Science.gov

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

    DOE PAGES

    V. N. Ivanovski; Umicevic, A.; Belosevic-Cavor, J.; ...

    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

  3. Spontaneous magnetization in Ni-Al and Ni-Fe layered double hydroxides.

    PubMed

    Coronado, Eugenio; Galán-Mascarós, José R; Martí-Gastaldo, Carlos; Ribera, Antonio; Palacios, Elías; Castro, Miguel; Burriel, Ramón

    2008-10-06

    Layered double hydroxides containing paramagnetic Ni (II) and diamagnetic/paramagnetic Al (III)/Fe (III) ions have been prepared and characterized. Ni 2Al(OH) 6(NO 3). nH 2O ( 1), Ni 2Fe(OH) 6(NO 3). nH 2O ( 2), Ni 2Fe(OH) 6(C 6H 8O 4) 0.5. nH 2O ( 3), and Ni 2Fe(OH) 6(C 10H 16O 4) 0.5. nH 2O ( 4) were prepared by coprecipitation at controlled pH as polycrystalline materials with the typical brucite-like structure, with alternating layers of hydroxide and the corresponding anions, which determine the interlayer separation. Magnetic studies show the appearance of spontaneous magnetization between 2 and 15 K for these compounds. Interestingly, the onset temperature for spontaneous magnetization follows a direct relationship with interlayer separation, since this is the only magnetic difference between compounds 2, 3, and 4. Magnetic and calorimetric data indicate that long-range magnetic ordering is not occurring in any of these materials, but rather a freezing of the magnetic system in 3D due to the magnetic disorder and competing intra- and interlayer interactions. Thus, these hydrotalcite-like magnetic materials can be regarded as spin glasses.

  4. 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.

  5. 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.

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

    SciTech Connect

    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, 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.

  7. Phase separation in equiatomic AlCoCrFeNi high-entropy alloy.

    PubMed

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

    2013-09-01

    The microstructure of the as-cast AlCoCrFeNi high entropy alloy has been investigated by transmission electron microscopy and atom probe tomography. The alloy shows a very pronounced microstructure with clearly distinguishable dendrites and interdendrites. In both regions a separation into an Al-Ni rich matrix and Cr-Fe-rich precipitates can be observed. Moreover, fluctuations of single elements within the Cr-Fe rich phase have been singled out by three dimensional atom probe measurements. The results of investigations are discussed in terms of spinodal decomposition of the alloying elements inside the Cr-Fe-rich precipitates.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Microstructural characterization of Ni-22Fe-22Cr-6Al metallic foam by transmission electron microscopy.

    PubMed

    Kim, Hyung Giun; Lee, Taeg Woo; Lee, Jae Young; Lee, Eui Sung; Oh, Kwon Oh; Lee, Chang Woo; Lim, Sung Hwan

    2012-01-01

    Ni-22Fe-22Cr-6Al metallic foam, prepared using a thermomechanical treatment and alloying elements, was studied via transmission electron microscopy (TEM) in order to clarify the relationship between the mechanical properties and the nanoscale microstructural characteristics. Due to the unique porous structure of the metallic foam, TEM specimens were prepared using an embedding-process-assisted-ion-milling technique and a focused-ion-beam method. The Cr-, Fe- and Al-clustered regions around the surface of the metallic foam were investigated using elemental maps. The Ni(3)Al (γ') precipitates, which can affect the mechanical properties of the Ni-Fe-Cr (γ) matrix, were characterized in the metallic foam.

  14. 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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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 DO3 Fe3Al, Co3Al, and Ni3Al 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 DO3 lattice. 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 is added as a ternary element.

  15. 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 PAGES

    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

  16. 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.

  17. Equation of State of an AlCoCrCuFeNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Li, Gong; Xiao, Daihong; Yu, Pengfei; Zhang, Lijun; Liaw, Peter K.; Li, Yanchun; Liu, Riping

    2015-08-01

    The pressure-volume (P-V) relationship of the AlCoCrCuFeNi high-entropy alloy (HEA) at room temperature has been studied using in situ high-pressure energy-dispersive x-ray diffraction with synchrotron radiation at high pressures. The equation of state of the AlCoCrCuFeNi HEA is determined by the calculation of the radial distribution function. The experimental results indicate that the HEA keeps a stable face-centered-cubic + body-centered-cubic structure in the experimental pressure range from 0 GPa to 24 GPa.

  18. 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.

  19. 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.

  20. 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.

  1. Microstructures and Mechanical Properties of NiTiFeAlCu High-Entropy Alloys with Exceptional Nano-precipitates

    NASA Astrophysics Data System (ADS)

    Zhang, Yanqiu; Wang, Sibing; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

    2017-01-01

    Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the Ni32Ti32Fe12Al12Cu12 high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. Ni20Ti20Fe20Al20Cu20 alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization.

  2. Microstructures and Mechanical Properties of NiTiFeAlCu High-Entropy Alloys with Exceptional Nano-precipitates

    NASA Astrophysics Data System (ADS)

    Zhang, Yanqiu; Wang, Sibing; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

    2016-10-01

    Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the Ni32Ti32Fe12Al12Cu12 high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. Ni20Ti20Fe20Al20Cu20 alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization.

  3. Creep behavior of a {beta}{prime}(NiAl) precipitation strengthened ferritic Fe-Cr-Ni-Al alloy

    SciTech Connect

    Zhu, S.M.; Tjong, S.C.; Lai, J.K.L.

    1998-05-22

    Creep in precipitation-strengthened alloys usually exhibits a pronounced transition in the stress vs creep rate relationship due to dislocations bypassing of particles by climb at low stresses. In the present study, a single-slope behavior is observed in creep of {beta}{prime}(NiAl) strengthened ferritic Fe-19Cr-4Ni-2Al alloy in the temperature range 873--923 K. The alloy exhibits anomalously high values of apparent stress exponent and activation energy (980 kJ/mol). Transmission electron microscopy examination of the deformation microstructure reveals the occurrence of attractive dislocation/particle interaction, a feature which is usually observed in dispersion-strengthened alloys. Such an attractive dislocation particle interaction makes the local climb of dislocations over particles a realistic configuration at low stresses. The creep data are analyzed by the back-stress approach and by the recent dislocation-climb theories based on attractive interaction between dislocations and particles. By considering a back stress, all data can be rationalized by a power-law with a stress exponent of 4 and a creep activation energy close to the self-diffusion energy of the matrix lattice. Local climb together with the attractive but not strong interactions between the dislocations and particles is suggested to be the operative deformation mechanism at low stresses and to account for the single-slope behavior in the stress/creep rate relationship of this alloy.

  4. Dislocations in nanostructured two-phase Fe30Ni20Mn20Al30.

    PubMed

    Wu, X; Baker, I

    2013-03-01

    In a previous study, the dislocations in Fe(30)Ni(20)Mn(25)Al(25) (at. %), which consist of 50 nm wide alternating b.c.c. and B2 phases, were shown to have a/2<111> Burgers vectors after room temperature deformation. The dislocations were found to glide in pairs on both {110} and {112} slip planes and were relatively widely separated in the b.c.c. phase, where the dislocations were uncoupled, and closely spaced in the B2 phase, where the dislocations were connected by an anti-phase boundary. In this article, we analyze the dislocations in the two ~5 nm-wide B2 phases in a related two-phase alloy Fe(30)Ni(20)Mn(20)Al(30), with compositions Fe-23Ni-21Mn-24Al and Fe-39Ni-12Mn-34Al, compressed to ~3% strain at a strain rate 5 × 10(-4) s(-1) at 873 K (the lowest temperature at which substantial plastic flow was observed). It is shown that slip occursby the glide of a<100> dislocations. A review of the literature suggests that the differences in the observed slip vector between these B2 phases could be due to the differences in composition, differences in deformation temperature, or possibly both.

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

    DOE PAGES

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; ...

    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

  6. 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.

  7. 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.

  8. 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.

  9. Evolution of dislocation structures in cyclically deformed NiAl-Fe

    SciTech Connect

    Kallingal, C.G.; Matsugi, K.; Stoloff, N.S.; Rajan, K.

    1995-08-01

    The microstructures of NiAl-Fe (Ni, 50.3at % Al, 0.28 at% Fe) polycrystals tested in HCF (high cycle fatigue) below and above the DBTT (ductile to brittle transition temperature) viz., 673 K, 823 K, 873 K and 928 K at different stress amplitudes were observed by transmission electron microscopy. The microstructure consisted of low energy dislocation networks and dislocation cells. The fundamental features of the dislocation structures are described. Misorientation angles between cells were measured from Kikuchi patterns obtained from cells through microdiffraction. The misorientations across the cell walls were found to increase with increase in the stress amplitude to which the material was subjected during cycling. The mechanisms for the formation and evolution of these structures are discussed on the basis of existing theoretical models. The implications of these substructures on the mechanical properties are also discussed.

  10. 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.

  11. Modeling of the Site Preference in Ternary B2-Ordered Ni-Al-Fe Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo H.; Khalil, Joseph; Noebe, Ronald D.

    2002-01-01

    The underlying equilibrium structure, site substitution behavior, and lattice parameter of ternary Ni-Fe-Al alloys are determined via Monte Carlo-Metropolis computer simulations and analytical calculations using the BFS method for alloys for the energetics. As a result of the theoretical calculations presented, a simple approach based on the energetics of small atomic clusters is introduced to explain the observed site preference schemes.

  12. 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.

  13. 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)

  14. 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.

  15. Electronic, magnetic and Fermi properties investigates on quaternary Heusler NiCoCrAl, NiCoCrGa and NiFeCrGa

    NASA Astrophysics Data System (ADS)

    Wei, Xiao-Ping; Zhang, Ya-Ling; Chu, Yan-Dong; Sun, Xiao-Wei; Sun, Ting; Guo, Peng; Deng, Jian-Bo

    2015-07-01

    Using the full-potential local-orbital minimum-basis method within the framework of density functional theory, we study the electronic, magnetic and Fermi properties of three quaternary Heusler compounds: NiCoCrAl, NiCoCrGa and NiFeCrGa. Results identify that these compounds are half-metallic ferromagnets with integer spin magnetic moment, and their spin moments follow the Slater-Pauling rule. Accordingly, the origin of gap and magnetic moment are also discussed. In addition, the Fermi surface is further plotted to explore the behavior of electronic states in the vicinity of Fermi level for these compounds. Finally, we argue the influence of tetragonal deformation on electronic and magnetic properties. Meanwhile, the possible L21 disorder is also discussed for NiCoCrAl and NiCoCrGa.

  16. Carbon nanotube growth on AlN support: Comparison between Ni and Fe chemical states and morphology

    NASA Astrophysics Data System (ADS)

    Eren, Baran; Marot, Laurent; Steiner, Roland; de los Arcos, Teresa; Düggelin, Marcel; Mathys, Daniel; Goldie, Kenneth N.; Olivieri, Vesna; Meyer, Ernst

    2014-08-01

    In this work, carbon nanotubes (CNTs) are grown from Ni and Fe nanoparticles supported on a rough AlN surface. Although, identical experimental parameters are used during dewetting (island formation) via thermal treatment, Ni particles appear metallic and larger, whereas Fe particles are smaller and slightly oxidized. This difference in the nanoparticle chemical state and morphology reflects to CNTs during catalytic chemical vapor deposition in terms of their CNT growth mode and size: tip-growth mode for Ni catalyst with CNT diameters of up to 40 nm, whereas base-growth mode for Fe with CNT diameters typically less than 10 nm are observed.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Mg, Al, Si, Ca, Ti, Fe, and Ni abundance for a sample of solar analogues

    NASA Astrophysics Data System (ADS)

    López-Valdivia, Ricardo; Bertone, Emanuele; Chávez, Miguel

    2017-01-01

    We report on the determination of chemical abundances of 38 solar analogues, including 11 objects previously identified as super metal-rich stars. We have measured the equivalent widths for 34 lines of 7 different chemical elements (Mg, Al, Si, Ca, Ti, Fe, and Ni) in high-resolution (R ˜ 80 000) spectroscopic images, obtained at the Observatorio Astrofísico Guillermo Haro (Sonora, Mexico), with the Cananea High-resolution Spectrograph. We derived chemical abundances using ATLAS12 model atmospheres and the Fortran code MOOG. We confirmed the super metallicity status of 6 solar analogues. Within our sample, BD+60 600 is the most metal-rich star ([Fe/H]=+0.35 dex), while for HD 166991 we obtained the lowest iron abundance ([Fe/H]=-0.53 dex). We also computed the so-called [Ref] index for 25 of our solar analogues, and we found, that BD+60 600 ([Ref]=+0.42) and BD+28 3198 ([Ref]=+0.34) are good targets for exoplanet search.

  4. 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.

  5. 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.

  6. Structural and microstructural study of nanostructured Fe{sub 50}Al{sub 40}Ni{sub 10} powders produced by mechanical alloying

    SciTech Connect

    Hadef, F.; Otmani, A.; Djekoun, A.; Greneche, J.M.

    2011-08-15

    A nanostructured Fe{sub 50}Al{sub 40}Ni{sub 10} mixture was prepared by mechanical alloying of elemental Fe, Al and Ni powders in a planetary ball mill. Structural and microstructural changes during the milling process were followed by X-ray diffraction technique. The patterns so obtained were analyzed using the Maud program. An ordered B2 FeAl phase is formed after 1 h of milling. The observed lattice expansion is related to the production of antisite defects; Fe{sub Al} and Al{sub Fe}. During the intermediate stages of milling, the mechanical alloying process gives rise to a mixture of two BCC {alpha}{sub i}-Fe(Al,Ni) (i = 1,2) structures with the same crystallite size but different lattice parameters, microstrains and proportions. The BCC {alpha}{sub 2}-Fe(Al,Ni) disappeared after 4 h, only the B2 FeAl and BCC {alpha}{sub 1}-Fe(Al,Ni) solid solution persist over prolonged milling times. - Research highlights: {yields} Fe{sub 50}Al{sub 40}Ni{sub 10} was prepared by MA from Fe, Al and Ni powders in a planetary ball mill. {yields} B2 FeAl is formed after 1 h of MA. Lattice expansion is related to Fe{sub Al} and Al{sub Fe} defects. {yields} MA gives rise to 2 BCC structures with the same L but different a, <{sigma}{sup 2}>{sup 1/2} and %.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Low-temperature heat capacity upon the transition from paramagnetic to ferromagnetic Heusler alloys Fe2 MeAl ( Me = Ti, V, Cr, Mn, Fe, Co, Ni)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Lukoyanov, A. V.

    2016-07-01

    The heat capacity of band magnets Fe2 MeAl ( Me = Ti, V, Cr, Mn, Fe, Co, Ni) ordered in crystal structure L21 has been measured in the range 2 K ≤ T ≤ 50 K. The dependences of the Debye temperature ΘD, the Sommerfeld coefficient γ, and the temperature-independent contribution to heat capacity C 0 on the number of valence electrons z in the alloys have been determined.

  13. 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.

  14. 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.

  15. 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.

  16. Processing of AlCoCrFeNiTi high entropy alloy by atmospheric plasma spraying

    NASA Astrophysics Data System (ADS)

    Löbel, M.; Lindner, T.; Kohrt, C.; Lampke, T.

    2017-03-01

    High Entropy Alloys (HEA) are gaining increasing interest due to their unique combination of properties. Especially the combination of high mechanical strength and hardness with distinct ductility makes them attractive for numerous applications. One interesting alloy system that exhibits excellent properties in bulk state is AlCoCrFeNiTi. A high strength, wear resistance and high-temperature resistance are the necessary requirements for the application in surface engineering. The suitability of blended, mechanically ball milled and inert gas atomized feedstock powders for the development of atmospheric plasma sprayed (APS) coatings is investigated in this study. The ball milled and inert gas atomized powders were characterized regarding their particle morphology, phase composition, chemical composition and powder size distribution. The microstructure and phase composition of the thermal spray coatings produced with different feedstock materials was investigated and compared with the feedstock material. Furthermore, the Vickers hardness (HV) was measured and the wear behavior under different tribological conditions was tested in ball-on-disk, oscillating wear and scratch tests. The results show that all produced feedstock materials and coatings exhibit a multiphase composition. The coatings produced with inert gas atomized feedstock material provide the best wear resistance and the highest degree of homogeneity.

  17. Mechanical Properties of High Entropy Alloy Al0.1CoCrFeNi for Peripheral Vascular Stent Application.

    PubMed

    Alagarsamy, Karthik; Fortier, Aleksandra; Komarasamy, Mageshwari; Kumar, Nilesh; Mohammad, Atif; Banerjee, Subhash; Han, Hai-Chao; Mishra, Rajiv S

    2016-12-01

    High entropy alloys (HEAs) are new class of metallic materials with five or more principal alloying elements. Due to this distinct concept of alloying, the HEAs exhibit unique properties compared to conventional alloys. The outstanding properties of HEAs include increased strength, superior wear resistance, high temperature stability, increased fatigue properties, good corrosion, and oxidation resistance. Such characteristics of HEAs have generated significant interest among the scientific community. However, their applications are yet to be explored. This paper discusses the mechanical behavior and microstructure of Al0.1CoCrFeNi HEA subjected to thermo-mechanical processing, and its potential application in peripheral vascular stent implants that are prone to high failure rates. Results show that Al0.1CoCrFeNi alloy possesses characteristics that compare well against currently used stent materials and it can potentially find use in peripheral vascular stent implants and extend their life-cycle.

  18. Sintering and heat treatment of Al15Ti5Co35Ni25Fe20 high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Górecki, K.; Zýka, J.; Malek, J.; Horvát, J.; Čapek, J.; Bała, P.

    2017-02-01

    The new Al15Ti5Co35Ni25Fe20 high entropy alloy was obtained by the powder metallurgy from the elemental powders (-325 mesh). The obtained alloy should be characterized by the dual BCC + FCC phase microstructure according to the valence electron concentration calculations (VEC=7.9). The main aim of the research was to determine the optimal conditions for sintering and heat treatment of Al15Ti5Co35Ni25Fe20 high entropy alloy. The alloy was sintered for 40 minutes at 600 °C for the preliminary consolidation of the powders and initial diffusion of the material. Then samples were annealed at various temperatures: 700, 800, 900, 1000 °C for 1 hour. Samples after annealing were characterized by the XRD and SEM. For the chosen temperature the annealing time was elongated to 2, 3, 5, 10 and 20 hours. The chemical homogeneity was determined.

  19. 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.

  20. Structure and properties of cast and splat-quenched high-entropy Al-Cu-Fe-Ni-Si alloys

    NASA Astrophysics Data System (ADS)

    Bashev, V. F.; Kushnerov, O. I.

    2017-01-01

    The effect of the composition and cooling rate of the melt on the microhardness, phase composition, and fine-structure parameters of as-cast and splat-quenched (SQ) high-entropy (HE) Al-Cu-Fe-Ni-Si alloys was studied. The quenching was performed by conventional splat-cooling technique. The cooling rate was estimated to be 106 K/s. Components of the studied HE alloys were selected taking into account both criteria for designing and estimating their phase composition, which are available in the literature and based on the calculations of the entropy and enthalpy of mixing, and the difference between atomic radii of components as well. According to X-ray diffraction data, the majority of studied Al-Cu-Fe-Ni-Si compositions are two-phase HE alloys, the structure of which consists of disordered solid solutions with bcc and fcc structures. At the same time, the Al0.5CuFeNi alloy is single-phase in terms of X-ray diffraction and has an fcc structure. The studied alloys in the as-cast state have a dendritic structure, whereas, after splat quenching, the uniform small-grained structure is formed. It was found that, as the volume fraction of bcc solid solution in the studied HE alloys increases, the microhardness increases; the as-cast HE Al-Cu-Fe-Ni-Si alloys are characterized by higher microhardness compared to that of splat-quenched alloys. This is likely due to the more equilibrium multiphase state of as-cast alloys.

  1. 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.

  2. 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.

  3. 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)

  4. 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.

  5. Effect of decomposition of the Cr-Fe-Co rich phase of AlCoCrCuFeNi high entropy alloy on magnetic properties.

    PubMed

    Singh, S; Wanderka, N; Kiefer, K; Siemensmeyer, K; Banhart, J

    2011-05-01

    Splat-quenched, as-cast and aged (2h at 600 °C after casting) AlCoCrCuFeNi high entropy alloys were investigated by means of transmission electron microscopy and three-dimensional atom probe (3D-AP). 3D-AP revealed anti-correlated fluctuations of the Cr and Fe-Co compositions in Cr-Fe-Co-rich regions of the as-cast alloy. The ferromagnetic behavior of AlCoCrCuFeNi high entropy alloy was correlated with the decomposition of the Cr-Fe-Co-rich regions into ferromagnetic Fe-Co-rich and antiferromagnetic Cr-rich domains, the size of which was determined by statistical analysis of 3D-AP data. The splat-quenched alloy showed a softer magnetic behavior as compared to the as-cast and aged alloys. The aged alloy possessed a higher saturation magnetization and coercivity as compared to the as-cast alloy.

  6. 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.

  7. Vertical spin transport in Al with Pd/Al/Ni80Fe20 trilayer films at room temperature by spin pumping

    PubMed Central

    Kitamura, Yuta; Shikoh, Eiji; Ando, Yuichiro; Shinjo, Teruya; Shiraishi, Masashi

    2013-01-01

    Spin pumping enables the vertical transport of pure spin current through Al in a Pd/Al/Ni80Fe20(Py) trilayer film, in which the Py acts as a spin battery. The spin current injected into the Al flows through the Al to reach the Pd, resulting in the generation of electromotive forces due to the inverse spin Hall effect in the Pd. The electromotive forces decreased with increasing thickness of the Al layer. A simple model based on the theory by Tserkovnyak et al., allows an estimation of the spin coherence of the vertical spin transport in the Al of 61 nm. This comparatively short coherence is attributed to a reduction in spin pumping efficiency because of the roughness of the Al/Py interface.

  8. Vertical spin transport in Al with Pd/Al/Ni80Fe20 trilayer films at room temperature by spin pumping

    NASA Astrophysics Data System (ADS)

    Kitamura, Yuta; Shikoh, Eiji; Ando, Yuichiro; Shinjo, Teruya; Shiraishi, Masashi

    2013-04-01

    Spin pumping enables the vertical transport of pure spin current through Al in a Pd/Al/Ni80Fe20(Py) trilayer film, in which the Py acts as a spin battery. The spin current injected into the Al flows through the Al to reach the Pd, resulting in the generation of electromotive forces due to the inverse spin Hall effect in the Pd. The electromotive forces decreased with increasing thickness of the Al layer. A simple model based on the theory by Tserkovnyak et al., allows an estimation of the spin coherence of the vertical spin transport in the Al of 61 nm. This comparatively short coherence is attributed to a reduction in spin pumping efficiency because of the roughness of the Al/Py interface.

  9. Specific features of the electrical resistivity of half-metallic ferromagnets Fe2MeAl (Me = Ti, V, Cr, Mn, Fe, Ni)

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    The transport properties of half-metallic ferromagnetic Heusler alloys Fe2MeAl (where Me = Ti, V, Cr, Mn, Fe, and Ni are 3 d transition elements) have been measured in the temperature range of 4-900 K. The specific features in the behavior of the electrical resistivity have been considered in terms of the two-current conduction model, which takes into account the presence of an energy gap in the electron spectrum of the alloys near the Fermi level.

  10. Nature of the interfaces between the constituent phases in the high entropy alloy CoCrCuFeNiAl.

    PubMed

    Welk, Brian A; Williams, Robert E A; Viswanathan, Gopal B; Gibson, Mark A; Liaw, Peter K; Fraser, Hamish L

    2013-11-01

    The interfaces between the phase separated regions in the dendritic grains of laser-deposited samples of the high entropy alloy CoCrCuFeNiAl have been studied using aberration-corrected analytical (scanning) transmission electron microscopy ((S)TEM). The compositional variations have been determined using energy dispersive x-ray spectroscopy (EDS) in (S)TEM. It was found that between B2, consisting mainly of Al, Ni, Co, and Fe, and disordered bcc phase, consisting mainly of Cr and Fe, there is a transition region, approximately 1.5 nm in width, over which the chemical composition changes from the B2 to that of the bcc phase. The crystal structure of this interfacial region is also B2, but with very different sublattice occupancy than that of the adjacent B2 compound. The structural aspects of the interface between the ordered B2 phase and the disordered bcc phase have been characterized using high angle annular dark-field (HAADF) imaging in STEM. It has been determined that the interfaces are essentially coherent, with the lattice parameters of the two B2 regions and the disordered bcc phase being more or less the same, the uncertainty arising from possible relaxations from the proximity of the surfaces of the thin foils used in imaging of the microstructures. Direct observations show that there is a planar continuity between all three constituent phases.

  11. 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.

  12. The effect of composition and cooling rate on the structure of rapidly solidified (Fe, Ni)3Al-C alloy

    NASA Technical Reports Server (NTRS)

    Myers, S. A.; Koch, C. C.

    1989-01-01

    The quench rate-metastable structure dependence in the Fe-20Ni-8Al-2C wt pct alloy has been experimentally studied. The nonequilibrium gamma-prime and gamma phases were noted in foils 65-100 microns thick, while at higher quench rates (thinner samples) the matrix was found to be in a disordered fcc gamma phase with kappa carbide precipitates. With the addition of silicon to the alloys, the nonequilibrium gamma-prime and gamma structures are observed at higher cooling rates.

  13. Laser surface alloying of FeCoCrAlNi high-entropy alloy on 304 stainless steel to enhance corrosion and cavitation erosion resistance

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Wu, C. L.; Zhang, C. H.; Guan, M.; Tan, J. Z.

    2016-10-01

    FeCoCrAlNi high-entropy alloy coating was synthesized with premixed high-purity Co, Cr, Al and Ni powders on 304 stainless steel by laser surface alloying, aiming at improving corrosion and cavitation erosion resistance. Phase constituents, microstructure and microhardness were investigated using XRD, SEM, and microhardness tester, respectively. The cavitation erosion and electrochemical corrosion behavior of FeCoCrAlNi coating in 3.5% NaCl solution were also evaluated using an ultrasonic vibrator and potentiodynamic polarization measurement. Experimental results showed that with appropriate laser processing parameters, FeCoCrAlNi coating with good metallurgical bonding to the substrate could be achieved. FeCoCrAlNi coating was composed of a single BCC solid solution. The formation of simple solid solutions in HEAs was the combined effect of mixing entropy (ΔSmix), mixing enthalpy (ΔHmix), atom-size difference (δ) and valence electron concentration (VEC), and the effect of ΔSmix was much larger than that of the other factors. The microhardness of the FeCoCrAlNi coating was ~3 times that of the 304 stainless steel. Both the corrosion and cavitation erosion resistance of the coating were improved. The cavitation erosion resistance for FeCoCrAlNi HEA coating was ~7.6 times that of 304 stainless steel. The corrosion resistance was also improved as reflected by a reduction in the current density of one order of magnitude as compared with 304 stainless steel.

  14. 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.

  15. 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.

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

    DOE PAGES

    Meng, Fanling; Qiu, Jingwen; Baker, Ian; ...

    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. Friction Stir Processing of a High Entropy Alloy Al0.1CoCrFeNi

    NASA Astrophysics Data System (ADS)

    Kumar, N.; Komarasamy, M.; Nelaturu, P.; Tang, Z.; Liaw, P. K.; Mishra, R. S.

    2015-05-01

    High entropy alloys are a new class of metallic materials with a potential for use in structural applications. However, most of the studies have focused on microhardness and compressive strength measurements for mechanical properties determination. This study presents the tensile deformation behavior of a single-phase, face-centered cubic Al0.1CoCrFeNi high entropy alloy (HEA). Friction stir processing was carried out to refine the grain size. Scanning electron microscopy and electron backscatter diffraction were carried out for microstructural examination. The grain size of the alloy was on the order of millimeters in the as-received condition. The average grain size after friction stir processing of the alloy was 14 ± 10 micrometers. The mechanical properties were determined through microhardness measurement and mini-tensile tests. The friction stir processed alloy showed a total elongation of ~75% for the mini-tensile sample used and yield strength of 315 MPa. It is an exceptional combination of strength and ductility. Friction stress was determined to be 174 MPa and the Hall-Petch coefficient was 371 MPa ( µm)1/2. Such a high value of Hall-Petch coefficient suggests that grain boundary strengthening can be a very effective strengthening mechanism for the HEA Al0.1CoCrFeNi.

  18. The influence of the X atoms and Al 3p occupied states in AlTiX2(X=Fe,Cu,Co,Ni) intermetallics

    NASA Astrophysics Data System (ADS)

    Fu, Hongzhi; Chen, Dong; Cheng, Xinlu; Gao, Tao; Yang, Xiangdong

    2007-01-01

    The electronic structures of the ternary (Heusler) L21-phase compounds AlTiX2(X=Fe,Cu,Co,Ni) are calculated by first-principles using full potential linearized augmented plane wave (FLAPW) method with the generalized gradient approximation (GGA). The ab initio results are analyzed with a simplified model for Al-based compounds containing transition metal (TM) atoms. The results show that the total density of state (DOS) depends strongly on the positions of TM atoms, and the TM d DOS not only connects with the pseudo-gap which is the indication of the stability of the intermetallic ternary Hume-Rothery (H-R) alloys, but also plays a crucial role in hybridization with other element valence electrons. However, the Al 3s states are repelled far away from the Fermi energy in all studied samples, and the Al 3d states are far more extended-like in the character than the d states. Furthermore, the total DOSs in all the studied samples are modulated by Al 3p states and the Al 3p states are more sensitive than d states to change in the electronic interactions. Then, the Al 3p is also responsible for the major part of the H-R stability of the intermetallic compounds which we have concerned with here. Indeed, the DOSs of the studied alloys show a pseudo-gap near the Fermi level, commonly attributed to the H-R phenomenon. Especially, the AlCu2Ti has more particular flat total DOS than the other AlTiX2 alloys (X=Fe,Co,Ni), which shows the so-called half-metallic behavior or poor metallic character.

  19. AlM2B2 (M  =  Cr, Mn, Fe, Co, Ni): a group of nanolaminated materials

    NASA Astrophysics Data System (ADS)

    Kádas, K.; Iuşan, D.; Hellsvik, J.; Cedervall, J.; Berastegui, P.; Sahlberg, M.; Jansson, U.; Eriksson, O.

    2017-04-01

    Combining theory with experiments, we study the phase stability, elastic properties, electronic structure and hardness of layered ternary borides AlCr2B2, AlMn2B2, AlFe2B2, AlCo2B2, and AlNi2B2. We find that the first three borides of this series are stable phases, while AlCo2B2 and AlNi2B2 are metastable. We show that the elasticity increases in the boride series, and predict that AlCr2B2, AlMn2B2, and AlFe2B2 are more brittle, while AlCo2B2 and AlNi2B2 are more ductile. We propose that the elasticity of AlFe2B2 can be improved by alloying it with cobalt or nickel, or a combination of them. We present evidence that these ternary borides represent nanolaminated systems. Based on SEM measurements, we demonstrate that they exhibit the delamination phenomena, which leads to a reduced hardness compared to transition metal mono- and diborides. We discuss the background of delamination by analyzing chemical bonding and theoretical work of separation in these borides.

  20. 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

    2016-12-01

    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.

  1. Structure-Property Relationship of Cu-Al-Ni-Fe Shape Memory Alloys in Different Quenching Media

    NASA Astrophysics Data System (ADS)

    Saud, Safaa N.; Hamzah, E.; Abubakar, T.; Farahany, S.

    2014-01-01

    This paper presents the effects of heat treatments using various quenching media on the phase transformation parameters and microstructure parameters. The effects of different quenching methods, step-quenched and up-quenched, in various media were evaluated by using differential scanning calorimetry, field emission electron microscopy, energy-dispersive spectrometry, atomic force microscopy, x-ray diffraction, and Vicker's hardness. The variations of the structure and properties of Cu-Al-Ni-Fe shape memory alloys were linked to the variations of morphology, type, and stabilization of the obtained phase. From the DSC results, the use of ice water as a quenching medium produced the highest transformation temperatures, while a brine solution-quenching medium resulted in the highest change of the entropy and enthalpy. Additionally, it was found that the best grain refinement was observed through the use of an oil-quenching medium, due to its high cooling rate.

  2. Control of spin current by a magnetic YIG substrate in NiFe/Al nonlocal spin valves

    NASA Astrophysics Data System (ADS)

    Dejene, F. K.; Vlietstra, N.; Luc, D.; Waintal, X.; Ben Youssef, J.; van Wees, B. J.

    2015-03-01

    We study the effect of a magnetic insulator [yttrium iron garnet (YIG)] substrate on the spin-transport properties of Ni80Fe20/Al nonlocal spin valve (NLSV) devices. The NLSV signal on the YIG substrate is about two to three times lower than that on a nonmagnetic SiO2 substrate, indicating that a significant fraction of the spin current is absorbed at the Al/YIG interface. By measuring the NLSV signal for varying injector-to-detector distances and using a three-dimensional spin-transport model that takes spin-current absorption at the Al/YIG interface into account, we obtain an effective spin-mixing conductance G↑↓≃5 -8 ×1013Ω-1m-2 . We also observe a small, but clear, modulation of the NLSV signal when rotating the YIG magnetization direction with respect to the fixed spin polarization of the spin accumulation in the Al. Spin relaxation due to thermal magnons or roughness of the YIG surface may be responsible for the observed small modulation of the NLSV signal.

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

    SciTech Connect

    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 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.

  4. 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.

  5. A Ni-free ZrCuFeAlAg bulk metallic glass with potential for biomedical applications.

    PubMed

    Liu, Yan; Wang, Yi-Mei; Pang, Hui-Fang; Zhao, Qiu; Liu, Lin

    2013-06-01

    The mechanical properties and biocompatibility of an Ni-free Zr-based bulk metallic glass (BMG) Zr60.14Cu22.31Fe4.85Al9.7Ag3 were investigated in detail to evaluate its potential as a biomaterial. The BMG was found to have a low Young's modulus of 82±1.9GPa, a high strength of 1720±28MPa and a high fracture toughness of 94±19MPam(1/2), as well as good fatigue strength over 400MPa. The corrosion behavior of the alloy was investigated in simulated body fluid (SBF) by electrochemical measurements, which indicates that the Zr-based BMG has a better corrosion resistance than pure Zr and Ti6Al4V. X-ray photoelectron spectroscopy analysis revealed that the passive film formed on the BMG surface is enriched in Al- and Zr-oxides, which could account for the good corrosion resistance of the BMG. On the other hand, metal ion release of the BMG in SBF was determined by inductively coupled plasma mass spectrometry after the BMG was immersed in SBF at 37°C for 30days, showing a ppb (ngml(-1)) level of metal ion release. The in vitro test via cell culture indicates that the BMG exhibits a cytotoxicity of Grade 0-1, which is as good as Ti6Al4V alloy. Cell adhesion morphological analysis shows that the cells were flattened and well spread out on the surfaces of the BMG, showing that the BMG had good biocompatibility. The combination of good mechanical properties and biocompatibility demonstrates that the Ni-free Zr-based BMG studied in this work is a good candidate for a new type of load-bearing biomedical material.

  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.

    PubMed

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

    2016-08-08

    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

    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.

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

    DOE PAGES

    Sharma, Aayush; Singh, Prashant; Johnson, Duane D.; ...

    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

  10. 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

  11. Electronic structure and magnetic properties in T2AlB2 (T =Fe, Mn, Cr, Co, and Ni) and their alloys

    NASA Astrophysics Data System (ADS)

    Ke, Liqin; Harmon, Bruce N.; Kramer, Matthew J.

    2017-03-01

    The electronic structure and intrinsic magnetic properties of Fe2AlB2 -related compounds and their alloys have been investigated using density functional theory. For Fe2AlB2 , the crystallographic a axis is the easiest axis, which agrees with experiments. The magnetic ground state of Mn2AlB2 is found to be ferromagnetic in the basal a b plane, but antiferromagnetic along the c axis. All 3 d dopings considered decrease the magnetization and Curie temperature in Fe2AlB2 . Electron doping with Co or Ni has a stronger effect on the decreasing of Curie temperature in Fe2AlB2 than hole doping with Mn or Cr. However, a larger amount of Mn doping on Fe2AlB2 promotes the ferromagnetic to antiferromagnetic transition. A very anisotropic magnetoelastic effect is found in Fe2AlB2 : the magnetization has a much stronger dependence on the lattice parameter c than on a or b , which is explained by electronic-structure features near the Fermi level. Dopings of other elements on B and Al sites are also discussed.

  12. Electronic structure and magnetic properties in T2AlB2 (T = Fe, Mn, Cr, Co, and Ni) and their alloys

    DOE PAGES

    Ke, Liqin; Harmon, Bruce N.; Kramer, Matthew J.

    2017-03-20

    In this study, the electronic structure and intrinsic magnetic properties of Fe2AlB2-related compounds and their alloys have been investigated using density functional theory. For Fe2AlB2, the crystallographic a axis is the easiest axis, which agrees with experiments. The magnetic ground state of Mn2AlB2 is found to be ferromagnetic in the basal ab plane, but antiferromagnetic along the c axis. All 3d dopings considered decrease the magnetization and Curie temperature in Fe2AlB2. Electron doping with Co or Ni has a stronger effect on the decreasing of Curie temperature in Fe2AlB2 than hole doping with Mn or Cr. However, a larger amountmore » of Mn doping on Fe2AlB2 promotes the ferromagnetic to antiferromagnetic transition. A very anisotropic magnetoelastic effect is found in Fe2AlB2: the magnetization has a much stronger dependence on the lattice parameter c than on a or b, which is explained by electronic-structure features near the Fermi level. Dopings of other elements on B and Al sites are also discussed.« less

  13. Long-term high-velocity oxidation and hot corrosion testing of several NiCrAl and FeCrAl base oxide dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.; Deadmore, D. L.; Whittenberger, J. D.

    1982-01-01

    Several oxide dispersion strengthened (ODS) alloys have been tested for cyclic, long-term, high gas-velocity resistance to oxidation at 1100 C and hot corrosion at 900 C. Both nominally Ni-16Cr-4Al and Fe-20Cr-4.5Al ODS alloys were subjected up to about 2500 cycles, where each cycle consisted of 1 hr in a hot, Mach 0.3 combusted gas stream followed by a 3-min quench in an ambient temperature, Mach 0.3 air blast. For comparison to existing technology, a coated superalloy was simultaneously tested. The ODS iron alloy exhibited clearly superior behavior, surviving 3800 oxidation and 2300 hot corrosion cycles essentially unscathed. While the ODS nickel alloys exhibited adequate oxidation resistance, the long-term hot corrosion resistance could be marginal, since the best life for such alloys under these conditions was only about 1100 cycles. However, the hot corrosion resistance of the ODS Ni-base alloys is excellent in comparison to that of traditional superalloys.

  14. Abrasion Resistance of Al-Ni-Mm-Fe Amorphous and Nanocrystalline Composite Coating on the Surface of AZ91 Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Z. B.; Liang, X. B.; Chen, Y. X.; Xu, B. S.

    An Al-Ni-Mm-Fe amorphous and nanocrystalline composite coating was prepared onto the surface of AZ91 magnesium alloy by high velocity arc spraying process. And the microstructure of the coating was analyzed by scanning electron microscope (TEM) and X-ray diffraction (XRD). The analysis results indicated that the coating consists of amorphous, nanocrystalline and crystalline phases. It has a dense structure with a low porosity of about 2.0%. Its average micro Vickers hardness value is about 330 HV0.1, which is five times than that of AZ91 magnesium alloy (62 HV0.1) and four times than that of pure Al coating (71 HV0.1). The abrasion tests showed that the Al-Ni-Mm-Fe coating exhibits a good abrasion resistance.

  15. Corrosion of alumina-forming austenitic steel Fe-20Ni-14Cr-3Al-0.6Nb-0.1Ti in supercritical water

    NASA Astrophysics Data System (ADS)

    Nie, S. H.; Chen, Y.; Ren, X.; Sridharan, K.; Allen, T. R.

    2010-04-01

    The oxidation behavior of alumina-forming austenitic (AFA) steel Fe-20Ni-14Cr-3Al-0.6Nb-0.1Ti has been examined after exposure to supercritical water (SCW) at 500 °C and 25 MPa pressure and with a dissolved oxygen content of 25 wppb, for exposure periods of 1300 h, 1700 h and 3000 h. A double layer oxide structure developed on all samples, consisting specifically of a Fe-rich outer hematite layer and an inner layer of Al-Cr-Fe-rich oxide containing a small fraction of FCC Ni-rich metal. Additionally, a thin Ni-rich layer in the bulk alloy close to the oxide/metal interface was also observed. Based on weight gain measurements, the oxidation resistance of the AFA steel was superior to other austenitic alloys, 800H, D9, and 316 stainless steel, tested under similar conditions. The formation of the protective Al-Cr-Fe-rich oxide layer may provide good long-term protection against corrosion in SCW environment.

  16. Reverse Shape Memory Effect Related to α → γ Transformation in a Fe-Mn-Al-Ni Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Peng, Huabei; Huang, Pan; Zhou, Tiannan; Wang, Shanling; Wen, Yuhua

    2017-02-01

    In this study, we investigated the shape memory behavior and phase transformations of solution-treated Fe43.61Mn34.74Al13.38Ni8.27 alloy between room temperature and 1173 K (900 °C). This alloy exhibits the reverse shape memory effect resulting from the phase transformation of α (bcc) → γ (fcc) between 673 K and 1073 K (400 °C and 800 °C) in addition to the shape memory effect resulting from the martensitic reverse transformation of γ' (fcc) → α (bcc) below 673 K (400 °C). There is a high density of hairpin-shaped dislocations in the α phase undergoing the martensitic reverse transformation of γ' → α. The lath γ phase, which preferentially nucleates and grows in the reversed α phase, has the same crystal orientation with the reverse-transformed γ' martensite. However, the vermiculate γ phase, which is precipitated in the α phase between lath γ phase, has different crystal orientations. The lath γ phase is beneficial to attaining better reverse shape memory effect than the vermiculate γ phase.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    For the first time, a face-centered-cubic, single-crystal CoCrFeNiAl0.3 (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.

  6. 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.

  7. Influence of topography and Co domain walls on the magnetization reversal of the FeNi layer in FeNi/Al2O3/Co magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Romanens, F.; Vogel, J.; Kuch, W.; Fukumoto, K.; Camarero, J.; Pizzini, S.; Bonfim, M.; Petroff, F.

    2006-11-01

    We have studied the magnetization reversal dynamics of FeNi/Al2O3/Co magnetic tunnel junctions deposited on step-bunched Si substrates using magneto-optical Kerr effect and time-resolved x-ray photoelectron emission microscopy combined with x-ray magnetic circular dichroism (XMCD-PEEM). Different reversal mechanisms have been found depending on the substrate miscut angle. Larger terraces (smaller miscut angles) lead to a higher nucleation density and stronger domain wall pinning. The width of domain walls with respect to the size of the terraces seems to play an important role in the reversal. We used the element selectivity of XMCD-PEEM to reveal the strong influence of the stray field of domain walls in the hard magnetic layer on the magnetic switching of the soft magnetic layer.

  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. Positron annihilation study of structural relaxation and crystallization in a metallic glass Al80Fe8Mo7Ni5 alloy

    NASA Astrophysics Data System (ADS)

    Abo-Elsoud, M.

    2013-04-01

    Kinetic transformations induced in the metallic glass Al80Fe8Mo7Ni5 by thermal treatments from the amorphous to the crystallized state, following the variation of the Doppler broadening of the positron annihilation line-shaped S-and W-parameters were reported. The behavior of the annihilation line-shape shows reversible and non-reversible contributions. Crystallization of the sample appears as a three-stage process. The corresponding crystallization process consists of only one activation enthalpy, Eai. The mean value obtained for Eai is: Eam=(3.65±0.14) eV. In-situ high-temperature X-ray diffraction showed that the crystallization was a complex involving growth of the Al7Fe8Mo crystalline phase along with crystallization of the amorphous matrix Al phase at T ≈500 °C. Electron micrograph with image analysis of the scanning electron microscopy pictures confirmed the presence of fcc-Al and Al7Fe8Mo crystalline phase.

  10. AlCoCrCuFeNi high entropy alloy cluster growth and annealing on silicon: A classical molecular dynamics simulation study

    NASA Astrophysics Data System (ADS)

    Xie, Lu; Brault, Pascal; Thomann, Anne-Lise; Bauchire, Jean-Marc

    2013-11-01

    Molecular dynamics simulations are carried out for describing deposition and annealing processes of AlCoCrCuFeNi high entropy alloy (HEA) thin films. Deposition results in the growth of HEA clusters. Further annealing between 300 K and 1500 K leads to a coalescence phenomenon, as described by successive jump in the root mean square displacement of atoms. The simulated X-ray diffraction patterns during annealing reproduces the main feature of the experiments: a phase transition of the cluster structure from bcc to fcc.

  11. Microstructure and room-temperature mechanical properties of Fe{sub 30}Ni{sub 20}Mn{sub 35}Al{sub 15}

    SciTech Connect

    Liao Yifeng; Baker, Ian

    2008-11-15

    A novel alloy with nominal composition Fe{sub 30}Ni{sub 20}Mn{sub 35}Al{sub 15} was prepared by arc melting. Secondary electron microscopy and transmission electron microscopy examinations showed that it had a eutectoid structure, consisting of alternating FCC and B2 lamellae, whose widths were {approx} 500 nm and {approx} 200 nm, respectively. The room-temperature yield strength and Vickers hardness of the as-cast alloy were 740 {+-} 30 MPa and HV310 {+-} 15, respectively, and the alloy exhibited {approx} 8% elongation under tension.

  12. 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.

  13. 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.

  14. Formation of Sn-M (M=Fe, Al, Ni) alloy nanoparticles by DC arc-discharge and their electrochemical properties as anodes for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Gao, Song; Huang, Hao; Wu, Aimin; Yu, Jieyi; Gao, Jian; Dong, Xinglong; Liu, Chunjing; Cao, Guozhong

    2016-10-01

    A direct current arc-discharge method was applied to prepare the Sn-M (M=Fe, Al, Ni) bi-alloy nanoparticles. Thermodynamic is introduced to analyze the energy circumstances for the formation of the nanoparticles during the physical condensation process. The electrochemical properties of as-prepared Sn-M alloy nanoparticles are systematically investigated as anodes of Li-ion batteries. Among them, Sn-Fe nanoparticles electrode exhibits high Coulomb efficiency (about 71.2%) in the initial charge/discharge (257.9 mA h g-1/366.6 mA h g-1) and optimal cycle stability (a specific reversible capacity of 240 mA h g-1 maintained after 20 cycles) compared with others. Large differences in the electrochemical behaviors indicate that the chemical composition and microstructure of the nanoparticles determine the lithium-ion storage properties and the long-term cyclic stability during the charge/discharge process.

  15. Solid-state reactions during mechanical alloying of ternary Fe-Al-X (X=Ni, Mn, Cu, Ti, Cr, B, Si) systems: A review

    NASA Astrophysics Data System (ADS)

    Hadef, Fatma

    2016-12-01

    The last decade has witnessed an intensive research in the field of nanocrystalline materials due to their enhanced properties. A lot of processing techniques were developed in order to synthesis these novel materials, among them mechanical alloying or high-energy ball milling. In fact, mechanical alloying is one of the most common operations in the processing of solids. It can be used to quickly and easily synthesize a variety of technologically useful materials which are very difficult to manufacture by other techniques. One advantage of MA over many other techniques is that is a solid state technique and consequently problems associated with melting and solidification are bypassed. Special attention is being paid to the synthesis of alloys through reactions mainly occurring in solid state in many metallic ternary Fe-Al-X systems, in order to improve mainly Fe-Al structural and mechanical properties. The results show that nanocrystallization is the common result occurring in all systems during MA process. The aim of this work is to illustrate the uniqueness of MA process to induce phase transformation in metallic Fe-Al-X (X=Ni, Mn, Cu, Ti, Cr, B, Si) systems.

  16. 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.

  17. Microstructure and Wear Behavior of Atmospheric Plasma-Sprayed AlCoCrFeNiTi High-Entropy Alloy Coating

    NASA Astrophysics Data System (ADS)

    Tian, Li-Hui; Xiong, Wei; Liu, Chuan; Lu, Sheng; Fu, Ming

    2016-12-01

    Due to the advantages such as high strength, high hardness and good wear resistance, high-entropy alloys (HEAs) attracted more and more attentions in recent decades. However, most reports on HEAs were limited to bulk materials. Although a few of studies on atmospheric plasma-sprayed (APS) HEA coatings were carried out, the wear behavior, especially the high-temperature wear behavior of those coatings has not been investigated till now. Therefore, in this study, APS was employed to deposit AlCoCrFeNiTi high-entropy alloy coating using mechanically alloyed AlCoCrFeNiTi powder as the feedstock. The phase structure of the initial powder, the feedstock powder and the as-sprayed coating was examined by an x-ray diffractometer. The surface morphology of the feedstock powder and the microstructure of the as-sprayed coating were analyzed by field emission scanning electron microscopy and energy-dispersive spectroscopy. The bonding strength and the microhardness of the as-sprayed coating were tested. The wear behavior of the coating at 25, 500, 700 and 900 °C was investigated by analysis of the wear surface morphology and measurements of the volume wear rate and the coefficient of friction.

  18. Effect of Ti content on the microstructure and mechanical behavior of (Fe36Ni18Mn33Al13)100–xTix high entropy alloys

    DOE PAGES

    Wang, Zhangwei; Wu, Margaret; Cai, Zhonghou; ...

    2016-06-13

    The microstructure and mechanical properties studies of a series of two-phase f.c.c./B2 (ordered b.c.c.) lamellar-structured, high entropy alloys (HEA) Fe36Ni18Mn33Al13Tix with x up to 6 at. % Ti have been investigated. X-ray microanalysis in a TEM showed that the Ti resided mostly in the B2 phase. The lamellar spacing decreased significantly with increasing Ti content from 1.56 μm for the undoped alloy to 155 nm with an addition of 4 at. % Ti, leading to a sharp increase in room-temperature yield strength,σy, from 270 MPa to 953 MPa, but with a concomitant decrease in ductility from 22% elongation to 2.3%.more » Annealing at 1173 K for 20 h greatly increased the lamellar spacing of Fe36Ni18Mn33Al13Ti4 to 577 nm, producing a corresponding decrease in σy to 511 MPa. The yield strengths of all the doped alloys decreased significantly when tensile tested at 973 K with a concomitant increase in ductility due to softening of the B2 phase. The fracture mode changed from cleavage at room temperature to a ductile dimple-type rupture at 973 K. Lastly, the results are discussed in terms of the Hall-Petch-type relationship.« less

  19. Effect of Electromagnetic Field on Microstructure and Properties of Bulk AlCrFeNiMo0.2 High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Dong, Yong; Jiang, Li; Tang, Zhongyi; Lu, Yiping; Li, Tingju

    2015-11-01

    The bulk AlCrFeNiMo0.2 high-entropy alloy was successfully prepared by vacuum medium frequency induction melting. The effects of electromagnetic field on microstructure and properties were investigated. The alloy possessed a mixed structure of B2 and BCC, and the phase types were not changed by the electromagnetic field treatment. The microstructure exhibited typical lamellar eutectic cell and rod eutectic cell structures. These eutectic cell structures were constituted by the AlNi-type intermetallic compound and the FeCr-type solid solution. With the increase of electromagnetic field intensity, the hardness increases, while the compressive fracture strength and fracture strain of the alloy first increases and then decreases. The alloy with 15 mT electromagnetic field has the largest fracture strength 2282.3 MPa, yield strength 1160.5 MPa, and fracture strain 0.29. The alloy shows typical ferromagnetic behavior, and the homogenized lamellar eutectic cell microstructure significantly decreased the specific saturation magnetizations.

  20. 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.

  1. Oxygen evolution from olivine M n1 -xMxP O4 (M =Fe ,Ni,Al,Mg) delithiated cathode materials

    NASA Astrophysics Data System (ADS)

    Snydacker, David H.; Wolverton, C.

    2017-01-01

    Olivine LiMnP O4 is a promising cathode material for Li-ion batteries. One drawback of this material is the propensity of its delithiated phase, MnP O4 , to evolve oxygen gas above approximately 200 °C. During thermal runaway of cells, this oxygen gas can burn the electrolyte and other cell components and thereby jeopardize safety. Partial substitution of Mn with M =Fe , Ni, Al, or Mg has been used to improve the lithium intercalation kinetics of L ixMnP O4 ; however, the effect of these substitutions on oxygen evolution is not fully documented. In this paper, we calculate phase diagrams and oxygen evolution diagrams for these M n1 -xMxP O4 delithiated cathode materials. To generate the phase diagrams, we use subregular solid-solution models and fit the energetic parameters of these models to density functional theory calculations of special quasirandom structures. The resulting thermodynamic models describe the effect of mixing on the initial temperature of oxygen evolution and on the cumulative amount of oxygen evolution at elevated temperatures. We find that addition of Fe increases the initial temperature and decreases the cumulative amount of oxygen evolution. M n0.5F e0.5P O4 exhibits an initial temperature 50 °C higher than MnP O4 and releases 70% less oxygen gas at 300 °C. Al is insoluble in MnP O4 , so addition of Al has no affect on the initial temperature. However, Al addition does slightly decrease the amount of oxygen evolution due to an inactive AlP O4 component. Mg and Ni both decrease the initial temperature of oxygen evolution, and therefore may worsen the safety of MnP O4 .

  2. 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.

  3. High-velocity deformation of Al0.3CoCrFeNi high-entropy alloy: Remarkable resistance to shear failure

    NASA Astrophysics Data System (ADS)

    Li, Z.; Zhao, S.; Diao, H.; Liaw, P. K.; Meyers, M. A.

    2017-02-01

    The mechanical behavior of a single phase (fcc) Al0.3CoCrFeNi high-entropy alloy (HEA) was studied in the low and high strain-rate regimes. The combination of multiple strengthening mechanisms such as solid solution hardening, forest dislocation hardening, as well as mechanical twinning leads to a high work hardening rate, which is significantly larger than that for Al and is retained in the dynamic regime. The resistance to shear localization was studied by dynamically-loading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed. It is therefore proposed that the excellent strain hardening ability gives rise to remarkable resistance to shear localization, which makes this material an excellent candidate for penetration protection applications such as armors.

  4. High-velocity deformation of Al0.3CoCrFeNi high-entropy alloy: Remarkable resistance to shear failure.

    PubMed

    Li, Z; Zhao, S; Diao, H; Liaw, P K; Meyers, M A

    2017-02-17

    The mechanical behavior of a single phase (fcc) Al0.3CoCrFeNi high-entropy alloy (HEA) was studied in the low and high strain-rate regimes. The combination of multiple strengthening mechanisms such as solid solution hardening, forest dislocation hardening, as well as mechanical twinning leads to a high work hardening rate, which is significantly larger than that for Al and is retained in the dynamic regime. The resistance to shear localization was studied by dynamically-loading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed. It is therefore proposed that the excellent strain hardening ability gives rise to remarkable resistance to shear localization, which makes this material an excellent candidate for penetration protection applications such as armors.

  5. Effect of aluminum on fine structure and distribution of chemical elements in high-entropy alloys Al x FeNiCoCuCr

    NASA Astrophysics Data System (ADS)

    Nadutov, V. M.; Makarenko, S. Yu.; Volosevich, P. Yu.

    2015-05-01

    Electron-microscopic and X-ray diffraction methods have been used to study the fine structure of cast high-entropy alloys (HEAs) Al x FeNiCoCuCr ( x = 1, 1.5, 1.8). Disperse precipitates with dimensions of 130-400 and 10-20 nm have been revealed, the character of distribution of which, as well as the amounts, dimensions, and shapes, change with increasing aluminum content. In the equiatomic HEA, copper-containing particles with an fcc structure have been found; in the alloy with x = 1.8, particles of bcc Al4Cu9 dominate. It has been shown that the most uniform distribution over the matrix is characteristic of Co, unlike other elements, among which Cu and Cr are distributed in the alloy extremely nonuniformly and predominantly enter into the precipitated particles and into clusters in the interparticle spaces, respectively.

  6. High-velocity deformation of Al0.3CoCrFeNi high-entropy alloy: Remarkable resistance to shear failure

    PubMed Central

    Li, Z.; Zhao, S.; Diao, H.; Liaw, P. K.; Meyers, M. A.

    2017-01-01

    The mechanical behavior of a single phase (fcc) Al0.3CoCrFeNi high-entropy alloy (HEA) was studied in the low and high strain-rate regimes. The combination of multiple strengthening mechanisms such as solid solution hardening, forest dislocation hardening, as well as mechanical twinning leads to a high work hardening rate, which is significantly larger than that for Al and is retained in the dynamic regime. The resistance to shear localization was studied by dynamically-loading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed. It is therefore proposed that the excellent strain hardening ability gives rise to remarkable resistance to shear localization, which makes this material an excellent candidate for penetration protection applications such as armors. PMID:28210000

  7. Complexation of desferricoprogen with trivalent Fe, Al, Ga, In and divalent Fe, Ni, Cu, Zn metal ions: effects of the linking chain structure on the metal binding ability of hydroxamate based siderophores.

    PubMed

    Enyedy, Eva A; Pócsi, István; Farkas, Etelka

    2004-11-01

    Complexes of the natural siderophore, desferricoprogen (DFC), with several trivalent and divalent metal ions in aqueous solution were studied by pH-potentiometry, UV-Vis spectrophotometry and cyclic voltammetry. DFC was found to be an effective metal binding ligand, which, in addition to Fe(III), forms complexes of high stability with Ga(III), Al(III), In(III), Cu(II), Ni(II) and Zn(II). Fe(II), however, is oxidized by DFC under anaerobic conditions and Fe(III) complexes are formed. By comparing the results with those of desferrioxamine B (DFB), it can be concluded that the conjugated beta-double bond slightly increases the stability of the hydroxamate chelates, consequently increases the stability of mono-chelated complexes of DFC. Any steric effect by the connecting chains arises only in the bis- and tris-chelated complexes. With metal ions possessing a relatively big ionic radius (Cu(II), Ni(II), Zn(II), In(III)) DFC, containing a bit longer chains than DFB, forms slightly more stable complexes. With smaller metal ions the trend is the opposite. Also a notable difference is that stable trinuclear complex, [Cu(3)L(2)], is formed with DFC but not with DFB. Possible bio-relevance of the Fe(II)/Fe(III) results is also discussed in the paper.

  8. 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.

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

    PubMed Central

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

    2014-01-01

    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

  10. 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.

  11. 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.

  12. Fabrication of CuAl1-xMxO2 (M = Fe, Cr)/Ni film delafossite compounds using spin coating and their microstructure and dielectric constant

    NASA Astrophysics Data System (ADS)

    Diantoro, Markus; Yuwita, Pelangi Eka; Olenka, Desyana; Nasikhudin

    2014-09-01

    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 CuAlO2. 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 CuAl1-xMxO2 delafossite compounds doped with Cr3+ and Fe3+ from the raw material of Cu(NO3)2˙3H2O, Al(NO3)3˙9H2O, Fe(NO3)3˙9H2O and Cr(NO3)3˙9H2O. 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 CuAl1-xMxO2/Ni delafossite films were successfully fabricated. The CuAl1-xFexO2 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 Al3+ 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 Cr3+ doped of CuAl1-xCrxO2 films with smaller effects.

  13. 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.

  14. 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.

  15. 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.

  16. Effects of Temperature on Serrated Flows of Al0.5CoCrCuFeNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    Compression behavior of the Al0.5CoCrCuFeNi high-entropy alloy (HEA) was studied at different temperatures from 673 K to 873 K at a low strain rate of 5 × 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. 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.

  17. Effects of Annealing on the Microstructure and Properties of 6FeNiCoCrAlTiSi High-Entropy Alloy Coating Prepared by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Pan, Ye; He, Yizhu

    2011-09-01

    The content of each constituent element in the newly developed high-entropy alloys is always restricted in equimolar or near-equimolar ratios to avoid the formation of complex brittle phases during the solidification process. In this article, a high-entropy alloy coating of 6FeNiCoCrAlTiSi has been prepared by laser cladding and subsequently annealed at 500, 750, 1000, and 1150 °C for 5 h. Surprisingly, the coating has a simple BCC solid solution phase with high microhardness, good resistance to softening, and high electrical resistivity properties. After annealing <750 °C, the coating shows high thermal stability, the electrical resistivity decreases slightly and the microhardness almost remains unchanged. After annealing above 750 °C, the microhardness of the coating slowly decreases with the decomposition of the supersaturated BCC solid solution.

  18. 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.

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

    DOE PAGES

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

    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

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

    DOE PAGES

    Chen, Shuying; Xie, Xie; Chen, Bilin; ...

    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

  1. 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.

  2. Microstructure and Corrosion Properties of AlCoCrFeNi High Entropy Alloy Coatings Deposited on AISI 1045 Steel by the Electrospark Process

    NASA Astrophysics Data System (ADS)

    Li, Q. H.; Yue, T. M.; Guo, Z. N.; Lin, X.

    2013-04-01

    Electrospark deposition (ESD) was employed to clad the AlCoCrFeNi high-entropy alloy (HEA) on AISI 1045 carbon steel. The relationship between the microstructure and corrosion properties of the HEA-coated specimens was studied and compared with that of the copper-molded cast HEA material. Two major microstructural differences were found between the cast HEA material and the HEA coatings. First, the cast material comprises both columnar and equiaxed crystals with a columnar-to-equiaxed transition (CET), whereas the HEA coatings consist of an entirely columnar crystal structure. The CET phenomenon was analyzed based on Hunt's criterion. Second, unlike the cast HEA material, there was no obvious Cr-rich interdendritic segregation and nano-sized precipitate distributed within the dendrites of the HEA coating. With regard to corrosion properties, the corrosion current of the HEA-coated specimen was significantly lower than for the 1045 steel and the cast HEA material. This was attributed to the ESD specimen having a relatively high Cr oxide and Al oxide content at the surface. Moreover, for the ESD specimen, the absence of Cr-rich interdendritic phase and second-phase precipitation resulted in a relatively uniform corrosion attack, which is different from the severe galvanic corrosion attack that occurred in the cast specimen.

  3. X-ray powder diffraction and 57Fe Mössbauer spectroscopy of synthetic trioctahedral micas {K}[Me3]Ni2+, Mg2+, Co2+, Fe2+; T = Al3+, Fe3+

    NASA Astrophysics Data System (ADS)

    Redhammer, G. J.; Amthauer, G.; Lottermoser, W.; Bernroider, M.; Tippelt, G.; Roth, G.

    2005-11-01

    Trioctahedral 1 M micas have been synthesized along (pseudo)binary joins using hydrothermal techniques and controlled oxygen fugacities. Octahedrally coordinated iron in annite {K}[Fe3]<AlSi3rangleO10(OH)2 was successively replaced by Co2+, Mg2+ and Ni2+ and tetrahedrally coordinated aluminum by Fe3+. Unit cell parameters decrease almost linearly with decreasing average radius of the octahedral cation/average M O bond length within the octahedral sheet. With increasing substitution of Fe2+ the octahedral sheet becomes more flattened, the ditrigonal distortion of the tetrahedral sheet increases up to a maximum value of ≈10° for micas with tetrahedral sheet compositions close to <AlSi3rangle and up to ≈14° for those containing a <FeSi3rangle tetrahedral sheet. All iron-bearing samples were studied by 57Fe Mössbauer spectroscopy. With increasing substitution of iron by smaller divalent cations the quadrupole splitting distribution (QSD) evolves from a broad bimodal distribution in annite to a smaller unimodal distribution in Mg2+ and Ni2+-rich samples so that for high substitution rates more regular local environments are dominating. These results, however, can not be interpreted in terms of an octahedral cation ordering scheme. For none of the micas investigated reliable Fe2+ M2/M1 area ratios can be extracted. fMoreover, the complete QSD is shifted towards higher quadrupole splitting values. Similar observations were obtained for substituting Fe2+ by Mg2+ and Ni2+ in tetra-ferri-annite free of octahedral coordinated trivalent cations. Unlike in the Al3+ bearing micas a third QSD component is missing which supports the claim that the appearance of this third QSD component is closely related to the presence of trivalent cations (Al3+, Fe3+) in octahedra coordination.

  4. Al-La-Ni (069)

    NASA Astrophysics Data System (ADS)

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

    This document is part of Part 1 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-La-Ni (069)' with the content:

  5. 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.

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

    PubMed

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

    2013-01-04

    [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(-1) of the Ni-A state shifted to 1971, 2086 and 2098 cm(-1) in the Ni-AL state. The g-values of g(x)=2.30, g(y)=2.23 and g(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.

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

    PubMed

    Feuerbacher, Michael

    2016-07-19

    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.

  8. Phase Evolution and Thermal Analysis of Nanocrystalline AlCrCuFeNiZn High Entropy Alloy Produced by Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Koundinya, N. T. B. N.; Sajith Babu, C.; Sivaprasad, K.; Susila, P.; Kishore Babu, N.; Baburao, J.

    2013-10-01

    A multi-component nanocrystalline AlCrCuFeNiZn high entropy alloy with 12 nm crystallite size was successfully synthesized using high energy ball milling. The progress of solid solution formation during milling was analyzed using XRD. A major portion of the HEA is observed to be BCC in crystal structure after 30 h of milling. Thermal analysis showed that HEA powders exhibited exponential oxidation characteristics. Thermal analysis showed that low activation energy was sufficient to start recrystallization because of high energy stored in the milled powders. The crystallite size after consolidation is in nanocrystalline range due to the sluggish diffusion of atoms and nanotwinning. After consolidation, the crystallite size is around 79 nm. Samples sintered at 850 °C for 2 h exhibited high hardness values of 700 ± 15 HV1.0, major volume fraction of the phases are having FCC crystal structure along with a minor phase having BCC crystal structure. Due to positive enthalpy mixing of Cu with other elements, decomposition of BCC to new FCC phases occurs.

  9. 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

  10. Microstructure and properties of 6FeNiCoSiCrAlTi high-entropy alloy coating prepared by laser cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Pan, Ye; He, Yizhu; Jiao, Huisheng

    2011-01-01

    The content of each constituent element in the newly developed high-entropy alloys (HEAs) is always restricted in equimolar or near-equimolar ratio in order to avoid the formation of complex brittle phases during the solidification process. In this study, a 6FeNiCoSiCrAlTi high-entropy alloy coating with simple BCC solid solution phase has been prepared by laser cladding on a low carbon steel substrate. The microstructure, hardness and magnetic properties have been investigated. The experimental results show that the tendency of component segregation in the conventional solidification microstructure of multi-component alloy is effectively relieved. The microstructure of the coating is mainly composed of equiaxed polygonal grains, discontinuous interdendritic segregation and nano-precipitates. EBSD observation confirms that the polygonal grains and interdendritic segregation have similar BCC structure with lots of low angle grain boundaries at the interface. The microhardness of the coating reaches 780 HV 0.5, which is much higher than most of the HEAs prepared by other methods. In addition, the coating shows excellent soft magnetic properties.

  11. 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.

  12. 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.

  13. 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.

  14. Microstructure and magnetic microstructure of the Pr 60Al 10Ni 10Cu 20-xFe x ( x=0, 4, 10, 15, 18) alloys observed by magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Pang, Z. Y.; Han, S. H.; Wang, Y. T.; Wang, W. H.; Han, B. S.

    2005-03-01

    The microstructure and magnetic microstructure of the Pr 60Al 10Ni 10Cu 20-xFe x ( x=0, 4, 10, 15, 18) alloys have been achieved simultaneously by employing a magnetic force microscope directly on the as-cast cylinder rod surface for the first time. By varying the content of Fe, the microstructure of the Pr-based alloy changes progressively from a full glassy state to a composite state with nanocrystalline particles embedded in the glassy matrix, and finally into a nanostructured state. The accompanying magnetic property gradually changes from paramagnetic to hard. The experiment directly evidences the existence of exchange coupling between the crystallites and the variety of the grain-size-dependent magnetic properties can be well explained by Löffler et al.'s new random-anisotropy model (Löffler, et al., Phys. Rev. Lett. 85 (9) (2000) 1990).

  15. Magnetic properties of hard-soft SrFe10Al2O19/Co0.8Ni0.2Fe2O4 ferrite synthesized by one-pot sol-gel auto-combustion

    NASA Astrophysics Data System (ADS)

    Torkian, Shahab; Ghasemi, Ali; Razavi, Reza Shoja

    2016-10-01

    SrFe10Al2O19/Co0.8Ni0.2Fe2O4 hard/soft nanocomposite ferrites with different content of soft phase have been prepared by simple one-pot sol-gel auto-combustion route. X-ray diffraction (XRD), field emission scanning electron microscopy and vibrating ample magnetometer were employed to analysis of structural and magnetic features of synthesized samples. XRD patterns reflect the formation of hard/soft composites of ferrites without the existence of any kind of secondary phases. Narrow size distributions of particles were formed by sol-gel method. Single smooth hysteresis loops of nanocomposites show the presence of exchange coupling between hard and soft phases. Nanocomposite with 15 wt% of soft phase reaches the highest Mr/Ms ratio of 0.63. Compared to the physical mixing of hard/ soft nanocomposites, the one-pot sol-gel auto-combustion method could be considered as a suitable method for synthesizing exchange coupled magnet.

  16. Domain structure and magnetization process of a giant magnetoimpedance geometry FeNi/Cu/FeNi(Cu)FeNi/Cu/FeNi sensitive element

    NASA Astrophysics Data System (ADS)

    Kurlyandskaya, G. V.; Elbaile, L.; Alves, F.; Ahamada, B.; Barrué, R.; Svalov, A. V.; Vas'kovskiy, V. O.

    2004-09-01

    The magnetization process and the magnetic domains of the FeNi (100 nm)/Cu (2.5 nm)/FeNi (100 nm)/Cu (480 nm)/FeNi (100 nm)/Cu (2.5 nm)/FeNi (100 nm) structure were studied. This geometry consists of two FeNi/Cu/FeNi trilayers with a thick in the direction perpendicular to the plane of the sensitive element and narrow in the direction of the flowing current Cu electrode in the centre. Ferromagnet/conductor/ferromagnet is the typical geometry of magnetoimpedance thin-film-based sensitive elements used to detect small magnetic fields. Multilayered structures were prepared by rf-sputtering in a magnetic field of 100 Oe applied perpendicular to the Cu electrode in order to induce transverse magnetic anisotropy. The magnetic measurements and magnetic domain structure observations were made in magnetic fields applied one at a time parallel or perpendicular to the Cu electrode. Different magnetization processes with non-homogeneous rotations in the first case and dominant multiple nucleation and merging of domains in the second one were observed.

  17. 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.

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

    DOE PAGES

    Wang, Z.; Gao, M. C.; Ma, S. G.; ...

    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

  19. Al-Co-Fe (030)

    NASA Astrophysics Data System (ADS)

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

    This document is part of Part 1 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-Co-Fe (030)' with the content:

  20. 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.

  1. 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).

  2. 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.

  3. 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.

  4. 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.

  5. Synthesis of AlNiCo core/shell nanopowders

    NASA Astrophysics Data System (ADS)

    Genc, A. M.; Akdeniz, M. V.; Ozturk, T.; Kalay, Y. E.

    2016-11-01

    Magnetic core/shell nanostructures have been recently received much interest owing to their utmost potential in permanent magnetic applications. In the present work, AlNiCo permanent magnet powders were synthesized by ball milling and a core/shell nanostructure was obtained using RF induced plasma. The effects of particle size and nanoshell structure on the magnetic properties were investigated in details. The coercivity of AlNiCo powders was found to increase with decreasing particle size, exclusively nanopowders encapsulated with Fe3O4 shell showed the highest coercivity values. The shell structure produced during plasma reaction was found to form a resistant layer against oxidation of metallic nanoparticles.

  6. 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.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    We present a study of the effective magnetization M eff and the effective damping parameter α eff by means of ferromagnetic resonance spectroscopy on the ferromagnetic (FM) materials Ni81Fe19 (NiFe) and Co40Fe40B20 (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 eff and α 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 eff and α 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 eff and α 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 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.

  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. 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.

  12. 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.

  13. Steam reforming of ethanol at moderate temperature: Multifactorial design analysis of Ni/La 2O 3-Al 2O 3, and Fe- and Mn-promoted Co/ZnO catalysts

    NASA Astrophysics Data System (ADS)

    Torres, José Antonio; Llorca, Jordi; Casanovas, Albert; Domínguez, Montserrat; Salvadó, Joan; Montané, Daniel

    Novel Co (10%) catalysts supported on ZnO and promoted with Fe and Mn (1%) were synthesized and characterized by high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS), X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). Their catalytic activity for steam reforming of ethanol was compared with that of Ni catalysts supported on La 2O 3-Al 2O 3. Experiments at 400 and 500 °C, steam to carbon ratios of 2 and 4, and a wide interval of contact time were analyzed following a multifactorial experimental design. At 500 °C and a steam to carbon molar ratio of 4, complete conversion of ethanol was achieved above a contact time of 200 g min mol -1 for all catalysts. The ratio of selectivity between hydrogen and methane was around 23 mol H2/mol CH4 in the Co catalysts, while it approached the thermodynamic equilibrium (5.7 mol H2/mol CH4) in the Ni catalysts. The Co catalysts do not promote methane-forming reactions like ethanol cracking and acetaldehyde decarbonilation, nor do they facilitate the reverse methane steam reforming reaction. The catalytic behavior of cobalt is enhanced by promotion with iron or manganese through the formation of bimetallic particles, which facilitates cobalt reducibility. This suggests that Co-Mn/ZnO and Co-Fe/ZnO catalysts have a good potential for their use for ethanol reforming at moderate temperature.

  14. 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.

  15. 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

  16. Preparation and Pore Structure Stability at High Temperature of Porous Fe-Al Intermetallics

    NASA Astrophysics Data System (ADS)

    Shen, P. Z.; Gao, H. Y.; Song, M.; He, Y. H.

    2013-12-01

    Porous Fe-Al intermetallics with different nominal compositions (from Fe-8 wt.% Al to Fe-50 wt.% Al) were fabricated by Fe and Al elemental powders through reaction synthesis. The effects of the Al content on the pore structure properties, and the comparison of pore structure stabilities at high-temperatures among the porous Fe-Al intermetallics and porous Ti, Ni, 316L stainless steel samples, were systematically studied. Results showed that the open porosity, maximum pore size, and permeability vary with the Al content. Porous Fe-(25-30 wt.%) Al intermetallics show good shape controllability and excellent pore structure stability at 1073 K in air, which suggests that these porous Fe-Al intermetallics could be used for filtration at high temperatures.

  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. 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

  19. Comparative study of NiFe{sub 2−x}Al{sub x}O{sub 4} ferrite nanoparticles synthesized by chemical co-precipitation and sol–gel combustion techniques

    SciTech Connect

    Gul, I.H.; Pervaiz, Erum

    2012-06-15

    Graphical abstract: AFM images of NiFe{sub 2}O{sub 4} ferrite nanoparticles at room temperature synthesized by sol–gel technique. Highlights: ► Particle size reduces to less than 30 nm. ► DC electrical resistivity increases with substitution of Cr{sup 3+}. ► Dielectric constant decreases. -- Abstract: A series of aluminum substituted Ni-ferrite nanoparticles have been synthesized by chemical co-precipitation and sol–gel techniques. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR), DC electrical resistivity and dielectric properties. Analysis of the X-ray diffraction pattern of all the samples confirmed the formation of spinel structure. The crystallite sizes remain within the range 25–41 ± 3 nm. FTIR measurements show two fundamental absorption bands, assigned to the vibration of tetrahedral and octahedral sites. DC electrical resistivity increases from 6.60 × 10{sup 7} to 6.9 × 10{sup 10} Ω cm as the Al{sup 3+} concentration increases from 0.00 to 0.50. The dielectric constant and loss tangent decreases with increasing Al{sup 3+} concentration from 22 to 14, 0.354 to 0.27 respectively at 5 MHz for all the samples. Impedance measurements as a function of frequency (1 kHz–5 MHz) at room temperature further helped in analyzing the electrical properties of the prepared samples.

  20. Features of phase and structure formation in high-entropy alloys of the AlCrFeCoNiCu x system ( x = 0, 0.5, 1.0, 2.0, 3.0)

    NASA Astrophysics Data System (ADS)

    Krapivka, N. A.; Firstov, S. A.; Karpets, M. V.; Myslivchenko, A. N.; Gorban', V. F.

    2015-05-01

    Alloys of the AlCrFeCoNiCu x system ( x = 0, 0.5, 1.0, 2.0, 3.0) were smelted by argon-arc smelting in pure argon. The phase composition and structure of fabricated alloys are investigated and their mechanical properties are determined. The results showed that an increase in the amount of copper in alloys leads to a change in the phase composition from single phase (bcc) to three phase (bcc + fcc1 + fcc2), which is accompanied by the structural change from coarse-grain polygonal structure to complex dendritic structure (primary dendrites (DR) + secondary dendrites (SDR) + interdendrite phase (ID)). The region of electron concentrations of alloys, in which bcc and fcc phases are present simultaneously, is determined. The limiting electron concentration of stability of the bcc lattice is found experimentally. Microhardness is measured and Young moduli of alloys over the entire range of varying the copper concentration are determined.

  1. Activity coefficients of NiO and CoO in CaO-Al2O3-SiO2 slag and their application to the recycling of Ni-Co-Fe-based end-of-life superalloys via remelting

    NASA Astrophysics Data System (ADS)

    Lu, Xin; Miki, Takahiro; Nagasaka, Tetsuya

    2017-01-01

    To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni-Co-Fe-based end-of-life (EoL) superalloys, knowledge of their activity coefficients in slags is essential. In this study, the activity coefficients of NiO and CoO in CaO-Al2O3-SiO2 slag, a candidate slag used for the EoL superalloy remelting process, were measured using gas/slag/metal equilibrium experiments. These activity coefficients were then used to consider the recycling efficiency of nickel and cobalt by remelting EoL superalloys using CaO-Al2O3-SiO2 slag. The activity coefficients of NiO and CoO in CaO-Al2O3-SiO2 slag both show a positive deviation from Raoult's law, with values that vary from 1 to 5 depending on the change in basicity. The activity coefficients of NiO and CoO peak in the slag with a composition near B = (%CaO)/(%SiO2) = 1, where B is the basicity. We observed that controlling the slag composition at approximately B = 1 effectively reduces the cobalt and nickel oxidation losses and promotes the oxidation removal of iron during the remelting process of EoL superalloys.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Li, Wei; Liu, Ping; Zhang, Ke; Ma, Fengcang; Liu, Xinkuan; Chen, Xiaohong; He, Daihua

    2014-08-01

    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.

  4. 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

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

    PubMed

    Li, Wei; Liu, Ping; Zhang, Ke; Ma, Fengcang; Liu, Xinkuan; Chen, Xiaohong; He, Daihua

    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.

  6. 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.

  7. [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.

  8. Longitudinal and perpendicular exchange bias in FeMn/(FeNi/FeMn)n multilayers

    NASA Astrophysics Data System (ADS)

    Sun, L.; Zhou, S. M.; Searson, P. C.; Chien, C. L.

    2003-05-01

    Exchange bias in ferromagnetic (FM)/antiferromagnetic (AF) bilayers is usually investigated in the longitudinal configuration with the exchange coupling established in the film plane. In this work, we report on the perpendicular exchange bias in FeMn(8 nm)/[FeNi(2 nm)/FeMn(8 nm)]n multilayers induced by perpendicular field cooling. The thin FeNi layers give rise to large values of the exchange field and coercivity, and n=15 allows a sufficiently large magnetization for the measurements. Even though the soft FeNi layers have an intrinsic in-plane anisotropy, perpendicular exchange bias has been observed after cooling in a perpendicular external field. The exchange field in the perpendicular configuration is about 0.85 that of the longitudinal case. In both the longitudinal and perpendicular configurations, the exchange field decreases quasilinearly with temperature. The squareness of perpendicular hysteresis loops decreases with increasing temperature.

  9. Structural, morphological and magnetic properties of Al3+ substituted Ni0.25Cu0.20Zn0.55AlxFe2-xO4 ferrites synthesized by solid state reaction route

    NASA Astrophysics Data System (ADS)

    Rahman, K. R.; Chowdhury, F.-U.-Z.; Khan, M. N. I.

    Ni-Cu-Zn ferrite materials have been extensively used in electronic materials because of their outstanding properties at high frequencies. This work investigates the impact of Al substitution on the structure, morphology and magnetic properties of Ni0.25Cu0.20Zn0.55AlxFe2-xO4 (x = 0.00, 0.05, 0.10, 0.15 and 0.20) prepared by solid state reaction method. X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), impedance analyzer and Vibrating Sample Magnetometer (VSM) were used to characterize the properties of the samples. The XRD study confirmed the cubic spinel structure with single phase for all the samples. The lattice constant, X-ray density and bulk density decrease while the porosity and grain size increase with the increase of Al content in the samples. The frequency dependence of the complex permeability sintered at 1200 °C has been measured for toroidal samples in the frequency range between 1 kHz and 120 MHz at room temperature. The decrease in initial permeability has been explained on the basis of variation in grain size. The temperature dependence of the initial permeability has been measured in the temperature range between from 30 to 250 °C. Curie temperature (Tc) has been estimated from the temperature dependence of the permeability spectra for all samples. It is found that Curie temperatures and initial permeability (μi‧) decrease on Al substitution. The saturation magnetization has been measured at room temperature and it was found to decrease with increasing of Al3+ ions.

  10. 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.

  11. FeNi-based magnetoimpedance multilayers: Tailoring of the softness by magnetic spacers

    NASA Astrophysics Data System (ADS)

    Svalov, A. V.; Fernandez, E.; Garcia-Arribas, A.; Alonso, J.; Fdez-Gubieda, M. L.; Kurlyandskaya, G. V.

    2012-04-01

    The microstructure and magnetic properties of sputtered permalloy films and FeNi(170 nm)/X/FeNi(170 nm) (X = Co, Fe, Gd, Gd-Co) sandwiches were studied. Laminating of the thick FeNi film with various spacers was done in order to control the magnetic softness of FeNi-based multilayers. In contrast to the Co and Fe spacers, Gd and Gd-Co magnetic spacers improved the softness of the FeNi/X/FeNi sandwiches. The magnetoimpedance responses were measured for [FeNi/Ti(6 nm)]2/FeNi and [FeNi/Gd(2 nm)]2/FeNi multilayers in a frequency range of 1-500 MHz: for all frequencies under consideration the highest magnetoimpedance variation was observed for [FeNi/Gd(2 nm)]2/FeNi multilayers.

  12. High strain rate deformation of NiAl

    SciTech Connect

    Maloy, S.A.; Gray, G.T. III; Darolia, R.

    1994-07-01

    NiAl is a potential high temperature structural material. Applications for which NiAl is being considered (such as rotating components in jet engines) requires knowledge of mechanical properties over a wide range of strain rates. Single crystal NiAl (stoichiometric and Ni 49.75Al 0.25Fe) has been deformed in compression along [100] at strain rates of 0.001, 0.1/s and 2000/s and temperatures of 76,298 and 773K. <111> slip was observed after 76K testing at a strain rate of 0.001/s and 298K testing at a strain rate of 2000/s. Kinking was observed after deformation at 298K and a strain rate of 0.001/s and sometimes at 298 K and a strain rate of 0.1/s. Strain hardening rates of 8200 and 4000 MPa were observed after 773 and 298K testing respectively, at a strain rate of 2000/s. Results are discussed in reference to resulting dislocation substructure.

  13. 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.

  14. 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.

  15. 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.

  16. Structure and function of [NiFe] hydrogenases.

    PubMed

    Ogata, Hideaki; Lubitz, Wolfgang; Higuchi, Yoshiki

    2016-11-01

    Hydrogenases catalyze the reversible conversion of molecular hydrogen to protons and electrons via a heterolytic splitting mechanism. The active sites of [NiFe] hydrogenases comprise a dinuclear Ni-Fe center carrying CO and CN(-) ligands. The catalytic activity of the standard (O2-sensitive) [NiFe] hydrogenases vanishes under aerobic conditions. The O2-tolerant [NiFe] hydrogenases can sustain H2 oxidation activity under atmospheric conditions. These hydrogenases have very similar active site structures that change the ligand sphere during the activation/catalytic process. An important structural difference between these hydrogenases has been found for the proximal iron-sulphur cluster located in the vicinity of the active site. This unprecedented [4Fe-3S]-6Cys cluster can supply two electrons, which lead to rapid recovery of the O2 inactivation, to the [NiFe] active site.

  17. Magnetic and optical properties of MgAl2O4-(Ni0.5Zn0.5)Fe2O4 thin films prepared by pulsed laser deposition.

    PubMed

    Misu, Takeshi; Sakamoto, Naonori; Shinozaki, Kazuo; Adachi, Nobuyasu; Suzuki, Hisao; Wakiya, Naoki

    2011-06-01

    Thin films composed of MgAl2O4 and (Ni0.5Zn0.5)Fe2O4 ([MA(100-x)-NZFx] films) were grown on fused SiO2 substrates by pulsed laser deposition. X-ray diffraction measurements revealed that the films were polycrystalline, and that their lattice constant varied linearly with composition, indicating the formation of a solid solution. The film with x=60 was paramagnetic and those with x ≥ 70 were ferromagnetic. The films had a transparency above 75% in the visible range, but the transparency decreased with the x value. The optical band gaps were 2.95, 2.55, 2.30 and 1.89 eV for x=20, 40, 60, 80 and 100, respectively. The Faraday rotation angle increased with x in the visible range, and the film with x=70 exhibited a value of 2000 degrees cm(-1) at 570 nm, which is comparable to the rotation angle of Y3Fe5O12. Owing to their high transparency, which extends into the visible range, the [MA(100-x)-NZFx] films can be used in novel magneto-optical devices.

  18. Magnetic and optical properties of MgAl2O4-(Ni0.5Zn0.5)Fe2O4 thin films prepared by pulsed laser deposition

    PubMed Central

    Misu, Takeshi; Sakamoto, Naonori; Shinozaki, Kazuo; Adachi, Nobuyasu; Suzuki, Hisao; Wakiya, Naoki

    2011-01-01

    Thin films composed of MgAl2O4 and (Ni0.5Zn0.5)Fe2O4 ([MA(100-x)-NZFx] films) were grown on fused SiO2 substrates by pulsed laser deposition. X-ray diffraction measurements revealed that the films were polycrystalline, and that their lattice constant varied linearly with composition, indicating the formation of a solid solution. The film with x=60 was paramagnetic and those with x ≥ 70 were ferromagnetic. The films had a transparency above 75% in the visible range, but the transparency decreased with the x value. The optical band gaps were 2.95, 2.55, 2.30 and 1.89 eV for x=20, 40, 60, 80 and 100, respectively. The Faraday rotation angle increased with x in the visible range, and the film with x=70 exhibited a value of 2000 degrees cm-1 at 570 nm, which is comparable to the rotation angle of Y3Fe5O12. Owing to their high transparency, which extends into the visible range, the [MA(100-x)-NZFx] films can be used in novel magneto-optical devices. PMID:27877399

  19. Structural and magnetic properties of electrospun FeCoNi magnetic nanofibers with nanogranular phases

    NASA Astrophysics Data System (ADS)

    Park, Ji Hea; Kweon, Soon C.; Kim, Sang Woo

    2012-02-01

    Structural and magnetic properties of silicon/aluminum-added and -free FeCoNi magnetic alloy nanofibers with nanogranular phases prepared by electrospinning and subsequent annealing of the PVP-blended ternary metal precursors in hydrogen atmosphere were investigated. The FeCoNi magnetic alloy nanofibers with evenly distributed nanocrystalline phases were formed, which are identified as γ-Fe1- x Ni x binary phase with face-centered cubic structure and α-CoFe phase with body-centered cubic structure. At elevated temperature, the α → γ structural martensitic transformation in the FeCoNi ternary alloys occurred due to the inhomogeneities in composition of the matrix during annealing of the alloy with metastable α-phase. In the Si/Al-added FeCoNi nanofibers, more than two phases with complicated-boundaries of the grains in and/or outside the nanofibers were formed as crystalline phases and amorphous phase. The amorphous phase consisted of Si and/or Al acted as an inhibitor diminishing α → γ transformation as well as an interparticle insulation layer. At low annealing temperature of 450 °C, the Si/Al-added nanofiber mainly consisted of metastable α-phase with a low-crystallinity surface structure and very small diameter of 13 nm was formed and showed an unexpectedly high coercivity, which attributed to the surface effects and/or high surface/volume ratio.

  20. Tetragonal magnetostriction and magnetoelastic coupling in Fe-Al, Fe-Ga, Fe-Ge, Fe-Si, Fe-Ga-Al, and Fe-Ga-Ge alloys

    NASA Astrophysics Data System (ADS)

    Restorff, J. B.; Wun-Fogle, M.; Hathaway, K. B.; Clark, A. E.; Lograsso, T. A.; Petculescu, G.

    2012-01-01

    This paper presents a comparative study on the tetragonal magnetostriction constant, λγ,2, [ = (3/2)λ100] and magnetoelastic coupling, b1, of binary Fe100-xZx (0 < x < 35, Z = Al, Ga, Ge, and Si) and ternary Fe-Ga-Al and Fe-Ga-Ge alloys. The quantities are corrected for magnetostrains due to sample geometry (the magnetostrictive form effect). Recently published elastic constant data along with magnetization measurements at both room temperature and 77 K make these corrections possible. The form effect correction lowers the magnetostriction by ˜10 ppm for high-modulus alloys and by as much as 30 ppm for low-modulus alloys. The elastic constants are also used to determine the values of the magnetoelastic coupling constant, b1. With the new magnetostriction data on the Fe-Al-Ga alloy, it is possible to show how the double peak magnetostriction feature of the binary Fe-Ga alloy flows into the single peak binary Fe-Al alloy. The corrected magnetostriction and magnetoelastic coupling data for the various alloys are also compared using the electron-per-atom ratio, e/a, as the common variable. The Hume-Rothery rules link the e/a ratio to the regions of phase stability, which appear to be intimately related to the magnetostriction versus the solute concentration curve in these alloys. Using e/a as the abscissa tends to align the peaks in the magnetostriction and magnetoelastic coupling for the Fe-Ga, Fe-Ge, Fe-Al, Fe-Ga-Al, and Fe-Ga-Ge alloys, but not for the Fe-Si alloys for which the larger atomic size difference may play a greater role in phase stabilization. Corrections for the form effect are also presented for the rhombohedral magnetostriction, λɛ,2, and the magnetoelastic coupling, b2, of Fe100-xGax (0 < x < 35) alloys.

  1. Coercive force reduction effect in FeCoV and FeNi films due to ultrathin FeNiMo layer

    NASA Astrophysics Data System (ADS)

    Nozawa, T.; Nouchi, N.; Morimoto, F.; Otani, A.

    2003-01-01

    The mechanism of the drastic coercive force reduction effect in essentially semi-hard FeCoV and FeNi films due to ultrathin FeNiMo layer has been examined. It is noted experimentally that a kind of a coupling of magnetic moments existing between ultrathin FeNiMo layer with anisotropic magnetization and semi-hard magnetic layer with anisotropic magnetization contributes to this drastic coercive force reducing effect.

  2. Analyzing the magnetic profile in NiFe/NiO bilayers

    NASA Astrophysics Data System (ADS)

    Tafur, Miguel; Nascimento, V. P.; Alayo, W.; Xing, Y. T.; Baggio-Saitovitch, E.

    2017-04-01

    The magnetic profile of the Si(100)/NiO(35 nm)/NiFe(10 nm)/Ta(1 nm) sample has been obtained by X-ray absorption spectroscopy (XAS) and the X-ray magnetic circular dichroism (XMCD). Two experimental procedures were used. In the procedure 1, the magnetic depth profile has been determines using samples deposited with different NiFe thicknesses, Si(100)/NiO(35 nm)/NiFe(t)/Ta(1 nm), t = 1 , 3 , 5 , 7 , 10 nm . In procedure 2, the sample (NiFe=10 nm), was thinned by several in situ sputtering cycles with Ar+ ions, followed by XAS and XMCD analysis. In both procedures, the calculated magnetic moments values tend to decrease close to interface with the NiO antiferromagnetic (AF) layer, however, this decreasement is more evidenced in the sputtered sample. There is no charge transfer between Ni and Fe in the inner part of the NiFe layer, a reduction of the morb /mspineff has been found at the NiFe/NiO interface. Procedure 1 emerged as the most indicated to analyse the interface region.

  3. Effect of mono- and bimetallic nanoparticles Fe, Ni, & Fe/Ni based on carbon nanocomposites on electrocatalytic properties of anodes

    NASA Astrophysics Data System (ADS)

    Ranabhat, K.; Pylinina, A. I.; Skripkin, K. S.; Sofronova, E. A.; Revina, A. A.; Kasatkin, V. E.; Patrikeev, L. N.; Lapshinsky, V. A.

    2016-10-01

    The optical properties of metallic Fe nanoparticles (NPs), Ni NPs and bimetallic Fe/Ni NPs produced under radiolysis in anaerobic condition based on a chemical reduction in the presence of oxygen and quercetin in reversed micellar solutions, and electrokinetic properties of nanoparticles carbon-based nanocomposites were studied. The possibility of the preparation of coating using different nanocomposites with anomalous electrocatalytic is addressed.

  4. Electromagnetic properties of Fe53Ni47 and Fe53Ni47/Cu granular composite materials in the microwave range

    NASA Astrophysics Data System (ADS)

    Massango, Herieta; Tsutaoka, Takanori; Kasagi, Teruhiro

    2016-09-01

    The electromagnetic proprieties of Fe53Ni47 granular composite materials and Fe53Ni47/Cu hybrid granular composites have been studied by measuring the relative complex permeability and permittivity spectra as well as the ac electrical conductivity. In the Fe53Ni47 composite, the variation of the ac conductivity at 1 kHz with the particle volume content shows an insulator-metal transition at the percolation threshold at 61 vol% particle content. A negative permeability spectrum due to the magnetic resonance in Fe53Ni47 particles was observed in the 85 vol% composite. Meanwhile, the negative permittivity spectrum caused by the plasmoinc state of the percolated Fe53Ni47 particle clusters appears at 90 vol%. The Fe53Ni47/Cu hybrid composite containing 85 vol% of Fe53Ni47/Cu hybrid particle as filers shows the percolative metallic properties; the ac conductivity increases with increasing the Cu particle volume fraction in the Fe53Ni47/Cu particle system. The negative permittivity spectrum appears above the Cu particle volume fraction of 0.16; the double negative characteristic was observed at that of 0.20 and 0.24 hybrid composites in the frequency range from 300 MHz to 1.8 GHz in the absence of the external magnetic field.

  5. Low-cost Fe--Ni--Cr alloys for high temperature valve applications

    DOEpatents

    Muralidharan, Govindarajan

    2017-03-28

    An Fe--Ni--Cr alloy is composed essentially of, in terms of weight percent: 1 to 3.5 Al, up to 2 Co, 15 to 19.5 Cr, up to 2 Cu, 23 to 40 Fe, up to 0.3 Hf, up to 4 Mn, 0.15 to 2 Mo, up to 0.15 Si, up to 1.05 Ta, 2.8 to 4.3 Ti, up to 0.5 W, up to 0.06 Zr, 0.02 to 0.15 C, 0.0001 to 0.007 N, balance Ni, wherein, in terms of atomic percent: 6.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.10, 0.33.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.065, 4.ltoreq.(Fe+Cr)/(Al+Ti+Zr+Hf+Ta).ltoreq.10, the alloy being essentially free of Nb and V.

  6. Magnetoresistance behavior of Ni80Fe20/Ru/Ni80Fe20 nanostripes

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    We present a systematic investigation on the effects of interlayer coupling on the magnetoresistance (MR) behavior of Ni80Fe20/Ru(/Ni80Fe20 trilayer nanostripes (NSs) as a function of temperature T . By changing from 0.8 nm to 1.7 nm, either a ferromagnetic or an antiferromagnetic (AFM) type of interlayer coupling was achieved, leading to a markedly different MR behavior. We observed that the MR response is a superimposition of AMR and GMR effects, and it is significantly dependent on temperature. For AFM coupled NSs, there is a transition from a pure AFM state to a reversed spin-flop phase due to enhanced ferromagnetic pin-hole coupling at low T. Our experimental results are in good agreement with micromagnetic simulations.

  7. 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.

  8. Nanostructurization of Fe-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Danilhenko, Vitaliy E.

    2017-03-01

    Data about an effect of cyclic γ-α-γ martensitic transformations on the structure state of reverted austenite Fe-31.7 wt.% Ni-0.06 wt.% C alloy are presented. The effect of multiple direct γ-α and reverse α-γ martensitic transformations on fragmentation of austenitic grains has been investigated by electron microscopy and X-ray diffraction methods. An ultrafine structure has been formed by nanofragmentation inside the initial austenite grains due to the successive misorientation of their crystal lattice. Austenite was nanofragmented as a result of multiple γ-α-γ martensitic transformations. Slow heating of the nanofragmented alloy at a rate below 2 °C/s results in nanograin refinement of the structure by multiplication of the reverted γ-phase orientations. The conditions of structure refinement up to ultrafine and nanocrystalline levels as a result of both shear and diffusion mechanisms of reverse α-γ transformation are determined.

  9. Thermal annealing and magnetic anisotropy of NiFe thin films on n+-Si for spintronic device applications

    NASA Astrophysics Data System (ADS)

    Lu, Q. H.; Huang, R.; Wang, L. S.; Wu, Z. G.; Li, C.; Luo, Q.; Zuo, S. Y.; Li, J.; Peng, D. L.; Han, G. L.; Yan, P. X.

    2015-11-01

    To ensure that the magnetic metal electrodes can meet the requirements of the spin injection, NiFe films prepared both on HfO2 dielectric layer and n+-Si directly by sputtering deposition, and treated by conventional furnace annealing and/or high vacuum magnetic field annealing were investigated. It was found that thermal annealing at 250 °C improved the crystalline quality and reduced surface roughness of the NiFe films, thus enhancing its saturation magnetization intensity. The 100 nm thick NiFe films had too large coercive force and saturation magnetization intensity in vertical direction to meet the requirements of Hanle curve detection. While, 30 nm thick NiFe films showed paramagnetic hysteresis loops in vertical direction, and the magnetization intensity of the sample after annealing at 250 °C for 30 min was less than 2% to the parallel when the external magnetic field was given between ±10 Oe. This was preferred to Hanle curve detection. The thin HfO2 dielectric layer between metal and Si partially suppressed the diffusion of Ni in NiFe into Si substrate and formation of NiSi, greatly enhancing the saturation magnetization intensity of the Al/NiFe/HfO2/Si sample by thermal annealing. Those results suggest that Al/NiFe/HfO2/Si structure, from the point view of magnetic electrodes, would be suitable for spin injection and detection applications.

  10. 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.

  11. 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.

  12. Novel Fe-Ni Nanoparticle Catalyst for the Production of CO- and CO2-free H2

    SciTech Connect

    Shen, W.; Huggins, F; Shah, N; Jacobs, G; Wang, Y; Shi, X; Huffman, G

    2008-01-01

    A novel nanoparticle impregnation method was used to prepare an Fe-Ni nanoparticle (np) catalyst supported on Mg(Al)O for the production of CO- and CO2-free H2 and carbon nanotubes (CNT) by non-oxidative dehydrogenation of methane. This novel catalyst and a catalyst of similar composition prepared by incipient wetness (IW) were evaluated for their catalytic performance and their structures were determined by several microscopic and spectroscopic techniques. Monosized Fe0.65-Ni0.35 oxide nanoparticles with an average particle size of 9 nm were prepared by thermal decomposition of an Fe-Ni oleate-surfactant complex in octadecene under reflux; these nanoparticles were dispersed onto a Mg(Al)O support to form a supported Fe-Ni np/Mg(Al)O catalyst. Compared with the Fe-Ni IW/Mg(Al)O catalyst, the nanoparticle catalyst was more easily reduced at a lower temperature (600 C in H2) and exhibited enhanced methane dehydrogenation and longer life-times at both 600 and 650 C. Each reduced Fe-Ni nanoparticle functioned as an active site for the growth of CNT. The CNT were in the form of multi-walled nanotubes (MWNT) of relatively uniform diameter. An invar-like Fe-Ni-C alloy phase is believed to be the active phase for methane dehydrogenation. The deactivation of the nanoparticle catalyst is principally due to encapsulation of catalyst particles by the CNT.

  13. Fabrication of NiAl Microreactors

    SciTech Connect

    Alman, D.E.; Wilson, R.D.; Dewey, T.; Paul, B.K.

    2000-07-01

    Chemical microreactors offer opportunities for portable powder generation, on-site waste remediation, point-of-use chemical synthesis, and heat-transfer. The material requirements for this application include chemical inertness and the ability to be fabricated into structures that contain internal features of complex geometries and small (<250 μm) dimensions. It has been recognized that materials with limited formability, like ceramics and intermetallics, will be required for high temperature applications. Reactors from these materials have been produced from powder tapes. However, problems associated with binder removal and sintering result in dimensional instability of the internal geometry which degrades the performance of the reactor. In this paper, a method for forming an array of internal microchannels in a NiAl device that avoids the dimensional instability of powder processing is demonstrated. Microchannels are precision machined (via laser ablation) into elemental Ni and Al foils. During bonding, the foils are converted into NiAl. Results show that this is a viable method for producing aluminide-based structures containing complex, internal features.

  14. A DFT study on the complex formation between desferrithiocin and metal ions (Mg(2+), Al(3+), Ca(2+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+)).

    PubMed

    Kaviani, Sadegh; Izadyar, Mohammad; Housaindokht, Mohammad Reza

    2017-04-01

    In recent years, Metal-chelating compounds, namely siderphores have been considered very much because of their crucial role in various fields of the environmental researches. Their importance lies in the fact that they are able to be bonded to a variety of metals in addition to iron. A theoretical study on the structures of desferrithiocin siderphore coordinated to Mg(2+), Al(3+), Ca(2+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+) and Zn(2+) metal ions was carried out, using the CAM-B3LYP/6-31G(d) level of the theory in the water. In order to understand the factors which control the stability, reactivity and the strength of toxic metals excretion as well as microbial uptake of the metal-siderphore complexes, we examined the stability and binding energies of the desferrithiocin and various metal ions with different spin states. The binding affinity of desferrithiocin to Fe(3+) (log β2=23.88) showed that the desferrithiocin can scavenge the excess iron(III) from the labile sources. Also, the binding energy values were well described by addition of the dispersion-corrected D3 functional. Because of the importance of the charge transfer in the complex formation, donor-acceptor interaction energies were evaluated. Based on this analysis, an increase in the effective nuclear charge increases E(2) values. Vibrational analysis showed that the critical bonds (CO stretching and CH bending) are in the range of 1300-1800cm(-1). Finally, some probable correlations between the complexation behavior and quantum chemistry descriptors have been analyzed.

  15. Mechanical properties and electronic structures of Fe-Al intermetallic

    NASA Astrophysics Data System (ADS)

    Liu, YaHui; Chong, XiaoYu; Jiang, YeHua; Zhou, Rong; Feng, Jing

    2017-02-01

    Using the first-principles calculations, the elastic properties, anisotropy properties, electronic structures, Debye temperature and stability of Fe-Al (Fe3Al, FeAl, FeAl2, Fe2Al5 and FeAl3) binary compounds were calculated. The formation enthalpy and cohesive energy of these Fe-Al compounds are negative, and show they are thermodynamically stable structures. Fe2Al5 has the lowest formation enthalpy, which shows the Fe2Al5 is the most stable of Fe-Al binary compounds. These Fe-Al compounds display disparate anisotropy due to the calculated different shape of the 3D curved surface of the Young's modulus and anisotropic index. Fe3Al has the biggest bulk modulus with the value 233.2 GPa. FeAl has the biggest Yong's modulus and shear modulus with the value 296.2 GPa and 119.8 GPa, respectively. The partial density of states, total density of states and electron density distribution maps of the binary Fe-Al binary compounds are analyzed. The bonding characteristics of these Fe-Al binary compounds are mainly combination by covalent bond and metallic bonds. Meanwhile, also exist anti-bond effect. Moreover, the Debye temperatures and sound velocity of these Fe-Al compounds are explored.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Point defects quenched in NiAl and related intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Fan, Jiawen

    1991-08-01

    Point defects in the highly ordered B2 compounds NiAl, CoAl and FeAl were studied using the perturbed gamma-gamma angular correlations (PAC) technique. Quadrupole interactions detected at dilute In-111 probes on Al sites in NiAl and CoAl were identified with complexes containing one or two vacancies in the first atomic shell. Measurements on rapidly quenched NiAl and CoAl exhibited increases in site fractions of vacancy-probe complexes caused by formation of thermal defects. Site fractions were analyzed using the law of mass action to obtain absolute vacancy concentrations. PAC is shown to be a powerful new technique for the quantitative study of equilibrium defects in solids. For NiAl, the vacancy concentration quenched-in from a given temperature was found to be independent of composition over the range 50.4 to 53.5 at. pct. Ni, identifying the Schottky defect (vacancy pair) as the dominant equilibrium defect, and ruling out the so-called triple defect. Formation energies and entropies of Schottky pairs were determined to be 2.66(8) and 3.48(12) eV, and 12(1) and 17(2) k sub B, respectively, for NiAl and CoAl. The entropies suggest huge vacancy concentrations, 13 pct. at the melting temperatures of NiAl and CoAl. Migration energies of Ni and Co vacancies were found to be 1.8(2) and 2.5(2) eV, respectively. FeAl exhibited complex behavior. A low temperature regime was detected in NiAl and CoAl within which vacancies are mobile but do not anneal out, so that the vacancy concentration remains constant. In NiAl, this 'bottleneck' regime extends from 350 to 700 C. Vacancies were found to be bound to the In probes with an energy very close to 0.20 eV in NiAl and CoAl. An explanation of the bottleneck is proposed in terms of saturation of all lattice sinks. This annealing bottleneck should exist in a wide range of intermetallic compounds when there is a sufficiently high vacancy concentration.

  3. 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...

  4. Correlation between bias fields and magnetoresistance in CoPt biased FeNi/Ta/FeNi GMR heterosystems

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Sahoo, S.; Echtenkamp, W.; Binek, Ch.

    2009-03-01

    Exchange coupled magnetic hard layer (HL)/ soft layer (SL) thin films show SL biasing in close analogy to conventional exchange bias systems with antiferromagnetic pinning.^1 Here we study CoPt(35nm)/FeNi450nm/Ta(d)/FeNi450nm heterostructures with d between 0.7 and 5nm. The CoPt films have in-plane magnetic anisotropy and pin the adjacent FeNi SL films. The latter are exchange coupled from top via Ta spacer layers with FeNi in a GMR-type architecture. We use AGFM and SQUID magnetometry to study the FeNi magnetization reversal with (CoPt) and without (vacuum) pinning layer proximity. The two minor FeNi hysteresis loops of the GMR trilayer reveal different biasing effects due to the distinct exchange interaction at the respective interfaces. The FeNi/CoPt coupling is systematically tuned via a series of set fields which allow partial demagnetization of the pinning layer. Moreover we study the correlation between the overall and minor magnetization reversals and the corresponding magnetoresistance effects for various temperature between T=20 and 400K. ^1Ch. Binek, S. Polisetty, Xi He and A. Berger, Phys. Rev. Lett. 96, 067201 (2006). Financial support by NSF through Career DMR-0547887, MRSEC DMR-0820521 and the NRI.

  5. Positive exchange bias in a Ni 80Fe 20/Ni xFe 1-xO thin-film bilayer

    NASA Astrophysics Data System (ADS)

    Lin, K.-W.; Tzeng, Y.-M.; Guo, Z.-Y.; Liu, C.-Y.; van Lierop, J.

    2006-09-01

    We have measured positive exchange bias in a Ni 80Fe 20/Ni xFe 1-xO thin-film nanocrystallite system. A series of solid solution Ni xFe 1-xO 40 nm thick films capped with 25 nm thick Ni 80Fe 20 were deposited using a range of %O 2/Ar bombardment energies (i.e. End-Hall voltages). Proper tuning of the deposition conditions results in a Ni 80Fe 20/Ni xFe 1-xO (30%O 2/Ar) based bilayer that exhibits a positive exchange bias loop shift of Hex˜60 Oe at 150 K.

  6. Ternary rare-earth aluminium intermetallics RE10TAl3 (RE = Y, Ho, Tm, Lu; T = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) with an ordered anti-Co2Al5 structure.

    PubMed

    Benndorf, Christopher; Eckert, Hellmut; Janka, Oliver

    2017-01-24

    Twenty new rare-earth metal rich intermetallic aluminium compounds, RE10TAl3 (RE = Y, Ho, Tm, Lu; T = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt), were synthesized by arc melting the elements. The compounds crystallize, in analogy to e.g. the respective Cd representatives, with a ternary ordered structure as anti-type to the hexagonal Co2Al5 type, with the space group P63/mmc. The three crystallographically independent rare-earth metal sites occupy the aluminium positions of the aristotype, while the transition metal and aluminium atoms are ordered on the two cobalt sites. Like other rare-earth rich compounds the RE10TX3 members also exhibit transition-metal-centred T@RE6 trigonal prisms as striking structural building units. The prepared compounds have been investigated by susceptibility measurements and (27)Al solid-state MAS-NMR measurements conducted on the Pauli-paramagnetic Y and Lu compounds. Some compounds show a certain amount of disorder as seen from the single crystal structure analysis and from signal broadening in the NMR investigations. By separating Knight shifts from second-order quadrupolar shifts via field dependent measurements, monotonic trends can be discerned regarding the effect of the T atom valence electron concentration and period number, as well as the effect of the closed 4f shell contributed in the Lu compounds. The results confirm that a comparison of Knight shifts within a series of isotypic compounds can reveal important electronic structure information in intermetallic systems.

  7. 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.

  8. 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.

  9. Isotopic fractionation associated with [NiFe]- and [FeFe]-hydrogenases

    SciTech Connect

    Yang, Hui; Gandhi, Hasand; Cornish, Adam J.; Moran, James J.; Kreuzer, Helen W.; Ostrom, Nathaniel; Hegg, Eric L.

    2016-01-30

    Hydrogenases catalyze the reversible formation of H2 from electrons and protons with high efficiency. Understanding the relationships between H2 production, H2 uptake, and H2-H2O exchange can provide insight into the metabolism of microbial communities in which H2 is an essential component in energy cycling. In this manuscript, we used stable H isotopes (1H and 2H) to probe the isotope effects associated with three [FeFe]-hydrogenases and three [NiFe]-hydrogenases. All six hydrogenases displayed fractionation factors for H2 formation that were significantly less than 1, producing H2 that was severely depleted in 2H relative to the substrate, water. Consistent with differences in their active site structure, the fractionation factors for each class appear to cluster, with the three [NiFe]-hydrogenases (α = 0.27-0.40) generally having smaller values than the three [FeFe]-hydrogenases (α = 0.41-0.55). We also obtained isotopic fractionation factors associated with H2 uptake and H2-H2O exchange under conditions similar to those utilized for H2 production, providing us with a more complete picture of the three reactions catalyzed by hydrogenases. The fractionation factors determined in our studies can be used as signatures for different hydrogenases to probe their activity under different growth conditions and to ascertain which hydrogenases are most responsible for H2 production and/or uptake in complex microbial communities.

  10. Formation of layered Fe(II)-Al(III)-hydroxides during reaction of Fe(II) with aluminum oxide.

    PubMed

    Elzinga, Evert J

    2012-05-01

    The reactivity of aqueous Fe(II) with aluminum oxide in anoxic solutions was investigated with batch kinetic experiments combined with Fe K edge X-ray absorption spectroscopy measurements to characterize Fe(II) sorption products. Formation of Fe(II)-Al(III)-layered double hydroxides with an octahedral sheet structure similar to nikischerite (NaFe(II)(6) Al(3)(SO(4))(2)(OH)(18) (H(2)O)(12)) was observed within a few hours during sorption at pH 7.5 and aqueous Fe(II) concentrations of 1-3 mM. These Fe(II) phases are composed of brucite-like Fe(II)(OH)(2) sheets with partial substitution of Al(III) for Fe(II), charge balanced by anions coordinated along the basal planes. Their fast rate of formation suggests that these previously unrecognized Fe(II) phases, which are structurally and compositionally similar to green rust, may be an important sink of Fe(II) in suboxic and anoxic geochemical environments, and impact the fate of structurally compatible trace metals, such as Co(II), Ni(II), and Zn(II), as well as redox-reactive species including Cr(VI) and U(VI). Further studies are required to assess the thermodynamics, formation kinetics, and stability of these Fe(II) minerals under field conditions.

  11. Magnetoimpedance of FeNi-based asymmetric sensitive elements

    NASA Astrophysics Data System (ADS)

    Chlenova, A. A.; Svalov, A. V.; Kurlyandskaya, G. V.; Volchkov, S. O.

    2016-10-01

    [Ti/FeNi]5/Ti/Cu/Ti/[FeNi/Ti]x (x=0-5) multilayers were prepared by sputtering. Their magnetic properties and magnetoimpedance were studied focusing on future technological applications. Both (ΔZ/Z)max and (ΔR/R)max values showed a tendency to decrease with a decrease of the number of magnetic layers of the top multilayer. Such a parameter as an even or odd number of layers is important for the MI value. In the field interval of technological interest all [Ti/FeNi]5/Ti/Cu/Ti/[FeNi/Ti]x structures show similar sensitivities of about 70%/Oe for ΔR/R ratios but the lower the number of magnetic layers in the top multilayer, the higher the operating frequency.

  12. 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.

  13. Insulating 'nanocables': Invar Fe Ni alloy nanorods inside BN nanotubes

    NASA Astrophysics Data System (ADS)

    Bando, Y.; Ogawa, K.; Golberg, D.

    2001-10-01

    Here we present the results on synthesis, structural and chemical analysis of insulating boron nitride (BN) nanotubes (NTs) which have been filled with conducting Invar Fe-Ni alloy (˜60 at.% Fe; ˜40 at.% Ni) nanorods. The result was accomplished by a two-step process: (i) carbon (C) NTs containing Invar alloy nanoparticles placed at the tube tips were synthesized by plasma-assisted chemical vapor deposition (CVD) on an Invar Fe-Ni alloy substrate; and (ii) the material was heated to the melting point of the alloy (1723 K) in a flow of B 2O 3 and N 2 gases and held for 30 min. During this second stage, simultaneous filling of NTs with the Fe-Ni melt through capillarity and chemical modification of C tubular shells to form BN tubules occurred.

  14. Low-frequency creep in CoNiFe films.

    NASA Technical Reports Server (NTRS)

    Bartran, D. S.; Bourne, H. C., Jr.; Chow, L. G.

    1972-01-01

    Domain wall motion excited by slow rise-time, bipolar, hard-axis pulses in vacuum deposited CoNiFe films from 1500 to 2000 A thick is studied. The results are consistent with those of comparable NiFe films. Furthermore, the wall coercivity is found to be the most significant sample property correlated to the low-frequency creep properties of all the samples.

  15. Ferromagnetic resonance in FeCoNi electroplated wires

    NASA Astrophysics Data System (ADS)

    García-Miquel, H.; Bhagat, S. M.; Lofland, S. E.; Kurlyandskaya, G. V.; Svalov, A. V.

    2003-08-01

    We have investigated the microwave properties (ferromagnetic resonance and ferromagnetic antiresonance) of FeCoNi magnetic tubes created by electroplating on CuBe wire. Important parameters such as the g factor, magnetization, anisotropy field, and damping parameter were obtained from the measurements. One sample, prepared by a method which entails rf-sputtering deposition of an additional FeNi layer, shows a clear ferromagnetic antiresonance.

  16. Phase Decomposition in the Fe-rich Fe-Ni-S System from 900 Degrees C to 300 Degrees C--Application to Meteoritic Metal

    NASA Astrophysics Data System (ADS)

    Ma, L.; Williams, D. B.; Goldstein, J. I.

    1995-09-01

    phase forms in the Fe-Ni-S system at higher temperatures (500 degrees C) than in the Fe-Ni and Fe-Ni (P) systems (<400 degrees C) [4]. Because the tetrataenite phase forms in the Fe-Ni-S system at higher temperatures, the tetrataenite rim in chondrites should be much wider than that in other meteorites where phase growth is controlled by the presence of P. It is possible that the Ni distribution in the metal phases of chondrites is dictated by the g/FeS and g/FeS/g' tie-line variations rather than by a/g tie-lines in the case of iron or stony iron meteorites. References: [1] Holland-Duffield C. E. et al. (1991) Meteoritics, 26, 97-103. [2] Kullerud G. (1963) Carnegie Inst. Wash. Yearb., 62, 175-189. [3] Clark L. A. and Kullerud G. (1963) Econ. Geol., 58, 853-885. [4] Yang C. W. (1994) Ph.D. dissertation, Lehigh Univ.

  17. Development of Fe-Mn-Al-X-C alloys

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    Development of a low cost Cr-free, iron-base alloy for aerospace applications involves both element substitution and enhancement of microstructural strengthening. When Mn is substituted for Ni and Al or Si is substituted for Cr, large changes occur in the mechanical and thermal stability of austenite in FeMnAlC alloys. The in situ strength of MC or M2C (M = Ti, V, Hf, Ta, or Mo) in FeMnAlC alloys was determined. The high temperature tensile strength depends more on the distribution of carbides than the carbide composition. Precipitation of a high volume percent-ordered phase was achieved in Fe2OMnlONi6Al6Ti (lC) alloys. As case, these alloys have a homogeneous austenitic structure. After solutioning at 1100 C for 5 hr followed by aging at 600 C for 16 hr, gamma prime or a perovskite carbide is precipitated. Overaging occurs at 900 C where eta is precipitated.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    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°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°C are found to be 0.0178 and 0.0279mV/°C, respectively.

  20. Compressive strength of directionally solidified NiAl-NiAlNb intermetallics at 1200 and 1300 K

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    Results are presented from measurements of 1200 K and 1300 K compressive properties of two directionally solidified NiAl-NiAlNb compositions (in at. pct): Ni-41.75Al-16.5Nb (eutectic composition) and Ni-47.5Al-8.9Nb-1.3C (Al-rich composition). Results showed that the strength of the eutectic was a factor of 2 greater than that of the Al-rich composition. However, the analysis of the compressive stress-strain data indicated that the deformation mechanism was the same in both materials.

  1. 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.

  2. 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.

  3. Magnetic properties of Al/57Fe/Cr multilayers

    NASA Astrophysics Data System (ADS)

    Jani, Snehal; Lakshmi, N.; Jain, Vishal; Reddy, V. R.; Gupta, Ajay; Venugopalan, K.

    2013-06-01

    Conversion Electron Mössbauer Spectroscopy (CEMS) and DC magnetization are used to compare magnetic properties of as-deposited multilayer (MLS) and Fe2CrAl thin film made from Al/57Fe/Cr MLS deposited by ion beam sputtering and then annealed in UHV. Interdiffusion of elements on annealing sample-1 at 500°C leads to formation of a single, disordered film of Fe2CrAl as evidenced by hyperfine field values obtained by CEMS in the film which compares well with that in bulk Fe2CrAl. CEMS also shows contributions from Fe, Fe/Cr and Fe/Al interfaces in the MLS. Saturation magnetization of as-deposited sample-1 is much less than pure Fe due to reduced Fe thickness because of interface formation and also reduction in Fe-Fe interaction due to intervening Al and Cr layers.

  4. 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.

  5. 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.

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

    DOE PAGES

    Wang, Zhangwei; Baker, Ian; Cai, Zhonghou; ...

    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

  7. Fabrication of Fe-Al nanoparticles by selective oxidation of Fe-Al thin films

    NASA Astrophysics Data System (ADS)

    Jang, Pyungwoo; Shin, Seungchan; Jung, Chip-Sup; Kim, Kwang-Ho; Seomoon, Kyu

    2013-04-01

    The possibility of a new technique for fabricating nanoparticles from thin films using selective oxidation in an atmosphere mixture of water vapor and hydrogen was investigated. Fe-5wt.%Al films were RF-sputtered and annealed in the atmosphere mixture at 900°C for up to 200 min, in order to oxidize aluminum selectively. Thermodynamics simulation showed that temperatures exceeding 800°C are necessary to prevent iron from being oxidized, as confirmed by the depth profile of XPS. As the annealing time increased, the morphology of the 200-nm Fe-Al films changed from the continuous to the discontinuous type; thus, particulate Fe-Al films formed after 100 min. The particulate 10- to 100-nm Fe-Al films showed super-paramagnetic behavior after the oxidation. Thus, a new technique for fabricating nanoparticles was successfully introduced using selective oxidation.

  8. Improving the low temperature ductility of NiAl. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Guha, Sumit

    1992-01-01

    The intermetallic NiAl exhibits excellent potential as a structural material for application in air-breathing and single-stage-to-orbit engines. Unfortunately NiAl is brittle at ambient temperature, which is partly attributed to the lack of five independent slip systems as required by von Mises criterion for uniform, volume conserving deformation since the operative group of zone axes (100) slip offers only three independent slip systems. Isostructural FeAl, however, deforms by group of zone axes (111) slip at room temperature which provides five independent slip systems. Thus, it was decided to macroalloy NiAl with Fe to promote group of zone axes (111) slip thereby possibly improving the ductility. For Ni - 30 at. (percent) Al - 20 at. (percent) Fe having essentially bcc microstructure indicated up to 6 percent tensile elongation combined with high yield strength (about 800 MPa). The results compare favorably with those of stoichiometric Ni - 50 at. (percent) Al which, however, deforms by group of zone axes (100) slip at room temperature. The multi-phase alloy approach has proven even more successful for Ni - 20 at. (percent) Al - 30 at. (percent) Fe. The high temperature ductility of the multi-phase alloy was attributed to deformation transfer across interphase boundaries and the crack stopping action of the constituent gamma/gamma' phase. While the constituent phase became increasingly brittle, the beta' phase became more ductile at elevated temperatures. Thus the multi-phase alloy did not exhibit any elevated temperature embrittlement. Similarly, while the beta' phase became weak at high temperatures, the gamma/gamma' phase exhibited better strength retention leading to the improved elevated temperature strength of the multi-phase alloy. Thus, the multi-phase alloy benefits from both its constituent phases, with each phase alleviating the disadvantages associated with the other phase over any temperature range. The multi-phase alloy approach is suggested as a

  9. Structural stability of ternary C22–Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and C22–Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) compounds

    SciTech Connect

    Colinet, Catherine; Crivello, Jean-Claude; Tedenac, Jean-Claude

    2013-09-15

    The crystal and electronic structures, and the thermodynamic properties of Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) ternary compounds in the Fe{sub 2}P-type structure have been investigated by means of first principle calculations. The calculated structural parameters are in good agreement with the experimental data. The total electronic densities of states as well as the Bader charges of the atoms have been computed. Both electronic and size effects allow to explain the stability of the ternary Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) compounds. - Graphical abstract: Valence charge electronic localization function (ELF) calculated for Zr{sub 6}Sb{sub 2}Co compound. Display Omitted - Highlights: • Structural stability of Zr{sub 6}X{sub 2}T′ compounds (X: p element, T′: late transition metal) in the Fe{sub 2}P-type structure. • First principles calculation of lattice parameters and enthalpies of formation. • Electronic densities of state in the series Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu). • Electronic densities of state in the series Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te)

  10. Nickel recovery from electronic waste II electrodeposition of Ni and Ni-Fe alloys from diluted sulfate solutions.

    PubMed

    Robotin, B; Ispas, A; Coman, V; Bund, A; Ilea, P

    2013-11-01

    This study focuses on the electrodeposition of Ni and Ni-Fe alloys from synthetic solutions similar to those obtained by the dissolution of electron gun (an electrical component of cathode ray tubes) waste. The influence of various parameters (pH, electrolyte composition, Ni(2+)/Fe(2+) ratio, current density) on the electrodeposition process was investigated. Scanning electron microscopy (SEM) and X-ray fluorescence analysis (XRFA) were used to provide information about the obtained deposits' thickness, morphology, and elemental composition. By controlling the experimental parameters, the composition of the Ni-Fe alloys can be tailored towards specific applications. Complementarily, the differences in the nucleation mechanisms for Ni, Fe and Ni-Fe deposition from sulfate solutions have been evaluated and discussed using cyclic voltammetry and potential step chronoamperometry. The obtained results suggest a progressive nucleation mechanism for Ni, while for Fe and Ni-Fe, the obtained data points are best fitted to an instantaneous nucleation model.

  11. Structural study of radiolytic catalysts Ni-Ce/Al2O3 and Ni-Pt/Al2O3

    NASA Astrophysics Data System (ADS)

    Seridi, F.; Chettibi, S.; Keghouche, N.; Beaunier, P.; Belloni, J.

    2017-01-01

    Ni-Ce and Ni-Pt bimetallic catalysts supported over α-Al2O3 are synthesized by using co-impregnation method, and then reduced, each via radiolytic process or thermal H2-treatment. For Ni-Ce/Al2O3, the structural study reveals that Ce is alloyed with Ni as Ce2Ni7 nanoparticles in the radiation-reduced catalysts, while it segregates to the surface in the form of CeO2 in the H2-reduced catalysts. For Ni-Pt/Al2O3 radiolytic catalysts, Ni, Pt, NiPt and Ni3Pt nanoparticles, which size is 3.5 nm, are observed. When the radiation-reduced samples are tested in the benzene hydrogenation, they both display high conversion rate. However, the Ni-Pt/Al2O3 is more efficient than Ni-Ce/Al2O3. The performance of the catalysts is correlated with the high dispersion of the metal and the presence of intermetallic Ni-Pt and Ni-Ce phases. It is compared to that of other radiolytic monometallic/oxide catalysts of the literature.

  12. 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.

  13. The role of boron in ductilizing Ni3Al

    NASA Technical Reports Server (NTRS)

    Vedula, K.; Shabel, B. S.; Khadkikar, P. S.

    1987-01-01

    Ductilization of Ni3Al at room temperature by microalloying with boron has been primarily attributed to the increased grain boundary cohesion in the presence of boron. However, another aspect of the role played by boron in ductilizing Ni3Al is revealed when the Hall-Petch relationships for Ni3Al and B-doped Ni3Al are compared. A shallower slope for the B-doped Ni3Al compared to that for Ni3Al indicates a reduced resistance to slip propagation across grain boundaries, and therefore reduced stress concentration at boundaries, in the presence of boron. This comparison of Hall-Petch relationships was carried out by generating data for powder processed B-doped Ni3Al at various grain sizes and by compiling data for Ni3Al from the literature. In addition, the room temperature fracture of B-doped Ni3Al has been shown to initiate along certain grain boundaries. The fracture eventually occurs by transgranular ductile tearing.

  14. Controllable synthesis and enhanced microwave absorbing properties of Fe3O4/NiFe2O4/Ni heterostructure porous rods

    NASA Astrophysics Data System (ADS)

    Li, Yana; Wu, Tong; Jin, Keying; Qian, Yao; Qian, Naxin; Jiang, Kedan; Wu, Wenhua; Tong, Guoxiu

    2016-11-01

    We developed a coordinated self-assembly/precipitate transfer/sintering method that allows the controllable synthesis of Fe3O4/NiFe2O4/Ni heterostructure porous rods (HPRs). A series of characterizations confirms that changing [Ni2+] can effectively control the crystal size, internal strain, composition, textural characteristics, and properties of HPRs. Molar percentages of Ni and NiFe2O4 in HPRs increase with [Ni2+] in various Boltzmann function modes. Saturation magnetization Ms and coercivity Hc show U-shaped change trends because of crystal size, composition, and interface magnetic coupling. High magnetic loss is maintained after decorating NiFe2O4 and Ni on the surface of Fe3O4 PRs. Controlling the NiFe2O4 interface layers and Ni content can improve impedance matching and dielectric losses, thereby leading to lighter weight, stronger absorption, and broader absorption band of Fe3O4/NiFe2O4/Ni HPRs than Fe3O4 PRs. An optimum EM wave absorbing property was exhibited by Fe3O4/NiFe2O4/Ni HPRs formed at [Ni2+] = 0.05 M. The maximum reflection loss (RL) reaches -58.4 dB at 13.68 GHz, which corresponds to a 2.1 mm matching thickness. The absorbing bandwidth (RL ≤ -20 dB) reaches 14.4 GHz with the sample thickness at 1.6-2.4 and 2.8-10.0 mm. These excellent properties verify that Fe3O4/NiFe2O4/Ni HPRs are promising candidates for new and effective absorptive materials.

  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. Modulated exchange bias in NiFe/CoO/α-Fe2O3 trilayers and NiFe/CoO bilayers

    NASA Astrophysics Data System (ADS)

    Li, X.; Lin, K.-W.; Yeh, W.-C.; Desautels, R. D.; van Lierop, J.; Pong, Philip W. T.

    2017-02-01

    While the exchange bias in ferromagnetic/antiferromagnetic (FM/AF) bilayer and FM1/AF/FM2 trilayer configurations has been widely investigated, the role of an AF2 layer in FM/AF1/AF2 trilayer configurations is still not well understood. In this work, the magnetic properties of NiFe/CoO, NiFe/α-Fe2O3 bilayers, and NiFe/CoO/α-Fe2O3 trilayer were studied comparatively. The microstructure and chemical composition were characterized. Temperature dependent magnetometry reveals increased irreversibility temperature in NiFe/CoO/α-Fe2O3 trilayer compared with NiFe/CoO bilayer. The magnetic hysteresis loops show that the exchange bias (Hex) and coercivity (Hc) depend strongly on the anisotropy of AF layer (CoO, α-Fe2O3 and CoO/α-Fe2O3). Our work shows that the AF1/AF2 interfacial interactions can be used effectively for tuning the exchange bias in FM/AF1/AF2 trilayers.

  17. 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.

  18. Notch effects on room temperature tensile and bend properties of Ni3Al and Ni3Al+B

    NASA Technical Reports Server (NTRS)

    Khadkikar, P. S.; Rigney, J. D.; Lewandowski, J. J.; Vedula, K.

    1989-01-01

    The notched mechanical properties of Ni3Al and Ni3Al+B prepared by powder metallurgy techniques have been determined in both tension and bending at room temperature. Tensile tests performed using double-notched specimens containing relatively blunt notches produced intergranular fracture in both Ni3Al and Ni3Al+B, with evidence of fracture initiating in an intergranular manner ahead of the blunt notch in both cases. Estimates of notched fracture toughness from bend tests and of local grain boundary fracture stress from the notched tensile tests suggest an increase in these values with boron addition.

  19. 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.

  20. Synthesis and properties of Fe/Ni nanotubes

    NASA Astrophysics Data System (ADS)

    Kozlovskiy, A. L.; Zdorovets, M. V.; Kadyrzhanov, K. K.

    2016-09-01

    Fe/Ni nanotubes were formed in pores of polyethylenterephtalate-based template matrices by electrochemical deposition. The inner diameter, wall height, and thickness of the nanostructures, as well as the elemental and phase compositions, can be controlled by varying the deposition conditions. The volume deposition rate constants have been determined for each potential difference, due to which the nanostructure growth could be controlled. An X-ray diffraction analysis of the samples obtained at a potential difference of 1-1.6 V has revealed their composition to correspond to the substitutional solid solution, with an iron atom replaced by a nickel atom and dominance of the bcc a-Fe phase. The samples obtained at a potential difference of 1.8-2 V contain the bcc a-Fe phase and fcc Ni phase; the fcc phase dominates in the sample obtained at a potential difference of 2 V, which can be related to the high Ni content in nanotubes.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. The effect of carbon on the microstructures, mechanical properties, and deformation mechanisms of thermo-mechanically treated Fe40.4Ni11.3Mn34.8Al7.5Cr6 high entropy alloys

    DOE PAGES

    Wang, Zhangwei; Baker, Ian; Guo, Wei; ...

    2017-03-01

    We investigated the effects of cold rolling followed by annealing on the mechanical properties and dislocation substructure evolution of undoped and 1.1 at. % carbon-doped Fe40.4Ni11.3Mn34.8Al7.5Cr6 high entropy alloys (HEAs). X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT) were employed to characterize the microstructures. The as-cast HEAs were coarse-grained and single phase f.c.c., whereas the thermo-mechanical treatment caused recrystallization (to fine grain sizes) and precipitation (a B2 phase for the undoped HEA; and a B2 phase, and M23C6 and M7C3 carbides for the C-doped HEA). Carbon, which was found to have segregated tomore » the grain boundaries using APT, retarded recrystallization. The reduction in grain size resulted in a sharp increase in strength, while the precipitation, which produced only a small increase in strength, probably accounted for the small decrease in ductility for both undoped and C-doped HEAs. For both undoped and C-doped HEAs, the smaller grain-sized material initially exhibited higher strain hardening than the coarse-grained material but showed a much lower strain hardening at large tensile strains. Wavy slip in the undoped HEAs and planar slip in C-doped HEAs were found at the early stages of deformation irrespective of grain size. At higher strains, dislocation cell structures formed in the 19 μm grain-sized undoped HEA, while microbands formed in the 23 μm grain-sized C-doped HEA. Conversely, localized dislocation clusters were found in both HEAs at the finest grain sizes (5 μm). The inhibition of grain subdivision by the grain boundaries and precipitates lead to the transformation from regular dislocation configurations consisting of dislocation-cells and microbands to irregular dislocation configurations consisting of localized dislocation clusters, which further account for the decrease in ductility. Our investigation of the formation mechanism

  7. Nonreciprocal spin wave spectroscopy of thin Ni-Fe stripes

    NASA Astrophysics Data System (ADS)

    Khalili Amiri, Pedram; Rejaei, Behzad; Vroubel, Marina; Zhuang, Yan

    2007-08-01

    The authors report on the observation of nonreciprocal spin wave propagation in a thin (˜200nm) patterned Ni-Fe stripe. The spin wave transmission spectrum is measured using a pair of microstrip lines as antennas. The nonreciprocity of surface wave dispersion brought about by an adjacent aluminum ground leads to a nonreciprocal coupling of the antennas. The effects of Ni-Fe film conductivity, thickness, and reflections caused by the lateral confinement of the magnetic stripe are discussed. The nonreciprocity observed in this structure can potentially be used to realize nonreciprocal microwave devices on silicon.

  8. Nanocrystalline NiAl Coating Prepared by HVOF Thermal Spraying

    NASA Astrophysics Data System (ADS)

    Enayati, M. H.; Karimzadeh, F.; Tavoosi, M.; Movahedi, B.; Tahvilian, A.

    2011-03-01

    Nanocrystalline NiAl intermetallic powder was prepared by mechanical alloying (MA) of Ni50Al50 powder mixture and then deposited on low carbon steel substrates by high velocity oxy fuel (HVOF) thermal spray technique using two sets of spraying parameters. X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM), differential scanning calorimetry (DSC), and hardness test were used to characterize the prepared powders and coatings. The MA of Ni50Al50 powder mixture led to the formation of NiAl intermetallic compound. The resulting powder particles were three dimensional in nature with irregular morphology and a crystallite size of ~10 nm. This powder was thermally sprayed by HVOF technique to produce coating. The deposited coating had a nanocrystalline structure with low oxide and porosity contents. The hardness of coatings was in the range of 5.40-6.08 GPa, which is higher than that obtained for NiAl coating deposited using conventional powders.

  9. 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.

  10. High temperature dispersion strengthening of NiAl

    NASA Technical Reports Server (NTRS)

    Sherman, M.; Vedula, K.

    1986-01-01

    A potential high temperature strengthening mechanism for alloys based on the intermetallic compound NiAl was investigated. This study forms part of an overall program at NASA Lewis Research Center for exploring the potential of alloys based on NiAl for high temperature applications. An alloy containing 2.26 at% Nb and produced by hot extrusion of blended powders was examined in detail using optical and electron microscopy. Interdiffusion between the blended Nb and NiAl powders results in the formation of intermediate phases. A fine dispersion of precipitates of a hexagonal, ordered NiAlNb phases in a matrix of NiAl can be produced and this results in strengthening of the alloy by interfering with dislocation motion at high temperature. These precipitates are, however, found to coarsen during the high temperature (1300 K) deformation at slow strain rates and this may impose some limitatioins on the use of this strengthening mechanism.

  11. Synthesis and consolidation of γ-Ni-Fe nanoalloy powder

    NASA Astrophysics Data System (ADS)

    Lee, J. S.; Nam, J. G.; Knorr, P.

    1999-04-01

    The present work studies the synthesis and consolidation of γ-Ni-Fe nanoalloy powder by the mechano-chemical process comprising high-energy ball-milling of NiO-Fe2O3 powder and a subsequent hydrogen reduction process. To examine the formation mechanism of the nanoalloy powder, the effect of the oxide powder char-acteristics on the reduction process and alloying was investigated by varying the ball-milling time. The reduction process and the alloying of the γ-Ni-Fe phase proved to accelerate as the ball-milling time increased. However, prolonged milling (for 30 hours) retarded the reduction of Fe2O3 as well as the alloying process. The densification process of the Ni-Fe nanoalloy powder strongly depended on the degree of agglomeration which results in enhancing homogeneous sintering. The limited densification of the nanoalloy powder originates from the high degree of particle agglomeration. While intra-agglomerate porosity is easily eliminated in the course of sintering, it is found to resist densification. The limitation of the sintered density could be overcome by increasing the green density of the powder compacts. Full density was achieved by starting with a green density of 72% theoretical density.

  12. Fe-Ni-bearing serpentines from the saprolite horizon of Caribbean Ni-laterite deposits: new insights from thermodynamic calculations

    NASA Astrophysics Data System (ADS)

    Villanova-de-Benavent, Cristina; Domènech, Cristina; Tauler, Esperança; Galí, Salvador; Tassara, Santiago; Proenza, Joaquín A.

    2016-10-01

    Fe-Ni-bearing serpentine from the saprolite horizon is the main Ni ores in hydrous silicate-type Ni laterites and formed by chemical weathering of partially serpentinized ultramafic rocks under tropical conditions. During lateritization, Mg, Si, and Ni are leached from the surface and transported downwards. Fe2+ is oxidized to Fe3+ and fixed as insoluble Fe-oxyhydroxides (mostly goethite) that incorporate Ni. This Ni is later leached from goethite and incorporated in secondary serpentine and garnierite. As a result, a serpentine-dominated saprolite horizon forms over the ultramafic protolith, overlapped by a Fe-oxyhydroxide-dominated limonite horizon. The serpentine from the protolith (serpentine I) is of hydrothermal origin and yields similar Ni (0.10-0.62 wt.% NiO) and lower Fe (mostly 1.37-5.81 wt.% FeO) concentrations than the primary olivine. In contrast, Fe-Ni-bearing serpentine from the saprolite (serpentine II) shows significantly higher and variable Fe and Ni contents, typically ranging from 2.23 to 15.59 wt.% Fe2O3 and from 1.30 to 7.67 wt.% NiO, suggesting that serpentine get enriched in Fe and Ni under supergene conditions. This study presents detailed mineralogical, textural, and chemical data on this serpentine II, as well as new insights by thermodynamic calculations assuming ideal solution between Fe-, Ni- and Mg-pure serpentines. The aim is to assess if at atmospheric pressure and temperature Fe-Ni-bearing serpentine can be formed by precipitation. Results indicate that the formation of serpentine II under atmospheric pressure and temperature is thermodynamically supported, and pH, Eh, and the equilibrium constant of the reaction are the parameters that affect the results more significantly.

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

    DOE PAGES

    Samolyuk, German D.; Xue, Haizhou; Bei, Hongbin; ...

    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 effects 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 in Ni.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. The effect of deposition temperature on the intermixing and microstructure of Fe/Ni thin film

    NASA Astrophysics Data System (ADS)

    Chen, Shang-Da; Wang, Tao; Zheng, De-Li; Zhou, Yi-Chun

    2010-12-01

    The physical vapour deposition of Ni atoms on α-Fe(001) surface under different deposition temperatures were simulated by molecular dynamics to study the intermixing and microstructure of the interfacial region. The results indicate that Ni atoms hardly penetrate into Fe substrate while Fe atoms easily diffuse into Ni deposition layers. The thickness of the intermixing region is temperature-dependent, with high temperatures yielding larger thicknesses. The deposited layers are mainly composed of amorphous phase due to the abnormal deposition behaviour of Ni and Fe. In the deposited Ni-rich phase, the relatively stable metallic compound B2 structured FeNi is found under high deposition temperature conditions.

  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. Solid-state synthesis and phase transformations in Ni/Fe films: Structural and magnetic studies

    NASA Astrophysics Data System (ADS)

    Myagkov, V. G.; Zhigalov, V. C.; Bykova, L. E.; Bondarenko, G. N.

    2006-10-01

    We have used X-ray diffraction, volume magnetocrystalline anisotropy constant and resistance measurements to study solid-state synthesis in Ni(0 0 1)/Fe(0 0 1), Ni/Fe(0 0 1) and Ni/Fe thin films with the atomic ratio between Fe and Ni of 1:1 (1Fe:1Ni), and 3:1 (3Fe:1Ni). We have found that the formation of Ni 3Fe and NiFe phases in the 1Fe:1Ni films takes place at temperatures ˜620 and ˜720 K, correspondingly. In the case of the 3Fe:1Ni films the solid-state synthesis starts with Ni 3Fe and NiFe phase formation at the same temperatures as for the 1Fe:1Ni films. The increasing of annealing temperature above 820 K leads to the nucleation of a paramagnetic γpar phase at the FeNi/Fe interface. The final products of solid-state synthesis in the Ni(0 0 1)/Fe(0 0 1) thin films are crystallites which consist of the epitaxially intergrown NiFe and γpar phases according to the [1 0 0](0 0 1)NiFe||[1 0 0](0 0 1) γpar orientation relationship. The crystalline perfection and epitaxial growth of the (NiFe+ γpar) crystallites on the MgO(0 0 1) surface allow to distinguish (0 0 2) γpar and (0 0 2)NiFe X-ray peaks (the cell parameters are: a( γpar)=0.3600±0.0005 nm and a(NiFe)=0.3578±0.0005 nm, correspondingly). At low temperatures the paramagnetic γpar phase undergoes the martensite γ→α' phase transition which can be hindered by thermal and epitaxial strains and epitaxial clamping with a MgO substrate. On the basis of the studies of the thin-film solid-state synthesis we predict the existence of two novel structural phase transformations at the temperatures of about 720 and 820 K for alloys of the invar region of the Fe-Ni system.

  2. 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.

  3. NiFe/CoFe/Cu/CoFe/MnIr spin valves studied by ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Timopheev, A. A.; Sobolev, N. A.; Pogorelov, Y. G.; Bunyaev, S. A.; Teixeira, J. M.; Cardoso, S.; Freitas, P. P.; Kakazei, G. N.

    2013-05-01

    Ion-beam deposited (Glass/Ta/NiFe/CoFe/Cu/CoFe/MnIr/Ta) spin valves (SVs) with a Cu-spacer thickness (tCu) varying from 14 to 28 Å have been studied by ferromagnetic resonance (FMR) and magnetoresistance (MR) measurements. With respect to the interlayer coupling strength between the free and fixed ferromagnetic layers, the samples have been divided in those with a weak coupling (for tCu > 16 Å) and a strong coupling regimes (for tCu ≤ 16 Å). The FMR behavior in these two regimes is quite different. For the weakly coupled series, there are two well-defined FMR peaks stemming from the free and fixed layers. Their in-plane angular dependences exhibit 180° and 360° symmetries, respectively. For the strongly coupled SVs, the resonance modes are hybridized and possess features of both layers simultaneously. The main coupling mechanism between the two layers, as concluded from the FMR and MR measurements, is the Néel "orange-peel" magnetostatic interaction, accompanied by a direct exchange due to pinholes in the Cu spacer for tCu < 17 Å.

  4. Defect controlled magnetism in FeP/graphene/Ni(111)

    PubMed Central

    Bhandary, Sumanta; Eriksson, Olle; Sanyal, Biplab

    2013-01-01

    Spin switching of organometallic complexes by ferromagnetic surfaces is an important topic in the area of molecular nanospintronics. Moreover, graphene has been shown as a 2D surface for physisorption of molecular magnets and strain engineering on graphene can tune the spin state of an iron porphyrin (FeP) molecule from S = 1 to S = 2. Our ab initio density functional calculations suggest that a pristine graphene layer placed between a Ni(111) surface and FeP yields an extremely weak exchange interaction between FeP and Ni whereas the introduction of defects in graphene shows a variety of ferromagnetic and antiferromagnetic exchange interactions. Moreover, these defects control the easy axes of magnetization, strengths of magnetic anisotropy energies and spin-dipolar contributions. Our study suggests a new way of manipulating molecular magnetism by defects in graphene and hence has the potential to be explored in designing spin qubits to realize logic operations in molecular nanospintronics. PMID:24296980

  5. Orientation relationships of Laves phase and NiAl particles in an AFA stainless steel

    NASA Astrophysics Data System (ADS)

    Trotter, Geneva; Baker, Ian

    2015-12-01

    The alumina-forming austenitic (AFA) stainless steel, Fe-20Cr-30Ni-2Nb-5Al (in at. %) was solutionized at 1250 °C in order to obtain a fully austenitic microstructure and then aged for up to 1325 h at 800 °C to precipitate the Laves phase and B2-NiAl particles typically found in AFAs. This paper describes detailed analyses of the orientation relationships between these particles and the matrix which were determined by transmission electron microscopy. Four variants of the (1 1 1)m//(0 0 0 1)p, ?m//? orientation relationship proposed by Denham and Silcock (J. Iron Steel Inst. 207 (1969) p.582) were observed for the Laves phase, and six variants of the (1 1 1)m//(0 1 1)p, ?m//? Kurdjumov-Sachs relationship were observed for the B2-NiAl phase.

  6. 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.

  7. 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.

  8. Giant Magnetoresistance and Coercivity of electrodeposited multilayered FeCoNi/Cu and CrFeCoNi/Cu

    NASA Astrophysics Data System (ADS)

    Shakya, P.; Cox, B.; Davis, D.

    2012-02-01

    The effect of Cr addition on electrodeposited multilayered nanowires CrFeCoNi/Cu was investigated from a magnetic property perspective: current perpendicular to the plane-Giant Magnetoresistance (CPP-GMR) and Coercivity (BH loops). The magnetic behavior of multilayered nanowires of CrFeNiCo/Cu was also affected by the alloy deposition potential, alloy pulsing time (layer thickness) and number of bilayers. Furthermore, the addition of Cr influenced both the nanowires GMR and Coercivity. Cr addition to the ferromagnetic FeCoNi layer induced a reduction in the room temperature GMR from 10.64% to 5.62%; however, the magnetic saturation field decreased from 0.45 to 0.27 T. The increase in the number of bilayers, from 1000 to 2500, resulted in a higher GMR value, 14.56% with 0.35 T magnetic saturation field. Addition of Cr to the ferromagnetic layer decreased the coercivity from 0.015 to 0.0054 T. Low saturation field CPP-GMR nanowires showing low coercivity at room temperature opens a new door for magnetic sensing devices. To the best of our knowledge, this is the first study on electrodeposited CrFeCoNi/Cu multilayered nanowires.

  9. 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.

  10. Phase equilibria and structural investigations in the system Al-Fe-Si.

    PubMed

    Marker, Martin C J; Skolyszewska-Kühberger, Barbara; Effenberger, Herta S; Schmetterer, Clemens; Richter, Klaus W

    2011-12-01

    The Al-Fe-Si system was studied for an isothermal section at 800 °C in the Al-rich part and at 900 °C in the Fe-rich part, and for half a dozen vertical sections at 27, 35, 40, 50 and 60 at.% Fe and 5 at.% Al. Optical microscopy and powder X-ray diffraction (XRD) was used for initial sample characterization, and Electron Probe Microanalysis (EPMA) and Scanning Electron Microscopy (SEM) of the annealed samples was used to determine the exact phase compositions. Thermal reactions were studied by Differential Thermal Analysis (DTA). Our experimental results are generally in good agreement with the most recent phase diagram versions of the system Al-Fe-Si. A new ternary high-temperature phase τ12 (cF96, NiTi2-type) with the composition Al48Fe36Si16 was discovered and was structurally characterized by means of single-crystal and powder XRD. The variation of the lattice parameters of the triclinic phase τ1 with the composition Al2+x Fe3Si3-x (-0.3 < x < 1.3) was studied in detail. For the binary phase FeSi2 only small solubility of Al was found in the low-temperature modification LT-FeSi2 (ζβ ) but significant solubility in the high-temperature modification HT-FeSi2 (ζα ) (8.5 at.% Al). It was found that the high-temperature modification of FeSi2 is stabilized down to much lower temperature in the ternary, confirming earlier literature suggestions on this issue. DTA results in four selected vertical sections were compared with calculated sections based on a recent CALPHAD assessment. The deviations of liquidus values are significant suggesting the need for improvement of the thermodynamic models.

  11. Tuneable magnetic properties of hydrothermally synthesised core/shell CoFe2O4/NiFe2O4 and NiFe2O4/CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Almeida, Trevor P.; Moro, Fabrizio; Fay, Michael W.; Zhu, Yanqiu; Brown, Paul D.

    2014-05-01

    Core/shell hetero-nanostructures of hydrothermally synthesised cobalt and nickel ferrites are shown to exhibit novel magnetic properties. The compositions and phase distributions of homogeneous Co0.5Ni0.5Fe2O4, and core/shell NiFe2O4-Core/CoFe2O4-Shell and CoFe2O4-Core/NiFe2O4-Shell nanoparticles (NPs) are confirmed using high-resolution transmission electron microscopy and electron energy loss spectroscopy. SQUID magnetometry investigations demonstrate that, at room temperature, homogeneous Co0.5Ni0.5Fe2O4 NPs ( 8 nm in diameter) are in the super-paramagnetic state, the magnetisation of NiFe2O4-Core/CoFe2O4-Shell NPs ( 11 nm in diameter) is partially blocked, whilst CoFe2O4-Core/NiFe2O4-Shell NPs ( 11 nm in diameter) are in a blocked state. In particular, NiFe2O4-Core/CoFe2O4-Shell NPs exhibit twice the out-of-phase χ″ susceptibility of CoFe2O4-Core/NiFe2O4-Shell NPs, being dominated by the magnetisation of the core ferrite phase. Hence, when exposed to a high-frequency magnetic field, it is considered that the high χ″ susceptibility of NiFe2O4-Core/CoFe2O4-Shell NPs will promote large magnetically induced heating effects, making these core/shell NPs strong candidates for hyperthermia applications.

  12. Investigation of nanostructures based on Ni80Fe20/(Ni80Fe20)20Mn80 bilayers with a unidirectional exchange anisotropy

    NASA Astrophysics Data System (ADS)

    Blinov, I. V.; Korolev, A. V.; Krinitsina, T. P.; Matveev, S. A.; Milyaev, M. A.; Popov, V. V.; Ustinov, V. V.

    2012-08-01

    The magnetic properties of nanostructures based on Ni80Fe20/(Ni80Fe20)20Mn80 bilayers have been investigated depending on the thickness of the antiferromagnetic layer and the material of the substrate. The possibility of using the antiferromagnetic alloy (Ni80Fe20)20Mn80 as the material for the pinning layer in spin valves has been considered.

  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/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.

  15. 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]).

  16. Influence of He-ion irradiation on thin NiMn/FeNi exchange bias films

    NASA Astrophysics Data System (ADS)

    Cantelli, V.; von Borany, J.; Grenzer, J.; Fassbender, J.; Kaltofen, R.; Schumann, J.

    2006-04-01

    Using synchrotron x-ray diffraction and reflectivity, we studied the transition from the paramagnetic NiMn phase to the chemically ordered, antiferromagnetic L10 phase of NiMn/Fe19Ni81 thin films deposited on a Si/SiO2 substrate as a function of the annealing temperature. The transformation to a dominating L10-ordered NiMn film takes place between 300 and 400 °C irrespective of the irradiation. This is also consistent with magnetization reversal measurements of the corresponding permalloy layers. The benefit of the ion irradiation is a reduction of the mosaicity for both the NiMn and the permalloy film, and a smoothening of internal interfaces.

  17. Influence of He-ion irradiation on thin NiMn/FeNi exchange bias films

    SciTech Connect

    Cantelli, V.; Borany, J. von; Grenzer, J.; Fassbender, J.; Kaltofen, R.; Schumann, J.

    2006-04-15

    Using synchrotron x-ray diffraction and reflectivity, we studied the transition from the paramagnetic NiMn phase to the chemically ordered, antiferromagnetic L1{sub 0} phase of NiMn/Fe{sub 19}Ni{sub 81} thin films deposited on a Si/SiO{sub 2} substrate as a function of the annealing temperature. The transformation to a dominating L1{sub 0}-ordered NiMn film takes place between 300 and 400 deg. C irrespective of the irradiation. This is also consistent with magnetization reversal measurements of the corresponding permalloy layers. The benefit of the ion irradiation is a reduction of the mosaicity for both the NiMn and the permalloy film, and a smoothening of internal interfaces.

  18. Theoretical insights into [NiFe]-hydrogenases oxidation resulting in a slowly reactivating inactive state.

    PubMed

    Breglia, Raffaella; Ruiz-Rodriguez, Manuel Antonio; Vitriolo, Alessandro; Gonzàlez-Laredo, Rubén Francisco; De Gioia, Luca; Greco, Claudio; Bruschi, Maurizio

    2017-01-01

    [NiFe]-hydrogenases catalyse the relevant H2 → 2H(+) + 2e(-) reaction. Aerobic oxidation or anaerobic oxidation of this enzyme yields two inactive states called Ni-A and Ni-B. These states differ for the reactivation kinetics which are slower for Ni-A than Ni-B. While there is a general consensus on the structure of Ni-B, the nature of Ni-A is still controversial. Indeed, several crystallographic structures assigned to the Ni-A state have been proposed, which, however, differ for the nature of the bridging ligand and for the presence of modified cysteine residues. The spectroscopic characterization of Ni-A has been of little help due to small differences of calculated spectroscopic parameters, which does not allow to discriminate among the various forms proposed for Ni-A. Here, we report a DFT investigation on the nature of the Ni-A state, based on systematic explorations of conformational and configurational space relying on accurate energy calculations, and on comparisons of theoretical geometries with the X-ray structures currently available. The results presented in this work show that, among all plausible isomers featuring various protonation patterns and oxygenic ligands, the one corresponding to the crystallographic structure recently reported by Volbeda et al. (J Biol Inorg Chem 20:11-22, 19)-featuring a bridging hydroxide ligand and the sulphur atom of Cys64 oxidized to bridging sulfenate-is the most stable. However, isomers with cysteine residues oxidized to terminal sulfenate are very close in energy, and modifications in the network of H-bond with neighbouring residues may alter the stability order of such species.

  19. 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}.

  20. 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.

  1. 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.

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

    DOE PAGES

    Shao, Lin; Chen, Di; Wei, Chaochen; ...

    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

  3. Enhanced dechlorination of 2,4-dichlorophenol by recoverable Ni/Fe-Fe3O4 nanocomposites.

    PubMed

    Xu, Cancan; Liu, Rui; Chen, Lvjun; Tang, Jialu

    2016-10-01

    Ni/Fe-Fe3O4 nanocomposites were synthesized for dechlorination of 2,4-dichlorophenol (2,4-DCP). The effects of the Ni content in Ni/Fe-Fe3O4 nanocomposites, solution pH, and common dissolved ions on the dechlorination efficiency were investigated, in addition to the reusability of the nanocomposites. The results showed that increasing content of Ni in Ni/Fe-Fe3O4 nanocomposites, from 1 to 5wt.%, greatly increased the dechlorination efficiency; the Ni/Fe-Fe3O4 nanocomposites had much higher dechlorination efficiency than bare Ni/Fe nanoparticles. Ni content of 5wt.% and initial pH below 6.0 was found to be the optimal conditions for the catalytic dechlorination of 2,4-DCP. Both 2,4-DCP and the intermediate product 2-chlorophenol (2-CP) were completely removed, and the concentration of the final product phenol was close to the theoretical phenol production from complete dechlorination of 20mg/L of 2,4-DCP, after 3hr reaction at initial pH value of 6.0, 3g/L Ni/Fe-Fe3O4, 5wt.% Ni content in the composite, and temperature of 22°C. 2,4-DCP dechlorination was enhanced by Cl(-) and inhibited by NO3(-) and SO4(2-). The nanocomposites were easily separated from the solution by an applied magnetic field. When the catalyst was reused, the removal efficiency of 2,4-DCP was almost 100% for the first seven uses, and gradually decreased to 75% in cycles 8-10. Therefore, the Ni/Fe-Fe3O4 nanocomposites can be considered as a potentially effective tool for remediation of pollution by 2,4-DCP.

  4. First-principles study of Ni-Al intermetallic compounds under various temperature and pressure

    NASA Astrophysics Data System (ADS)

    Wen, Zhiqin; Zhao, Yuhong; Hou, Hua; Tian, Jinzhong; Han, Peide

    2017-03-01

    The pressure dependence behaviors of structural and mechanical properties as well as the effect of temperature on thermodynamic properties of Ni-Al ordered intermetallic compounds (i. e. Ni3Al, Ni5Al3, NiAl, Ni2Al3 and NiAl3) are investigated in details by implementing first-principles calculations. The calculated lattice parameters, bulk modulus and its pressure derivative are well in agreement with available experimental and theoretical values at zero pressure. All the compounds are mechanically stable with pressure going up to 50 GPa, and the volume change resistance of nickel aluminum alloys can be improved by increasing pressure and Ni concentration. The shear deformation resistance, elastic stiffness and microhardness of nickel aluminum alloys can be strengthened by increasing the content of Ni5Al3 and Ni2Al3, and pressure can also enhance these properties of Ni5Al3, NiAl and Ni2Al3. The ductility of Ni3Al, Ni5Al3 and NiAl can be improved by increasing pressure, while brittle nature turns into ductile nature in 20-30 GPa and 10-20 GPa for Ni2Al3 and NiAl3, respectively. Furthermore, the elastic anisotropy of Ni3Al, Ni5Al3, Ni2Al3 and NiAl3 enhances with pressure, while NiAl shows few change with pressure increasing. In addition, Ni3Al is the most sensitive to pressure change among considered compounds. Finally, the Debye temperature, linear thermal expansion coefficient and heat capacity of these compounds are calculated using the quasi-harmonic Debye model in pressure ranging from 0 to 50 GPa and temperature ranging from 0 to 1200 K to elucidate the relationships between thermodynamic parameters and temperature under various pressure. The results are helpful insights into the study of nickel aluminum alloys.

  5. Structural ordering tendencies in the new ferromagnetic Ni-Co-Fe-Ga-Zn Heusler alloys

    NASA Astrophysics Data System (ADS)

    Dannenberg, Antje; Siewert, Mario; Gruner, Markus E.; Wuttig, Manfred; Entel, Peter

    In search for new ferromagnetic shape memory alloys (FSMA) we have calculated structural energy differences, magnetic exchange interaction constants and mixing energies of quaternary (X1X2)YZ Heusler alloys with X1,X2,Y =Ni,Co,Fe and Z=Ga, Zn using density functional theory. The comparison of the energy profiles of (NiCo)FeZ, (FeNi)CoZ, and (FeCo)NiZ with Z=Ga and Zn as a function of the tetragonal distortion c / a reveals that the energetically preferred ordering type is (NiCo)FeGa and (NiCo)FeZn which shows that Fe prefers to occupy the same cubic sublattice as Ga or Zn what implies that Fe favors Co and Ni as nearest neighbors, respectively. The Curie temperatures of (NiCo)FeGa and (NiCo)FeZn are high of the order of 600 K. (NiCo)FeGa, which has the same valence electron concentration (e/a=7.5) as Ni2MnGa and also possesses a high martensitic transformation temperature (>500 K), is of interest for future magnetic shape memory devices.

  6. The porous silicon morphology effect on the growth of electrodeposited FeNi alloy

    NASA Astrophysics Data System (ADS)

    Ouir, S.; Fortas, G.; Sam, S.; Aliouat, H.; Manseri, A.; Belaroussi, Y.; Gabouze, N.; Khereddine, A. Y.

    2012-03-01

    In this work, we report on cathodic deposition of FeNi thin films into porous silicon (PS) formed on n-type Si. Macroporous and mesoporous silicon layers were formed at constant potential or current density. The electrodeposited thin films were characterized by Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). The magnetic properties of the FeNi layers were investigated by hysteresis loops measurements. SEM images of the FeNi films indicate that tubular and granular forms were obtained depending on the porous silicon surface morphology. Moreover, the FeNi films compositions are found to depend on the porous silicon microstructure. Finally, the XRD spectra of the deposited films show the presence of FeNi (111) and FeNi (220) peaks. The FeNi (111) peak has been shown for all polarization potentials, in agreement with results reported in the literature.

  7. 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.

  8. 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.

  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. 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.

  11. Stabilization of itinerant (band) magnetism in FeAl by Ga substitution for Al

    NASA Astrophysics Data System (ADS)

    Papaconstantopoulos, D. A.; Mazin, I. I.; Hathaway, K. B.

    2001-06-01

    Band structure calculations of FeGa1-xAlx have been performed, to further investigate the stability of ferromagnetism in FeAl. The Stoner parameter increases by about 20% at the FeGa end. This is also confirmed by our spin-polarized calculations. We conclude that Ga substitution for Al is likely to stabilize the elusive (or illusive) ferromagnetic state in FeAl.

  12. 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.

  13. High frequency characteristics of NiO/(FeCo/NiO) 10 multilayers with exchange anisotropy

    NASA Astrophysics Data System (ADS)

    Chen, Jihong; Tang, Dongming; Li, Yuwei; Zhang, Baoshan; Yang, Yi; Lu, Mu; Lu, Huaixian

    2010-10-01

    [NiO/Fe 65Co 35] 10 exchange-coupled multilayer films for high frequency applications are fabricated, and their static magnetic property and microwave permeability are studied systematically. Both exchange bias field and ferromagnetic resonance frequency of the multilayers increase with decreasing Fe 65Co 35 thickness, which means that the microwave properties such as permeability and FMR frequency can be controlled by changing Fe 65Co 35 thickness in the exchange-coupled films. Ferromagnetic resonance frequencies beyond 7 GHz of the films are measured and reported for the first time.

  14. Room temperature ductility of NiAl-strengthened ferritic steels: Effects of precipitate microstructure

    SciTech Connect

    Teng, Z.K.; Liu, C.T.; Miller, M.K.; Ghosh, G.; Kenik, E.A.; Huang, S.; Liaw, P.K.

    2012-04-11

    The effects of precipitate microstructure on the room temperature ductility of a series of carefully designed Fe-Al-Ni-Cr-Mo steels were investigated. Transmission electron microscopy (TEM), ultra small angle X-ray scattering (USAXS), and atom probe tomography (APT) were conducted to quantify the nano-scaled precipitates. The accuracy of the characterization results was verified by a numerical analysis. Three point bending tests results demonstrated that ductility was a function of the precipitate volume fraction and the Al and Ni concentrations in the Fe matrix, these relationships were discussed in terms of possible mechanisms. The ductility was also found to be independent of the precipitate size and inter-particle spacing in the studied range, which was validated by a theoretical model.

  15. 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

    2016-05-05

    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.

  16. Eutectic superalloys strengthened by delta Ni3Cb lamellae, and gamma prime, Ni3Al precipitates.

    NASA Technical Reports Server (NTRS)

    Lemkey, F. D.; Thompson, E. R.

    1972-01-01

    Bivariant eutectic alloys, located on a liquidus surface within the Ni-Cb-Cr-Al quaternary, were identified which permitted the production of aligned delta Ni3Cb lamellae within a nichrome matrix containing the fcc precipitate gamma prime Ni3Al. The volume fraction of delta and gamma prime could be varied significantly by compositional changes. After directional solidification certain alloys possessed improved ductility and corrosion resistance with respect to the Ni3Al-Ni3Cb eutectic, while their values of tensile and creep strength approached or exceeded those for the Ni3Al-Ni3Cb pseudobinary system. The mechanical properties of the directionally solidified alloy, Ni-19.7 wt % Cb-6.0 wt % Cr-2.5 wt % Al, were evaluated. Its longitudinal strength in tension and creep was found to be superior to all advanced nickel base superalloys. It is thus demonstrated that useful properties for gas turbine airfoil applications can be achieved by reinforcing a strong and tough gamma nichrome matrix containing precipitated gamma prime by a strong lamellar intermetallic compound having greater strength at elevated temperature.

  17. 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.

  18. 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)

  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. 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

    2016-08-26

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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.

  2. The structure and magnetic properties of FeNiN films

    NASA Astrophysics Data System (ADS)

    Wang, H. Y.; Jun-Liu, Huang, H. S.; Mao, W. H.; Chen, H.; Zhang, H. Y.; He, Y. J.; Jiang, E. Y.

    2002-02-01

    FeNiN films with 0-56 at % Ni concentrations were prepared by dual ion beam sputtering in a nitrogen-argon gas mixture. Effects of nitrogen and nickel concentrations on the structure and magnetic properties of FeNiN films have been studied. FeNiN films with lower nickel and nitrogen concentrations contained the bcc α-(FeNi) phase, films with 8-12 at % nitrogen and 5-25 at % Ni concentrations contained α″-(Fe, Ni)16N2 and γ'-(Fe, Ni)4N phases, and films with 30-56 at % Ni concentrations consisted of a mixture of fcc γ-FeNi alloy and γ'-(Fe, Ni)4N phases. The FeNiN films with 8-12 at % nitrogen and 5-15 at % nickel concentrations showed high saturation magnetization of 2.2-2.3 T and low coercivity of 96-110 A/m. The variation of the magnetic properties was attributed to the change in the structure of the films.

  3. 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.

  4. 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.

  5. 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

  6. 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].

  7. 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.

  8. Fabrication and Characterization of Ni-P-CoNiCrAlY Composite Coatings

    NASA Astrophysics Data System (ADS)

    Heydari, H.; Monirvaghefi, S. M.; Hadipour, Ali

    2017-02-01

    In this study, Ni-P-CoNiCrAlY composite coatings were deposited on 310 stainless steel. The surface morphology and cross-sectional observations were carried out using scanning electron microscopy and optical microscopy. The high-temperature corrosion of all coatings was evaluated by cyclic oxidation method. According to the results, the amounts of CoNiCrAlY particles co-deposited in all samples coated at pH = 4.7 were higher than that of those produced at pH = 6.7. Also, the surface roughness of all composite coatings coated at pH = 6.7 is lower than the coatings produced at pH = 4.7. The Ni-P-(3 g/l) CoNiCrAlY deposit produced at pH = 6.7 had the best corrosion resistance among other coatings.

  9. Fabrication and Characterization of Ni-P-CoNiCrAlY Composite Coatings

    NASA Astrophysics Data System (ADS)

    Heydari, H.; Monirvaghefi, S. M.; Hadipour, Ali

    2017-03-01

    In this study, Ni-P-CoNiCrAlY composite coatings were deposited on 310 stainless steel. The surface morphology and cross-sectional observations were carried out using scanning electron microscopy and optical microscopy. The high-temperature corrosion of all coatings was evaluated by cyclic oxidation method. According to the results, the amounts of CoNiCrAlY particles co-deposited in all samples coated at pH = 4.7 were higher than that of those produced at pH = 6.7. Also, the surface roughness of all composite coatings coated at pH = 6.7 is lower than the coatings produced at pH = 4.7. The Ni-P-(3 g/l) CoNiCrAlY deposit produced at pH = 6.7 had the best corrosion resistance among other coatings.

  10. From Fe3O4 /NiO bilayers to NiFe2O4 -like thin films through Ni interdiffusion

    NASA Astrophysics Data System (ADS)

    Kuschel, O.; Buß, R.; Spiess, W.; Schemme, T.; Wöllermann, J.; Balinski, K.; N'Diaye, A. T.; Kuschel, T.; Wollschläger, J.; Kuepper, K.

    2016-09-01

    Ferrites with (inverse) spinel structure display a large variety of electronic and magnetic properties, making some of them interesting for potential applications in spintronics. We investigate the thermally induced interdiffusion of Ni2 + ions out of NiO into Fe3O4 ultrathin films, resulting in off-stoichiometric nickel ferrite-like thin layers. We synthesized epitaxial Fe3O4 /NiO bilayers on Nb-doped SrTiO3(001) substrates by means of reactive molecular beam epitaxy. Subsequently, we performed an annealing cycle comprising three steps at temperatures of 400 ∘C , 600 ∘C , and 800 ∘C under an oxygen background atmosphere. We studied the changes of the chemical and electronic properties as result of each annealing step with help of hard x-ray photoelectron spectroscopy and found a rather homogeneous distribution of Ni and Fe cations throughout the entire film after the overall annealing cycle. For one sample we observed a cationic distribution close to that of the spinel ferrite NiFe2O4 . Further evidence comes from low-energy electron diffraction patterns indicating a spinel-type structure at the surface after annealing. Site- and element-specific hysteresis loops performed by x-ray magnetic circular dichroism uncovered the antiferrimagnetic alignment between the octahedral coordinated Ni2 + and Fe3 + ions and the Fe3 + ion in tetrahedral coordination. We find a quite low coercive field of 0.02 T, indicating a rather low defect concentration within the thin ferrite films.

  11. 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.

  12. 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.

  13. 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.

  14. Saturation and forced volume magnetostrictions of Fe-rich FeZr and FeNiZr amorphous alloys

    NASA Astrophysics Data System (ADS)

    Tange, H.; Kamimori, T.; Goto, M.; Fukamichi, K.

    1990-12-01

    The saturation and forced volume magnetostrictions, ac susceptibility have been investigated for Fe 90Zr 10 and Fe 90-xNi xZr 10 amorphous alloys. The linear magnetostriction in the re-entrant spin glass state exhibits a hysteresis due to a remarkable magnetic after effect. The temperature dependence of the forced volume magnetostriction shows a peak at the spin freezing temperature.

  15. 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.

  16. Atomistic structure of the coherent Ni/Ni[sub 3]Al interface

    SciTech Connect

    Farkas, D. . Dept. of Materials Science and Engineering); Campos, M.F. de; Souze, R.M. de; Goldenstein, H. . Dept. de Metalurgia)

    1994-02-01

    Most Ni-based superalloys are strengthened by the presence of coherent precipitates of an ordered fcc bases phase, known as [gamma][prime]. This phase is basically Ni[sub 3]Al. The precipitates are coherent up to a certain size and they present a cubic shape with faces oriented in the (100) planes of both matrix and precipitate. The detailed atomistic structure of this interface has not been studied. Interest in the use of ordered intermetallic compounds as possible structural materials has resulted in a large amount of work in Ni[sub 3]Al and in particular, the development of interatomic potentials for the Ni-Al system using the embedded atom technique. These potentials have been employed in the simulation of a variety of defects in Ni[sub 3]Al, including dislocation cores, grain boundaries and free surfaces. However, there is no simulation of the Ni/Ni[sub 3]Al interface structure using the embedded atom method. The objective of the present work is to carry out such a simulation. Besides the practical importance of the interface in superalloys, it is the simplest type of interface that can be modeled and it is a good starting point for interface work using the embedded atom technique.

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

    NASA Astrophysics Data System (ADS)

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

    1989-02-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  19. 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.

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

    DOE PAGES

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; ...

    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

  2. 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.

  3. 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

  4. Structural evolution in mechanically alloyed Al-Fe powders

    SciTech Connect

    Mukhopadhyay, D.K.; Suryanarayana, C.; Froes, F.H.

    1995-08-01

    The structural evolution in mechanically alloyed binary aluminum-iron powder mixtures containing 1, 4, 7.3, 10.7, and 25 at pct Fe was investigated using X-ray diffraction (XRD) and electron microscopic techniques. The constitution (number and identity of phases present), microstructure (crystal size, particle size), and transformation behavior of the powders on annealing were studied. The solid solubility of Fe in Al has been extended up to at least 4.5 at. pct, which is close to that observed using rapid solidification (RS) (4.4 at. pct), compared with the equilibrium value of 0.025 at. pct Fe at room temperature. Nanometer-sized grains were observed in as-milled crystalline powders in all compositions. Increasing the ball-to-powder weight ratio (BPR) resulted in a faster rate of decrease of crystal size. A fully amorphous phase was obtained in the Al-25 at. pct Fe composition, and a mixed amorphous phase plus solid solution of Fe in Al was developed in the Al-10.7 at. pct Fe alloy, agreeing well with the predictions made using the semiempirical Miedema model. Heat treatment of the mechanically alloyed powders containing the supersaturated solid solution or the amorphous phase resulted in the formation of the Al{sub 3}Fe intermetallic in all but the Al-25 at. pct Fe powders. In the Al-25 at. pct Fe powder, formation of nanocrystalline Al{sub 5}Fe{sub 2} was observed directly by milling. Electron microscope studies of the shock-consolidated mechanically alloyed Al-10.7 and 25 at. pct Fe powders indicated that nanometer-sized grains were retained after compaction.

  5. Evaluation of nickel for positive electrode components in Li-Al/FeS cells

    NASA Astrophysics Data System (ADS)

    Smaga, J. A.; Battles, J. E.

    1982-03-01

    A series of tests were performed to examine the suitability of pure Ni positive electrodes, which have an oxidation potential of 2.2 V, in Li-Al/FeS batteries. A prismatic bicell was employed for the trials with the positive current collector sandwiched between the positive electrode halves, which were covered with Ni screens. The battery was run at 450 C for 31-153 days using different cells. Electrodes were then sectioned, cleaned, measured for thickness, evaluated for reactions, and examined microscopically and metallographically. Largest utilization gains were observed with a LiCl-rich electrolyte. Iron layers, with a thickness up to 6 microns, were found on the Ni components, but were considered too small to display significant life-shortening effects. Cells assembled in less than fully charged conditions showed noticeable intergranular corrosion, a process which was eliminated by using finer Fe particles in the positive electrode mix.

  6. Precessional damping of Fe magnetic moments in a FeNi film

    NASA Astrophysics Data System (ADS)

    Buschhorn, Stefan; Brüssing, Frank; Abrudan, Radu; Zabel, Hartmut

    2011-04-01

    We report on the element-resolved precessional dynamics of Fe magnetic moments in a homogeneous FeNi thin film. In our pump-probe experiment the magnetic system is excited by a magnetic field pulse from a stripline. The instantaneous response to the field-pulse excitation is monitored as a function of time in a stroboscopic measurement using element-selective x-ray resonant magnetic scattering (XRMS). Our data show that Fe and Ni moments are aligned parallel to each other at all times, while they oscillate around the effective field direction given by the step field pulse and applied bias field. The field dependence of the precessional motion and damping of Fe magnetic moments is analysed and compared with time-resolved magneto-optical Kerr effect (tr-MOKE) measurement data from the literature, showing good agreement. Additional studies prove the capability of our setup to conduct temperature-dependent studies. In the case of the presented FeNi system no changes in the frequency or damping behaviour are observed within a temperature range of 150-350 K.

  7. Spin-Wave Modes in Exchange-Coupled FePt/FeNi Bilayer Films

    NASA Astrophysics Data System (ADS)

    Li, Shu-Fa; He, Pan; Cheng, Chu-Yuan; Zhou, Shi-Ming; Lai, Tian-Shu

    2014-01-01

    A simple magnetic modulation structure of the exchange-coupling FePt/FeNi bilayer film is fabricated and studied for its magnetization dynamics using time-resolved magneto-optical polar Kerr spectroscopy. It is found that two spin-wave modes can be excited. One is fixed at ~3.2 GHz in frequency for any external field and may serve as a frequency-stabilized spin-wave filter, while the other is external field dependent. In contrast, only the external field-dependent mode is excited in single-layer FeNi, supporting the localized origin of the mode at ~3.2 GHz, which is confined to a thin exchange-coupling region. The other external field-dependent mode in frequency is attributed to the Kittel mode.

  8. Structural stability of NiCoFeCrAlx high-entropy alloy from ab initio theory

    NASA Astrophysics Data System (ADS)

    Tian, Fuyang; Delczeg, Lorand; Chen, Nanxian; Varga, Lajos Karoly; Shen, Jiang; Vitos, Levente

    2013-08-01

    First-principles alloy theory predicts that at room temperature the paramagnetic NiCoFeCrAlx high entropy alloys adopt the face centered cubic (fcc) structure for x≲0.60 and the body centered cubic (bcc) structure for x≳1.23, with an fcc-bcc duplex region in between the two pure phases. The calculated single- and polycrystal elastic parameters exhibit strong composition and crystal structure dependence. Based on the present theoretical findings, it is concluded that alloys around the equimolar NiCoFeCrAl composition have superior mechanical performance as compared to the single-phase regions.

  9. 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.

  10. 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.

  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. 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.

  13. 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

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

    PubMed

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

    2014-06-07

    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.

  15. Fusion of 48Ti+58Fe and 58Ni+54Fe below the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Stefanini, A. M.; Montagnoli, G.; Corradi, L.; Courtin, S.; Bourgin, D.; Fioretto, E.; Goasduff, A.; Grebosz, J.; Haas, F.; Mazzocco, M.; Mijatović, T.; Montanari, D.; Pagliaroli, M.; Parascandolo, C.; Scarlassara, F.; Strano, E.; Szilner, S.; Toniolo, N.; Torresi, D.

    2015-12-01

    Background: No data on the fusion excitation function of 48Ti+58Fe in the energy region near the Coulomb barrier existed prior to the present work, while fusion of 58Ni+54Fe was investigated in detail some years ago, down to very low energies, and clear evidence of fusion hindrance was noticed at relatively high cross sections. 48Ti and 58Fe are soft and have a low-lying quadrupole excitation lying at ≈800 -900 keV only. Instead, 58Ni and 54Fe have a closed shell (protons and neutrons, respectively) and are rather rigid. Purpose: We aim to investigate (1) the possible influence of the different structures of the involved nuclei on the fusion excitation functions far below the barrier and, in particular, (2) whether hindrance is observed in 48Ti+58Fe , and to compare the results with current coupled-channels models. Methods: 48Ti beams from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro were used. The experimental setup was based on an electrostatic beam separator, and fusion-evaporation residues (ERs) were detected at very forward angles. Angular distributions of ERs were measured. Results: Fusion cross sections of 48Ti+58Fe have been obtained in a range of nearly six orders of magnitude around the Coulomb barrier, down to σ ≃2 μ b . The sub-barrier cross sections of 48Ti+58Fe are much larger than those of 58Ni+54Fe . Significant differences are also observed in the logarithmic derivatives and astrophysical S factors. No evidence of hindrance is observed, because coupled-channels calculations using a standard Woods-Saxon potential are able to reproduce the data in the whole measured energy range. Analogous calculations for 58Ni+54Fe predict clearly too large cross sections at low energies. The two fusion barrier distributions are wide and display a complex structure that is only qualitatively fit by calculations. Conclusions: It is pointed out that all these different trends originate from the dissimilar low-energy nuclear structures of

  16. 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.

  17. Discrimination and quantification of Fe and Ni abundances in Genesis solar wind implanted collectors using X-ray standing wave fluorescence yield depth profiling with internal referencing

    SciTech Connect

    Choi, Y.; Eng, P.; Stubbs, J.; Sutton, S. R.; Schmeling, M.; Veryovkin, I. V.; Burnett, D.

    2016-08-21

    In this paper, X-ray standing wave fluorescence yield depth profiling was used to determine the solar wind implanted Fe and Ni fluences in a silicon-on-sapphire (SoS) Genesis collector (60326). An internal reference standardization method was developed based on fluorescence from Si and Al in the collector materials. Measured Fe fluence agreed well with that measured previously by us on a sapphire collector (50722) as well as SIMS results by Jurewicz et al. Measured Ni fluence was higher than expected by a factor of two; neither instrumental errors nor solar wind fractionation effects are considered significant perturbations to this value. Impurity Ni within the epitaxial Si layer, if present, could explain the high Ni fluences and therefore needs further investigation. As they stand, these results are consistent with minor temporally-variable Fe and Ni fractionation on the timescale of a year.

  18. Discrimination and quantification of Fe and Ni abundances in Genesis solar wind implanted collectors using X-ray standing wave fluorescence yield depth profiling with internal referencing

    DOE PAGES

    Choi, Y.; Eng, P.; Stubbs, J.; ...

    2016-08-21

    In this paper, X-ray standing wave fluorescence yield depth profiling was used to determine the solar wind implanted Fe and Ni fluences in a silicon-on-sapphire (SoS) Genesis collector (60326). An internal reference standardization method was developed based on fluorescence from Si and Al in the collector materials. Measured Fe fluence agreed well with that measured previously by us on a sapphire collector (50722) as well as SIMS results by Jurewicz et al. Measured Ni fluence was higher than expected by a factor of two; neither instrumental errors nor solar wind fractionation effects are considered significant perturbations to this value. Impuritymore » Ni within the epitaxial Si layer, if present, could explain the high Ni fluences and therefore needs further investigation. As they stand, these results are consistent with minor temporally-variable Fe and Ni fractionation on the timescale of a year.« less

  19. Effect of Ni-to-Fe ratio on structure and properties of Ni-Fe-B-Si-Nb coatings fabricated by laser processing

    NASA Astrophysics Data System (ADS)

    Li, Ruifeng; Li, Zhuguo; Huang, Jian; Zhang, Peilei; Zhu, Yanyan

    2011-02-01

    Ni-Fe-B-Si-Nb coatings have been deposited on mild steel substrates using high power laser cladding process followed by laser remelting. The influence of Ni-to-Fe concentration ratio in (Ni100-xFex)62B18Si18Nb2 (x = 55, 50, 45 and 40) powders on the phase composition and microstructure is analyzed by X-ray diffraction, scanning- and transmission-electron microscopies. The microhardness and corrosion resistance properties of the coatings are also measured. The results reveal that amorphous matrix layers are obtained for all coatings. The increase of the Ni-to-Fe ratio can promote the formation of γ(Fe-Ni) phase and decrease the formation of Fe2B phase and α-Fe phase. The coating with 1:1 ratio of Ni-to-Fe exhibits the highest microhardness of 1200 HV0.5 and superior corrosion resistance property due to its largest volume fraction of amorphous phase in the coating. Higher or lower than 1:1 ratio of Ni-to-Fe may result in lower amorphous forming ability. However, even that the coating with ratio of 3:2, shows a minimum of microhardness, it shows a better corrosion resistance than other two coatings.

  20. Fluorescence x-ray absorption fine structure studies of Fe-Ni-S and Fe-Ni-Si melts to 1600 K

    SciTech Connect

    Manghnani, M.H.; Hong, X.; Balogh, J.; Amulele, G.; Sekar, M.; Newville, M.

    2008-04-29

    We report Ni K-edge fluorescence x-ray absorption fine structure spectra (XAFS) for Fe{sub 0.75}Ni{sub 0.05}S{sub 0.20} and Fe{sub 0.75}Ni{sub 0.05}Si{sub 0.20} ternary alloys from room temperature up to 1600 K. A high-temperature furnace designed for these studies incorporates two x-ray transparent windows and enables both a vertical orientation of the molten sample and a wide opening angle, so that XAFS can be measured in the fluorescence mode with a detector at 90{sup o} with respect to the incident x-ray beam. An analysis of the Ni XAFS data for these two alloys indicates different local structural environments for Ni in Fe{sub 0.75}Ni{sub 0.05}S{sub 0.20} and Fe{sub 0.75}Ni{sub 0.05}Si{sub 0.20} melts, with more Ni-Si coordination than Ni-S coordination persisting from room temperature through melting. These results suggest that light elements such as S and Si may impact the structural and chemical properties of Fe-Ni alloys with a composition similar to the earth's core.

  1. 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.

  2. 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

    2016-12-01

    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.

  3. Strength of "Light" Ferritic and Austenitic Steels Based on the Fe - Mn - Al - C System

    NASA Astrophysics Data System (ADS)

    Kaputkina, L. M.; Svyazhin, A. G.; Smarygina, I. V.; Kindop, V. E.

    2017-01-01

    The phase composition, the hardness, the mechanical properties at room temperature, and the resistance to hot (950 - 1000°C) and warm (550°C) deformation are studied for cast deformable "light" ferritic and austenitic steels of the Fe - (12 - 25)% Mn - (0 - 15)% Al - (0 - 2)% C system alloyed additionally with about 5% Ni. The high-aluminum high-manganese low-carbon and carbonless ferritic steels at a temperature of about 0.5 T melt have a specific strength close to that of the austenitic steels and may be used as weldable scale-resistant and wear-resistant materials. The high-carbon Fe - (20 - 24)% Mn - (5 - 9)% Al - 5% Ni - 1.5% C austenitic steels may be applied as light high-strength materials operating at cryogenic temperatures after a solution treatment and as scale- and heat-resistant materials in an aged condition.

  4. Graphite Reinforced Fe-Al-X Composites for Slide Bearing Applications

    NASA Astrophysics Data System (ADS)

    Ko, Se-Hyun; Lee, Wonsik; Jang, Jin Man; Kim, Il-Ho; Shin, Seong-Gun

    The Fe-Al-X(Cu, Ni, Ti) composites reinforced with graphite particles were fabricated employing the powder metallurgy process for slide bearing applications. In all samples, graphite particles of 6 wt.% were added. Elemental powders were mixed to specific compositions with a powder lubricant, and then the mixed powders were compacted at 500 MPa. The green compacts were heated to 450°C to remove the lubricant and sintered at 1200°C for 1 h. The sintering was conducted in vacuum. The sintering of binary Fe-Al-graphite system showed low density and growth in dimension. Complex addition of Cu, Ni and Ti improved the sinterability of green compacts due to occurrence of partial liquid phases. Hardness of sintered samples strongly depended on dimensional change during sintering. The samples of high hardness showed better wear resistance properties.

  5. 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.

  6. Thermoelectric properties of Fe and Al co-added Ge

    NASA Astrophysics Data System (ADS)

    Sasaki, Takayuki; Kurosaki, Ken; Yusufu, Aikebaier; Ohishi, Yuji; Muta, Hiroaki; Yamanaka, Shinsuke

    2017-04-01

    The polycrystalline bulk samples of Fe and Al co-added Ge were synthesized by melt-spinning followed by spark plasma sintering and the thermoelectric properties were examined. Here, Al acts as a p-type dopant, while Fe is expected to form FeGe2 as precipitates. Since the lattice mismatch between Ge and FeGe2 is small (<4%), they would coherently connect with each other, reducing the thermal conductivity without affecting the electrical transport. In this study, a reduction in thermal conductivity was achieved by dispersing the FeGe2 precipitates in the Al-doped Ge matrix, while they had little influences on both the carrier mobility and the Seebeck coefficient. As the results, the maximum ZT value of 0.13 was obtained at 773 K, which is three times higher than that of single-crystal Ge reported by the authors’ group [Y. Ohishi et al., Jpn. J. Appl. Phys. 55, 051301 (2016)].

  7. Properties of Ni and Ni–Fe nanowires electrochemically deposited into a porous alumina template

    PubMed Central

    Shimanovich, Dmitry L; Yanushkevich, Kazimir I; Prischepa, Sergej L; Outkina, Elena A

    2016-01-01

    The comparative analysis of the electrochemical deposition of Ni and Ni–Fe nanowires (NWs) into ordered porous alumina templates is presented. The method developed allows for obtaining NWs of 50 ± 5 nm in diameter and 25 μm in length, i.e., with an aspect ratio of 500. XRD data demonstrate the polycrystalline nature of Ni and Ni–Fe in a face-centered cubic close-packed lattice. Both fabricated materials, Ni and Ni–Fe, have shown ferromagnetic properties. The specific magnetization value of Ni–Fe NWs in the alumina template is higher than that of the Ni sample and bulk Ni, also the Curie temperature of the Ni–Fe sample (790 K) is higher than that of the Ni sample one or bulk Ni. PMID:28144520

  8. The temperature and strain rate dependence of the flow stress of single crystal NiAl deformed along <110>

    SciTech Connect

    Maloy, S.A.; Gray, G.T. III

    1995-12-31

    Single crystal NiAl and Ni-49.75Al-0.25Fe have been deformed along <110> at temperatures of 77, 298 and 773K and strain rates of 0.001/s, and 2000/s. The flow stress of <110> NiAl is rate and temperature sensitive. The 0.25 at.% Fe addition resulted in a small increase in flow stress at strain rates of 0.001 and 0.1/s at 298 and 77K. A significant decrease in the work hardening rate is observed after deformation at 77K and a strain rate of 2000/s. Coarse [110] slip traces are observed after deformation at a strain rate of 2000/s at 77K, while no slip traces were observed after deformation under all other conditions. TEM observations reveal distinct [110] slip bands after deformation at 77K and a strain rate of 2000/s.

  9. Cooperativity and Dynamics Increase the Performance of NiFe Dry Reforming Catalysts.

    PubMed

    Kim, Sung Min; Abdala, Paula Macarena; Margossian, Tigran; Hosseini, Davood; Foppa, Lucas; Armutlulu, Andac; van Beek, Wouter; Comas-Vives, Aleix; Copéret, Christophe; Müller, Christoph

    2017-02-08

    The dry reforming of methane (DRM), i.e., the reaction of methane and CO2 to form a synthesis gas, converts two major greenhouse gases into a useful chemical feedstock. In this work, we probe the effect and role of Fe in bimetallic NiFe dry reforming catalysts. To this end, monometallic Ni, Fe, and bimetallic Ni-Fe catalysts supported on a MgxAlyOz matrix derived via a hydrotalcite-like precursor were synthesized. Importantly, the textural features of the catalysts, i.e., the specific surface area (172-178 m(2)/gcat), pore volume (0.51-0.66 cm(3)/gcat), and particle size (5.4-5.8 nm) were kept constant. Bimetallic, Ni4Fe1 with Ni/(Ni + Fe) = 0.8, showed the highest activity and stability, whereas rapid deactivation and a low catalytic activity were observed for monometallic Ni and Fe catalysts, respectively. XRD, Raman, TPO, and TEM analysis confirmed that the deactivation of monometallic Ni catalysts was in large due to the formation of graphitic carbon. The promoting effect of Fe in bimetallic Ni-Fe was elucidated by combining operando XRD and XAS analyses and energy-dispersive X-ray spectroscopy complemented with density functional theory calculations. Under dry reforming conditions, Fe is oxidized partially to FeO leading to a partial dealloying and formation of a Ni-richer NiFe alloy. Fe migrates leading to the formation of FeO preferentially at the surface. Experiments in an inert helium atmosphere confirm that FeO reacts via a redox mechanism with carbon deposits forming CO, whereby the reduced Fe restores the original Ni-Fe alloy. Owing to the high activity of the material and the absence of any XRD signature of FeO, it is very likely that FeO is formed as small domains of a few atom layer thickness covering a fraction of the surface of the Ni-rich particles, ensuring a close proximity of the carbon removal (FeO) and methane activation (Ni) sites.

  10. Tailoring the magnetic properties of CoFeNi alloys with variations in copper contents

    NASA Astrophysics Data System (ADS)

    Lee, Jeong Oh; Kim, Hyun Kyung; Kim, Gyeung Ho; Jeung, Won Young

    2006-04-01

    CoFeNi alloys are some of the most studied soft magnetic materials because of their superior properties over FeNi alloys as write head core materials in hard disk drives. Pulsed electrodeposition was shown to be an interesting approach to vary the crystalline structure of the fcc-bcc mixed phase CoFeNi and CoFeNiCu films without changing the composition and the grain size by using a single bath. The permeability μ of CoFeNiCu films plated from bath composition exceeded 4.6×106. Coercivity Hc was 20-73 A/m. The high saturation magnetic flux Bs was 1.8 T. The soft magnetic CoFeNiCu film prepared satisfies all the requirements needed for the preparation of magnetic recording heads, as all magnetic properties were improved in this direction.

  11. 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.

  12. 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.

  13. Fe and Ni Isotope Composition of Metal Grains from CH and CB Chondrites

    NASA Astrophysics Data System (ADS)

    Weyrauch, M.; Weyer, S.; Zipfel, J.

    2016-08-01

    Early condensates may be represented by zoned metals in CH and CBb chondrites. They display higher concentrations of Ni and more refractory elements in cores than in rims, and lighter Fe and Ni isotope signatures in cores than in rims.

  14. 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.

  15. {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.

  16. Structure and Properties of Magnetic (Co, Fe, Fe{sub 3}C and Ni) Carbon Beads

    SciTech Connect

    Leonowicz, Marcin; Izydorzak, Marta; Pomogailo, Anatolii D.; Dzhardimalieva, Gulzhian I.

    2010-12-02

    Nanoparticles exhibit unique physical properties due to the surface or quantum-size effects. Particular attention has been focused on magnetic nanoparticles and substantial progress has been done in this field. In this work magnetic composites, consisting of elementary metals or carbides nanocrystallites, stabilized in carbon matrix, were prepared by the procedure comprising formation of appropriate metal acrylamide complexes, followed by frontal polymerization and pyrolysis of the polymer at various temperatures. Application of frontal polymerization and further pyrolysis enables formation of composite beads consisting of Co, Fe, Fe{sub 3}C or Ni nanocrystallites stabilized in carbon matrix. It was found that the lowest pyrolysis temperature, which enables the production of metallic nanocrystallites, was 673 K for Co and Ni, and 773 K for Fe. The magnetic properties of the beads, percentage of the metallic component, their composition and shape depended on the pyrolysis temperature. Extracts on the basis of composites containing Fe{sub 3}C showed no cytotoxicity, whereas those containing Co and Ni exhibited negligible cytotoxicity up to concentrations of 6.25 mg/ml.

  17. Phase Evolution and Ni-Fe Granular Growth of Saprolitic Laterite Ore-CaO Mixtures during Reductive Roasting

    NASA Astrophysics Data System (ADS)

    Luo, Jun; Li, Guanghui; Peng, Zhiwei; Rao, Mingjun; Zhang, Yuanbo; Jiang, Tao

    2016-12-01

    The correlations between phase evolution, fusion behavior, and Ni-Fe granules growth of laterite ore-CaO mixtures during reductive roasting have been investigated. The minimum melting point of 1220°C of the CaO-MgO-Al2O3-SiO2 system with 17-36 wt.% CaO is demonstrated via phase diagram analysis, and this point is decreased in the presence of FeO. This reveals that the fusion behavior in close association with the Fe-Ni granular growth can be regulated by altering the contents of CaO and FeO. Promoting the generation of diopside (CaMgSi2O6) may reduce the operating temperature from 1300-1350°C to 1150-1200°C, which ensures sufficient melting phase content. Moreover, reducing the CO partial fraction lowers the fusion temperature but hinders the growth of Ni-Fe grains. The average size of Ni-Fe granules in the reduced mixture with 17 wt.% CaO reaches nearly 20 μm at 1200°C for 1 h in a 100 vol.% CO atmosphere.

  18. Thermally Induced Structural Transformations of Fe40Ni40P14B6 Amorphous Alloy

    NASA Astrophysics Data System (ADS)

    Vasić, Milica M.; Roupcová, Pavla; Pizúrová, Naděžda; Stevanović, Sanja; Blagojević, Vladimir A.; Žák, Tomáš; Minić, Dragica M.

    2016-01-01

    Thermal stability and thermally induced structural transformations of Fe40Ni40P14B6 amorphous alloy were examined under non-isothermal and isothermal conditions. Formation of metastable α-(Fe,Ni), and stable γ-(Fe,Ni) and (Fe,Ni)3(P,B) crystalline phases as the main crystallization products was observed, while the presence of small amounts of other crystalline phases like Fe23B6 and Fe2NiB was indicated by electron diffraction in HRTEM. Thermomagnetic curve indicated that Fe content in different crystalline phases is very different, resulting in markedly different Curie temperatures after crystallization. Transmission electron microscopy and atomic force microscopy study suggested multiple-layered platelet-shaped morphology, both on the surface and in the bulk of the crystallized alloy sample. The thermal treatment heating rate and maximum temperature affected surface roughness and grain size inhomogeneity.

  19. Single crystal EPR study of the Ni center of NiFe hydrogenase

    NASA Astrophysics Data System (ADS)

    Geßner, Ch.; Trofanchuk, O.; Kawagoe, K.; Higuchi, Y.; Yasuoka, N.; Lubitz, W.

    1996-07-01

    EPR spectra of single crystals of NiFe hydrogenase from Desulfovibrio vulgaris Miyazaki F were evaluated and yielded the g-tensors of the Ni center for two different states of enzyme. The g-values associated with these states are identical to those measured in frozen solutions for the ready (NiB) and the unready (NiA) form of the Ni center. Directions of the g-tensor axes were determined relative to the crystal symmetry axes. The obtained changes of g-values and tensor axes orientations between NiA and NiB can be explained by a structural difference involving modification of a cysteine sulfur ligand.

  20. The direct role of selenocysteine in [NiFeSe] hydrogenase maturation and catalysis.

    PubMed

    Marques, Marta C; Tapia, Cristina; Gutiérrez-Sanz, Oscar; Ramos, Ana Raquel; Keller, Kimberly L; Wall, Judy D; De Lacey, Antonio L; Matias, Pedro M; Pereira, Inês A C

    2017-03-20

    Hydrogenases are highly active enzymes for hydrogen production and oxidation. [NiFeSe] hydrogenases, in which selenocysteine is a ligand to the active site Ni, have high catalytic activity and a bias for H2 production. In contrast to [NiFe] hydrogenases, they display reduced H2 inhibition and are rapidly reactivated after contact with oxygen. Here we report an expression system for production of recombinant [NiFeSe] hydrogenase from Desulfovibrio vulgaris Hildenborough and study of a selenocysteine-to-cysteine variant (Sec489Cys) in which, for the first time, a [NiFeSe] hydrogenase was converted to a [NiFe] type. This modification led to severely reduced Ni incorporation, revealing the direct involvement of this residue in the maturation process. The Ni-depleted protein could be partly reconstituted to generate an enzyme showing much lower activity and inactive states characteristic of [NiFe] hydrogenases. The Ni-Sec489Cys variant shows that selenium has a crucial role in protection against oxidative damage and the high catalytic activities of the [NiFeSe] hydrogenases.

  1. Strain engineering for controlled growth of thin-film FeNi L10

    NASA Astrophysics Data System (ADS)

    Frisk, Andreas; Hase, Thomas P. A.; Svedlindh, Peter; Johansson, Erik; Andersson, Gabriella

    2017-03-01

    FeNi thin films in the L10 phase were successfully grown by magnetron sputtering on HF-etched Si≤ft(0 0 1\\right) substrates on Cu/Cu100‑x Ni x buffers. The strain of the FeNi layer, {{(c/a)}\\text{FeNi}} , was varied in a controlled manner by changing the Ni content of the Cu100‑x Ni x buffer layer from x=0~\\text{at}. % to x=90~\\text{at}. % , which influenced the common in-plane lattice parameter of the CuNi and FeNi layers. The presence of the L10 phase was confirmed by resonant x-ray diffraction measurements at various positions in reciprocal space. The uniaxial magnetocrystalline anisotropy energy {{K}\\text{U}} is observed to be smaller (around 0.35 MJ m‑3) than predicted for a perfect FeNi L10 sample, but it is larger than for previously studied films. No notable variation in {{K}\\text{U}} with strain state {{(c/a)}\\text{FeNi}} is observed in the range achieved (0.99≲ {{(c/a)}\\text{FeNi}}≲ 1.02 ), which is in agreement with theoretical predictions.

  2. Phase stability and magnetic behavior of FeCrCoNiGe high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Huang, Shuo; Vida, Ádám; Molnár, Dávid; Kádas, Krisztina; Varga, Lajos Károly; Holmström, Erik; Vitos, Levente

    2015-12-01

    We report an alternative FeCrCoNiGe magnetic material based on FeCrCoNi high-entropy alloy with Curie point far below the room temperature. Investigations are done using first-principles calculations and key experimental measurements. Results show that the equimolar FeCrCoNiGe system is decomposed into a mixture of face-centered cubic and body-centered cubic solid solution phases. The increased stability of the ferromagnetic order in the as-cast FeCrCoNiGe composite, with measured Curie temperature of 640 K, is explained using the exchange interactions.

  3. 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.

  4. In-plane magnetic anisotropies in Ni/FeMn and Ni90Fe10/FeMn exchange biased bilayers

    NASA Astrophysics Data System (ADS)

    Pires, M. J. M.; de Oliveira, R. B.; Martins, M. D.; Ardisson, J. D.; Macedo, W. A. A.

    2007-12-01

    The in-plane magnetic anisotropy in Ni/FeMn and Ni90Fe10/FeMn exchange-biased bilayers prepared by co-evaporation under molecular beam epitaxy conditions is investigated employing longitudinal magneto-optical Kerr effect (MOKE) and ferromagnetic resonance (FMR). The exchange anisotropy was induced by a magnetic field cooling immediately after the deposition of the bilayers. Besides the induced term, the presence of an additional uniaxial anisotropy in the FM layers was detected both by MOKE and FMR, and the characteristic directions of these two anisotropy terms are not coincident. The interplay between the anisotropy contributions is discussed considering micromagnetic simulations and the in-plane resonance condition for different magnetic field orientation. X-ray diffraction, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy were used to complement the characterization of the samples.

  5. Magnetic coupling of stripe domains in FePt/Ni80Fe20 bilayers

    NASA Astrophysics Data System (ADS)

    Álvarez, N. R.; Gómez, J. E.; Vásquez Mansilla, M.; Pianciola, B.; Actis, D. G.; Gilardi, G. J.; Leiva, L.; Milano, J.; Butera, A.

    2017-03-01

    Equiatomic FePt in the A1 soft magnetic phase and Ni80Fe20 (permalloy) thin films form a stripe-like magnetic domain structure above a critical thickness. This critical thickness is considerably different in the two alloys and allows us to study the influence of the magnetic coupling in the domain configuration in bilayers. Using dc magnetron sputtering techniques, we fabricated two different sets of FePt/Ni80Fe20 bilayers, keeping one thickness fixed and varying the other, and investigated the dc magnetic properties and the magnetic domain configuration of the structure. In all cases, magnetization reversal occurred at a single coercive field, indicating a relatively strong magnetic exchange coupling between both layers. The observed stripe period was also consistent with a model of spring magnet-like behavior. However, for certain values of FePt and permalloy thickness a complex nonparallel double stripe structure was found, which may be attributed to the influence of the dipolar stray field of the thicker layer on the stripe structure of the thinner film.

  6. Oxidation sulfidation resistance of Fe-Cr-Ni alloys

    DOEpatents

    Natesan, Ken; Baxter, David J.

    1984-01-01

    High temperature resistance of Fe-Cr-Ni alloy compositions to oxidative and/or sulfidative conditions is provided by the incorporation of about 1-8 wt. % of Zr or Nb and results in a two-phase composition having an alloy matrix as the first phase and a fine grained intermetallic composition as the second phase. The presence and location of the intermetallic composition between grains of the matrix provides mechanical strength, enhanced surface scale adhesion, and resistance to corrosive attack between grains of the alloy matrix at temperatures of 500.degree.-1000.degree. C.

  7. Improved oxidation sulfidation resistance of Fe-Cr-Ni alloys

    DOEpatents

    Natesan, K.; Baxter, D.J.

    1983-07-26

    High temperature resistance of Fe-Cr-Ni alloy compositions to oxidative and/or sulfidative conditions is provided by the incorporation of about 1 to 8 wt % of Zr or Nb and results in a two-phase composition having an alloy matrix as the first phase and a fine grained intermetallic composition as the second phase. The presence and location of the intermetallic composition between grains of the matrix provides mechanical strength, enhanced surface scale adhesion, and resistance to corrosive attack between grains of the alloy matrix at temperatures of 500 to 1000/sup 0/C.

  8. 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.

  9. 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.

  10. Characterization of NiFe oxyhydroxide electrocatalysts by integrated electronic structure calculations and spectroelectrochemistry

    PubMed Central

    Goldsmith, Zachary K.; Harshan, Aparna K.; Gerken, James B.; Galli, Giulia; Stahl, Shannon S.

    2017-01-01

    NiFe oxyhydroxide materials are highly active electrocatalysts for the oxygen evolution reaction (OER), an important process for carbon-neutral energy storage. Recent spectroscopic and computational studies increasingly support iron as the site of catalytic activity but differ with respect to the relevant iron redox state. A combination of hybrid periodic density functional theory calculations and spectroelectrochemical experiments elucidate the electronic structure and redox thermodynamics of Ni-only and mixed NiFe oxyhydroxide thin-film electrocatalysts. The UV/visible light absorbance of the Ni-only catalyst depends on the applied potential as metal ions in the film are oxidized before the onset of OER activity. In contrast, absorbance changes are negligible in a 25% Fe-doped catalyst up to the onset of OER activity. First-principles calculations of proton-coupled redox potentials and magnetizations reveal that the Ni-only system features oxidation of Ni2+ to Ni3+, followed by oxidation to a mixed Ni3+/4+ state at a potential coincident with the onset of OER activity. Calculations on the 25% Fe-doped system show the catalyst is redox inert before the onset of catalysis, which coincides with the formation of Fe4+ and mixed Ni oxidation states. The calculations indicate that introduction of Fe dopants changes the character of the conduction band minimum from Ni-oxide in the Ni-only to predominantly Fe-oxide in the NiFe electrocatalyst. These findings provide a unified experimental and theoretical description of the electrochemical and optical properties of Ni and NiFe oxyhydroxide electrocatalysts and serve as an important benchmark for computational characterization of mixed-metal oxidation states in heterogeneous catalysts. PMID:28265083

  11. Effect of Ti content on the microstructure and mechanical behavior of (Fe36Ni18Mn33Al13)100–xTix high entropy alloys

    SciTech Connect

    Wang, Zhangwei; Wu, Margaret; Cai, Zhonghou; Chen, Si; Baker, Ian

    2016-06-13

    The microstructure and mechanical properties studies of a series of two-phase f.c.c./B2 (ordered b.c.c.) lamellar-structured, high entropy alloys (HEA) Fe36Ni18Mn33Al13Tix with x up to 6 at. % Ti have been investigated. X-ray microanalysis in a TEM showed that the Ti resided mostly in the B2 phase. The lamellar spacing decreased significantly with increasing Ti content from 1.56 μm for the undoped alloy to 155 nm with an addition of 4 at. % Ti, leading to a sharp increase in room-temperature yield strength,σy, from 270 MPa to 953 MPa, but with a concomitant decrease in ductility from 22% elongation to 2.3%. Annealing at 1173 K for 20 h greatly increased the lamellar spacing of Fe36Ni18Mn33Al13Ti4 to 577 nm, producing a corresponding decrease in σy to 511 MPa. The yield strengths of all the doped alloys decreased significantly when tensile tested at 973 K with a concomitant increase in ductility due to softening of the B2 phase. The fracture mode changed from cleavage at room temperature to a ductile dimple-type rupture at 973 K. Lastly, the results are discussed in terms of the Hall-Petch-type relationship.

  12. oxide and FeNi alloy: product dependence on the reduction ability

    NASA Astrophysics Data System (ADS)

    Cao, Jungang; Qin, Yuyang; Li, Minglun; Zhao, Shuyuan; Li, Jianjun

    2014-12-01

    Based on the sol-gel combustion method, stoichiometric Fe3+, Mn2+, Ni2+ ions and citric acid were chosen as the initial reactants for the preparation of magnetic particles. Due to the different reduction ability of metal ions, completely different magnetic products (MnFe2O4 oxide and FeNi alloy) were obtained by heating the flakes at 600 °C under nitrogen atmosphere. MnFe2O4 particles exhibit superparamagnetic behavior at room temperature, and martensitic phase transformation is observed magnetically at 125 K for FeNi alloy particles.

  13. 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.

  14. 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.

  15. 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.

  16. An APFIM/AEM Study of Phase Decompositions in Fe-Ni Alloys at Low Temperatures

    NASA Technical Reports Server (NTRS)

    Zhang, J.; Miller, M. K.; Williams, D. B.; Goldstein, J. I.

    1992-01-01

    A combined atom probe field ion microscopy and analytical electron microscopy characterization has been performed on laboratory aged martensitic and austenitic specimens of FeNi and FeNiP alloys. These techniques revealed that the martensitic 24.1 and 28.6 at.% Ni alloys decomposed during aging for 1 year at 300 C to form face centered cubic precipitates of approx. 56 at.% Ni in a body centered cubic matrix containing approx. 20 at.% Ni. Some thin platelets were observed in the field ion micrographs of the austenitic Fe-42.9 at. % Ni alloy and the Fe-43.2 at.% Ni-0.44 at.% P alloy after aging at 400 and 350 C. Atom probe analysis revealed phosphorus clustering in the ternary alloy aged at 300 C.

  17. Structures and magnetic properties of electroless Ni multilayers on Fe/Si substrate.

    PubMed

    Chen, Wen Jauh; Hsieh, Shu Huei; Liu, Wei Long; Chen, Wan Ling

    2010-07-01

    Nanosized single and multiple layers of electroless Ni films were deposited on Fe film. The multilayer films consisting of a Fe/(Ni1 Ni2)n structure, where Ni1 and Ni2 denote various electroless Ni films deposited in plating baths with different pH values, and n denotes layer numbers and equals to 2, 4, 8, and 16, were formed by alternately changing the pH value of plating baths under controlled deposition time during the deposition process. The ensuing results showed that the boundaries between films are almost even. The deposition of various electroless Ni films on Fe film can increase the coercivity and squareness ratio of Fe film.

  18. Microporous Ni@NiO nanoparticles prepared by chemically dealloying Al3Ni2@Al nanoparticles as a high microwave absorption material

    NASA Astrophysics Data System (ADS)

    Pang, Yu; Xie, Xiubo; Li, Da; Chou, Wusheng; Liu, Tong

    2017-03-01

    The Al3Ni2@Al nanoparticles (NPs) were prepared from Ni45Al55 master alloy by hydrogen plasma-metal reaction method, and were subsequently dealloyed to produce porous Ni@NiO NPs of 36 nm. The pore size ranges from 0.7 to 1.6 nm, leading to large specific surface area of 69.5 m2/g and big pore volume of 0.507 cc/g. The saturation magnetization (MS) and coercivity (HC) of the microporous Ni@NiO NPs are 11.5 emu/g and 5.2 Oe. They exhibit high microwave absorption performance with a minimum reflection coefficient (RC) of -86.9 dB and an absorption bandwidth of 2.6 GHz (RC≤-10 dB) at thickness of 4.5 mm. The enhanced microwave absorption properties are attributed to the synergistic effect of the magnetic Ni core and dielectric NiO shell, and the micropore architecture. The NPs with micropore morphology and core/shell structure open a new way to modify the microwave absorption performance.

  19. 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.

  20. Nanoscale design of Ni-Al shape memory alloys.

    PubMed

    Subramaniyan, Arun K; Sun, C T

    2009-02-25

    Nanoscale design of Ni-Al alloys was performed to optimize the phase transformation behavior. The distribution of nickel and aluminum atoms was identified as a key parameter in the phase transformation process. A design criterion based on thermal expansion asymmetry was proposed. The effectiveness of the design criterion was validated using molecular dynamics simulations.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys

    DOE PAGES

    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

  6. An advanced Ni-Fe layered double hydroxide electrocatalyst for water oxidation.

    PubMed

    Gong, Ming; Li, Yanguang; Wang, Hailiang; Liang, Yongye; Wu, Justin Z; Zhou, Jigang; Wang, Jian; Regier, Tom; Wei, Fei; Dai, Hongjie

    2013-06-12

    Highly active, durable, and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions, including water-splitting and rechargeable metal-air batteries. Here, we report the synthesis of ultrathin nickel-iron layered double hydroxide (NiFe-LDH) nanoplates on mildly oxidized multiwalled carbon nanotubes (CNTs). Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-LDH. The crystalline NiFe-LDH phase in nanoplate form is found to be highly active for oxygen evolution reaction in alkaline solutions. For NiFe-LDH grown on a network of CNTs, the resulting NiFe-LDH/CNT complex exhibits higher electrocatalytic activity and stability for oxygen evolution than commercial precious metal Ir catalysts.

  7. 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.

  8. Novel H2-oxidizing [NiFeSe]hydrogenase from Desulfovibrio vulgaris Miyazaki F.

    PubMed

    Nonaka, Kyoshiro; Nguyen, Nga T; Yoon, Ki-Seok; Ogo, Seiji

    2013-04-01

    [NiFeSe]hydrogenases are promising biocatalysts in H2-based technology due to their high catalytic activity and O2-stability. Here, we report purification and characterization of a new membrane-associated [NiFeSe]hydrogenase from Desulfovibrio vulgaris Miyazaki F ([NiFeSe]DvMF). The [NiFeSe]DvMF was composed of two subunits, corresponding to a large subunit of 58.3 kDa and a small subunit of 29.3 kDa determined by SDS-PAGE. Unlike conventional [NiFeSe]hydrogenases having catalytic bias toward H2-production, the [NiFeSe]DvMF showed 11-fold higher specific activity of H2-oxidation (2444 U/mg) than that of H2-production (217 U/mg). At the optimal reaction temperature of the enzyme (65°C), the specific activity of H2-oxidation could reach up to 21,553 U/mg. Amperometric assays of the [NiFeSe]DvMF clearly indicated that the enzyme had a remarkable O2-stability. According to the amino acid sequence alignment, the conserved cysteine residue at position 281 in medial cluster of other [NiFeSe]hydrogenases was specifically replaced by a serine residue (Ser281) in the [NiFeSe]DvMF. These results indicate that the [NiFeSe]DvMF can play as a new H2-oxidizing and O2-stable biocatalyst, along with providing helpful insights into the structure-function relationship of [NiFeSe]hydrogenases.

  9. 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.

  10. Metastable Phases of Rapidly Solidified Al-Rich Al-Fe Alloys

    DTIC Science & Technology

    1984-01-01

    same contrast. 20 FIGURE 9. Convergent beam diffraction pattern taken from a single crystal globular "S" phase. 21 FIGURE 10. The flower -like phase. 21...FIGURE 11. Convergent beam diffraction pattern obtained from the flower -like phase. 21 iii "- "’., % i ’ % " PAGE FIGURE 12. At-i wt.% Fe. Cellular...any of the previously reported aluminum-rich phases (Al3Fe, AlxFe, AI6Fe, A19Fe2, or AlmFe) [2,3]. An additional flower - shaped phase was detected in

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Fe Segregation Effects on Grain Boundary Migration in Al

    NASA Astrophysics Data System (ADS)

    Mendelev, Mikhail; Srolovitz, David; Ackland, Graeme; Han, Seungwu

    2004-03-01

    We investigate the effect of Fe impurities on grain boundary migration in Al. We fit a new interatomic potential to experimental data and our first principles results. This potential is validated by comparing simulated and experimental liquid Al-Fe alloy structure factors. This potential was used to simulate boundary migration in pure Al. The boundary velocity vs. driving force data at several temperatures were used to extract the boundary mobility and the activation energy for boundary migration. The activation energy was found to be at least an order of magnitude smaller than that obtained from experiment. This discrepancy is presumably associated with impurities in the Al samples. Therefore, we examined the effect of Fe on boundary migration in Al by determining the heat of segregation and the Fe diffusivity in Al as input to the Cahn-Lücke-Stüwe analytical impurity drag model. This analysis showed that even extremely small quantities of Fe (less than 1 ppm) in Al can reduce the grain boundary mobility by two orders of magnitude at T=723 K and even more at lower T, consistent with the extant experimental data.

  18. 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.

  19. Synthesis Mechanism and Strengthening Effects of Laminated NiAl by Reaction Annealing

    NASA Astrophysics Data System (ADS)

    Du, Yan; Fan, Guohua; Wang, Qingwei; Geng, Lin

    2017-01-01

    N iA l with a laminated microstructure has been fabricated by reaction annealing of Ni-Al system at 1473 K (1200 °C). The laminated NiAl shows heterogeneity of chemical gradient and bimodal grain size distribution. The objective of this study is to investigate the synthesis mechanism and the strengthening effect of this laminated NiAl, therefore to promote further application of NiAl as a high-temperature structural material. Heat treatments at 1473 K (1200 °C) and subsequent characterization were utilized to study the synthesis mechanism. It shows that in original Al regions NiAl nuclei precipitate from Al(Ni) liquid phase and form fine-grained NiAl layers, whereas in original Ni regions NiAl nuclei precipitate from Ni(Al) saturated solution through diffusion and form coarse-grained NiAl layers. Moreover, heterogeneity of chemical gradient is generated through diffusion during annealing. The mechanical properties of laminated NiAl have also been studied via nanoindentation method. It shows that both chemical gradient and bimodal grain size distribution could strengthen the laminated NiAl.

  20. 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.

  1. 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.

  2. 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.

  3. Strongly Coupled FeNi Alloys/NiFe2O4@Carbonitride Layers-Assembled Microboxes for Enhanced Oxygen Evolution Reaction.

    PubMed

    Ma, Yangde; Dai, Xiaoping; Liu, Mengzhao; Yong, Jiaxi; Qiao, Hongyan; Jin, Axiang; Li, Zhanzhao; Huang, Xingliang; Wang, Hai; Zhang, Xin

    2016-12-21

    Hydrogen produced from electrocatalytic water splitting is a promising route due to the sustainable powers derived from the solar and wind energy. However, the sluggish kinetics at the anode for water splitting makes the highly effective and inexpensive electrocatalysts desirable in oxygen evolution reaction (OER) by structure and composition modulations. Metal-organic frameworks (MOFs) have been intensively used as the templates/precursors to synthesize complex hollow structures for various energy-related applications. Herein, an effective and facile template-engaged strategy originated from bimetal MOFs is developed to construct hollow microcubes assembled by interconnected nanopolyhedron, consisting of intimately dominant FeNi alloys coupled with a small NiFe2O4 oxide, which was confined within carbonitride outer shell (denoted as FeNi/NiFe2O4@NC) via one-step annealing treatment. The optimized FeNi/NiFe2O4@NC exhibits excellent electrocatalytic performances toward OER in alkaline media, showing 10 mA·cm(-2) at η = 316 mV, lower Tafel slope (60 mV·dec(-1)), and excellent durability without decay after 5000 CV cycles, which also surpasses the IrO2 catalyst and most of non-noble catalysts in the OER, demonstrating a great perspective. The superior OER performance is ascribed to the hollow interior for fast mass transport, in situ formed strong coupling between FeNi alloys and NiFe2O4 for electron transfer, and the protection of carbonitride layers for long stability.

  4. 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.

  5. Large magnetostriction in directionally solidified FeGa and FeGaAl alloys

    NASA Astrophysics Data System (ADS)

    Srisukhumbowornchai, N.; Guruswamy, S.

    2001-12-01

    The magnetostriction of Fe-x at. % Ga (x=15, 20, and 27.5) was measured, for alloys processed under different directional solidification conditions, and the effect of partial substitution of Ga with Al on the magnetostriction of the alloys was examined. Magnetostriction measurements were carried out at different prestress levels varying from 0 to 55 MPa. Ga additions in the range of 15-27.5 at. % Ga in Fe were found to improve the magnetostriction of the disordered bcc phase of Fe by as much as 1 order of magnitude. The applied fields for saturation magnetostriction and the hysteresis observed were small. Magnetostriction values as high as 271×10-6 were obtained in polycrystalline Fe-27.5 at. % Ga rods prepared using a directional growth (DG) process at a growth rate of 22.5 mm/h. This process, which is essentially a seedless vertical Bridgman technique, resulted in near [001] textured polycrystalline Fe-Ga alloys. The preferred [001] crystallographic orientation of the DG alloys was approximately 14° away from the rod direction. For Ga contents between 15 and 27.5 at. % in Fe, the Ga atoms increase the Fe-Fe spacing in the disordered bcc (A2) phase and reduce the magnetic moment of Fe. Substitution of Ga with Al has a significant effect on the magnetostriction of the Fe-Ga alloys. Small substitution of 5 at. % Al for Ga in the Fe-20 at. % Ga alloy increases the magnetostriction in Fe, and the value is slightly larger than that of the Fe-20 at. % Ga alloy. A higher substitution amount of Al tends to decrease the magnetostriction.

  6. 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.

  7. Segregation-Induced Subsurface Restructuring of FeAl(100)

    NASA Astrophysics Data System (ADS)

    Kottche, M.; Graupner, H.; Hammer, L.; Heinz, K.; Zehner, D. M.

    1996-03-01

    For FeAl, the stacking sequence in the [100] direction of the bulk crystal (CsCl structure) consists of alternating, single element planes. After sputtering, the selvedge region is depleted in Al. Following annealing to 350 ^circC, Al segregates to the surface region and a c(2 x 2) structure develops.(H. Graupner, L. Hammer, K. Müller, and D. M. Zehner, Surf. Sci. 322 (1995) 103. Research is sponsored by the *University of Erlangen-Nürnberg, Germany and DAAD, and the **Division of Materials Sciences, U.S. Department of Energy, under contract DE-AC05-84OR21400 with Lockheed Martin Energy Systems, Inc.) We have used low-energy electron diffraction (LEED) and Auger electron spectroscopy to investigate the structure and composition of this surface. From a detailed LEED I-V analysis, it has been determined that the subsurface region of the (100) surface orders with annealing, to form a stable Fe_3Al slab which is capped by an Al top layer and acts as an interface to the bulk FeAl. Within the limits of error, the interfacial Fe_3Al is similar to the bulk phase with some slight geometric rippling of the layers containing both elements. Annealing to higher temperatures leads to additional Al diffusion and eliminates the restructuring, resulting in a (1 x 1) phase.

  8. 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.

  9. 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.

  10. Magnetization damping of an L10-FeNi thin film with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Ogiwara, Misako; Iihama, Satoshi; Seki, Takeshi; Kojima, Takayuki; Mizukami, Shigemi; Mizuguchi, Masaki; Takanashi, Koki

    2013-12-01

    We studied on the magnetic damping constants (α) for L10-FeNi and disordered FeNi employing three kinds of measurement methods. An L10-FeNi thin film exhibited high perpendicular magnetic anisotropy of 7.1 × 106 erg cm-3. At magnetic fields (H) lower than 2 kOe, α was estimated to be 0.091 ± 0.003. However, it was reduced down to 0.013 ± 0.001 with H, indicating that extrinsic contributions enhance α. The intrinsic α = 0.013 ± 0.001 was comparable to α = 0.009 ± 0.002 for the disordered FeNi. This suggests that L10-FeNi is a candidate achieving high magnetic anisotropy and low magnetization damping simultaneously.

  11. Structural and magnetic properties of FeNi thin films fabricated on amorphous substrates

    NASA Astrophysics Data System (ADS)

    Tashiro, T. Y.; Mizuguchi, M.; Kojima, T.; Koganezawa, T.; Kotsugi, M.; Ohtsuki, T.; Takanashi, K.

    2015-05-01

    FeNi films were fabricated by sputtering and rapid thermal annealing on thermally amorphous substrates to realize the formation of an L10-FeNi phase by a simple method. Structural and magnetic properties of FeNi films were investigated by varying the annealing temperature. L10-FeNi superlattice peaks were not observed in X-ray diffraction patterns, indicating no formation of L10-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.

  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. Switching characteristics of NiFe free layer with respect to hard axis field

    NASA Astrophysics Data System (ADS)

    Lee, Young-Woo; Yoon, Sang-Min; Kim, Cheolgi; Kim, Chong-Oh

    2004-05-01

    The switching characteristics of NiFe free layers is investigated with respect to hard axis field in magnetic tunnel junctions. An AC magnetic field is swept along easy axis with a Helmholtz coil. As the hard axis field increases, the coercivity and the squareness of magnetoresistance loops decrease. When the hard axis field is larger than +/-16.5Oe, the NiFe free layer is saturated in the hard direction and switching coercivity decreases to the constant value of 2.6Oe. Switching loops of NiFe layer shift as the NiFe free layer is magnetized along the hard direction. This shift is induced by the stray field of the NiFe free layer.

  14. Electrochemical sensing behaviour of Ni doped Fe{sub 3}O{sub 4} nanoparticles

    SciTech Connect

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

    2014-01-28

    Ni doped Fe{sub 3}O{sub 4} 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 Fe{sub 3}O{sub 4} nanoparticles. The optical property of Ni doped Fe{sub 3}O{sub 4} nanoparticles were studied by DRS UV-Visible analysis. The electrochemical sensing property of pure and Ni doped Fe{sub 3}O{sub 4} nanoparticles were examined using uric acid as an analyte. The obtained results indicated that the Ni doped Fe{sub 3}O{sub 4} nanoparticles exhibited higher electrocatalytic activity towards uric acid.

  15. Unusual high-spin Fe5 +-Ni3 + state and strong ferromagnetism in the mixed perovskite SrFe0.5Ni0.5O3

    NASA Astrophysics Data System (ADS)

    Fan, Fengren; Li, Zhengwei; Zhao, Zhen; Yang, Ke; Wu, Hua

    2016-12-01

    The charge-spin-orbital state plays a vital role in correlated oxides with mixed transition-metal elements, and it is often a matter of debate. Here, we address this issue for the newly synthesized unusual high-valence perovskite SrFe1 -xNixO3 , using an analysis of crystal-field level diagrams, density functional calculations, and Monte Carlo simulations. We have identified the formal high-spin Fe5 +(t2g 3, S =3 /2 ) and high-spin Ni3 +(t2g 5eg2 , S =3 /2 ) state for SrFe0.5Ni0.5O3 , rather than the previously suggested high-spin Fe4 +(t2g 3eg1, S =2 ) and low-spin Ni4 + (t2g 6, S =0 ) state. Moreover, our model and the present results well explain the observed small lattice variation of SrFe1 -xNixO3 (0 ≤x ≤0.5 ) and the above room temperature ferromagnetic order in SrFe0.5Ni0.5O3 regardless of a Fe-Ni atomic order or disorder.

  16. 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.

  17. High temperature oxidation of beta-NiAl

    NASA Technical Reports Server (NTRS)

    Koychak, J. K.; Mitchell, T. E.; Smialek, J. L.

    1985-01-01

    The oxidation of single crystal beta-NiAl has been studied primarily using electron microscopy. Oriented metastable Al2O3 phases form during transient oxidation at 800 C. Specific orientation relationships exist on all metal orientations studied and are a result of the small mismatch along aligned close-packed directions in the cation sublattices of the metal and oxide. Transformation of the metastable Al2O3 phases at 1100 C results in an oxide morphology described as the 'lacey' structure of alpha-Al2O3 scales. This structure results from impingement of oriented patches of alpha-Al2O3 as the transformation initiates and moves radially parallel to the surface. Scale growth occurs by diffusion along high angle grain boundaries. A drastic reduction in oxidation rate accompanies the change in oxide morphology.

  18. Development of FeNiMoB thin film materials for microfabricated magnetoelastic sensors

    SciTech Connect

    Liang Cai; Gooneratne, Chinthaka; Cha, Dongkyu; Chen Long; Kosel, Jurgen; Gianchandani, Yogesh

    2012-12-01

    Metglas{sup TM} 2826MB foils of 25-30 {mu}m thickness with the composition of Fe{sub 40}Ni{sub 38}Mo{sub 4}B{sub 18} have been used for magnetoelastic sensors in various applications over many years. This work is directed at the investigation of {approx}3 {mu}m thick iron-nickel-molybdenum-boron (FeNiMoB) thin films that are intended for integrated microsystems. The films are deposited on Si substrate by co-sputtering of iron-nickel (FeNi), molybdenum (Mo), and boron (B) targets. The results show that dopants of Mo and B can significantly change the microstructure and magnetic properties of FeNi materials. When FeNi is doped with only Mo its crystal structure changes from polycrystalline to amorphous with the increase of dopant concentration; the transition point is found at about 10 at. % of Mo content. A significant change in anisotropic magnetic properties of FeNi is also observed as the Mo dopant level increases. The coercivity of FeNi films doped with Mo decreases to a value less than one third of the value without dopant. Doping the FeNi with B together with Mo considerably decreases the value of coercivity and the out-of-plane magnetic anisotropy properties, and it also greatly changes the microstructure of the material. In addition, doping B to FeNiMo remarkably reduces the remanence of the material. The film material that is fabricated using an optimized process is magnetically as soft as amorphous Metglas{sup TM} 2826MB with a coercivity of less than 40 Am{sup -1}. The findings of this study provide us a better understanding of the effects of the compositions and microstructure of FeNiMoB thin film materials on their magnetic properties.

  19. Development of FeNiMoB thin film materials for microfabricated magnetoelastic sensors

    NASA Astrophysics Data System (ADS)

    Liang, Cai; Gooneratne, Chinthaka; Cha, Dongkyu; Chen, Long; Gianchandani, Yogesh; Kosel, Jurgen

    2012-12-01

    MetglasTM 2826MB foils of 25-30 μm thickness with the composition of Fe40Ni38Mo4B18 have been used for magnetoelastic sensors in various applications over many years. This work is directed at the investigation of ˜3 μm thick iron-nickel-molybdenum-boron (FeNiMoB) thin films that are intended for integrated microsystems. The films are deposited on Si substrate by co-sputtering of iron-nickel (FeNi), molybdenum (Mo), and boron (B) targets. The results show that dopants of Mo and B can significantly change the microstructure and magnetic properties of FeNi materials. When FeNi is doped with only Mo its crystal structure changes from polycrystalline to amorphous with the increase of dopant concentration; the transition point is found at about 10 at. % of Mo content. A significant change in anisotropic magnetic properties of FeNi is also observed as the Mo dopant level increases. The coercivity of FeNi films doped with Mo decreases to a value less than one third of the value without dopant. Doping the FeNi with B together with Mo considerably decreases the value of coercivity and the out-of-plane magnetic anisotropy properties, and it also greatly changes the microstructure of the material. In addition, doping B to FeNiMo remarkably reduces the remanence of the material. The film material that is fabricated using an optimized process is magnetically as soft as amorphous MetglasTM 2826MB with a coercivity of less than 40 Am-1. The findings of this study provide us a better understanding of the effects of the compositions and microstructure of FeNiMoB thin film materials on their magnetic properties.

  20. 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.

  1. First-principles-based kinetic Monte Carlo studies of diffusion of hydrogen in Ni–Al and Ni–Fe binary alloys

    DOE PAGES

    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

  2. Tailoring the magnetoimpedance effect of NiFe/Ag multilayer

    NASA Astrophysics Data System (ADS)

    Corrêa, M. A.; Bohn, F.; Chesman, C.; da Silva, R. B.; Viegas, A. D. C.; Sommer, R. L.

    2010-07-01

    The magnetoimpedance (MI) effect was investigated in NiFe/Ag multilayered (ML) and ML/SiO2/Ag/SiO2/ML structured multilayered (SD) ferromagnetic films grown by magnetron sputtering. The MI measurements were performed with an impedance analyzer over a wide frequency range, from 10 MHz to 1.8 GHz. Sample geometries are mainly responsible for the different MI behaviours and by considering the entire frequency range, distinct mechanisms responsible for MI changes were associated. For the ML sample, a maximum value of 80%, associated with the appearance of ferromagnetic resonance (FMR), was reached at around 1 GHz. For the SD sample, the striking feature is the existence of two distinct frequency ranges with high MI% values of 80% at around 100 MHz, related to the skin and magnetoinductive effects, and of 120% at around 1 GHz, associated with the strong skin and FMR effect.

  3. Theory of the Invar Effect in FeNi Alloy

    NASA Astrophysics Data System (ADS)

    Kakehashi, Yoshiro

    1981-07-01

    Anomalous thermal expansion of FeNi alloy is calculated on the basis of Liberman-Pettifor’s virial theorem and the full single site approximation in the functional integral method. Results explain well the Invar effect. In general, the electronic contribution to the thermal expansion consists of three terms, i.e. the positive term proportional to the specific heat, the local moment term caused by the temperature variation of the amplitudes of the local moments and the term due to the s-d charge transfer. It is verified that the large negative thermal expansion of the electron system is caused by the local moment term. The lattice parameter, the bulk modulus at T{=}0 K and other magnetic quantities are also calculated, which are consistent with the experimental results.

  4. 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.

  5. 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.

  6. 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.

  7. Study on NiO/Fe interface with X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Feng, Chun; Zhang, Jing-Yan; Teng, Jiao; Wang, Fu-Ming

    2010-12-01

    Different monolayers (ML) of Fe atoms were deposited on NiO (001) substrates or NiO underlayers using molecular beam epitaxy (MBE), pulse laser deposition (PLD), and magnetron sputtering (MS). The magnetic properties and microstructure of the films were studied. The apparent magnetic dead layer (MDL) is found to exist at the NiO/Fe interfaces of the MBE sample (about 2 ML MDL), the PLD sample (about 3 ML MDL), and the MS sample (about 4 ML MDL). X-ray photoelectron spectroscopy indicates the presence of ionic Fe (Fe2+ or Fe3+) and metallic Ni at the NiO/Fe interfaces, which may be due to the chemical reactions between Fe and NiO layers. This also leads to the formation of MDL. The thickness of the MDL and the reaction products are related with the deposition energy of the atoms on the substrates. The interfacial reactions are effectively suppressed by inserting a thin Pt layer at the NiO/Fe interface.

  8. Exchange interaction at the interface of Fe-NiO nanocomposites

    SciTech Connect

    Pati, S.P.; Bhushan, B.

    2010-12-15

    Fe-NiO nanocomposites with Fe to NiO ratio 20:80, 30:70 and 50:50 were prepared by a chemical route. X-ray diffraction and TEM measurements showed the presence of {alpha}-Fe and NiO phases in the prepared nanocomposites having an average crystallite size 17 nm. HRTEM image showed a structurally disordered phase at the Fe-NiO interface. Moessbauer spectra of the nanocomposites consist of a doublet along with a sextet corresponding to relaxed and blocked {alpha}-Fe phases, respectively. The dc magnetization measurements in field-cooled condition show a shift of hysteresis loop and an enhancement of coercive field at low temperature confirming the presence of exchange bias at Fe-NiO interfaces. The irreversibility observed in the FC and ZFC magnetization measurements also points to exchange bias effect. -- Graphical abstract: Fe-NiO nanocomposites exhibited some structural disordered region at the interface as revealed by HRTEM. A prominent shift in the hysteresis loops in field cooled condition confirmed the presence of exchange bias at Fe-NiO interfaces. The irreversibility observed in M-T measurements also points to exchange bias effect. Display Omitted

  9. 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

  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. 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.

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

    SciTech Connect

    Ishiyama, S.; Eto, M.; Mishima, Y.; Miura, S.; Suzuki, T.

    1995-12-31

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

  13. The melting curve of Ni to 125 GPa: implications for Earth's Fe rich core alloy

    NASA Astrophysics Data System (ADS)

    Lord, O. T.; Wood, I. G.; Dobson, D. P.; Vocadlo, L.; Thomson, A. R.; Wann, E.; Wang, W.; Edgington, A.; Morard, G.; Mezouar, N.; Walter, M. J.

    2014-12-01

    The melting curve of Ni has been determined to 125 GPa using laser-heated diamond anvil cell (LH-DAC) experiments and two melting criteria: the appearance of liquid diffuse scattering (LDS) during in situ X-ray diffraction (XRD) and simultaneous plateaux in temperature vs. laser power functions [1]. Our melting curve (Fig. 1) is in good agreement with most theoretical studies [e.g. 2] and the available shock wave data (Fig. 2). It is, however, dramatically steeper than the previous off-line LH-DAC studies in which the determination of melting was based on the visual observation of motion aided by the laser speckle method [e.g. 3]. We estimate the melting point of Ni at the inner-core boundary (ICB; 330 GPa) to be 5800±700 K (2σ), ~2500 K higher than the estimate based on the laser speckle method [3] and within error of Fe (6230±500 K) as determined in a similar in situ LH-DAC study [4]. We find that laser speckle based melting curves coincide with the onset of rapid sub-solidus recrystallization, suggesting that visual observations of motion may have misinterpreted dynamic recrystallization as melt convection. Our new melting curve suggests that the reduction in ICB temperature due to the alloying of Ni with Fe is likely to be significantly smaller than would be expected had the earlier experimental Ni melting studies been correct. We have applied our methodology to a range of other transition metals (Mo, Ti, V, Cu). In the case of Mo, Ti and V the melting curves are in good agreement with the shock compression and theoretical melting studies but hotter and steeper than those based on the laser speckle method, as with Ni. Cu is an exception in which all studies agree, including those employing the laser speckle method. These results go a long way toward resolving the the long-standing controversy over the phase diagrams of the transition metals as determined from static LH-DAC studies on the one hand, and theoretical and dynamic compression studies on the other

  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. 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.

  16. High ferromagnetic transition temperature in multiferroic BiFe0.95Ni0.05O3 compound

    NASA Astrophysics Data System (ADS)

    Yoo, Y. J.; Hwang, J. S.; Lee, Y. P.; Park, J. S.; Kang, J.-H.; Kim, J.; Lee, B. W.; Seo, M. S.

    2013-10-01

    We have prepared BiFe0.95Ni0.05O3 by the standard solid-state reaction and rapid sintering. The structural analysis by x-ray diffraction for BiFe0.95Ni0.05O3 shows rhombohedral perovskite structure (R3c), and lattice constants a and c of BiFe0.95Ni0.05O3 are slightly increased as compared to those of BiFeO3. The Raman studies present the increase of oxygen vacancy by the Ni2+ substitution. The magnetic properties of BiFe0.95Ni0.05O3 are greatly improved, owing to the enhanced ferromagnetic interaction caused by the Fe/Ni coupling. BiFe0.95Ni0.05O3 sample is ferromagnetic with a cluster-glass state unlike the antiferromagnetic BiFeO3-based compounds.

  17. 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

  18. Distal [FeS]-Cluster Coordination in [NiFe]-Hydrogenase Facilitates Intermolecular Electron Transfer

    PubMed Central

    Petrenko, Alexander; Stein, Matthias

    2017-01-01

    Biohydrogen is a versatile energy carrier for the generation of electric energy from renewable sources. Hydrogenases can be used in enzymatic fuel cells to oxidize dihydrogen. The rate of electron transfer (ET) at the anodic side between the [NiFe]-hydrogenase enzyme distal iron–sulfur cluster and the electrode surface can be described by the Marcus equation. All parameters for the Marcus equation are accessible from Density Functional Theory (DFT) calculations. The distal cubane FeS-cluster has a three-cysteine and one-histidine coordination [Fe4S4](His)(Cys)3 first ligation sphere. The reorganization energy (inner- and outer-sphere) is almost unchanged upon a histidine-to-cysteine substitution. Differences in rates of electron transfer between the wild-type enzyme and an all-cysteine mutant can be rationalized by a diminished electronic coupling between the donor and acceptor molecules in the [Fe4S4](Cys)4 case. The fast and efficient electron transfer from the distal iron–sulfur cluster is realized by a fine-tuned protein environment, which facilitates the flow of electrons. This study enables the design and control of electron transfer rates and pathways by protein engineering. PMID:28067774

  19. 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.

  20. Microstructure and magnetic properties of mechanically alloyed FeSiBAlNi (Nb) high entropy alloys

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Zheng, Zhou; Xu, Jing; Wang, Yan

    2014-04-01

    In this paper, the effects of milling duration and composition on the microstructure and magnetic properties of equi-atomic FeSiBAlNi and FeSiBAlNiNb high entropy alloys during mechanical alloying have been investigated using X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy and alternating gradient magnetometry. The amorphous high entropy alloys have been successfully fabricated using the mechanical alloying method. The results show that the Nb addition prolongs the milling time for the formation of the fully FeSiBAlNi amorphous phase and decreases the glass forming ability. However, FeSiBAlNiNb amorphous high entropy alloy has the higher thermal stability and heat resisting properties. Moreover, the as-milled FeSiBAlNi(Nb) powders are soft-magnetic materials indicated by their low coercivity. The saturation magnetization of the as-milled FeSiBAlNi(Nb) powders decreases with prolonging of the milling time and shows the lowest value when the amorphous high entropy alloys are formed. It suggests that the as-milled products with solid solution phases show the better soft-magnetic properties than those with fully amorphous phases. The Nb addition does not improve the soft-magnetic properties of the FeSiBAlNi high entropy alloys. Rather, both amorphous high entropy alloys have similar soft-magnetic properties after a long milling time.

  1. FeNi-based magnetic layered nanostructures: Magnetic properties and giant magnetoimpedance

    NASA Astrophysics Data System (ADS)

    Kurlyandskaya, G. V.; Svalov, A. V.; Fernandez, E.; Garcia-Arribas, A.; Barandiaran, J. M.

    2010-05-01

    Magnetic properties and the magnetoimpedance (MI) effect were studied for a series of [Fe20Ni80/Ti]n/Fe20Ni80 (n=0 to 5) nanostructures, prepared by dc magnetron sputtering. The thickness of the FeNi layers was selected as 170 nm in order to avoid the appearance of the "transcritical" state that takes place for thicker layers. First, the influence of the Ti layer thickness was determined for n=1 trilayers, with Ti layers ranging from 2 to 20 nm. The minimum coercivity corresponded to a Ti layer of about 6 nm. Second, the magnetic properties and MI responses were studied for different [FeNi/Ti]n/FeNi structures at a fixed Ti layer thickness of 6 nm. The complex impedance was measured for a frequency range of 1-300 MHz. The highest value of the MI was obtained in the sample [FeNi/Ti]5/FeNi with the largest total thickness.

  2. 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.

  3. 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.

  4. 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

  5. Enhanced and broadband microwave absorption of flake-shaped Fe and FeNi composite with Ba ferrites

    NASA Astrophysics Data System (ADS)

    Li, Wangchang; Lv, Junjun; Zhou, Xiang; Zheng, Jingwu; Ying, Yao; Qiao, Liang; Yu, Jing; Che, Shenglei

    2017-03-01

    In order to achieve a broad bandwidth absorber at high frequency, the composites of M-type ferrite BaCo1.0Ti1.0Fe10O19 (BaM) with flaked carbonyl iron powders (CIP) and flaked Fe50Ni50 were prepared to optimize the surface impedance in broadband frequency, respectively. The diameter of the flaked carbonyl iron powders (CIP) and Fe50Ni50 is in the range of 5-10 μm and 10-20 μm and the thickness of the CIP and Fe50Ni50 is close to 200 nm and 400 nm, respectively. The complex permeability and permittivity show that the addition of BaM obviously reduces the values of real part of permittivity and imaginary part of the permeability which can enhance the matched-wave-impedance. The absorption bands less than -10 dB of CIP-BaM and FeNi-BaM absorber approach to 5.5 GHz (5.7-11.2 GHz) and 7 GHz (11-18 GHz) at 1.5 mm. However, the bands of CIP and FeNi are only 1.9 GHz (4.7-6.6 GHz) and 2.1 GHz (4.0-6.1 GHz). Hence, the electromagnetic match property is greatly improved by BaM ferrites, and this composite shows a broaden absorption band.

  6. 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.

  7. 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.

  8. 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.

  9. Supergene neoformation of Pt-Ir-Fe-Ni alloys: multistage grains explain nugget formation in Ni-laterites

    NASA Astrophysics Data System (ADS)

    Aiglsperger, Thomas; Proenza, Joaquín A.; Font-Bardia, Mercè; Baurier-Aymat, Sandra; Galí, Salvador; Lewis, John F.; Longo, Francisco

    2016-11-01

    Ni-laterites from the Dominican Republic host rare but extremely platinum-group element (PGE)-rich chromitites (up to 17.5 ppm) without economic significance. These chromitites occur either included in saprolite (beneath the Mg discontinuity) or as `floating chromitites' within limonite (above the Mg discontinuity). Both chromitite types have similar iridium-group PGE (IPGE)-enriched chondrite normalized patterns; however, chromitites included in limonite show a pronounced positive Pt anomaly. Investigation of heavy mineral concentrates, obtained via hydroseparation techniques, led to the discovery of multistage PGE grains: (i) Os-Ru-Fe-(Ir) grains of porous appearance are overgrown by (ii) Ni-Fe-Ir and Ir-Fe-Ni-(Pt) phases which are overgrown by (iii) Pt-Ir-Fe-Ni mineral phases. Whereas Ir-dominated overgrowths prevail in chromitites from the saprolite, Pt-dominated overgrowths are observed within floating chromitites. The following formation model for multistage PGE grains is discussed: (i) hypogene platinum-group minerals (PGM) (e.g. laurite) are transformed to secondary PGM by desulphurization during serpentinization; (ii) at the stages of serpentinization and/or at the early stages of lateritization, Ir is mobilized and recrystallizes on porous surfaces of secondary PGM (serving as a natural catalyst) and (iii) at the late stages of lateritization, biogenic mediated neoformation (and accumulation) of Pt-Ir-Fe-Ni nanoparticles occurs. The evidence presented in this work demonstrates that in situ growth of Pt-Ir-Fe-Ni alloy nuggets of isometric symmetry is possible within Ni-laterites from the Dominican Republic.

  10. s-process nucleosynthesis in massive stars: new results on {sup 60}Fe, {sup 62}Ni and {sup 64}Ni

    SciTech Connect

    Domingo-Pardo, C.; Dillmann, I.; Faestermann, T.; Korschinek, G.; Lachner, J.; Maiti, M.; Poutivtsev, M.; Rugel, R.; Giesen, U.; Nolte, R.; Goerres, J.; Uberseder, E.; Wiescher, M.; Heil, M.; Reifarth, R.; Horn, S.; Koechli, S.; Neuhausen, J.; Schumann, D.; Kaeppeler, F.

    2009-01-28

    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,{gamma}) 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 {sup 60}Fe, {sup 62}Ni and {sup 64}Ni are reported. {sup 60}Fe is mostly produced during the short convective C shell burning phase, where peak densities of {approx}10{sup 11} cm{sup -3} are reached, prior to the SN explosion. The stellar (n,{gamma}) cross section of {sup 60}Fe could be measured with a 1 {mu}g 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 {sup 62}Ni, whereas in this case, the number of {sup 63}Ni nuclei produced were determined via accelerator mass spectroscopy at the Maier-Leibnitz-Laboratorium in Garching/Munich. The (n,{gamma}) cross section of {sup 64}Ni 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 lowbar TOF of CERN for the future campaign in 2009.

  11. hypD as a marker for [NiFe]-hydrogenases in microbial communities of surface waters.

    PubMed

    Beimgraben, Christian; Gutekunst, Kirstin; Opitz, Friederike; Appel, Jens

    2014-06-01

    Hydrogen is an important trace gas in the atmosphere. Soil microorganisms are known to be an important part of the biogeochemical H2 cycle, contributing 80 to 90% of the annual hydrogen uptake. Different aquatic ecosystems act as either sources or sinks of hydrogen, but the contribution of their microbial communities is unknown. [NiFe]-hydrogenases are the best candidates for hydrogen turnover in these environments since they are able to cope with oxygen. As they lack sufficiently conserved sequence motifs, reliable markers for these enzymes are missing, and consequently, little is known about their environmental distribution. We analyzed the essential maturation genes of [NiFe]-hydrogenases, including their frequency of horizontal gene transfer, and found hypD to be an applicable marker for the detection of the different known hydrogenase groups. Investigation of two freshwater lakes showed that [NiFe]-hydrogenases occur in many prokaryotic orders. We found that the respective hypD genes cooccur with oxygen-tolerant [NiFe]-hydrogenases (groups 1 and 5) mainly of Actinobacteria, Acidobacteria, and Burkholderiales; cyanobacterial uptake hydrogenases (group 2a) of cyanobacteria; H2-sensing hydrogenases (group 2b) of Burkholderiales, Rhizobiales, and Rhodobacterales; and two groups of multimeric soluble hydrogenases (groups 3b and 3d) of Legionellales and cyanobacteria. These findings support and expand a previous analysis of metagenomic data (M. Barz et al., PLoS One 5:e13846, 2010, http://dx.doi.org/10.1371/journal.pone.0013846) and further identify [NiFe]-hydrogenases that could be involved in hydrogen cycling in aquatic surface waters.

  12. hypD as a Marker for [NiFe]-Hydrogenases in Microbial Communities of Surface Waters

    PubMed Central

    Beimgraben, Christian; Gutekunst, Kirstin; Opitz, Friederike

    2014-01-01

    Hydrogen is an important trace gas in the atmosphere. Soil microorganisms are known to be an important part of the biogeochemical H2 cycle, contributing 80 to 90% of the annual hydrogen uptake. Different aquatic ecosystems act as either sources or sinks of hydrogen, but the contribution of their microbial communities is unknown. [NiFe]-hydrogenases are the best candidates for hydrogen turnover in these environments since they are able to cope with oxygen. As they lack sufficiently conserved sequence motifs, reliable markers for these enzymes are missing, and consequently, little is known about their environmental distribution. We analyzed the essential maturation genes of [NiFe]-hydrogenases, including their frequency of horizontal gene transfer, and found hypD to be an applicable marker for the detection of the different known hydrogenase groups. Investigation of two freshwater lakes showed that [NiFe]-hydrogenases occur in many prokaryotic orders. We found that the respective hypD genes cooccur with oxygen-tolerant [NiFe]-hydrogenases (groups 1 and 5) mainly of Actinobacteria, Acidobacteria, and Burkholderiales; cyanobacterial uptake hydrogenases (group 2a) of cyanobacteria; H2-sensing hydrogenases (group 2b) of Burkholderiales, Rhizobiales, and Rhodobacterales; and two groups of multimeric soluble hydrogenases (groups 3b and 3d) of Legionellales and cyanobacteria. These findings support and expand a previous analysis of metagenomic data (M. Barz et al., PLoS One 5:e13846, 2010, http://dx.doi.org/10.1371/journal.pone.0013846) and further identify [NiFe]-hydrogenases that could be involved in hydrogen cycling in aquatic surface waters. PMID:24727276

  13. Method for measurement of diffusivity: Calorimetric studies of Fe/Ni multilayer thin films

    SciTech Connect

    Liu, JX; Barmak, K

    2015-07-15

    A calorimetric method for the measurement of diffusivity in thin film multilayers is introduced and applied to the Fe Ni system. Using this method, the diffusivity in [Fe (25 nm)/Ni (25 nm)](20) multilayer thin films is measured as 4 x 10(-3)exp(-1.6 +/- 0.1 eV/ k(B)T) cm(2)/s, respectively. The diffusion mechanism in the multilayers and its relevance to laboratory synthesis of L1(0) ordered FeNi are discussed. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  14. Cyclic voltammetric study of Co-Ni-Fe alloys electrodeposition in sulfate medium

    SciTech Connect

    Hanafi, I.; Daud, A. R.; Radiman, S.

    2013-11-27

    Electrochemical technique has been used to study the electrodeposition of cobalt, nickel, iron and Co-Ni-Fe alloy on indium tin oxide (ITO) coated glass substrate. To obtain the nucleation mechanism, cyclic voltammetry is used to characterize the Co-Ni-Fe system. The scanning rate effect on the deposition process was investigated. Deposition of single metal occurs at potential values more positive than that estimated stability potential. Based on the cyclic voltammetry results, the electrodeposition of cobalt, nickel, iron and Co-Ni-Fe alloy clearly show that the process of diffusion occurs is controlled by the typical nucleation mechanism.

  15. 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.

  16. Spin Reorientation Transition in Magnetically Coupled Fe/Cu/Ni/Cu(001)

    NASA Astrophysics Data System (ADS)

    Choi, H. J.; Ling, W. L.; Wolfe, J. H.; Toyama, F.; Paik, S.; Bovensiepen, U.; Qiu, Z. Q.; Scholl, A.; Nolting, F.; Anders, S.

    2001-03-01

    We investigated Spin Reorientation Transition (SRT) of Fe film in Fe/Cu/Ni/Cu(001) where the Fe layer is magnetically coupled to the perpendicular magnetization of Ni with the interlayer coupling strength being controlled by the Cu thickness. With in situ surface magneto-optic Kerr effect measurement, we show that the Fe-Ni interlayer coupling results in an alternating alignment of the Fe magnetization with Cu thickness for Fe film thinner than the SRT thickness dR, but has no effect for Fe film thicker than dR. The SRT thickness dR, defined as the onset of in-plane magnetization, was found to be independent of the Fe-Ni interlayer coupling. Within the SRT pseudo-gap region, however, the magnetic remanence exhibits oscillatory behavior with Cu thickness with a periodicity exactly half of that in the oscillatory interlayer coupling. This result shows that the strip domains are severely modified by the strength of the Fe-Ni interlayer coupling. To provide more detailed information, element specific domain imaging was taken in this system using photoemission electron microscope at the Advanced Light Source of Lawrence Berkeley National Laboratory.

  17. NiO/Fe(001): Magnetic anisotropy, exchange bias, and interface structure

    NASA Astrophysics Data System (ADS)

    Młyńczak, E.; Luches, P.; Valeri, S.; Korecki, J.

    2013-06-01

    The magnetic and structural properties of NiO/Fe epitaxial bilayers grown on MgO(001) were studied using magnetooptic Kerr effect (MOKE) and conversion electron Mössbauer 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 57Fe-CEMS. An iron oxide phase (Fe3+4Fe2+1O7), as thick as 31 Å, 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.

  18. 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.

  19. Crystallization behavior of a melt-spun Fe-Ni based steel

    NASA Technical Reports Server (NTRS)

    Michal, G. M.; Laxmanan, V.; Glasgow, T. K.

    1987-01-01

    Whether Fe-Ni-based alloys solidify with a bcc or fcc structure has been observed by many investigators to be a stronger function of kinetics and undercooling than strictly free-energy minimization. Such behavior has been observed in an Fe(52.8)Ni(28.7)Al(3.4)Ti(6.1)B(9.0) alloy. The alloy was cast as ribbons about 45 microns thick using a dual free-jet variation of chillbock melt spinning against a Cu wheel. Optical, X-ray, and electron analyses of the as-cast and annealed ribbons were performed. A microstructure of at least four layers containing combinations of ecc, bcc, and amorphous phases in differing proportions was observed in the as-cast ribbon. The midthickness layer had the most unusual features, containing fcc grains about 75 nm in size encompassing spherulitic regions as large as 15 microns comprised of fcc grains about 25 nm in size. The crystallization sequence responsible for the as-cast microstructure is discussed in terms of the competition between the formation of bcc and fcc phases as influenced by undercooling, recalescence, and variations in cooling rate experienced by the as-cast ribbon.

  20. Synthesis and cyclic oxidation behavior of a (Ni, Pt) Al coating on a desulfurized Ni-base superalloy

    SciTech Connect

    Zhang, Y.; Lee, W.Y.; Haynes, J.A.; Wright, I.G.; Pint, B.A.; Cooley, K.M.; Liaw, P.K.

    1999-10-01

    The influences of sulfur impurities and Pt incorporation on the scale adhesion behavior of aluminide coatings were studied and compared. Low-sulfur NiAl coatings were prepared on a desulfurized, yttrium-free, single-crystal Ni-based superalloy by a modified version of a conventional aluminizing procedure based on chemical vapor deposition. The sulfur level in the resulting NiAl coatings was measured to be less than {approximately}0.5 ppmw by glow-discharge mass spectroscopy. Platinum-modified aluminide coatings were synthesized by first electroplating a thin layer of Pt({approximately}7 {micro}m) on the superalloy, followed by the same low-sulfur aluminizing procedure. The measured sulfur content in the (Ni,Pt)Al coating was substantially higher than that of the low-sulfur NiAl coating due to contamination during the Pt electroplating process. A very adherent {alpha}-Al{sub 2}O{sub 3} scale formed on the grain surfaces of the low-sulfur NiAl coating during cyclic oxidation testing at 1,150 C, but scale spallation eventually occurred over many of the NiAl grain boundaries. In contrast, despite the higher level of sulfur in the (NI,Pt)Al coating, a very adherent scale was formed over both the coating grain surfaces and grain boundaries during thermal cycling. These results suggest that Pt additions can mitigate the detrimental influence of sulfur on scale adhesion.

  1. Poly(o-phenylenediamine)/NiCoFe2O4 nanocomposites: Synthesis, characterization, magnetic and dielectric properties

    NASA Astrophysics Data System (ADS)

    Kannapiran, Nagarajan; Muthusamy, Athianna; Chitra, Palanisamy; Anand, Siddeswaran; Jayaprakash, Rajan

    2017-02-01

    In this study, poly(o-phenylenediamine) (PoPD)/NiCoFe2O4 nanocomposites were synthesized by in-situ oxidative chemical polymerization method with different amount of NiCoFe2O4 nanoparticles. The NiCoFe2O4 nanoparticles were prepared by auto-combustion method. The structural, morphological, thermal properties of the synthesized PoPD/NiCoFe2O4 nanocomposites were characterized by fourier transform infrared spectrum (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Magnetic properties of NiCoFe2O4 nanoparticles and PoPD/NiCoFe2O4 nanocomposites were studied by vibrating sample magnetometer (VSM). The FTIR and XRD techniques were used to confirm the formation of PoPD/NiCoFe2O4 nanocomposites. The average crystalline size of NiCoFe2O4 nanoparticles and PoPD/NiCoFe2O4 nanocomposites were calculated from XRD. From the SEM analysis, spherical morphology of the PoPD was confirmed. The TGA results showed that the NiCoFe2O4 nanoparticles have improved the thermal stability of PoPD. Dielectric properties of PoPD/NiCoFe2O4 nanocomposites at different temperatures have been carried in the frequency range 50 Hz to 5 MHz.

  2. Room Temperature Ductility of NiAl-strengthened Ferritic Steels: Effects of Precipitate Microstructure and Hot Rolling

    SciTech Connect

    Teng, Zhenke; Liu, Chain T; Miller, Michael K; Ghosh, Gautam; Kenik, Edward A; Huang, Shenyan; Liaw, Peter K

    2012-01-01

    The effects of precipitate microstructure on the room temperature ductility of a series of carefully designed Fe-Al-Ni-Cr-Mo steels were investigated. Transmission electron microscopy (TEM), ultra small angle X-ray scattering (USAXS), and atom probe tomography (APT) were conducted to quantify the nano-scaled precipitates. The accuracy of the characterization results was verified by a numerical analysis. Three point bending tests results demonstrated that ductility was a function of the precipitate volume fraction and the Al and Ni concentrations in the Fe matrix, these relationships were discussed in terms of possible mechanisms. The ductility was also found to be independent of the precipitate size and inter-particle spacing in the studied range, which was validated by a theoretical model.

  3. 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.

  4. Non-epitaxially Grown, Oriented L10 FeNiPt Films and Their Magnetic Properties

    NASA Astrophysics Data System (ADS)

    Yan, M. L.; Xu, Y. F.; Sellmyer, D. J.

    2004-03-01

    We report on Ni doped, nonepitaxial L10 FePt thin films with strong texturing. The Ni is used to control and adjust magnetic properties of the films for use as an extremely high-density perpendicular recording media. The FeNiPt films were deposited directly on Si wafers with a (FeNi/Pt)n multilayer structure and subsequent rapid thermal annealing (RTA). Microstructural evolution of the nonepitaxial growth was investigated by XRD. The data show only (00l) peaks, indicating high (001) texture of the FeNiPt films. In comparison with FePt, the (00l) peak positions shifted to higher angle, meaning that Ni is partially substituted for Fe on the L10 lattice. Magnetic properties of these films were investigated by SQUID. The coercivity, measured at room temperature, was about 5 kOe for the film with 10% Ni substitution. This value is suitable for reading and writing in a practical recording media. The coherence length of interaction and temperature dependence of the coercivity are also discussed.

  5. Reinforced magnetic properties of Ni-doped BiFeO3 ceramic

    NASA Astrophysics Data System (ADS)

    Hwang, J. S.; Yoo, Y. J.; Lee, Y. P.; Kang, J.-H.; Lee, K. H.; Lee, B. W.; Park, S. Y.

    2016-08-01

    Multiferroic materials attract considerable interest because of the wide range of potential applications such as spintronic devices, data storage devices and sensors. As a strong candidate for the applications among the limited list of single-phase multiferroic materials, BiFeO3 (BFO) is a quite attractive material due to its multiferroic properties at room temperature (RT). However, BFO is widely known to have large leakage current and small spontaneous polarization due to the existence of crystalline defects such as oxygen vacancies. Furthermore, the magnetic moment of pure BFO is very weak owing to its antiferromagnetic nature. In this paper, the effects of Ni2+ substitution on the magnetic properties of bulk BFO were investigated. BFO, and BiFe0.99Ni0.01O3, BiFe0.98Ni0.02O3 and BiFe0.97Ni0.03O3 (BFNO: Ni-doped BFO) ceramics were prepared by solid-state reaction and rapid sintering, and analyzed by structural and magnetic-property measurements. The leakage current density was measured at RT by using a standard ferroelectric tester. All the Ni-doped BFO samples exhibited the similar rhombohedral perovskite structure ( R3c) to that of BFO. The magnetic properties of Ni-doped BFO were much enhanced with respect to BFO prepared at the same conditions, because the enhanced ferromagnetic interaction is caused by the Fe/Ni coupling.

  6. Processing and mechanical properties of NiAl-based in-situ composites. Ph. D. Thesis Final report

    SciTech Connect

    Johnson, D.R.

    1994-05-01

    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.

  7. 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.

  8. Processing and properties of FeAl-bonded composites

    SciTech Connect

    Schneibel, J.H.; Subramanian, R.; Alexander, K.B.; Becher, P.F.

    1996-12-31

    Iron aluminides are thermodynamically compatible with a wide range of ceramics such as carbides, borides, oxides, and nitrides, which makes them suitable as the matrix in composites or cermets containing fine ceramic particulates. For ceramic contents varying from 30 to 60 vol.%, composites of Fe-40 at. % Al with WC, TiC, TiB{sub 2}, and ZrB{sub 2} were fabricated by conventional liquid phase sintering of powder mixtures. For ceramic contents from 70 to 85 vol.%, pressureless melt infiltration was found to be a more suitable processing technique. In FeAl-60 vol.% WC, flexure strengths of up to 1.8 GPa were obtained, even though processing defects consisting of small oxide clusters were present. Room temperature fracture toughnesses were determined by flexure testing of chevron-notched specimens. FeAl/WC and FeAl/TiC composites containing 60 vol.% carbide particles exhibited K{sub Q} values around 20 MPa m{sup 1/2}. Slow crack growth measurements carried out in water and in dry oxygen suggest a relatively small influence of water-vapor embrittlement. It appears therefore that the mechanical properties of iron aluminides in the form of fine ligaments are quite different from their bulk properties. Measurements of the oxidation resistance, dry wear resistance, and thermal expansion of iron aluminide composites suggest many potential applications for these new materials.

  9. Preparation of soft magnetic composites for Fe particles coated with (NiZn)Fe2O4 via microwave treatment

    NASA Astrophysics Data System (ADS)

    Peng, Yuandong; Nie, Junwu; Zhang, Wenjun; Bao, Chongxi; Ma, Jian; Cao, Yang

    2015-12-01

    Soft magnetic composites (SMCs) of Fe particles coated with fine particle Ni0.5Zn0.5Fe2O4 ferrite were prepared via microwave heat treatment, and the magnetic properties and microstructures of these composites were investigated. The results show that a well-distributed Ni0.5Zn0.5Fe2O4 coating layer was formed on the surface of the Fe particles upon microwave annealing. The SMCs sample treated by microwave heating at 800 °C for 30 min under N2 had a perfect insulation layer between the Fe particles and showed stable permeability and low core loss as well as good magnetic characteristics over a wide frequency range.

  10. 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.

  11. Structure and microwave absorption properties of (Pr,Dy)Ni4Fe alloy

    NASA Astrophysics Data System (ADS)

    Xiong, Jilei; Pan, Shunkang; Qiao, Ziqiang

    2017-03-01

    The DyxPr1-xNi4Fe (x=0.0, 0.1, 0.2, 0.3, 0.4) alloys were synthesized by arc-smelting and high energy ball milling method. The structure, morphology, particle size and electromagnetic parameters of the powder were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser diffraction-based particle size analyzer and vector network analyzer (VNA), respectively. The results reveal that the DyxPr1-xNi4Fe compounds are crystallized in PrNi4Fe structure. The minimum absorption peak frequency of DyxPr1-xNi4Fe shifts towards higher frequency region upon the Fe content. The minimum reflection loss of the DyxPr1-xNi4Fe alloys increases first and then decreases with increasing Dy substitution. The Dy0.3Pr0.7Ni4Fe alloy possess the best absorbing properties: the minimum reflection loss is -31.65 dB at 15.28 GHz with the best matching thickness d =1.0 mm and the reflection loss with the thickness ranging of 1.0-4.0 mm could reach -10 dB.

  12. The Fe/Ni ratio in ionized nebulae: clues on dust depletion patterns

    NASA Astrophysics Data System (ADS)

    Delgado-Inglada, G.; Mesa-Delgado, A.; García-Rojas, J.; Rodríguez, M.; Esteban, C.

    2016-03-01

    We perform a homogeneous analysis of the Fe/Ni abundance ratio in eight Galactic planetary nebulae and three Galactic H II regions that include the Orion nebula, where we study four nebular zones and one shocked region. We use [Fe II], [Fe III], and [Ni III] lines, and ionization correction factors (ICFs) that account for the unobserved ions. We derive an ICF for nickel from an extensive grid of photoionization models. We compare our results with those derived by other authors for 16 neutral clouds in the solar neighbourhood with available Fe/Ni ratios in the literature. We find an excellent agreement between the ionized nebulae and the diffuse clouds, with both types of regions showing a clear correlation between the Fe/Ni ratios and the iron and nickel depletion factors. The trend shows that the objects with a relatively low depletion have near solar Fe/Ni ratios whereas at higher depletions the Fe/Ni ratio increases with the depletion. Our results confirm that, compared to iron atoms, nickel ones are more efficiently stuck to the dust grains in ambients where dust formation or growth have been more efficient.

  13. Striped domains in soft magnetic FeNiN thin films

    NASA Astrophysics Data System (ADS)

    Wang, X. F.; Li, B. L.; Wu, P.; Zhang, B. F.; Li, X. L.; Li, Z. Q.; Bai, H. L.; Jiang, E. Y.

    2007-02-01

    FeNiN thin films with good soft magnetic properties were synthesized on Si (1 0 0) substrates at 473 K by RF magnetron sputtering; all the films have a thickness of around 500 nm. The dependence of phase structure and magnetic properties on nickel concentrations and RF power were systematically investigated. With increasing nickel contents from XNi = 5.0% to XNi = 65.5%, FeNiN thin films deposited at P_{N _{2}} = 10.0{%} turn from a main bcc α-(Fe,Ni) phase coexisting with γ'-phase to fcc γ-(FeNi3)4N phase. With the RF power larger than 160 W, the samples deposited at P_{N _{2 }} = 3.0% all show clear reproducible striped domains at the films' surfaces, which is explained by the high enough perpendicular anisotropy and the small stress in the film. A completely ordered structure of (FeNi)N0.0324-phase forms at PW = 300 W. The FeNiN thin films prepared at different RF power show smooth surfaces and good soft magnetic properties compared with corresponding FeN compounds. The optimum soft magnetic properties with MS of ~ 1900 emu cm-3, HC of ~1 Oe are obtained at P_{N _{2 }} = 3.0% and PW = 300 W at 473 K.

  14. Novel synthesis of Ni-ferrite (NiFe{sub 2}O{sub 4}) electrode material for supercapacitor applications

    SciTech Connect

    Venkatachalam, V.; Jayavel, R.

    2015-06-24

    Novel nanocrystalline NiFe{sub 2}O{sub 4} has been synthesized through combustion route using citric acid as a fuel. Phase of the synthesized material was analyzed using powder X-ray diffraction. The XRD study revealed the formation of spinel phase cubic NiFe{sub 2}O{sub 4} with high crystallinity. The average crystallite size of NiFe{sub 2}O{sub 4} nanomaterial was calculated from scherrer equation. The electrochemical properties were realized by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The electrode material shows a maximum specific capacitance of 454 F/g with pseudocapacitive behavior. High capacitance retention of electrode material over 1000 continuous charging-discharging cycles suggests its excellent electrochemical stability. The results revealed that the nickel ferrite electrode is a potential candidate for energy storage applications in supercapacitor.

  15. Novel synthesis of Ni-ferrite (NiFe2O4) electrode material for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Venkatachalam, V.; Jayavel, R.

    2015-06-01

    Novel nanocrystalline NiFe2O4 has been synthesized through combustion route using citric acid as a fuel. Phase of the synthesized material was analyzed using powder X-ray diffraction. The XRD study revealed the formation of spinel phase cubic NiFe2O4 with high crystallinity. The average crystallite size of NiFe2O4 nanomaterial was calculated from scherrer equation. The electrochemical properties were realized by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The electrode material shows a maximum specific capacitance of 454 F/g with pseudocapacitive behavior. High capacitance retention of electrode material over 1000 continuous charging-discharging cycles suggests its excellent electrochemical stability. The results revealed that the nickel ferrite electrode is a potential candidate for energy storage applications in supercapacitor.

  16. Development of ODS-Fe{sub 3}Al alloys

    SciTech Connect

    Wright, I.G.; Pint, B.A.; Tortorelli, P.F.; McKamey, C.G.

    1997-12-01

    The overall goal of this program is to develop an oxide dispersion-strengthened (ODS) version of Fe{sub 3}Al that has sufficient creep strength and resistance to oxidation at temperatures in the range 1000 to 1200 C to be suitable for application as heat exchanger tubing in advanced power generation cycles. The main areas being addressed are: (a) alloy processing to achieve the desired alloy grain size and shape, and (b) optimization of the oxidation behavior to provide increased service life compared to semi-commercial ODS-FeCrAl alloys intended for the same applications. The recent studies have focused on mechanically-alloyed powder from a commercial alloy vendor. These starting alloy powders were very clean in terms of oxygen content compared to ORNL-produced powders, but contained similar levels of carbon picked up during the milling process. The specific environment used in milling the powder appears to exert a considerable influence on the post-consolidation recrystallization behavior of the alloy. A milling environment which produced powder particles having a high surface carbon content resulted in a consolidated alloy which readily recrystallized, whereas powder with a low surface carbon level after milling resulted in no recrystallization even at 1380 C. A feature of these alloys was the appearance of voids or porosity after the recrystallization anneal, as had been found with ORNL-produced alloys. Adjustment of the recrystallization parameters did not reveal any range of conditions where recrystallization could be accomplished without the formation of voids. Initial creep tests of specimens of the recrystallized alloys indicated a significant increase in creep strength compared to cast or wrought Fe{sub 3}Al, but the specimens failed prematurely by a mechanism that involved brittle fracture of one of the two grains in the test cross section, followed by ductile fracture of the remaining grain. The reasons for this behavior are not yet understood. The

  17. 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

  18. Oxidation-driven surface dynamics on NiAl(100)

    DOE PAGES

    Qin, Hailang; Chen, Xidong; Li, Liang; ...

    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

  19. 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.

  20. 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.