements. These findings introduce enhancement of coating system by substrate surface modification to allow atomic diffusion.

  7. The formation of twinned austenite in Fe-10Cr-10Ni-2W maraging steel

    SciTech Connect

    Suk, J.I.; Hong, S.H.; Nam, S.W. )

    1991-12-01

    The precipitation hardening mechanisms in high strength maraging steels have been studied in detail by many investigators, but limited information is available on the formation of austenite during aging. Some investigations have been concerned with the understanding of the effect of reverted austenite formed during aging on the mechanical properties. However, only a few investigations have been reported on the morphology and crystallographic feature of austenite. Shiang and Wayman first reported the twin-related and coupled morphology of Widmanstatten austenite plates which were frequently observed in maraging steel. In addition, Ameyama et al. reported the morphology and crystallographic features of austenite formed in ferrite grain during aging in a two-phase stainless steel, and found that each side of the austenite pair of twins satisfies the Kurdjumov-Sachs (K-S) orientation relationship with the parent phase. The morphology and crystallographic features of the reverted austenite formed during aging of Fe-10Cr-10Ni-2W stainless maraging steel have been investigated in this paper. The major strengthening precipitate in Fe-10Cr-10Ni-2W maraging steels has been identified as the rod-shaped {eta}-Ni{sub 3}Ti phase in our previous study. The peculiar morphology of the austenite, i.e., twinned austenite, also has been found in our studies of maraging steel in the Fe-10Cr-10Ni-2W lath martensite. In addition, computer simulation of the diffraction pattern is used to confirm the orientation relationships, such as the Kurdjumov-Sachs (K-S) relationship, the Nishiyama-Wasserman (N-W) relationship and the twin relationship by comparisons with the experimentaly observed results.

  8. Precipitation Strengthening in Al-Ni-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Fan, Yangyang; Huang, Kai; Makhlouf, Makhlouf M.

    2015-12-01

    Precipitation hardening of eutectic and hypoeutectic Al-Ni alloys by 2 to 4 wt pct. manganese is investigated with focus on the effect of the alloys' chemical composition and solidification cooling rate on microstructure and tensile strength. Within the context of the investigation, mathematical equations based on the Orowan Looping strengthening mechanism were used to calculate the strengthening increment contributed by each of the phases present in the aged alloy. The calculations agree well with measured values and suggest that the larger part of the alloy's yield strength is due to the Al3Ni eutectic phase, this is closely followed by contribution from the Al6Mn particles, which precipitate predominantly at grain boundaries.

  9. First-principles investigations of Ni3Al(111) and NiAl(110) surfaces at metal dusting conditions

    SciTech Connect

    Saadi, Souheil

    2011-03-01

    We investigate the structure and surface composition of the {gamma}{prime}-Ni{sub 3}Al(111) and {beta}-NiAl(110) alloy surfaces at conditions relevant for metal dusting corrosion related to catalytic steam reforming of natural gas. In regular service as protective coatings, nickel-aluminum alloys are protected by an oxide scale, but in case of oxide scale spallation, the alloy surface may be directly exposed to the reactive gas environment and vulnerable to metal dusting. By means of density functional theory and thermochemical calculations for both the Ni{sub 3}Al and NiAl surfaces, the conditions under which CO and OH adsorption is to be expected and under which it is inhibited, are mapped out. Because CO and OH are regarded as precursors for nucleating graphite or oxide on the surfaces, phase diagrams for the surfaces provide a simple description of their stability. Specifically, this study shows how the CO and OH coverages depend on the steam to carbon ratio (S/C) in the gas and thereby provide a ranking of the carbon limits on the different surface phases.

  10. Observations of Al, Fe and Ca(+) in Mercury's Exosphere

    NASA Technical Reports Server (NTRS)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

    We report 5-(sigma) tangent column detections of Al and Fe, and strict 3-(sigma) tangent column upper limits for Ca(+) in Mercury's exosphere obtained using the HIRES spectrometer on the Keck I telescope. These are the first direct detections of Al and Fe in Mercury's exosphere. Our Ca(-) observation is consistent with that reported by The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft.

  11. Adherent Al2O3 scales formed on undoped NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1987-01-01

    Changes in the spalling behavior of Al2O3 scales formed on an undoped NiCrAl alloy are described. Two samples of Ni-15Cr-13Al (wt pct), one a control and the other sanded, were subjected to 25 oxidation cycles. It is observed that adherent scales formed on the sanded sample; however, the control sample had speckled, spalled scales. The data reveal that the adherent scales are caused by repeated removal of surface layers after each oxidation cycle. It is determined that interfacial segregation of sulfur influences spallation and sulfur removal increases bonding. The effect of moisture on scale adhesions is investigated.

  12. Effect of Complex Inclusion Particles on the Solidification Structure of Fe-Ni-Mn-Mo Alloy

    NASA Astrophysics Data System (ADS)

    Park, Jun Seok; Lee, Changhee; Park, Joo Hyun

    2012-12-01

    The effect of combinations of several deoxidizers, i.e., Mg-Al, Mg-Ti, Al-Ti, and Ce-Al, on the solidification structure of Fe-2 mass pct Ni-1 mass pct Mn-1 mass pct Mo alloy melt was investigated using a melt sampling and quenching method. Using this method, we evaluated the catalytic potency of several complex inclusion particles by taking the inclusion evolution process into account. Fine equiaxed crystals were obtained in the Mg-Ti-deoxidized steel wherein the MgO(MgAl2O4)-TiN complex compounds formed. However, the longer the holding time at high temperatures, the larger the fraction of Ti2O3, and very fine TiN formed because of microsegregation during solidification, resulting in poor equiaxed crystals. When the steel was deoxidized with Mg-Al, the initial structure was dominantly columnar. However, the longer the holding time, the larger the fraction of MgAl2O4 spinel, resulting in the formation of fine equiaxed crystals. Ce-Al complex deoxidation provided a relatively small portion of equiaxed crystals, whereas Ti-Al deoxidation produced the fewest equiaxed crystals because of the formation of alumina. The effectiveness of each inoculant particle for the crystallization of the primary δ-iron was explained well by the lattice disregistry concept.

  13. Mechanical properties of several Fe-Ni meteorites

    SciTech Connect

    Mulford, Roberta N; El - Dasher, Bassem

    2010-10-28

    The strength and elastic constants of meteorites are of increasing interest as predictions of meteorite impacts on earth come within the realm of possibility. In addition, meteorite impacts on extraterrestrial bodies provide an excellent sampling tool for evaluation of planetary compositions and properties. Fe-Ni meteorites provide a well-defined group of materials of fairly uniform composition. Iron-nickel meteorites exhibit a unique lamellar microstructure, a Widmanstatten structure, consisting of small regions with steep-iron-nickel composition gradients. This microstructure is found in the Fe-Ni system only in meteorites, and is believed to arise as a result of slow cooling in a planetary core or other large mass. Meteorites with compositions consisting of between 5 and 17% nickel in iron are termed 'octahedrite,' and further characterized according to the width of the Ni-poor kamacite bands; 'fine,' (0.2-0.5 mm) 'medium,' (0.5-1.3 mm) and 'coarse,' (1.5-3.3 mm). Many meteorites have inclusions and structures indicating that the material has been shocked at some point early in its evolution. Several Iron-nickel meteorites have been examined using Vickers and spherical indentation, x-ray fluorescence, and EBSD. Direct observation of mechanical properties in these highly structured materials provides a valuable supplement to bulk measurements, which frequently exhibit large variation in dynamic properties, even within a single sample. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens. Additional meteorite specimens have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon re-entry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure.

  14. Fabrication and properties of functionally graded NiAl/Al2O3 composites

    NASA Technical Reports Server (NTRS)

    Miller, D. P.; Lannutti, J. J.; Noebe, R. D.

    1993-01-01

    A modified sedimentation process was used in the production of a functionally gradient material (FGM), NiAl/Al2O3. A simple finite element model was used to guide our design and fabrication efforts by estimating residual stress states as a function of composite structure. This approach could lead to tailored designs that enhance or avoid specific residual stress states. Thermal cycling tests were factored into the model to predict time dependent or steady-state internal temperature and stress profiles. Four-point bend tests were conducted to establish the mechanical load-displacement behavior of a single interlayer FGM at room temperature, 800 and 1000 K. Room temperature bend strength of the FGM was 3-4 times that of the base NiAl. At elevated temperatures, composite fracture occurred in a gradual, noncatastrophic mode involving NiAl retardation of a succession of cracks originating in the alumina face.

  15. Exponentially decaying magnetic coupling in sputtered thin film FeNi/Cu/FeCo trilayers

    SciTech Connect

    Wei, Yajun Akansel, Serkan; Thersleff, Thomas; Brucas, Rimantas; Lansaker, Pia; Leifer, Klaus; Svedlindh, Peter; Harward, Ian; Celinski, Zbigniew; Ranjbar, Mojtaba; Dumas, Randy K.; Jana, Somnath; Pogoryelov, Yevgen; Karis, Olof; Åkerman, Johan

    2015-01-26

    Magnetic coupling in trilayer films of FeNi/Cu/FeCo deposited on Si/SiO{sub 2} substrates have been studied. While the thicknesses of the FeNi and FeCo layers were kept constant at 100 Å, the thickness of the Cu spacer was varied from 5 to 50 Å. Both hysteresis loop and ferromagnetic resonance results indicate that all films are ferromagnetically coupled. Micromagnetic simulations well reproduce the ferromagnetic resonance mode positions measured by experiments, enabling the extraction of the coupling constants. Films with a thin Cu spacer are found to be strongly coupled, with an effective coupling constant of 3 erg/cm{sup 2} for the sample with a 5 Å Cu spacer. The strong coupling strength is qualitatively understood within the framework of a combined effect of Ruderman-Kittel-Kasuya-Yosida and pinhole coupling, which is evidenced by transmission electron microscopy analysis. The magnetic coupling constant surprisingly decreases exponentially with increasing Cu spacer thickness, without showing an oscillatory thickness dependence. This is partially connected to the substantial interfacial roughness that washes away the oscillation. The results have implications on the design of multilayers for spintronic applications.

  16. Exponentially decaying magnetic coupling in sputtered thin film FeNi/Cu/FeCo trilayers

    NASA Astrophysics Data System (ADS)

    Wei, Yajun; Akansel, Serkan; Thersleff, Thomas; Harward, Ian; Brucas, Rimantas; Ranjbar, Mojtaba; Jana, Somnath; Lansaker, Pia; Pogoryelov, Yevgen; Dumas, Randy K.; Leifer, Klaus; Karis, Olof; Åkerman, Johan; Celinski, Zbigniew; Svedlindh, Peter

    2015-01-01

    Magnetic coupling in trilayer films of FeNi/Cu/FeCo deposited on Si/SiO2 substrates have been studied. While the thicknesses of the FeNi and FeCo layers were kept constant at 100 Å, the thickness of the Cu spacer was varied from 5 to 50 Å. Both hysteresis loop and ferromagnetic resonance results indicate that all films are ferromagnetically coupled. Micromagnetic simulations well reproduce the ferromagnetic resonance mode positions measured by experiments, enabling the extraction of the coupling constants. Films with a thin Cu spacer are found to be strongly coupled, with an effective coupling constant of 3 erg/cm2 for the sample with a 5 Å Cu spacer. The strong coupling strength is qualitatively understood within the framework of a combined effect of Ruderman-Kittel-Kasuya-Yosida and pinhole coupling, which is evidenced by transmission electron microscopy analysis. The magnetic coupling constant surprisingly decreases exponentially with increasing Cu spacer thickness, without showing an oscillatory thickness dependence. This is partially connected to the substantial interfacial roughness that washes away the oscillation. The results have implications on the design of multilayers for spintronic applications.

  17. Magnetic and Dielectric Property Studies in Fe- and NiFe-Based Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Sharma, Himani; Jain, Shubham; Raj, Pulugurtha Markondeya; Murali, K. P.; Tummala, Rao

    2015-10-01

    Metal-polymer composites were investigated for their microwave properties in the frequency range of 30-1000 MHz to assess their application as inductor cores and electromagnetic isolation shield structures. NiFe and Fe nanoparticles were dispersed in epoxy as nanocomposites, in different volume fractions. The permittivity, permeability, and loss tangents of the composites were measured with an impedance analyzer and correlated with the magnetic properties of the particle such as saturation magnetization and field anisotropy. Fe-epoxy showed lower magnetic permeability but improved frequency stability, compared to the NiFe-epoxy composites of the same volume loading. This is attributed to the differences in nanoparticle's structure such as effective metal core size and particle-porosity distribution in the polymer matrix. The dielectric properties of the nanocomposites were also characterized from 30 MHz to 1000 MHz. The instabilities in the dielectric constant and loss tangent were related to the interfacial polarization relaxation of the particles and the dielectric relaxation of the surface oxides.

  18. Studies on the Sliding Wear Performance of Plasma Spray Ni-20Cr and Ni3Al Coatings

    NASA Astrophysics Data System (ADS)

    Kaur, Maninder; Singh, Harpreet; Singh, Balraj; Singh, Bhupinder

    2010-01-01

    Two metallic powders namely Ni-20Cr and Ni3Al were coated on AISI 309 SS steel by shrouded plasma spray process. The wear behavior of the bare, Ni-20Cr and Ni3Al-coated AISI 309 SS steel was investigated according to ASTM Standard G99-03 on a Pin-on-Disc Wear Test Rig. The wear tests were carried out at normal loads of 30 and 50 N with a sliding velocity of 1 m/s. Cumulative wear rate and coefficient of friction (μ) were calculated for all the cases. The worn-out surfaces were then examined by scanning electron microscopy analysis. Both the as-sprayed coatings exhibited typical splat morphology. The XRD analysis indicated the formation of Ni phase for the Ni-20Cr coating and Ni3Al phase for the Ni3Al coating. It has been concluded that the plasma-sprayed Ni-20Cr and Ni3Al coatings can be useful to reduce the wear rate of AISI 309 SS steel. The coatings were found to be adherent to the substrate steel during the wear tests. The plasma-sprayed Ni3Al coating has been recommended as a better choice to reduce the wear of AISI 309 SS steel, in comparison with the Ni-20Cr coating.

  19. Alloy development and processing of FeAl: An overview

    SciTech Connect

    Maziasz, P.J.; Goodwin, G.M.; Alexander, D.J.; Viswanathan, S.

    1997-03-01

    In the last few years, considerable progress has been made in developing B2-phase FeAl alloys with improved weldability, room-temperature ductility, and high-temperature strength. Controlling the processing-induced microstructure is also important, particularly for minimizing trade-offs in various properties. FeAl alloys have outstanding resistance to high-temperature oxidation, sulfidation, and corrosion in various kinds of molten salts due to formation of protective Al{sub 2}O{sub 3} scales. Recent work shows that FeAl alloys are carburization-resistant as well. Alloys with 36 to 40 at. % Al have the best combination of corrosion resistance and mechanical properties. Minor alloying additions of Mo, Zr, and C, together with microalloying additions of B, produce the best combination of weldability and mechanical behavior. Cast FeAl alloys, with 200 to 400 {mu}m grain size and finely dispersed ZrC, have 2 to 5% tensile ductility in air at room-temperature, and a yield strength > 400 MPa up to about 700 to 750{degrees}C. Extruded ingot metallurgy (I/M) and powder metallurgy (P/M) materials with refined grain sizes ranging from 2 to 50 {mu}m, can have 10 to 15% ductility in air and be much stronger, and can even be quite tough, with Charpy impact energies ranging from 25 to 105 J at room-temperature. This paper highlights progress made in refining the alloy composition and exploring processing effects on FeAl for monolithic applications. It also includes recent progress on developing FeAl weld-overlay technology, and new results on welding of FeAl alloys. It summarizes some of the current industrial testing and interest for applications.

  20. Role of defect coordination environment on point defects formation energies in Ni-Al intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Tennessen, Emrys; Rondinelli, James

    We present a relationship among the point defect formation energies and the bond strengths, lengths, and local coordination environment for Ni-Al intermetallic alloys based on density functional calculations, including Ni3Al, Ni5Al3, NiAl,Ni3Al4, Ni2Al3 and NiAl3. We find the energetic stability of vacancy and anti-site defects for the entire family can be attributed primarily to changes in interactions among first nearest neighbors, owing to spatially localized charge density reconstructions in the vicinity of the defect site. We also compare our interpretation of the local coordination environment with a DFT-based cluster expansion and discuss the performance of each approach in predicting defect stability in the Ni-Al system.

  1. Electrical, magnetic, and corrosion resistance properties of TiO2 nanotubes filled with NiFe2O4 quantum dots and Ni-Fe nanoalloy

    NASA Astrophysics Data System (ADS)

    Bahgat, Mohamed; Farghali, Ahmed A.; Moustafa, Ahmed F.; Khedr, Mohamed H.; Mohassab-Ahmed, Mohassab Y.

    2013-06-01

    This work was carried out as an integral part of a project aiming to improve the catalytic, electrical, magnetic, and mechanical properties of synthesized TiO2NTs filled with metal ferrites. TiO2 nanotubes in the anatase-phase (TiO2NTs) were prepared using a hydrothermal method followed by ion exchange and phase transformation. The obtained TiO2NTs were filled with NiFe2O4 quantum dots (QDs) and then reacted at 600 °C in a reducing atmosphere to produce TiO2NTs filled with Ni-Fe nanoalloy. The effect of the TiO2NTs' coating on the dissolution rate of Ni-Fe nanoalloy in 0.5 M HCl solution was monitored chemically using a weight-loss technique that was performed at different temperatures. The TiO2NTs' coating exhibited high protective performance and amazing corrosion resistance. The magnetic properties of the TiO2NTs filled with NiFe2O4 QDs and Ni-Fe nanoalloy compacts were analyzed by a vibrating sample magnetometer. The electrical conductivity-temperature dependence of anatase TiO2NTs, anatase TiO2NTs filled with NiFe2O4 quantum dots, anatase TiO2NTs filled with Ni-Fe nanoalloy, and NiFe2O4 was measured in the temperature range of 25-850 °C. The conductivity increased with temperature, indicating the semiconductor-like nature of the sample. During cooling, the conductivity retains values higher than that obtained during heating.

  2. Selective recovery of dissolved Fe, Al, Cu, and Zn in acid mine drainage based on modeling to predict precipitation pH.

    PubMed

    Park, Sang-Min; Yoo, Jong-Chan; Ji, Sang-Woo; Yang, Jung-Seok; Baek, Kitae

    2015-02-01

    Mining activities have caused serious environmental problems including acid mine drainage (AMD), the dispersion of mine tailings and dust, and extensive mine waste. In particular, AMD contaminates soil and water downstream of mines and generally contains mainly valuable metals such as Cu, Zn, and Ni as well as Fe and Al. In this study, we investigated the selective recovery of Fe, Al, Cu, Zn, and Ni from AMD. First, the speciation of Fe, Al, Cu, Zn, and Ni as a function of the equilibrium solution pH was simulated by Visual MINTEQ. Based on the simulation results, the predicted pHs for the selective precipitation of Fe, Al, Cu, and Zn/Ni were determined. And recovery yield of metals using simulation is over 99 %. Experiments using artificial AMD based on the simulation results confirmed the selective recovery of Fe, Al, Cu, and Zn/Ni, and the recovery yields of Fe/Al/Cu/Zn and Fe/Al/Cu/Ni mixtures using Na2CO3 were 99.6/86.8/71.9/77.0 % and 99.2/85.7/73.3/86.1 %, respectively. After then, the simulation results were applied to an actual AMD for the selective recovery of metals, and the recovery yields of Fe, Al, Cu, and Zn using NaOH were 97.2, 74.9, 66.9, and 89.7 %, respectively. Based on the results, it was concluded that selective recovery of dissolved metals from AMD is possible by adjusting the solution pH using NaOH or Na2CO3 as neutralizing agents. PMID:25231736

  3. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  4. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids were observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. The voids resulted from an excess number of oxygen vacancies near the oxidemetal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidation of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al, Cr)2O3 and Ni(Al, Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationship between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  5. Directional alignment of FeCo crystallites in Si/NiFe/Ru/FeCoB multilayer with high anisotropy field above 500 Oe.

    PubMed

    Hirata, Ken-Ichiro; Gomi, Shunsuke; Nakagawa, Shigeki

    2011-03-01

    In-plane magnetic anisotropy and crystal structure of FeCoB layer on Si/NiFe/Ru underlayer were investigated by using X-Ray Diffraction (XRD) measurement. A pole-figure measurement of XRD showed directionally tilted alignment of FeCo crystallites in Si/NiFe/Ru/FeCoB multilayered film with high in-plane anisotropy field H(k) but no directional alignment was found in FeCoB single layered film. The higher H(k) appeared in the Si/NiFe/Ru/FeCoB multilayered configuration with the thicker FeCoB layer. Since Ru crystallites in a multiunderlayer configuration exhibited no directional alignment, the surface structure of underlayer should be no main reason for the directional alignment of FeCo crystallites deposited on it. The dependence of hickness of FeCoB layer in Si/NiFe/Ru/FeCoB film on H(k) indicated that the in-plane magnetic anisotropy is caused by not only the structure of Ru underlayer but also oblique incidence effect of sputtered particles, which is attained in configuration of Facing Targets Sputtering (FTS) system. From these experimental results, remarkably high H(k) of 540 Oe was obtained. PMID:21449466

  6. Point defect processes in neutron irradiated Ni, Fe-15Cr-16Ni and Ti-added modified SUS316SS

    NASA Astrophysics Data System (ADS)

    Horiki, M.; Yoshiie, T.; Sato, K.; Xu, Q.

    2013-05-01

    The defect structures in Ni, Fe-15Cr-16Ni and Ti-added modified SUS316SS (modified SUS316) were examined after neutron irradiation below 0.3 dpa by the Japan Materials Testing Reactor and Belgian Reactor 2 to compare their defect structural evolution. The growth behaviour of interstitial-type dislocation loops (I-loops), stacking fault tetrahedra (SFTs) and voids was found to be quite different among these specimens. I-loops developed at lower temperatures in Ni than in Fe-15Cr-16Ni and modified SUS316, and more swelling occurred in Ni than in Fe-15Cr-16Ni. Finally, there were no voids in modified SUS316. These results were analysed in terms of the I-loop energy. A large discrepancy was found between the analytical results and experimental observations for Ni and modified SUS316, which suggests the formation of unfaulted I-loops directly from collision cascades. The growth of SFTs was detected in Fe-15Cr-16Ni and modified SUS316, and can be explained by a change in the dislocation bias of SFTs resulting from the absorption of alloying elements.

  7. Grain boundary character distribution of CuNiSi and FeNi alloys processed by severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Azzeddine, H.; Baudin, T.; Helbert, A. L.; Brisset, F.; Larbi, F. Hadj; Tirsatine, K.; Kawasaki, M.; Bradai, D.; Langdon, T. G.

    2015-04-01

    In this work the Grain Boundary Character Distribution (GBCD) in general and the relative proportion of low-Σ CSL (Coincidence Site Lattice) grain boundaries are determined through EBSD in Cu-2.5Ni-0.6Si (wt.%) and Fe-36Ni (wt.%) alloys after processing by high-pressure torsion, equal- channel angular pressing and accumulative roll bonding.

  8. Large spin pumping effect in antisymmetric precession of Ni79Fe21/Ru/Ni79Fe21

    NASA Astrophysics Data System (ADS)

    Yang, H.; Li, Y.; Bailey, W. E.

    2016-06-01

    In magnetic trilayer structures, a contribution to the Gilbert damping of ferromagnetic resonance arises from spin currents pumped from one layer to another. This contribution has been demonstrated for layers with weakly coupled, separated resonances, where magnetization dynamics are excited predominantly in one layer and the other layer acts as a spin sink. Here, we show that trilayer structures in which magnetizations are excited simultaneously, antisymmetrically, show a spin-pumping effect roughly twice as large. The antisymmetric (optical) mode of antiferromagnetically coupled Ni79Fe21(8 nm)/Ru/Ni79Fe21(8 nm) trilayers shows a Gilbert damping constant greater than that of the symmetric (acoustic) mode by an amount as large as the intrinsic damping of Py ( Δα≃0.006 ). The effect is shown equally in field-normal and field-parallel to film plane geometries over 3-25 GHz. The results confirm a prediction of the spin pumping model and have implications for the use of synthetic antiferromagnets (SAF)-structures in GHz devices.

  9. Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

    1996-01-01

    A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

  10. Influence of FeCrAl Content on Microstructure and Bonding Strength of Plasma-Sprayed FeCrAl/Al2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Luo, Fa; Zhou, Wancheng; Zhu, Dongmei

    2016-02-01

    Low-power plasma-sprayed FeCrAl/Al2O3 composite coatings with 1.5 mm thickness have been fabricated for radar absorption applications. The effects of FeCrAl content on the coating properties were studied. The FeCrAl presents in the form of a few thin lamellae and numerous particles, demonstrating relatively even distribution in all the coatings. Results show that the micro-hardness and porosity decrease with the increase in FeCrAl content. With FeCrAl content increasing from 28 to 47 wt.%, the bonding strength of the coatings with 1.5 mm thickness increases from 10.5 to 27 MPa, and the failure modes are composed of cohesive and adhesive failure, which are ascribed to the coating microstructure and the residual stress, respectively.

  11. An Assessment of the Al- Fe- N System

    NASA Astrophysics Data System (ADS)

    Hillert, Mats; Jonsson, Stefan

    1992-11-01

    The thermodynamic properties of the Al-Fe-N system are assessed, taking various types of information into account. For solid AIN, a description very similar to that given by JANAF is found to yield reasonable predictions for the solubility of A1N in face-centered cubic (fcc) Fe and in liquid Fe. An ionic two-sublattice model is applied to the liquid phase, containing two N species, N-3 and N0 The melting point of A1N is taken as 3068 K, and a required gas pressure of 9.75 bar is predicted. A sublimation point of 2690 K at 1 bar is also predicted. A plot of the liquidus surfaces in the Fe-rich end of the Al-Fe-N system is presented.

  12. Thermal plasma synthesis of Fe{sub 1−x}Ni{sub x} alloy nanoparticles

    SciTech Connect

    Raut, Suyog A.; Kanhe, Nilesh S.; Bhoraskar, S. V.; Mathe, V. L.; Das, A. K.

    2014-04-24

    Fe-Ni alloy nanoparticles are of great interest because of diverse practical applications in the fields such as magnetic fluids, high density recording media, catalysis and medicine. We report the synthesis of Fe-Ni nanoparticles via thermal plasma route. Thermal plasma assisted synthesis is a high temperature process and gives high yields of production. Here, we have used direct arc thermal plasma plume of 6kw as a source of energy at operating pressure 500 Torr. The mixture of Fe-Ni powder in required proportion (Fe{sub 1−x}Ni{sub x}; x=0.30, 0.32, 0.34, 0.36, 0.38 and 0.40) was made to evaporate simultaneously from the graphite anode in thermal plasma reactor to form Fe-Ni bimetallic nanoparticles. The as synthesized particles were characterized by X-Ray Diffraction (XRD), Thermo-Gravimetric Analysis/Differential Scanning Calorimtry (TGA/DSC)

  13. Structural and magnetic properties of FeNi thin films fabricated on amorphous substrates

    SciTech Connect

    Tashiro, T. Y.; Mizuguchi, M. Kojima, T.; Takanashi, K.; Koganezawa, T.; Kotsugi, M.; Ohtsuki, T.

    2015-05-07

    FeNi films were fabricated by sputtering and rapid thermal annealing on thermally amorphous substrates to realize the formation of an L1{sub 0}-FeNi phase by a simple method. Structural and magnetic properties of FeNi films were investigated by varying the annealing temperature. L1{sub 0}-FeNi superlattice peaks were not observed in X-ray diffraction patterns, indicating no formation of L1{sub 0}-ordered phase, however, the surface structure systematically changed with the annealing temperature. Magnetization curves also revealed a drastic change depending on the annealing temperature, which indicates the close relation between the morphology and magnetic properties of FeNi films fabricated on amorphous substrates.

  14. Molecular evolution of gas cavity in [NiFeSe] hydrogenases resurrected in silico.

    PubMed

    Tamura, Takashi; Tsunekawa, Naoki; Nemoto, Michiko; Inagaki, Kenji; Hirano, Toshiyuki; Sato, Fumitoshi

    2016-01-01

    Oxygen tolerance of selenium-containing [NiFeSe] hydrogenases (Hases) is attributable to the high reducing power of the selenocysteine residue, which sustains the bimetallic Ni-Fe catalytic center in the large subunit. Genes encoding [NiFeSe] Hases are inherited by few sulphate-reducing δ-proteobacteria globally distributed under various anoxic conditions. Ancestral sequences of [NiFeSe] Hases were elucidated and their three-dimensional structures were recreated in silico using homology modelling and molecular dynamic simulation, which suggested that deep gas channels gradually developed in [NiFeSe] Hases under absolute anaerobic conditions, whereas the enzyme remained as a sealed edifice under environmental conditions of a higher oxygen exposure risk. The development of a gas cavity appears to be driven by non-synonymous mutations, which cause subtle conformational changes locally and distantly, even including highly conserved sequence regions. PMID:26818780

  15. Molecular evolution of gas cavity in [NiFeSe] hydrogenases resurrected in silico

    NASA Astrophysics Data System (ADS)

    Tamura, Takashi; Tsunekawa, Naoki; Nemoto, Michiko; Inagaki, Kenji; Hirano, Toshiyuki; Sato, Fumitoshi

    2016-01-01

    Oxygen tolerance of selenium-containing [NiFeSe] hydrogenases (Hases) is attributable to the high reducing power of the selenocysteine residue, which sustains the bimetallic Ni-Fe catalytic center in the large subunit. Genes encoding [NiFeSe] Hases are inherited by few sulphate-reducing δ-proteobacteria globally distributed under various anoxic conditions. Ancestral sequences of [NiFeSe] Hases were elucidated and their three-dimensional structures were recreated in silico using homology modelling and molecular dynamic simulation, which suggested that deep gas channels gradually developed in [NiFeSe] Hases under absolute anaerobic conditions, whereas the enzyme remained as a sealed edifice under environmental conditions of a higher oxygen exposure risk. The development of a gas cavity appears to be driven by non-synonymous mutations, which cause subtle conformational changes locally and distantly, even including highly conserved sequence regions.

  16. NiFe2O4/graphene nanocomposites with tunable magnetic properties

    NASA Astrophysics Data System (ADS)

    Heidari, Elham Kamali; Ataie, Abolghasem; Sohi, Mahmoud Heydarzadeh; Kim, Jang-Kyo

    2015-04-01

    Novel NiFe2O4/graphene nanocomposites were synthesized via facile, one-pot solvothermal route, and the effects of processing conditions and composition on their magnetic properties have been studied. The nanocomposites consisted of monolayer graphene sheets decorated with uniformly dispersed NiFe2O4 nanoparticles of 6 nm in diameter. Increases in solvothermal temperature and time gave rise to improved crystallinity of NiFe2O4 nanoparticles and thus enhanced magnetic properties, while a high NiFe2O4 content resulted in a similar ameliorating effect on saturation magnetization, demonstrating tailored functional properties. A magnetic interaction between NiFe2O4/grahene was observed.

  17. Mössbauer and SEM study of Fe Al film

    NASA Astrophysics Data System (ADS)

    Sebastian, Varkey; Sharma, Ram Kripal; Lakshmi, N.; Venugopalan, K.

    2006-04-01

    Fe Al alloy with Fe/Al ratio of 3:1 was first prepared by argon arc melting. It was subsequently coated on glass slide and cellophane tape using an electron beam gun system to have a thickness of 2,000 Å. X-ray diffraction spectrum of the coated sample indicates a definite texture for the film with a preferential growth along the Fe(110) plane. SEM micrographs of the film showed the presence of nano islands of nearly 3 × 1012/m2 surface density. Composition of different parts of the film was determined using EDAX. Room temperature Fe-57 Mössbauer spectrum of coated sample showed the presence a quadrupole doublet with a splitting of 0.46 mm/s, which is typical of Al-rich iron compounds. MOKE study shows an in-plane magnetic moment.

  18. Microstructure and mechanical properties of sputter deposited Ni/Ni3Al multilayer films at elevated temperature

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Feng, Kai; Li, Zhuguo; Lu, Fenggui; Huang, Jian; Wu, Yixiong

    2016-08-01

    Nano-structured Ni/Ni3Al multilayer was prepared by magnetron sputtering, with individual layer thicknesses h varying from 10 to 160 nm. The microstructure and hardness of Ni/Ni3Al multilayer were investigated by X-ray diffraction, transmission electron microscopy and nanoindentation. The results show that the hardness increases with decreasing h for as-deposited and 500 °C annealed multilayers. When annealed at 700 °C, the hardness approach a peak value at h = 40 nm with followed by softening at smaller h. The influence of individual layer thickness, grain size as well as formation of ordered Ni3Al on strengthening mechanisms of Ni/Ni3Al multilayers at elevated temperature are discussed.

  19. Phonon densities of states of face-centered-cubic Ni-Fe alloys

    SciTech Connect

    Lucas, Matthew; Mauger, L; Munoz, Jorge A.; Halevy, I; Horwath, J; Semiatin, S L; Leontsev, S. O.; Stone, Matthew B; Abernathy, Douglas L; Xiao, Yuming; Chow, P; Fultz, B.

    2013-01-01

    Inelastic neutron scattering and nuclear resonant inelastic x-ray scattering were used to determine the phonon densities of states of face-centered-cubic Ni-Fe alloys. Increasing Fe concentration results in an average softening of the phonon modes. Chemical ordering of the Ni0.72Fe0.28 alloy results in a reduction of the partial vibrational entropy of the Fe atoms but does not significantly change the partial vibrational entropy of the Ni atoms. Changes in the phonon densities of states with composition and chemical ordering are discussed and analyzed with a cluster expansion method.

  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. Kinetics of NiO and NiCl2 hydrogen reduction as precursors and properties of produced Ni/Al2O3 and Ni-Pd/Al2O3 catalysts.

    PubMed

    Sokić, Miroslav; Kamberović, Željko; Nikolić, Vesna; Marković, Branislav; Korać, Marija; Anđić, Zoran; Gavrilovski, Milorad

    2015-01-01

    The objects of this investigation were the comparative kinetic analysis of the NiO and NiCl2 reduction by hydrogen during an induction period and elimination of the calcination during the synthesis of Ni/Al2O3 catalysts. The effect of temperature and time on NiO and NiCl2 reduction degrees was studied. Avrami I equation was selected as the most favorable kinetic model and used to determine activation energy of the NiO and NiCl2 reduction for the investigated temperature range (623-923 K) and time intervals (1-5 minutes). The investigation enabled reaching conclusions about the reaction ability and rate of the reduction processes. Afterward, Ni/Al2O3 catalysts were obtained by using oxide and chloride precursor for Ni. The catalysts were supported on alumina-based foam and prepared via aerosol route. Properties of the samples before and after low-temperature hydrogen reduction (633 K) were compared. Obtained results indicated that the synthesis of Ni/Al2O3 catalysts can be more efficient if chloride precursor for Ni is directly reduced by hydrogen during the synthesis process, without the calcination step. In addition, Ni-Pd/Al2O3 catalysts with different metal content were prepared by using chloride precursors. Lower reduction temperature was utilized and the chlorides were almost completely reduced at 533 K. PMID:25789335

  2. Kinetics of NiO and NiCl2 Hydrogen Reduction as Precursors and Properties of Produced Ni/Al2O3 and Ni-Pd/Al2O3 Catalysts

    PubMed Central

    Sokić, Miroslav; Kamberović, Željko; Nikolić, Vesna; Marković, Branislav; Korać, Marija; Anđić, Zoran; Gavrilovski, Milorad

    2015-01-01

    The objects of this investigation were the comparative kinetic analysis of the NiO and NiCl2 reduction by hydrogen during an induction period and elimination of the calcination during the synthesis of Ni/Al2O3 catalysts. The effect of temperature and time on NiO and NiCl2 reduction degrees was studied. Avrami I equation was selected as the most favorable kinetic model and used to determine activation energy of the NiO and NiCl2 reduction for the investigated temperature range (623–923 K) and time intervals (1–5 minutes). The investigation enabled reaching conclusions about the reaction ability and rate of the reduction processes. Afterward, Ni/Al2O3 catalysts were obtained by using oxide and chloride precursor for Ni. The catalysts were supported on alumina-based foam and prepared via aerosol route. Properties of the samples before and after low-temperature hydrogen reduction (633 K) were compared. Obtained results indicated that the synthesis of Ni/Al2O3 catalysts can be more efficient if chloride precursor for Ni is directly reduced by hydrogen during the synthesis process, without the calcination step. In addition, Ni-Pd/Al2O3 catalysts with different metal content were prepared by using chloride precursors. Lower reduction temperature was utilized and the chlorides were almost completely reduced at 533 K. PMID:25789335

  3. Deformation behavior of NiAl-based alloys containing iron, cobalt, and hafnium

    NASA Technical Reports Server (NTRS)

    Pank, D. R.; Koss, D. A.; Nathal, M. V.

    1989-01-01

    The effects of alloying additions on the mechanical properties of the B2 intermetallic NiAl have been investigated in both the melt-spun ribbon and consolidated, bulk form. The study is based on a matrix of NiAl-based alloys with up to 20 at. pct Co and Fe additions and with reduced Al levels in the range of 30-40 at. pct. Characterization of the melt-spun ribbon by optical and scanning electron microscopy indicates a range of microstructures, including single-phase beta, gamma-prime necklace phase surrounding either martensitic or beta grains, and a mixture of equiaxed martensitic and gamma-prime grains. Bend ductility is present in melt-spun and annealed ribbons exhibiting the gamma-prime necklace structure and in a single-phase beta material containing 20 at. pct Fe. The analysis of compressive flow behavior on consolidated, bulk specimens indicates that the single-phase beta alloys exhibit a continuous decrease in yield stress with increasing temperature and profuse microcracking at grain boundaries. In contrast, multiphase (gamma-prime + either martensite or beta) alloys tend to display a peak in flow stress between 600 and 800 K, with little or no signs of microcracking. In general, heat treatments which convert the martensitic grains to beta + gamma-prime result in improved strength at temperatures above 600 K and better resistance to crack initiation.

  4. Sound velocity and density of liquid Fe-Ni-Si under pressure: Application to the composition of planetary molten core

    NASA Astrophysics Data System (ADS)

    Terasaki, H. G.; Kuwabara, S.; Shimoyama, Y.; Takubo, Y.; Urakawa, S.; Nishida, K.; Takeuchi, A.; Suzuki, Y.; Uesugi, K.; Watanuki, T.; Katayama, Y.; Kondo, T.; Higo, Y.

    2014-12-01

    The cores of Mercury, Mars and Moon are reported to be partially/totally molten (e.g., Margot et al. 2007, Yoder et al. 2003, Williams et al. 2001). In order to constrain the core compositions of those bodies from observed and future-planned seismic data, sound velocity and density of the core material, i.e., liquid Fe-alloy, are necessary. In this study, we have performed simultaneous measurements on these physical properties of liquid Fe-Ni-Si alloys, which is one of the major candidates for the core constituent. The effects of pressure and Si content on these properties were studied. High pressure experiments were performed using 80-ton uniaxial press designed for CT measurement or 180-ton cubic type multi-anvil press installed at BL20XU and BL22XU beamlines of SPring-8 synchrotron facility, respectively. Used samples were Fe-Ni-Si with Si content of 10-30 at%. The sample pellet was sandwiched by the single crystal sapphire buffer rod for sound velocity measurement. P-wave sound velocity was measured using pulse-echo overlapping ultrasonic method. LiNbO3 transducer was attached to the backside of the anvil to generate and receive elastic wave signals. Density was determined based on 3D volume data obtained from CT measurement or X-ray absorption profile. The P-wave velocity (VP) and density of liquid Fe-Ni-Si were successfully measured up to 2.5 GPa and 1773 K. Obtained VP of the Fe-Ni-Si is found to increase rapidly with pressure below 1 GPa and increase gradually above 1 GPa. It is also found that VP increases slightly with Si content on the density-VP plot. These trends provide a constraint on the core composition of the planets and moon by comparing with observed data.

  5. Si/NiFe seed layers for Ru intermediate layer in perpendicular magnetic recording tape media

    NASA Astrophysics Data System (ADS)

    Saemma, Gaku; Takahashi, Shota; Matsunuma, Satoshi; Inoue, Tetsutaro; Nakagawa, Shigeki

    2012-04-01

    Si/NiFe seed layers prepared at room temperature is effective to attain better c-axis orientation of Ru intermediate layer in the FeCoB/Ru/CoPtCr-SiO2 granular type recording tape media. The crystallinity and c-axis orientation of Ru layer with Si/NiFe seed layers were improved than that without Si/NiFe seed layer deposited on the laminated FeCoB SULs. When the Ru is thicker than 8 nm, Δθ50 of the CoPtCr-SiO2 recording layer shows small value of about 6.5°. Furthermore, even though the Ru thickness was only 3 nm, the Δθ50 retained comparatively small value of 8.0°. Si/NiFe layer is effective as a seed layer for the Ru intermediate layer.

  6. First-principles-based kinetic Monte Carlo studies of diffusion of hydrogen in Ni–Al and Ni–Fe binary alloys

    SciTech Connect

    Tafen, De Nyago

    2015-02-14

    The diffusion of dilute hydrogen in fcc Ni–Al and Ni–Fe binary alloys was examined using kinetic Monte Carlo method with input kinetic parameters obtained from first-principles density functional theory. The simulation involves the implementation of computationally efficient energy barrier model that describes the configuration dependence of the hydrogen hopping. The predicted hydrogen diffusion coefficients in Ni and Ni89.4Fe10.6 are compared well with the available experimental data. In Ni–Al, the model predicts lower hydrogen diffusivity compared to that in Ni. Overall, diffusion prefactors and the effective activation energies of H in Ni–Fe and Ni–Al are concentration dependent of the alloying element. Furthermore, the changes in their values are the results of the short-range order (nearest-neighbor) effect on the interstitial diffusion of hydrogen in fcc Ni-based alloys.

  7. First-principles-based kinetic Monte Carlo studies of diffusion of hydrogen in Ni–Al and Ni–Fe binary alloys

    DOE PAGESBeta

    Tafen, De Nyago

    2015-02-14

    The diffusion of dilute hydrogen in fcc Ni–Al and Ni–Fe binary alloys was examined using kinetic Monte Carlo method with input kinetic parameters obtained from first-principles density functional theory. The simulation involves the implementation of computationally efficient energy barrier model that describes the configuration dependence of the hydrogen hopping. The predicted hydrogen diffusion coefficients in Ni and Ni89.4Fe10.6 are compared well with the available experimental data. In Ni–Al, the model predicts lower hydrogen diffusivity compared to that in Ni. Overall, diffusion prefactors and the effective activation energies of H in Ni–Fe and Ni–Al are concentration dependent of the alloying element.more » Furthermore, the changes in their values are the results of the short-range order (nearest-neighbor) effect on the interstitial diffusion of hydrogen in fcc Ni-based alloys.« less

  8. Monitoring of deformation induced microcracking in polycrystalline NiAl

    SciTech Connect

    Wanner, A.; Schietinger, B.; Bidlingmaier, T.; Zalkind, H.; Arzt, E.

    1995-08-01

    Microcracking in polycrystalline near-stoichiometric NiAl produced by room temperature plastic deformation under uniaxial compression was investigated by means of optical microscopy, velocity of sound measurements, and acoustic emission monitoring. Results show that strains greater than 2% are required to produce microcrack populations which can be evaluated by microscopical investigation or velocity of sound measurements. However, acoustic emission monitoring during compression testing indicates that microcracking starts at about 0.7% compressive plastic strain which is identical with the typical tensile fracture strain for NiAl. Thus it is concluded that there is little or no stable microcracking prior to failure in tension. Acoustic emission results show also that the process of microcracking does not primarily occur during the applied compressive deformation. A considerable fraction of the microcracking takes place during the quasi-elastic unloading following deformation.

  9. Force Field Development and Molecular Dynamics of [NiFe] Hydrogenase

    SciTech Connect

    Smith, Dayle MA; Xiong, Yijia; Straatsma, TP; Rosso, Kevin M.; Squier, Thomas C.

    2012-05-09

    Classical molecular force-field parameters describing the structure and motion of metal clusters in [NiFe] hydrogenase enzymes can be used to compare the dynamics and thermodynamics of [NiFe] under different oxidation, protonation, and ligation circumstances. Using density functional theory (DFT) calculations of small model clusters representative of the active site and the proximal, medial, and distal Fe/S metal centers and their attached protein side chains, we have calculated classical force-field parameters for [NiFe] in reduced and oxidized states, including internal coordinates, force constants, and atom-centered charges. Derived force constants revealed that cysteinate ligands bound to the metal ions are more flexible in the Ni-B active site, which has a bridging hydroxide ligand, than in the Ni-C active site, which has a bridging hydride. Ten nanosecond all-atom, explicit-solvent MD simulations of [NiFe] hydrogenase in oxidized and reduced catalytic states established the stability of the derived force-field parameters in terms of C{alpha} and metal cluster fluctuations. Average active site structures from the protein MD simulations are consistent with [NiFe] structures from the Protein Data Bank, suggesting that the derived force-field parameters are transferrable to other hydrogenases beyond the structure used for testing. A comparison of experimental H{sub 2}-production rates demonstrated a relationship between cysteinate side chain rotation and activity, justifying the use of a fully dynamic model of [NiFe] metal cluster motion.

  10. Compression and Tensile Creep of Binary NiAl

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2005-01-01

    Compression creep and long term tensile creep studies were conducted on cast and extruded binary NiAl in the temperature range 700-1200 K with the objectives of characterizing and understanding the creep mechanisms. Inverse and normal primary creep curves were observed in both compression and tension creep depending on stress and temperature although an asymmetrical response was observed under these two stress states. It was concluded that the primary creep of NiAl is limited by dislocation mobility. The stress exponents, n, for compression and tensile creep were similar varying between about 5 and 14. However, there were significant differences in the stress dependence of the activation energies for compression and tensile creep. The true activation energy for tensile creep, Q(sub c), was constant and equal to about 400 kJ/mol between 20 and 50 MPa but decreased to a constant value of 250 kJ/mol between 50 and 110 MPa. The activation energy was observed to be inversely stress dependent above 110 MPa. In contrast, Q(sub c) = 300 kJ/mol for compression creep was constant between 25 and 70 MPa and inversely dependent on the true stress above 70 MPa. A detailed discussion of the probable dislocation creep mechanisms governing compressive and tensile creep of NiAl is presented. It is concluded that the non-conservative motion of jogs on screw dislocations influenced the nature of the primary creep curves, where the climb of these jogs involves either the next nearest neighbor or the six-jump cycle vacancy diffusion mechanism. The probable natures of the atom-vacancy exchange that occur within the core of an edge dislocation undergoing climb in NiAl are schematically examined.

  11. Creep in single crystal Ni{sub 3}Al

    SciTech Connect

    Zhu, W.; Jones, I.P.; Fort, D.; Smallman, R.E.

    1997-12-31

    Single crystals of Ni{sub 3}Al (1 at.%Ta) with a compression axis of [{bar 1}23] were subject to creep at a stress of 550 MPa and a temperature of 520 C. Slip trace and TEM microstructural observations reveal that primary octahedral slip is responsible for the primary creep. In the secondary stage, cube cross slip (010) is operative. There is no obvious sign of inverse creep.

  12. Alloys based on NiAl for high temperature applications

    NASA Technical Reports Server (NTRS)

    Vedula, K. M.; Pathare, V.; Aslanidis, I.; Titran, R. H.

    1984-01-01

    The NiAl alloys for potential high temperature applications were studied. Alloys were prepared by powder metallurgy techniques. Flow stress values at slow strain rates and high temperatures were measured. Some ternary alloying additions (Hf, Ta and Nb) were identified. The mechanism of strengthening in alloys containing these additions appears to be a form of particle dislocation interaction. The effects of grain size and stoichiometry in binary alloys are also presented.

  13. Comparison of microwave absorption properties of SrFe12O19, SrFe12O19/NiFe2O4, and NiFe2O4 particles

    NASA Astrophysics Data System (ADS)

    Mehdipour, M.; Shokrollahi, H.

    2013-07-01

    In this study, ferrimagnetic (SrFe12O19, SrFe12O19/NiFe2O4, and NiFe2O4) nanostructure particles were synthesized by the co-precipitation of chloride salts using the sodium hydroxide solution. The resulting precursors were heat-treated at 1100 °C for 4 h. After cooling in the furnace, the ferrite powders were pressed at 10 bars and then sintered at 1200 °C for 4 h. The saturation magnetization was increased and the coercivity was decreased by sintering (because of morphology changing) and alternating of the ferrite kind. For example, at SrFe12O19, the saturation magnetization was increased from 291 G to 300 G and the coercivity was decreased from 2.8 kOe to 1.8 kOe by sintering. The microwave absorption properties of the nanostructure particles were studied by ferromagnetic resonance and transmit-line theories, as well as Reflection Loss plots. Before sintering, the RL spectra of SrFe12O19 and the composite were below -3 dB, but they reached -6 dB at 11.1 GHz for NiFe2O4. The RL spectra of the samples were increased by sintering due to reduction of porosity and damping factor. The maximum microwave absorption reached -35 dB (at resonance frequency) for the NiFe2O4 state.

  14. Development and High Temperature Property Evaluation of Ni-Co-Cr-Al Composite Electroforms

    NASA Astrophysics Data System (ADS)

    Srivastava, Meenu; Siju; Balaraju, J. N.; Ravisankar, B.

    2015-05-01

    Ni-Co-Cr-Al composite electroforms were developed with cobalt content of 10 and 40 wt.%. Cr and Al nano-particles were suspended in sulphamate electrolyte and co-deposited in the Ni-Co matrices. The surface morphology was investigated using field emission scanning electron microscope and the composition analyzed by energy-dispersive x-ray analysis. The oxidation resistance of the electroforms was studied from 600 to 1000 °C. The weight gain of Ni-10 wt.%Co-Cr-Al was less (better oxidation resistance) compared to Ni-Cr-Al and Ni-40 wt.%Co-Cr-Al. The x-ray diffraction studies revealed that the oxidation product formed on the surface of Ni-Cr-Al and Ni-10 wt.%Co-Cr-Al consisted of NiO and Al2O3, while Ni-40 wt.%Co-Cr-Al comprised oxides such as NiCo2O4, CrO3, CoO, NiO, and Al2O3. The hot corrosion behavior was investigated in 75%Na2SO4 + 25%NaCl environment at 800 °C. It was found that the hot corrosion resistance of the composite coating improved with increase in cobalt content. The probable composition suitable for high-temperature applications was found to be Ni-10 wt.%Co-Cr-Al.

  15. Magnetostatic interactions in mesoscopic Ni80Fe20 ring arrays

    NASA Astrophysics Data System (ADS)

    Wang, J.; Adeyeye, A. O.; Singh, N.

    2005-12-01

    We investigate, directly using magnetic force microscopy, the effect of magnetostatic interactions in arrays of Ni80Fe20 mesoscopic rings. The rings were fabricated on silicon substrate using deep ultraviolet lithography at 248 nm exposure wavelength. We observed that the transitions from onion-to-vortex and vortex-to-reverse onion magnetic states are strongly dependent on the edge-to-edge-spacing of the rings due to dipolar magnetostatic interaction. For a closely packed ring array, the transition from onion to vortex state occurs at a much lower field due to collective magnetic switching as compared with widely spaced rings. The remanent magnetic state is found to be very sensitive to the orientation of the applied field due to shape anisotropy.

  16. Supercooling and structure of levitation melted Fe-Ni alloys

    NASA Technical Reports Server (NTRS)

    Abbaschian, G. J.; Flemings, M. C.

    1983-01-01

    A study has been made of the effect of supercooling, quenching rate, growth inhibitors, and grain refiners on the structure of levitation-melted Fe- 25 pct Ni alloys. A combination of three morphologies, dendritic, spherical, and mixed dendritic and spherical, is observed in samples superheated or supercooled by less than 175 K. At larger supercooling, however, only the spherical morphology is observed. The grain size and the grain boundary shape are found to be strongly dependent on the subgrain morphology but not on the quenching temperature. Considerable grain growth is evident in samples with spherical and mixed morphologies but not in the dendriitic samples. The average cooling rates during solidification and the heat transfer coefficients at the metal-quenching medium boundary are calculated. For samples solidified in water, molten lead, and ceramic molds, the heat transfer coefficients are 0.41, 0.52, and 0.15 w/sq cm, respectively.

  17. Charge characteristics of Ni/Fe traction cells

    SciTech Connect

    DeLuca, W.; Biwer, R.; Tummillo, A.; Yao, N.

    1983-01-01

    In a series of tests performed on 6-V Ni/Fe modules, a range of recharge levels and charge rates were examined for three charge methods. The results show that higher discharge capacities are achieved at higher recharge Ah levels, but at lower Ah and Wh cycling efficiencies. However, when the modules are continuously cycled at any recharge level, repeatable module performance is obtained. Consequently, the optimum combination of module discharge capacity and cycle efficiency can be obtained for any given application by proper selection of the recharge level. It was also observed that at a fixed recharge level, module charge acceptance is virtually independent of the charge method. The tested modules also exhibited a self-discharge loss in capacity that was directly related to the length of the open-circuit stand time after charging and module state-of-charge. This paper describes the test procedures used, presents the test data, and discusses the results obtained. 6 figures.

  18. Shear faults and dislocation core structure simulations in B2 FeAl

    SciTech Connect

    Vailhe, C.; Farkas, D.

    1997-11-01

    Embedded atom potentials were derived for the Fe-Al system reproducing lattice and elastic properties of B2 FeAl. The structure and energy of vacancies, antisites and anti phase boundaries (APBs) were studied. A significant decrease in the APB energy was obtained for Fe-rich B2 alloys. Shear fault energies along the {l_brace}110{r_brace} and {l_brace}112{r_brace} planes were computed showing that stable planar faults deviated from the exact APB fault. Core structures and critical Peierls stress values were simulated for the <100> and <111> dislocations. The superpartials created in the dissociation reactions were not of the 1/2<111> type, but 1/8<334> in accordance with the stable planar fault in the {l_brace}110{r_brace} planes. The results obtained for these simulations are discussed in terms of the mechanical behavior of FeAl and in comparison with B2 NiAl.

  19. Oxidation of ion-implanted NiAl

    SciTech Connect

    Hanrahan, R.J. Jr.; Verink, E.D. Jr.; Withrow, S.P.

    1994-12-31

    The oxidation of NiAl is complicated by the formation of transient alumina phases which result in convoluted scales which are prone to spallation. We have investigated high-dose implantation of oxygen as a technique for forming a protective oxide layer on the surface of NiAl and thereby bypassing the conditions that lead to transient oxide formation. Single crystal specimens of high purity NiAl were implanted with 1 {times} 10{sup 18} {sup 18}O ions/cm{sup 2} at 160 keV. Implanted specimens were annealed for times ranging from 5 to 60 minutes in a reducing atmosphere. Oxidation experiments were conducted for periods ranging from 1 hour to 42 hours under both cyclic and isothermal conditions. Specimens in the as-implanted, annealed, and oxidized conditions were examined using Auger electron microscopy. Oxygen implantation followed by annealing was found to form an epitaxial oxide layer. This layer is stable for the duration of the oxidation experiments conducted in this study, and was found to result in reduced oxidation and improved resistance to scale spallation.

  20. Tribological properties of self-lubricating NiAl/Mo-based composites containing AgVO{sub 3} nanowires

    SciTech Connect

    Liu, Eryong; Gao, Yimin; Bai, Yaping; Yi, Gewen; Wang, Wenzhen; Zeng, Zhixiang; Jia, Junhong

    2014-11-15

    Silver vanadate (AgVO{sub 3}) nanowires were synthesized by hydrothermal method and self-lubricating NiAl/Mo-AgVO{sub 3} composites were fabricated by powder metallurgy technique. The composition and microstructure of NiAl/Mo-based composites were characterized and the tribological properties were investigated from room temperature to 900 °C. The results showed that NiAl/Mo-based composites were consisted of nanocrystalline B2 ordered NiAl matrix, Al{sub 2}O{sub 3}, Mo{sub 2}C, metallic Ag and vanadium oxide phase. The appearance of metallic Ag and vanadium oxide phase can be attributed to the decomposition of AgVO{sub 3} during sintering. Wear testing results confirmed that NiAl/Mo-based composites have excellent tribological properties over a wide temperature range. For example, the friction coefficient and wear rate of NiAl/Mo-based composites containing AgVO{sub 3} were significantly lower than the composites containing only metallic Mo or AgVO{sub 3} lubricant when the temperature is above 300 °C, which can be attributed to the synergistic lubricating action of metallic Mo and AgVO{sub 3} lubricants. Furthermore, Raman results indicated that the composition on the worn surface of NiAl-based composites was self-adjusted after wear testing at different temperatures. For example, Ag{sub 3}VO{sub 4} and Fe{sub 3}O{sub 4} lubricants were responsible for the improvement of tribological properties at 500 °C, AgVO{sub 3}, Ag{sub 3}VO{sub 4} and molybdate for 700 °C, and AgVO{sub 3} and molybdate for 900 °C of NiAl-based composites with the addition of metallic Mo and AgVO{sub 3}. - Highlights: • NiAl/Mo-AgVO{sub 3} nanocomposites were prepared by mechanical alloying and sintering. • AgVO{sub 3} decomposed to metallic Ag and vanadium oxide during the sintering process. • NiAl/Mo-AgVO{sub 3} exhibited superior tribological properties at a board temperature range. • Phase composition on the worn surface was varied with temperatures. • Self-adjusted action

  1. Eutectic superalloys strengthened by sigma, Ni3CB lamellae and gamma prime, Ni3Al precipitates

    NASA Technical Reports Server (NTRS)

    Lemkey, F. D.

    1973-01-01

    By means of a screening and solidification optimization study of certain alloys located on the gamma-sigma liquidus surface within the Ni-Cb-Cr-Al system, alloys with high temperature properties superior to those of all known superalloys were defined. One alloy, Ni - 19.7w/o Cb - 6.0w/o Cr - 2.5w/o Al, directionally solidified at 3 cm/hr met or exceeded each program goal. A second alloy, Ni-21.75 w/o Cb-2.55 w/o Al, although deficient in its inherent oxidation resistance, met the other program goals and combined a remarkable insensitivity of composite microstructure to solidification parameters with excellent low temperature toughness. This investigation demonstrated that useful properties for gas turbine airfoil application have been achieved by reinforcing a strong and tough gamma solid solution matrix containing precipitated gamma prime by a lamellar intermetallic compound Ni3 Cb having greater strength at elevated temperature.

  2. Performance of NiCrAlY Coatings Deposited by Oxyfuel Thermal Spraying in High Temperature Chlorine Environment

    NASA Astrophysics Data System (ADS)

    Habib, K. A.; Damra, M. S.; Carpio, J. J.; Cervera, I.; Saura, J. J.

    2014-10-01

    A microcrystalline Ni-22Cr-10Al-1Y (wt.%) coating was deposited on AISI 304 stainless steel by the oxyfuel thermal spray technique. The deposited coating was subjected to heat treatment to improve the microstructure characteristics and its corresponding high-temperature properties. The isothermal high-temperature corrosion behavior at 650 and 700 °C in synthetic air and in the presence of 1% Cl2 was investigated using thermogravimetric analysis, x-ray diffraction, and scanning electron microscopy with energy-dispersive x-ray spectroscopy. The results indicated that the deposited NiCrAlY coating possessed acceptable oxidation-corrosion resistance at 650 °C owing to the formation of extensive amounts of the protective oxide of Cr2O3; NiO and a lesser amount of a Cr1.12 Ni2,88 metallic phase are also formed. At 700 °C, the coating lost its protective characteristic because of the excessive consumption of thermodynamically stable phases by oxidation-chlorination process. In this case, the steel base and the coating were attacked by chlorine during the exposure time; the mass gain of the NiCrAlY coating was slightly higher and provided only a limited protection up to 11 h; thereafter, breakdown of the layer of oxides occurred and this is attributed to the formation of non-protective oxides mainly β-Fe2O3 and Fe21.33O32 and the depletion of chromium.

  3. Ni adsorption and Ni-Al LDH precipitation in a sandy aquifer: an experimental and mechanistic modeling study.

    PubMed

    Regelink, Inge C; Temminghoff, Erwin J M

    2011-03-01

    Mining activities and industries have created nickel (Ni) contaminations in many parts of the world. The objective of this study is to increase our understanding of Ni adsorption and Nickel-Aluminium Layered Double Hydroxide (Ni-Al LDH) precipitation to reduce Ni mobility in a sandy soil aquifer. At pH ≥ 7.2 both adsorption and Ni-Al LDH precipitation occurred. In batch experiments with the sandy soil up to 70% of oxalate-extractable Al was taken up in LDH formation during 56 days. In a long term column experiment 99% of influent Ni was retained at pH 7.5 due to Ni adsorption (≈ 34%) and Ni-Al LDH precipitation (≈ 66%) based on mechanistic reactive transport modeling. The subsequent leaching at pH 6.5 could be largely attributed to desorption. Our results show that even in sandy aquifers with relatively low Al content, Ni-Al LDH precipitation is a promising mechanism to immobilize Ni. PMID:21186070

  4. NiAl(110)/Cr(110) interface: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Liu, W.; Li, J. C.; Zheng, W. T.; Jiang, Q.

    2006-05-01

    The optimal geometries, thermodynamic properties, and electronic structures of NiAl(110)/Cr(110) interface are studied using a first-principle density functional plane-wave ultrasoft pseudopotential method. Surface energies of different NiAl surfaces are compared with those obtained based on the classical broken-bond rule. Simulation results indicate that the structure of Ni and Al placed in the hollow sites of Cr atoms at the interface is more thermodynamically stable, and the NiCr bonding is dominated by 3d electrons of Ni and Cr. It is found that NiAl(110)/Cr(110) alloying could lower brittleness of NiAl compounds. With simulated values of adhesion work and interface energy for NiAl(110)/Cr(110) system, its mechanical and thermodynamic properties are also discussed.

  5. Laser-wavelength dependence of the picosecond ultrasonic response of a NiFe/NiO/Si structure

    NASA Astrophysics Data System (ADS)

    Bosco, C. A.; Azevedo, A.; Acioli, L. H.

    2002-09-01

    Ultrafast optical excitation and detection of acoustic phonons has been used to analyze ultrathin films composed of NiFe/NiO/Si which are important for applications in magnetic storage and processing. Results are presented on the wavelength dependence of the ultrasonic response of the thin NiO film and bulk Si. Significant changes are observed between detection using the fundamental and the second harmonic of the femtosecond laser as the probe beam. Beatings between low order longitudinal phonons in the NiO layer are observed and measurements of its refractive index and absorption coefficients are performed.

  6. Redetermination of the Fe-rich portion of the Fe-Ni-Co phase diagram

    NASA Technical Reports Server (NTRS)

    Widge, S.; Goldstein, J. I.

    1977-01-01

    The iron rich portion of the Fe-Ni-Co ternary diagram was determined at four temperatures. The phase boundaries and tie-lines of the (alpha + gamma) phase field were measured by analyzing the alpha and gamma phases with an electron microprobe. Grain boundary allotrimorphs of the alpha phase were observed in the polished and etched sections of samples which were step cooled from the gamma phase into the (alpha + gamma) region. Widmanstaetten-type microstructures composed of gamma-precipitates were observed in samples which were directly heated from room temperature into the (alpha + gamma) region.

  7. Cyanide-bridged NiCr and alternate NiFe-NiCr magnetic ultrathin films on functionalized Si(100) surface.

    PubMed

    Tricard, Simon; Costa-Coquelard, Claire; Mazerat, Sandra; Rivière, Eric; Huc, Vincent; David, Christophe; Miserque, Frédéric; Jegou, Pascale; Palacin, Serge; Mallah, Talal

    2012-04-21

    Sequential growth in solution (SGS) was performed for the magnetic cyanide-bridged network obtained from the reaction of Ni(H(2)O)(2+) and Cr(CN)(6)(3-) (referred to as NiCr) on a Si(100) wafer already functionalized by a Ni(II) complex. The growth process led to isolated dots and a low coverage of the surface. We used the NiFe network as a template to improve the growth of the magnetic network. We elaborated alternate NiFe (paramagnetic)-NiCr (ferromagnetic) ultrathin films around 6 nm thick. The magnetic behaviour confirmed the alternate structure with the ferromagnetic zones isolated between the paramagnetic ones since the evolution of the blocking temperature is consistent with the evolution of the layers' thickness expected from the SGS process. PMID:22344390

  8. 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.

  9. Structural and magnetic properties of Ni/Fe nanostructures on Ir(111)

    NASA Astrophysics Data System (ADS)

    Iaia, Davide; Kubetzka, André; von Bergmann, Kirsten; Wiesendanger, Roland

    2016-04-01

    The structural and magnetic properties of one atomic layer thin nanostructures of Ni deposited on fcc Fe monolayer stripes on Ir(111) have been studied by (spin-resolved) scanning tunneling microscopy measurements. Ni grows dominantly in fcc stacking on Ir(111), whereas it forms a dense reconstruction pattern on Fe/Ir(111), with bridge site dislocation lines separating triangularly shaped fcc and hcp regions. In the interior of the Ni nanostructures, fcc and hcp areas are of comparable size, but the fcc stacking dominates at the edges. The magnetic nanoskyrmion lattice of Fe/Ir(111) undergoes a transition to ferromagnetism where covered with a single layer of Ni. The Ni/Fe bilayer islands show an out-of-plane easy axis and can be switched by external magnetic fields of only 1.0 T-1.5 T.

  10. Behavior of Ni, Zn and Cr during low temperature aqueous Fe oxidation processes on Mars

    NASA Astrophysics Data System (ADS)

    Zhao, Yu-Yan S.; McLennan, Scott M.

    2013-05-01

    The behavior of Ni(II), Zn(II) and Cr(III) during the melanterite (FeSO4·7H2O) to hematite (α-Fe2O3) oxidative transformations involving evolution pathways via jarosite ((H3O,K)Fe3(OH)6(SO4)2), schwertmannite (Fe8O8(OH)6(SO4)) and goethite (α-FeOOH) were investigated in an acidic saturated MgSO4 matrix. Results provide important clues about how elevated levels of trace elements are incorporated into the secondary Fe mineralogy assemblages found on Mars and the mechanism for formation of hematitic concretions at Meridiani Planum on Mars. Our results demonstrate that starting at the same concentrations in the initial solution, final amounts of Ni, Zn and Cr in hematite via different pathways are very different. In Path 1 (melanterite → jarosite → hematite), partitioning of Ni, Zn and Cr into jarosite and hematite (formed through dissolution of jarosite) is most likely in the order: Cr > Zn > Ni. In Path 2 (melanterite → schwertmannite → goethite → hematite), schwertmannite and goethite exhibited strong affinities for divalent Ni and Zn. During such a pathway, Ni should accumulate more than Zn by at least a factor of two, and partitioning of Ni, Zn and Cr to the hematite is most likely in the order: Cr > Ni > Zn. Therefore, our results suggest that the high Ni and moderate Zn distribution pattern observed in Meridiani hematitic spherule-bearing samples can be explained best by the schwertmannite-goethite to hematite pathway (Path 2), without need for an additional high Ni source in this region. Although the lack of goethite at Meridiani renders it uncertain if goethite ever served as a precursor to facilitate hematite formation, dehydration of nano-crystalline goethite is thermodynamically favored and cannot be ruled out. On the other hand, if hematitic concretions were formed by dissolution of jarosite (Path 1), then much higher initial Ni/Zn ratios than 1 in initial diagenetic fluids may be necessary to explain the elevated levels of Ni in the spherules

  11. Synthesis and characterization of lamellar and fibre-reinforced NiAl-Mo and NiAl-Cr

    NASA Astrophysics Data System (ADS)

    Haenschke, T.; Gali, A.; Heilmaier, M.; Krüger, M.; Bei, H.; George, E. P.

    2010-07-01

    Directionally solidified (DS) alloys of the eutectic systems NiAl-10Mo and NiAl-34Cr (at.%) are potential candidates for high-temperature structural applications. Here, these alloys were first arc-melted and drop-cast. Thereafter, they were directionally solidified (DS) at growth rates of 20 and 80 mm/h while rotating at a fixed rotation speed of 60 revolutions per minute. Specimens of the DS alloys were tested in three-point-bending and uniaxial compression to obtain mechanical properties, including the ductile to brittle transition temperature (DBTT). For the NiAl-Cr system DBTT was found to be around 300 °C. Microstructural observations revealed that in the section perpendicular to the growth direction a uniform distribution of fibres was observed. The expected decrease of the fibre diameter with increasing growth rate was not observed. Instead, the fibre diameter slightly increased with increasing crystal growth rates. First compression tests were performed to get insights into the creep behaviour of these fibre-reinforced microstructures.

  12. Utilization of Active Ni to Fabricate Pt-Ni Nanoframe/NiAl Layered Double Hydroxide Multifunctional Catalyst through In Situ Precipitation.

    PubMed

    Ren, Fumin; Wang, Zheng; Luo, Liangfeng; Lu, Haiyuan; Zhou, Gang; Huang, Weixin; Hong, Xun; Wu, Yuen; Li, Yadong

    2015-09-14

    Integration of different active sites into metallic catalysts, which may impart new properties and functionalities, is desirable yet challenging. Herein, a novel dealloying strategy is demonstrated to decorate nickel-aluminum layered double hydroxide (NiAl-LDH) onto a Pt-Ni alloy surface. The incorporation of chemical etching of Pt-Ni alloy and in situ precipitation of LDH are studied by joint experimental and theoretical efforts. The initial Ni-rich Pt-Ni octahedra transform by interior erosion into Pt3 Ni nanoframes with enlarged surface areas. Furthermore, owing to the basic active sites of the decorated LDH together with the metallic sites of Pt3 Ni, the resulting Pt-Ni nanoframe/NiAl-LDH composites exhibit excellent catalytic activity and selectivity in the dehydrogenation of benzylamine and hydrogenation of furfural. PMID:26241390

  13. Synthesis, characterization and low temperature electrical conductivity of Polyaniline/NiFe2O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Prasanna, G. D.; Prasad, V. B.; Jayanna, H. S.

    2015-02-01

    Conducting polymer/ferrite nanocomposites with an organized structure provide a new functional hybrid between organic and inorganic materials. The most popular among the conductive polymers is the polyaniline (PANI) due to its wide application in different fields. In the present work nickel ferrite (NiFe2O4) nanoparticles were prepared by sol-gel citrate-nitrate method with an average size of 21.6nm. PANI/NiFe2O4 nanoparticles were synthesized by a simple general and inexpensive in-situ polymerization in the presence of NiFe2O4 nanoparticles. The effects of NiFe2O4 nanoparticles on the dc-electrical properties of polyaniline were investigated. The structural components in the nanocomposites were identified from Fourier Transform Infrared (FTIR) spectroscopy. The crystalline phase of nanocomposites was characterized by X-Ray Diffraction (XRD). The Scanning Electron Micrograph (SEM) reveals that there was some interaction between the NiFe2O4 particles and polyaniline and the nanocomposites are composed of polycrystalline ferrite nanoparticles and PANI. The dc conductivity of polyaniline/NiFe2O4 nanocomposites have been measured as a function of temperature in the range of 80K to 300K. It is observed that the room temperature conductivity cRT decreases with increase in the relative content of NiFe2O4. The experimental data reveals that the resistivity increases for all composites with decrease of temperature exhibiting semiconductor behaviour.

  14. Electronic structure and properties of magnetic defects in Co(1+x)Al(1-x) and Fe(1+x)Al(1-x) alloys. Ph.D. Thesis - Paris Univ.

    NASA Technical Reports Server (NTRS)

    Abbe, D.

    1984-01-01

    CoAl and FeAl compounds are developed along two directions. Magnetic susceptibility and specific heat at low temperature on (NiCo)Al and (CoFe)Al ternary alloys are in good agreement with band calculations. Results on magnetization and specific heat under field at low temperature on nonstoichiometric compounds show clearly the importance of the nearest neighbor effects. In the case of CoAl, the isolated cobalt atoms substituting aluminum are characterized by a Kondo behavior, and, for FeAl, the isolated extra iron atoms are magnetic and polarize the matrix. Moreover, for the two compounds, clusters of higher order play a considerable part in the magnetic properties for CoAl, these clusters also seem to be characterized by a Kondo behavior, for FeAl, these clusters whose moment is higher than in the case of isolated atoms, could be constituted of excess parts of iron atoms.

  15. Evidence for Ni-56 yields Co-56 yields Fe-56 decay in type Ia supernovae

    NASA Technical Reports Server (NTRS)

    Kuchner, Marc J.; Kirshner, Robert P.; Pinto, Philip A.; Leibundgut, Bruno

    1994-01-01

    In the prevailing picture of Type Ia supernovae (SN Ia), their explosive burning produces Ni-56, and the radioactive decay chain Ni-56 yields Co-56 yields Fe-56 powers the subsequent emission. We test a central feature of this theory by measuring the relative strengths of a (Co III) emission feature near 5900 A and a (Fe III) emission feature near 4700 A. We measure 38 spectra from 13 SN Ia ranging from 48 to 310 days after maximum light. When we compare the observations with a simple multilevel calculation, we find that the observed Fe/Co flux ratio evolves as expected when the Fe-56/Co-56 abundance ratio follows from Ni-56 yields Co-56 yields Fe-56 decay. From this agreement, we conclude that the cobalt and iron atoms we observe through SN Ia emission lines are produced by the radioactive decay of Ni-56, just as predicted by a wide range of models for SN Ia explosions.

  16. Molecular evolution of gas cavity in [NiFeSe] hydrogenases resurrected in silico

    PubMed Central

    Tamura, Takashi; Tsunekawa, Naoki; Nemoto, Michiko; Inagaki, Kenji; Hirano, Toshiyuki; Sato, Fumitoshi

    2016-01-01

    Oxygen tolerance of selenium-containing [NiFeSe] hydrogenases (Hases) is attributable to the high reducing power of the selenocysteine residue, which sustains the bimetallic Ni–Fe catalytic center in the large subunit. Genes encoding [NiFeSe] Hases are inherited by few sulphate-reducing δ-proteobacteria globally distributed under various anoxic conditions. Ancestral sequences of [NiFeSe] Hases were elucidated and their three-dimensional structures were recreated in silico using homology modelling and molecular dynamic simulation, which suggested that deep gas channels gradually developed in [NiFeSe] Hases under absolute anaerobic conditions, whereas the enzyme remained as a sealed edifice under environmental conditions of a higher oxygen exposure risk. The development of a gas cavity appears to be driven by non-synonymous mutations, which cause subtle conformational changes locally and distantly, even including highly conserved sequence regions. PMID:26818780

  17. The dependence of Ni-Fe bioxide composites nanoparticles on the FeCl2 solution used

    PubMed Central

    2012-01-01

    Background Ni2O3- γ-Fe2O3 composite nanoparticles coated with a layer of 2FeCl3·5H2O can be prepared by co-precipitation and processing in FeCl2 solution. Using vibrating sample magnetometer (VSM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) diffraction techniques, the dependence of the preparation on the concentration of the FeCl2 treatment solution is revealed. Results The magnetization of the as-prepared products varied non-monotonically as the FeCl2 concentration increased from 0.020 M to 1.000 M. The Experimental results show that for the composite nanoparticles, the size of the γ-Fe2O3 phase is constant at about 8 nm, the Ni2O3 phase decreased and the 2FeCl3·5H2O phase increased with increasing concentration of FeCl2 solution. The magnetization of the as-prepared products mainly results from the γ-Fe2O3 core, and the competition between the reduction of the Ni2O3 phase with the increase of the 2FeCl3·5H2O phase resulted in the apparent magnetization varying non-monotonically. Conclusions When the concentration of FeCl2 treatment solution did not exceed 0.100 M, the products are spherical nanoparticles of size about 11 nm; their magnetization increased monotonically with increasing the concentration of FeCl2 solution due to the decreasing proportion of Ni2O3 phase. PMID:23110795

  18. Synthetic Active Site Model of the [NiFeSe] Hydrogenase

    PubMed Central

    Wombwell, Claire; Reisner, Erwin

    2015-01-01

    A dinuclear synthetic model of the [NiFeSe] hydrogenase active site and a structural, spectroscopic and electrochemical analysis of this complex is reported. [NiFe(‘S2Se2’)(CO)3] (H2‘S2Se2’=1,2-bis(2-thiabutyl-3,3-dimethyl-4-selenol)benzene) has been synthesized by reacting the nickel selenolate complex [Ni(‘S2Se2’)] with [Fe(CO)3bda] (bda=benzylideneacetone). X-ray crystal structure analysis confirms that [NiFe(‘S2Se2’)(CO)3] mimics the key structural features of the enzyme active site, including a doubly bridged heterobimetallic nickel and iron center with a selenolate terminally coordinated to the nickel center. Comparison of [NiFe(‘S2Se2’)(CO)3] with the previously reported thiolate analogue [NiFe(‘S4’)(CO)3] (H2‘S4’=H2xbsms=1,2-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)benzene) showed that the selenolate groups in [NiFe(‘S2Se2’)(CO)3] give lower carbonyl stretching frequencies in the IR spectrum. Electrochemical studies of [NiFe(‘S2Se2’)(CO)3] and [NiFe(‘S4’)(CO)3] demonstrated that both complexes do not operate as homogenous H2 evolution catalysts, but are precursors to a solid deposit on an electrode surface for H2 evolution catalysis in organic and aqueous solution. PMID:25847470

  19. H+-induced irradiation damage resistance in Fe- and Ni-based metallic glass

    NASA Astrophysics Data System (ADS)

    Zhang, Hongran; Mei, Xianxiu; Zhang, Xiaonan; Li, Xiaona; Wang, Yingmin; Sun, Jianrong; Wang, Younian

    2016-05-01

    In this study, use of 40-keV H+ ion for irradiating metallic glass Fe80Si7.43B12.57 and Ni62Ta38 as well as metallic tungsten (W) at fluences of 1 × 1018 and 3 × 1018 ions/cm2, respectively, was investigated. At the fluence of 1 × 1018 ions/cm2, a crystalline layer appeared in metallic glass Fe80Si7.43B12.57, with α-Fe as the major crystalline phase, coupled with a little Fe2B, Fe3B, and metastable β-Mn-type phase. Fe80Si7.43B12.57 exhibited good soft magnetic properties after irradiation. At the fluence of 3 × 1018 ions/cm2, Ni62Ta38 was found to be amorphous-based, with a little μ-NiTa and Ni3Ta phases. No significant irradiation damage phenomenon appeared in metallic glasses Fe80Si7.43B12.57 and Ni62Ta38. Blistering, flaking, and other damage occurred on the surface of metallic W, and the root-mean-square (RMS) roughness increased with the increase of fluence. Metallic glass Ni62Ta38 exhibited better resistance to H+ irradiation than Fe80Si7.43B12.57, both of which were superior to the metallic W.

  20. A study on the orientation inheritance in laminated NiAl produced by in situ reaction annealing.

    PubMed

    Du, Yan; Fan, Guohua; Geng, Lin

    2016-04-01

    In order to promote the performance of B2 NiAl by texture control of orientation during in situ processing, phase transformation in laminated NiAl with bimodal grain size distribution manufactured by reaction annealing of Ni and Al foils has been studied. It turned out that there existed a Kurdjumov-Sachs orientation relationship (K-S OR) between parent Ni and product NiAl by crystallography analysis according to the electron backscatter diffraction (EBSD) results. The parent Ni did not transform to the product NiAl directly but via the formation of Ni3Al firstly according to the transmission electron microscope (TEM) observation of the interface. This led to a new K-S OR between Ni3Al and NiAl with a small atomic misfit, which made less residual stress generated through the formation of Ni3Al than directly from the parent Ni. PMID:26867210

  1. Host Atom Diffusion in Ternary Fe-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Rohrberg, Diana; Spitzer, Karl-Heinz; Dörrer, Lars; Kulińska, Anna J.; Borchardt, Günter; Fraczkiewicz, Anna; Markus, Torsten; Jacobs, Michael H. G.; Schmid-Fetzer, Rainer

    2014-01-01

    In the Fe-rich corner of the Fe-Cr-Al ternary phase diagram, both interdiffusion experiments [1048 K to 1573 K (775 °C to 1300 °C)] and 58Fe tracer diffusion experiments [873 K to 1123 K (600 °C to 850 °C)] were performed along the Fe50Cr50-Fe50Al50 section. For the evaluation of the interdiffusion data, a theoretical model was used which directly yields the individual self-diffusion coefficients of the three constituents and the shift of the original interface of the diffusion couple through inverse modeling. The driving chemical potential gradients were derived using a phenomenological Gibbs energy function which was based on thoroughly assessed thermodynamic data. From the comparison of the individual self-diffusivities of Fe as obtained from interdiffusion profiles and independent 58Fe tracer diffusivities, the influence of the B2-A2 order-disorder transition becomes obvious, resulting in a slightly higher activation enthalpy for the bcc-B2 phase and a significantly lower activation entropy for this phase.

  2. 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.

  3. s-process nucleosynthesis in massive stars: new results on 60Fe, 62Ni and 64Ni

    NASA Astrophysics Data System (ADS)

    Domingo-Pardo, C.; Dillmann, I.; Faestermann, T.; Giesen, U.; Görres, J.; Heil, M.; Horn, S.; Käppeler, F.; Köchli, S.; Korschinek, G.; Lachner, J.; Maiti, M.; Marganiec, J.; Neuhausen, J.; Nolte, R.; Poutivtsev, M.; Reifarth, R.; Rugel, R.; Schumann, D.; Uberseder, E.; Voss, F.; Walter, S.; Wiescher, M.

    2009-01-01

    The s process synthesizes the elements between Fe and Sr in massive stars during two major evolutionary stages, convective core He burning and C shell burning. This scenario implies fascinating consequences for the chemical evolution of the star. For instance, the neutron capture rate at each isotope can have a big influence on the production of many of the subsequent higher mass isotopes. Correspondingly, one needs to know the (n,γ) cross sections of the involved isotopes with high accuracy in order to determine the abundance pattern reliably and to obtain a consistent picture of this stage. This contribution gives an overview on recent and future experiments for the Fe/Ni nucleosynthesis in massive stars. New results on 60Fe, 62Ni and 64Ni are reported. 60Fe is mostly produced during the short convective C shell burning phase, where peak densities of ~1011 cm-3 are reached, prior to the SN explosion. The stellar (n,γ) cross section of 60Fe could be measured with a 1 μg sample obtained at PSI (Switzerland), which was sufficient for an activation measurement using the intense, quasi-stellar neutron field for a thermal energy of 25 keV at the Karlsruhe Van de Graaff accelerator. The FZK accelerator was also used for an activation of 62Ni, whereas in this case, the number of 63Ni nuclei produced were determined via accelerator mass spectroscopy at the Maier-Leibnitz-Laboratorium in Garching/Munich. The (n,γ) cross section of 64Ni at a stellar temperature equivalent to 50 keV has been measured in a collaboration between FZK Karlsruhe and PTB Braunschweig. Finally, complementary time of flight measurements on the Fe and Ni isotopes over a broad energy range are planned at the white neutron source n_TOF of CERN for the future campaign in 2009.

  4. Interface-assisted magnetoresistance behavior for ultrathin NiFe films

    NASA Astrophysics Data System (ADS)

    Jiang, Shao-Long; Chen, Xi; Yang, Kang; Han, Gang; Teng, Jiao; Li, Xu-Jing; Yang, Guang; Liu, Qian-Qian; Liu, Yi-Wei; Ding, Lei; Yu, Guang-Hua

    2015-11-01

    Interface-assisted magnetoresistance (MR) behavior has been studied in Ta/MgO/NiFe/MgO/Ta multilayers by inserting a Mg metal layer between the NiFe layer and the top MgO layer. It is shown that MR ratio is about 31% larger than that in the films without Mg insertion. X-ray photoelectron spectroscopy and high resolution transmission electron microscope analyses show that the enhanced MR is primarily ascribed to effective control of chemical states at the NiFe/MgO interface and crystallization of the top MgO layer.

  5. NiO/Fe(001): Magnetic anisotropy, exchange bias, and interface structure

    SciTech Connect

    Mlynczak, E.; Luches, P.

    2013-06-21

    The magnetic and structural properties of NiO/Fe epitaxial bilayers grown on MgO(001) were studied using magnetooptic Kerr effect (MOKE) and conversion electron Moessbauer spectroscopy (CEMS). The bilayers were prepared under ultra high vacuum conditions using molecular beam epitaxy with oblique deposition. Two systems were compared: one showing the exchange bias (100ML-NiO/24ML-Fe), ML stands for a monolayer, and another where the exchange bias was not observed (50ML-NiO/50ML-Fe). For both, the magnetic anisotropy was found to be complex, yet dominated by the growth-induced uniaxial anisotropy. The training effect was observed for the 100ML-NiO/24ML-Fe system and quantitatively described using the spin glass model. The composition and magnetic state of the interfacial Fe layers were studied using {sup 57}Fe-CEMS. An iron oxide phase (Fe{sup 3+}{sub 4}Fe{sup 2+}{sub 1}O{sub 7}), as thick as 31 A, was identified at the NiO/Fe interface in the as-deposited samples. The ferrimagnetic nature of the interfacial iron oxide film explains the complex magnetic anisotropy observed in the samples.

  6. Hot Corrosion Performance of AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa Coatings Deposited by Atmospheric Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Tao, Chong; Wang, Lei; Cheng, Nailiang; Hu, Hengfa; Liu, Yang; Song, Xiu

    2016-04-01

    AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa coatings were deposited on 316L stainless steel substrate using atmospheric plasma spraying, respectively, in order to improve the oxidation and corrosion resistance. The hot corrosion performance of the coatings at 700 and 900 °C were studied, and the detailed microstructures and phase composition of the coatings were analyzed using x-ray diffraction, scanning electron microscope with energy dispersive spectrometer, and transmission electron microscope. The results show that both coatings are structurally featured by slatted layers, consisting of amorphous phase, Cr2O3, Ni3Al, and Al2O3. The hot corrosion resistance of AlO-CrO/NiCoCrAlYTa coating is better than that of AlO/NiCoCrAlYTa coating. This improvement is attributed to lower porosity and more compact Cr2O3 in AlO-CrO/NiCoCrAlYTa coating which performs better than Al2O3 in blocking further inward progress of corrosion and oxidization.

  7. Comparison of Fe-AlPILC and Fe-ZSM-5 catalysts used for degradation of methomyl

    NASA Astrophysics Data System (ADS)

    Lázár, Károly; Tomašević, Andjelka; Bošković, Goran; Kiss, Ernő

    2009-07-01

    Catalytic performances of Fe-AlPILC (14 wt.% Fe) and Fe-ZSM-5 (5 wt.% Fe) catalysts are compared in the wet oxidative degradation of methomyl. Fe-ZSM-5 exhibits outstanding whereas Fe-AlPILC shows only mediocre activity. Positions of iron are analysed in the two catalysts by Mössbauer spectroscopy. Iron is in highly dispersed state in Fe-AlPILC whereas in the other case a hematite/ZSM-5 composite is formed. The catalytic activity is attributed to iron located and stabilized in ionic dispersion.

  8. A Study of the Effect of Nanosized Particles on Transient Liquid Phase Diffusion Bonding Al6061 Metal-Matrix Composite (MMC) Using Ni/Al2O3 Nanocomposite Interlayer

    NASA Astrophysics Data System (ADS)

    Cooke, Kavian O.

    2012-06-01

    Transient liquid phase (TLP) diffusion bonding of Al-6061 containing 15 vol pct alumina particles was carried out at 873 K (600 °C) using electrodeposited nanocomposite coatings as the interlayer. Joint formation was attributed to the solid-state diffusion of Ni into the Al-6061 alloy followed by eutectic formation and isothermal solidification of the joint region. An examination of the joint region using an electron probe microanalyzer (EPMA), transmission electron microscopy (TEM), wavelength-dispersive spectroscopy (WDS), and X-ray diffraction (XRD) showed the formation of intermetallic phases such as Al3Ni, Al9FeNi, and Ni3Si within the joint zone. The result indicated that the incorporation of 50 nm Al2O3 dispersions into the interlayer can be used to improve the joint significantly.

  9. Production of biohydrogen by recombinant expression of [NiFe]-hydrogenase 1 in Escherichia coli

    PubMed Central

    2010-01-01

    Background Hydrogenases catalyze reversible reaction between hydrogen (H2) and proton. Inactivation of hydrogenase by exposure to oxygen is a critical limitation in biohydrogen production since strict anaerobic conditions are required. While [FeFe]-hydrogenases are irreversibly inactivated by oxygen, it was known that [NiFe]-hydrogenases are generally more tolerant to oxygen. The physiological function of [NiFe]-hydrogenase 1 is still ambiguous. We herein investigated the H2 production potential of [NiFe]-hydrogenase 1 of Escherichia coli in vivo and in vitro. The hyaA and hyaB genes corresponding to the small and large subunits of [NiFe]-hydrogenase 1 core enzyme, respectively, were expressed in BL21, an E. coli strain without H2 producing ability. Results Recombinant BL21 expressing [NiFe]-hydrogenase 1 actively produced H2 (12.5 mL H2/(h·L) in 400 mL glucose minimal medium under micro-aerobic condition, whereas the wild type BL21 did not produce H2 even when formate was added as substrate for formate hydrogenlyase (FHL) pathway. The majority of recombinant protein was produced as an insoluble form, with translocation of a small fraction to the membrane. However, the membrane fraction displayed high activity (~65% of total cell fraction), based on unit protein mass. Supplement of nickel and iron to media showed these metals contribute essentially to the function of [NiFe]-hydrogenase 1 as components of catalytic site. In addition, purified E. coli [NiFe]-hydrogenase 1 using his6-tag displayed oxygen-tolerant activity of ~12 nmol H2/(min·mg protein) under a normal aeration environment, compared to [FeFe]-hydrogenase, which remains inactive under this condition. Conclusions This is the first report on physiological function of E. coli [NiFe]-hydrogenase 1 for H2 production. We found that [NiFe]-hydrogenase 1 has H2 production ability even under the existence of oxygen. This oxygen-tolerant property is a significant advantage because it is not necessary to protect

  10. Characterization of thermochemical properties of Al nanoparticle and NiO nanowire composites

    NASA Astrophysics Data System (ADS)

    Wen, John Z.; Ringuette, Sophie; Bohlouli-Zanjani, Golnaz; Hu, Anming; Nguyen, Ngoc Ha; Persic, John; Petre, Catalin F.; Zhou, Y. Norman

    2013-04-01

    Thermochemical properties and microstructures of the composite of Al nanoparticles and NiO nanowires were characterized. The nanowires were synthesized using a hydrothermal method and were mixed with these nanoparticles by sonication. Electron microscopic images of these composites showed dispersed NiO nanowires decorated with Al nanoparticles. Thermal analysis suggests the influence of NiO mass ratio was insignificant with regard to the onset temperature of the observed thermite reaction, although energy release values changed dramatically with varying NiO ratios. Reaction products from the fuel-rich composites were found to include elemental Al and Ni, Al2O3, and AlNi. The production of the AlNi phase, confirmed by an ab initio molecular dynamics simulation, was associated with the formation of some metallic liquid spheres from the thermite reaction.

  11. Characterization of thermochemical properties of Al nanoparticle and NiO nanowire composites

    PubMed Central

    2013-01-01

    Thermochemical properties and microstructures of the composite of Al nanoparticles and NiO nanowires were characterized. The nanowires were synthesized using a hydrothermal method and were mixed with these nanoparticles by sonication. Electron microscopic images of these composites showed dispersed NiO nanowires decorated with Al nanoparticles. Thermal analysis suggests the influence of NiO mass ratio was insignificant with regard to the onset temperature of the observed thermite reaction, although energy release values changed dramatically with varying NiO ratios. Reaction products from the fuel-rich composites were found to include elemental Al and Ni, Al2O3, and AlNi. The production of the AlNi phase, confirmed by an ab initio molecular dynamics simulation, was associated with the formation of some metallic liquid spheres from the thermite reaction. PMID:23601907

  12. Characterization of thermochemical properties of Al nanoparticle and NiO nanowire composites.

    PubMed

    Wen, John Z; Ringuette, Sophie; Bohlouli-Zanjani, Golnaz; Hu, Anming; Nguyen, Ngoc Ha; Persic, John; Petre, Catalin F; Zhou, Y Norman

    2013-01-01

    Thermochemical properties and microstructures of the composite of Al nanoparticles and NiO nanowires were characterized. The nanowires were synthesized using a hydrothermal method and were mixed with these nanoparticles by sonication. Electron microscopic images of these composites showed dispersed NiO nanowires decorated with Al nanoparticles. Thermal analysis suggests the influence of NiO mass ratio was insignificant with regard to the onset temperature of the observed thermite reaction, although energy release values changed dramatically with varying NiO ratios. Reaction products from the fuel-rich composites were found to include elemental Al and Ni, Al2O3, and AlNi. The production of the AlNi phase, confirmed by an ab initio molecular dynamics simulation, was associated with the formation of some metallic liquid spheres from the thermite reaction. PMID:23601907

  13. Effect of external magnetic field on valence-electron structures of Fe and Ni in Invar, Permalloy and the other Fe-Ni alloys by using Kβ-to-Kα X-ray intensity ratios.

    PubMed

    Alım, Bünyamin; Han, İbrahim; Demir, Lütfü

    2016-06-01

    The effect of external magnetic field on the valence-electron structures of Fe and Ni in various Fe-Ni alloy compositions was investigated by using X-ray fluorescence spectroscopy. Firstly, Kβ-to-Kα X-ray intensity ratios of Fe and Ni in Invar (Fe0.64Ni0.36), Permalloy (Fe0.20Ni0.80) and FexNi1-x (x=0, 0.40, 0.52, 0.55, 0.61, and 1) alloys were measured without any magnetic field and under 0.5 and 1T external magnetic fields, separately. Later, the valence-electron structures of Fe and Ni in both pure form and alloys were obtained by comparison of measured X-ray intensity ratios with the results of multi-configurations Dirac-Fock (MCDF) calculations. The results obtained for valence-electron structures of Fe and Ni in various Fe-Ni alloys were evaluated in terms of magnetic field effect, delocalization and/or charge transfer phenomena. The results have shown that valence electron structure of Fe and Ni in Fe-Ni alloys are dependent on both external magnetic field and concentration of alloy elements. PMID:26974486

  14. 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.

  15. Oxidation-driven surface dynamics on NiAl(100)

    SciTech Connect

    Qin, Hailang; Chen, Xidong; Li, Liang; Sutter, Peter W.; Zhou, Guangwen

    2014-12-29

    Atomic steps, a defect common to all crystal surfaces, can play an important role in many physical and chemical processes. However, attempts to predict surface dynamics under nonequilibrium conditions are usually frustrated by poor knowledge of the atomic processes of surface motion arising from mass transport from/to surface steps. Using low-energy electron microscopy that spatially and temporally resolves oxide film growth during the oxidation of NiAl(100) we demonstrate that surface steps are impermeable to oxide film growth. The advancement of the oxide occurs exclusively on the same terrace and requires the coordinated migration of surface steps. The resulting piling up of surface steps ahead of the oxide growth front progressively impedes the oxide growth. This process is reversed during oxide decomposition. The migration of the substrate steps is found to be a surface-step version of the well-known Hele-Shaw problem, governed by detachment (attachment) of Al atoms at step edges induced by the oxide growth (decomposition). As a result, by comparing with the oxidation of NiAl(110) that exhibits unimpeded oxide film growth over substrate steps, we suggest that whenever steps are the source of atoms used for oxide growth they limit the oxidation process; when atoms are supplied from the bulk, the oxidation rate is not limited by the motion of surface steps.

  16. Oxidation-driven surface dynamics on NiAl(100)

    DOE PAGESBeta

    Qin, Hailang; Chen, Xidong; Li, Liang; Sutter, Peter W.; Zhou, Guangwen

    2014-12-29

    Atomic steps, a defect common to all crystal surfaces, can play an important role in many physical and chemical processes. However, attempts to predict surface dynamics under nonequilibrium conditions are usually frustrated by poor knowledge of the atomic processes of surface motion arising from mass transport from/to surface steps. Using low-energy electron microscopy that spatially and temporally resolves oxide film growth during the oxidation of NiAl(100) we demonstrate that surface steps are impermeable to oxide film growth. The advancement of the oxide occurs exclusively on the same terrace and requires the coordinated migration of surface steps. The resulting piling upmore » of surface steps ahead of the oxide growth front progressively impedes the oxide growth. This process is reversed during oxide decomposition. The migration of the substrate steps is found to be a surface-step version of the well-known Hele-Shaw problem, governed by detachment (attachment) of Al atoms at step edges induced by the oxide growth (decomposition). As a result, by comparing with the oxidation of NiAl(110) that exhibits unimpeded oxide film growth over substrate steps, we suggest that whenever steps are the source of atoms used for oxide growth they limit the oxidation process; when atoms are supplied from the bulk, the oxidation rate is not limited by the motion of surface steps.« less

  17. Oxidation-driven surface dynamics on NiAl(100)

    NASA Astrophysics Data System (ADS)

    Qin, Hailang; Chen, Xidong; Li, Liang; Sutter, Peter W.; Zhou, Guangwen

    2015-01-01

    Atomic steps, a defect common to all crystal surfaces, can play an important role in many physical and chemical processes. However, attempts to predict surface dynamics under nonequilibrium conditions are usually frustrated by poor knowledge of the atomic processes of surface motion arising from mass transport from/to surface steps. Using low-energy electron microscopy that spatially and temporally resolves oxide film growth during the oxidation of NiAl(100) we demonstrate that surface steps are impermeable to oxide film growth. The advancement of the oxide occurs exclusively on the same terrace and requires the coordinated migration of surface steps. The resulting piling up of surface steps ahead of the oxide growth front progressively impedes the oxide growth. This process is reversed during oxide decomposition. The migration of the substrate steps is found to be a surface-step version of the well-known Hele-Shaw problem, governed by detachment (attachment) of Al atoms at step edges induced by the oxide growth (decomposition). By comparing with the oxidation of NiAl(110) that exhibits unimpeded oxide film growth over substrate steps we suggest that whenever steps are the source of atoms used for oxide growth they limit the oxidation process; when atoms are supplied from the bulk, the oxidation rate is not limited by the motion of surface steps.

  18. Oxidation-driven surface dynamics on NiAl(100)

    PubMed Central

    Qin, Hailang; Chen, Xidong; Li, Liang; Sutter, Peter W.; Zhou, Guangwen

    2015-01-01

    Atomic steps, a defect common to all crystal surfaces, can play an important role in many physical and chemical processes. However, attempts to predict surface dynamics under nonequilibrium conditions are usually frustrated by poor knowledge of the atomic processes of surface motion arising from mass transport from/to surface steps. Using low-energy electron microscopy that spatially and temporally resolves oxide film growth during the oxidation of NiAl(100) we demonstrate that surface steps are impermeable to oxide film growth. The advancement of the oxide occurs exclusively on the same terrace and requires the coordinated migration of surface steps. The resulting piling up of surface steps ahead of the oxide growth front progressively impedes the oxide growth. This process is reversed during oxide decomposition. The migration of the substrate steps is found to be a surface-step version of the well-known Hele-Shaw problem, governed by detachment (attachment) of Al atoms at step edges induced by the oxide growth (decomposition). By comparing with the oxidation of NiAl(110) that exhibits unimpeded oxide film growth over substrate steps we suggest that whenever steps are the source of atoms used for oxide growth they limit the oxidation process; when atoms are supplied from the bulk, the oxidation rate is not limited by the motion of surface steps. PMID:25548155

  19. FeAl-TiC and FeAl-WC composites - melt infiltration processing, microstructure and mechanical properties

    SciTech Connect

    Subramanian, R.; Schneibel, J.H.

    1997-04-01

    TiC-based and WC-based cermets were processed with iron aluminide, an intermetallic, as a binder by pressureless melt infiltration to near full density (> 97 % theoretical density). Phase equilibria calculations in the quaternary Fe-Al-Ti-C and Fe-Al-W-C systems at 145{degrees}C were performed to determine the solubility of the carbide phases in liquid iron aluminide. This was done by using Thermocalc{trademark} and the results show that molten Fe-40 at.% Al in equilibrium with Ti{sub 0.512}C{sub 0.488} and graphite, dissolves 4.9 at% carbon and 64 atomic ppm titanium. In the Fe-Al-W-C system, liquid Fe-40 at.% Al in equilibrium with graphite dissolves about 5 at.% carbon and 1 at.% tungsten. Due to the low values for the solubility of the carbide phases in liquid iron aluminide, liquid phase sintering of mixed powders does not yield a dense, homogeneous microstructure for carbide volume fractions greater than 0.70. Melt infiltration of molten FeAl into TiC and WC preforms serves as a successful approach to process cermets with carbide contents ranging from 70 to 90 vol. %, to greater than 97% of theoretical density. Also, the microstructures of cermets prepared by melt infiltration were very homogeneous. Typical properties such as hardness, bend strength and fracture toughness are reported. SEM observations of fracture surfaces suggest the improved fracture toughness to result from the ductility of the intermetallic phase. Preliminary experiments for the evaluation of the oxidation resistance of iron aluminide bonded cermets indicate that they are more resistant than WC-Co cermets.

  20. Low-spin γ-Fe-Ni (γLS) proposed as a new mineral in Fe-Ni-bearing meteorites: Epitaxial intergrowth of γLS and tetrataenite as a possible equilibrium state at ~20-40 at% Ni

    NASA Astrophysics Data System (ADS)

    Rancourt, D. G.; Scorzelli, R. B.

    1995-09-01

    We argue that the so-called paramagnetic phase seen by Mössbauer spectroscopy in taenite lamella from octahedrite meteorites, ataxite meteorites, the metal particles of Fe-Ni-bearing chondrite meteorites, and synthetic particle-irradiated Fe-Ni alloys is a low-spin γ-Fe-Ni phase (γLS), related to the close packed low-spin phases seen in the pressure-temperature phase diagrams of both metallic Fe and synthetic Fe-Ni alloys and many other Fe-alloy systems. At a given composition, this γLS phase is quite distinct from the ordinary (high-spin) γ-phase (γHS) in that it has a different electronic structure associated with very different magnetic properties (small-moment antiferromagnetism versus large-moment ferromagnetism) and a lower lattice parameter. It should be considered a new mineral for which we suggest the name antitaenite. We further propose that in the meteorites γLS always occurs in a fine epitaxial intergrowth with tetrataenite (atomically ordered FeNi). This resolves outstanding difficulties in meteoritic and particle-irradiated Fe-Ni metallurgy.