Science.gov

Sample records for al cd ni

  1. Microstructural and Mössbauer properties of low temperature synthesized Ni-Cd-Al ferrite nanoparticles

    PubMed Central

    2011-01-01

    We report the influence of Al3+ doping on the microstructural and Mössbauer properties of ferrite nanoparticles of basic composition Ni0.2Cd0.3Fe2.5 - xAlxO4 (0.0 ≤ x ≤ 0.5) prepared through simple sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray, transmission electron microscopy (TEM), Fourier transformation infrared (FTIR), and Mössbauer spectroscopy techniques were used to investigate the structural, chemical, and Mössbauer properties of the grown nanoparticles. XRD results confirm that all the samples are single-phase cubic spinel in structure excluding the presence of any secondary phase corresponding to any structure. SEM micrographs show the synthesized nanoparticles are agglomerated but spherical in shape. The average crystallite size of the grown nanoparticles was calculated through Scherrer formula and confirmed by TEM and was found between 2 and 8 nm (± 1). FTIR results show the presence of two vibrational bands corresponding to tetrahedral and octahedral sites. Mössbauer spectroscopy shows that all the samples exhibit superparamagnetism, and the quadrupole interaction increases with the substitution of Al3+ ions. PMID:21851597

  2. First-principles study of the mechanical properties of NiAl microalloyed by M (Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd)

    NASA Astrophysics Data System (ADS)

    Zhang, Caili; Han, Peide; Li, Jinmin; Chi, Mei; Yan, Lingyun; Liu, Yanping; Liu, Xuguang; Xu, Bingshe

    2008-05-01

    Structural, electronic and elastic properties for NiAl with 4d alloying elements M (Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd) have been studied using the first-principles pseudopotential density functional method within a generalized gradient approximation. From the elastic constants, C11, C12, C44, bulk modulus B0, Young's modulus E, the shear modulus G, the ratios of shear modulus to bulk modulus G/B0, negative Cauchy pressure parameter (C12 - C44) and Poisson's ratio ν calculated after structural full relaxation, M (Tc, Ru, Rh, Pd) alloying addition in NiAl has been shown to increase the stiffness of NiAl and improve its ductility. The density of states and charge density contour involving alloying additions of Ru were further investigated to clarify the electronic causes of the alloying additions.

  3. Survey of trace elements (Al, As, Cd, Cr, Co, Hg, Mn, Ni, Pb, Se, and Si) in retail samples of flavoured and bottled waters.

    PubMed

    Barroso, M F; Ramos, S; Oliva-Teles, M T; Delerue-Matos, C; Sales, M G F; Oliveira, M B P P

    2009-01-01

    Concentrations of eleven trace elements (Al, As, Cd, Cr, Co, Hg, Mn, Ni, Pb, Se, and Si) were measured in 39 (natural and flavoured) water samples. Determinations were performed using graphite furnace electrothermetry for almost all elements (Al, As, Cd, Cr, Co, Mn, Ni, Pb, and Si). For Se determination hydride generation was used, and cold vapour generation for Hg. These techniques were coupled to atomic absorption spectrophotometry. The trace element content of still or sparkling natural waters changed from brand to brand. Significant differences between natural still and natural sparkling waters (p < 0.001) were only apparent for Mn. The Mann-Whitney U-test was used to search for significant differences between flavoured and natural waters. The concentration of each element was compared with the presence of flavours, preservatives, acidifying agents, fruit juice and/or sweeteners, according to the labelled composition. It was shown that flavoured waters generally increase the trace element content. The addition of preservatives and acidifying regulators had a significant influence on Mn, Co, As and Si contents (p < 0.05). Fruit juice can also be correlated to the increase of Co and As. Sweeteners did not provide any significant difference in Mn, Co, Se and Si content.

  4. [Determination of Al, Be, Cd, Co, Cr, Mn, Ni, Pb, Se and Tl in whole blood by atomic absorption spectrometry without preliminary sample digestion].

    PubMed

    Ivanenko, N B; Ivanenko, A A; Solov'ev, N D; Navolotskiĭ, D V; Pavlova, O V; Ganeev, A A

    2014-01-01

    Methods of whole blood trace element determination by Graphite furnace atomic absorption spectrometry (in the variant of Zeeman's modulation polarization spectrometry) have been proposed. They do not require preliminary sample digestion. Furnace programs, modifiers and blood dilution factors were optimized. Seronorm™ human whole blood reference materials were used for validation. Dynamic ranges (for undiluted blood samples) were: Al 8 ¸ 210 мg/L; Be 0.3 ¸ 50 мg/L; Cd 0.2 ¸ 75 мg/L; Сo 5 ¸ 350 мg/L; Cr 10 ¸ 100 мg/L; Mn 6 ¸ 250 мg/L; Ni 10 ¸ 350 мg/L; Pb 3 ¸ 240 мg/L; Se 10 ¸ 500 мg/L; Tl 2 ¸ 600 мg/L. Precision (RSD) for the middle of dynamic range ranged from 5% for Mn to 11 for Se.

  5. Structure and physical properties of RT{sub 2}Cd{sub 20} (R=rare earth, T=Ni, Pd) compounds with the CeCr{sub 2}Al{sub 20}-type structure

    SciTech Connect

    Burnett, V.W.; Yazici, D.; White, B.D.; Dilley, N.R.; Friedman, A.J.; Brandom, B.; Maple, M.B.

    2014-07-01

    Eleven new compounds, R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) and R Pd{sub 2}Cd{sub 20} (R=Ce, Pr, Sm), were grown as single crystals in high temperature cadmium-rich solutions. They crystallize in the cubic CeCr{sub 2}Al{sub 20}-type structure (Fd3{sup ¯}m, Z=8) as characterized by measurements of powder X-ray diffraction. Electrical resistivity, magnetization, and specific heat measurements were performed on R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) single crystals. Whereas YNi{sub 2}Cd{sub 20} and LaNi{sub 2}Cd{sub 20} exhibit unremarkable metallic behavior, when magnetic moments from localized 4f electron states (Gd{sup 3+}–Tb{sup 3+}) are embedded into this host, they exhibit ferromagnetic order with values of the Curie temperature T{sub C} for R Ni{sub 2}Cd{sub 20} (R=Gd, and Tb) which scale with the de Gennes factor. - Graphical abstract: Specific heat divided by temperature C/T vs. T for single crystals of R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Gd, and Tb). Left inset: Low temperature C/T vs. T{sup 2} for LaNi{sub 2}Cd{sub 20}. The solid line represents a linear fit of the data. Right inset: Low-temperature C/T data vs. T for R=Ce–Nd, Gd, and Tb; magnetic ordering temperatures are indicated by arrows. - Highlights: • R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) single crystals synthesized for the first time. • R Pd{sub 2}Cd{sub 20} (R=Ce, Pr, Sm) single crystals synthesized for the first time. • Single crystals are of good metallurgical quality (large RRR values). • NdNi{sub 2}Cd{sub 20} orders antiferromagnetically at T{sub N}=1.5 K. • R Ni{sub 2}Cd{sub 20} (R=Sm, Gd, Tb) order ferromagnetically.

  6. 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:

  7. 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.

  8. An analysis of point defects induced by In, Al, Ni, and Sn dopants in Bridgman-grown CdZnTe detectors and their influence on trapping of charge carriers

    NASA Astrophysics Data System (ADS)

    Gul, R.; Roy, U. N.; James, R. B.

    2017-03-01

    In this research, we studied point defects induced in Bridgman-grown CdZnTe detectors doped with Indium (In), Aluminium (Al), Nickel (Ni), and Tin (Sn). Point defects associated with different dopants were observed, and these defects were analyzed in detail for their contributions to electron/hole (e/h) trapping. We also explored the correlations between the nature and abundance of the point defects with their influence on the resistivity, electron mobility-lifetime (μτe) product, and electron trapping time. We used current-deep level transient spectroscopy to determine the energy, capture cross-section, and concentration of each trap. Furthermore, we used the data to determine the trapping and de-trapping times for the charge carriers. In In-doped CdZnTe detectors, uncompensated Cd vacancies (VCd-) were identified as a dominant trap. The VCd- were almost compensated in detectors doped with Al, Ni, and Sn, in addition to co-doping with In. Dominant traps related to the dopant were found at Ev + 0.36 eV and Ev + 1.1 eV, Ec + 76 meV and Ev + 0.61 eV, Ev + 36 meV and Ev + 0.86 eV, Ev + 0.52 eV and Ec + 0.83 eV in CZT:In, CZT:In + Al, CZT:In + Ni, and CZT:In + Sn, respectively. Results indicate that the addition of other dopants with In affects the type, nature, concentration (Nt), and capture cross-section (σ) and hence trapping (tt) and de-trapping (tdt) times. The dopant-induced traps, their corresponding concentrations, and charge capture cross-section play an important role in the performance of radiation detectors, especially for devices that rely solely on electron transport.

  9. 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.

  10. 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.

  11. 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

  12. 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.

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

    NASA Technical Reports Server (NTRS)

    Copland, Evan

    2007-01-01

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

  14. 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.

  15. 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.

  16. 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.

  17. 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...

  18. NiCd battery electrodes, C-150

    NASA Technical Reports Server (NTRS)

    Holleck, G.; Turchan, M.; Hopkins, J.

    1972-01-01

    Electrodes for a nongassing negative limited nickel-cadmium cell are discussed. The key element is the development of cadmium electrodes with high hydrogen overvoltage. For this, the following electrode structures were manufactured and their physical and electrochemical characteristics were evaluated: (1) silver-sinter-based Cd electrodes, (2) Teflon-bonded Cd electrodes, (3) electrodeposited Cd sponge, and (4) Cd-sinter structures.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Performance and Safety Characteristics of Sanyo NiCd Cells

    NASA Technical Reports Server (NTRS)

    Deng, Yi; Jeevarajan, Judith; Bragg, Bobby; Zhang, Wenlin

    2002-01-01

    NiCd batteries are widely used for high drain applications like power tools and also in other portable equipment like cameras, PCs, etc. NASA and Dreamtime Holdings, Inc. worked together to have the capability of a High Definition TV (HDTV) on the ISS and Space Shuttle. The Sanyo HD camcorder was used on the STS 105 fight in July, 2001 . The camcorder used two versions of a NiCd battery. One was a cOlnmercial off-the-shelf Sony BP90 battery pack that had Sanyo NiCd D cells. The other was a modified battery (FBP-90) made by Frezzi Energy, which also had the same Sanyo NiCd D cells. The battery has 10 NiCd D cells in series to form a 12 V pack with 5.0 Ah capacity. Our current study involved the perforn1ance and abuse tests on the Sanyo NiCd 5.0 Ah D cells. The best combination of charge/discharge current rate is 0.3C for charge and 1/2e for discharge within 200 cycles. No significant changes in capacity were observed in 200 cycles. The cell also showed capability of 5C (25.0A) high rate discharge. In overcharge and overdischarge tests, all tested cells passed the tests without venting. In imbalance tests, the battery pack could be charged and discharged only at relatively low current. At charge current of 1.0A or less, the imbalanced cells in the battery pack displayed relatively high temperatures during charge or discharge. The cells functioned normally during internal short and no mishap occurred during external short. Cells passed exposure tests at 80 C and no leakage till 150 C during heat-tovent tests.

  8. 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.

  9. 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.

  10. Development of a high capacity toroidal Ni/Cd cell

    NASA Technical Reports Server (NTRS)

    Holleck, G. L.; Foos, J. S.; Avery, J. W.; Feiman, V.

    1981-01-01

    A nickel cadmium battery design which can offer better thermal management, higher energy density and much lower cost than the state-of-the-art is emphasized. A toroidal Ni/Cd cell concept is described. It was critically reviewed and used to develop two cell designs for practical implementation. One is a double swaged and the other a swaged welded configuration.

  11. Development of a high capacity toroidal Ni/Cd cell

    NASA Astrophysics Data System (ADS)

    Holleck, G. L.; Foos, J. S.; Avery, J. W.; Feiman, V.

    1981-07-01

    A nickel cadmium battery design which can offer better thermal management, higher energy density and much lower cost than the state-of-the-art is emphasized. A toroidal Ni/Cd cell concept is described. It was critically reviewed and used to develop two cell designs for practical implementation. One is a double swaged and the other a swaged welded configuration.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Comparative studies of CdS, CdS:Al, CdS:Na and CdS:(Al-Na) thin films prepared by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Yılmaz, S.; Atasoy, Y.; Tomakin, M.; Bacaksız, E.

    2015-12-01

    In the present study, the spray pyrolysis technique was used to prepare pure CdS, 4 at.% Al-doped CdS, 4 at.% Na-doped CdS and (4 at.% Al, 4 at.% Na)-co-doped CdS thin films. It was found from X-ray diffraction data that all the specimens showed hexagonal wurtzite structure with the preferred orientation of (101). Scanning electron microscopy results indicated that 4 at.% Al-doping caused a grain growth in the morphology of CdS thin films whereas the 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping led to porous structure with small grains. The band gap value of CdS thin films increased to 2.42 eV after 4 at.% Al-doping. However, it reduced to 2.30 eV and 2.08 eV for 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping, respectively. The room temperature photoluminescence measurements illustrated that the peak intensity of CdS thin films enhanced with 4 at.% Al-doping while 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping caused a decline in the intensity. The maximum carrier concentration and minimum resistivity were obtained for 4 at.% Al-doped CdS thin films, which is associated with the grain growth. Furthermore, (4 at.% Al, 4 at.% Na)-co-doping gave rise to a slight reduction in the carrier concentration and a slight increment in the resistivity. As a result, it can be said that 4 at.% Al-doped CdS thin films exhibited the best electrical and optical properties, which is important for the opto-electronic applications.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. New NiCd Battery Standard and Guide

    NASA Technical Reports Server (NTRS)

    Milden, M. J.

    1982-01-01

    The preparation and contents guides designed to provide specifications and standards for NiCd batteries for space missions are discussed. Requirements were established to assure proper in orbit performance and compliance with handling procedures to minimize degradation. The guides were designed to benefit both industries and the military. The surveys include: reasons given for and against the use of flight batteries in systems tests; use of rechargeable batteries during space vehicle testing; and military standards and specifications.

  3. Hume-Rothery electron concentration rule across a whole solid solution range in a series of gamma-brasses in Cu-Zn, Cu-Cd, Cu-Al, Cu-Ga, Ni-Zn and Co-Zn alloy systems

    NASA Astrophysics Data System (ADS)

    Mizutani, U.; Noritake, T.; Ohsuna, T.; Takeuchi, T.

    2010-05-01

    The aim of the present work is to examine if the Hume-Rothery stabilisation mechanism holds across whole solid solution ranges in a series of gamma-brasses with especial attention to the role of vacancies introduced into the large unit cell. The concentration dependence of the number of atoms in the unit cell, N, for gamma-brasses in the Cu-Zn, Cu-Cd, Cu-Al, Cu-Ga, Ni-Zn and Co-Zn alloy systems was determined by measuring the density and lattice constants at room temperature. The number of itinerant electrons in the unit cell, e/uc, is evaluated by taking a product of N and the number of itinerant electrons per atom, e/a, for the transition metal element deduced earlier from the full-potential linearised augmented plane wave (FLAPW)-Fourier analysis. The results are discussed within the rigid-band model using as a host the density of states (DOS) derived earlier from the FLAPW band calculations for the stoichiometric gamma-brasses Cu5Zn8, Cu9Al4 and TM2Zn11 (TM = Co and Ni). A solid solution range of gamma-brasses in Cu-Zn, Cu-Cd, Cu-Al, Cu-Ga and Ni-Zn alloy systems is found to fall inside the existing pseudogap at the Fermi level. This is taken as confirmation of the validity of the Hume-Rothery stability mechanism for a whole solute concentration range of these gamma-brasses. An exception to this behaviour was found in the Co-Zn gamma-brasses, where orbital hybridisation effects are claimed to play a crucial role in stabilisation.

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

    SciTech Connect

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

    2000-02-11

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

  5. 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}.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Update: Viking Lander NiCd batteries. Year six

    NASA Technical Reports Server (NTRS)

    Britting, A. O., Jr.

    1982-01-01

    The performance of NiCd batteries on the Viking Mars landers is discussed. During evaluation, three of the four batteries were maintained in the discharged state. Battery charge regimes and close-together, deep-discharge, reconditioning cycles to retard degradation of batteries are discussed. The effect of elevated temperatures during Martian summer on battery performance were also considered. Tabulated data for average battery capacity as a function of time are given. A design uplink to allow more frequent, greater depth of discharge reconditioning cycles was proposed.

  17. 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.

  18. 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.

  19. 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.

  20. Construction of temperature compensated constant voltage (VT) curves for super Ni-Cd (tm) cells

    NASA Technical Reports Server (NTRS)

    Baer, David A.; Pickett, David F.; Pearce, James M.; Rao, Gopalakrishna

    1994-01-01

    Tests to establish current-voltage characteristics at selected temperatures for 9 a-h Super Nickel-Cadmium cells were conducted at Hughes Industrial Electronics Company's Electron Dynamics Division (HIEC/EDD) under sponsorship of NASA/GSFC through their prime spacecraft contractors Fairchild Space (SMEX/SAMPEX) and TRW (TOMSEP). Curves were constructed using techniques established by Webster, Ford, et al, at NASA/GSFC in the late 1960's - early 1970's time period for conventional nickel cadmium cells used on OAO and OSO aircraft. The NASA/GSFC techniques were slightly modified by HIEC/EDD to fit the Super Ni-Cd situation.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. Quantitative Characterization of the Toxicities of Cd-Ni and Cd-Cr Binary Mixtures Using Combination Index Method

    PubMed Central

    Zheng, Minyi; Qin, Meng; Zhang, Xin; Zeng, Honghu; Liang, Yanpeng

    2016-01-01

    Direct equipartition ray design was used to construct Cd-Ni and Cd-Cr binary mixtures. Microplate toxicity analysis was used to evaluate the toxicity of individual substance and the Cd-Ni and Cd-Cr mixtures on Chlorella pyrenoidosa and Selenastrum capricornutum. The interacting toxicity of the mixture was analyzed with concentration addition (CA) model. In addition, combination index method (CI) was proposed and used to quantitatively characterize the toxicity of the binary mixtures of Cd-Ni and Cd-Cr observed in experiment and find the degree of deviation from the predicted outcome of the CA model, that is, the intensity of interacting toxicity. Results indicate that most of the 20 binary mixtures exhibit enhancing and synergistic effect, and only Cd-Cr-R4 and Cd-Cr-R5 mixtures have relatively high antagonistic effects against C. pyrenoidosa. Based on confidence interval, CI can compare the intensities of interaction of the mixtures under varying levels of effect. The characterization methods are applicable for analyzing binary mixture with complex interaction. PMID:28044127

  1. Quantitative Characterization of the Toxicities of Cd-Ni and Cd-Cr Binary Mixtures Using Combination Index Method.

    PubMed

    Mo, Lingyun; Zheng, Minyi; Qin, Meng; Zhang, Xin; Liu, Jie; Qin, Litang; Zeng, Honghu; Liang, Yanpeng

    2016-01-01

    Direct equipartition ray design was used to construct Cd-Ni and Cd-Cr binary mixtures. Microplate toxicity analysis was used to evaluate the toxicity of individual substance and the Cd-Ni and Cd-Cr mixtures on Chlorella pyrenoidosa and Selenastrum capricornutum. The interacting toxicity of the mixture was analyzed with concentration addition (CA) model. In addition, combination index method (CI) was proposed and used to quantitatively characterize the toxicity of the binary mixtures of Cd-Ni and Cd-Cr observed in experiment and find the degree of deviation from the predicted outcome of the CA model, that is, the intensity of interacting toxicity. Results indicate that most of the 20 binary mixtures exhibit enhancing and synergistic effect, and only Cd-Cr-R4 and Cd-Cr-R5 mixtures have relatively high antagonistic effects against C. pyrenoidosa. Based on confidence interval, CI can compare the intensities of interaction of the mixtures under varying levels of effect. The characterization methods are applicable for analyzing binary mixture with complex interaction.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. Evaluation of advanced NiCd cell designs for NASA applications

    NASA Astrophysics Data System (ADS)

    di Stefano, S.; Halpert, G.; Yi, T. Y.; Dalton, P.; Hall, S.

    It is pointed out that an advanced NiCd cell based on a Hughes Aircraft Company design appears to show the most promise in the current generation of aerospace NiCd batteries. The cell was designed to ameliorate the major failure mechanisms of NiCd cells. This required cell design and process modifications and the use of alternate materials for some of the components (the most notable one being the substitution of zirconia cloth for nylon as the separator material). Recent reports in the literature indicate that the improvement in the performance of this technology appears to have been verified for GEO (geosynchronous)-type applications. The authors report on initial results of the evaluation of the advanced NiCd technology for applications of interest to NASA. They summarize the characteristics of cells based on the advanced technology from the time of manufacture to their current cell cycling status.

  8. Super NiCd Open-Circuit Storage and Low Earth Orbit (LEO) Life Test Evaluation

    NASA Technical Reports Server (NTRS)

    Baer, Jean Marie; Hwang, Warren C.; Ang, Valerie J.; Hayden, Jeff; Rao, Gopalakrishna; Day, John H. (Technical Monitor)

    2002-01-01

    This presentation discusses Air Force tests performed on super NiCd cells to measure their performance under conditions simulating Low Earth Orbit (LEO) conditions. Super NiCd cells offer potential advantages over existing NiCd cell designs including advanced cell design with improved separator material and electrode making processes, but handling and storage requires active charging. These tests conclude that the super NiCd cells support generic Air Force qualifications for conventional LEO missions (up to five years duration) and that handling and storage may not actually require active charging as previously assumed. Topics covered include: Test Plan, Initial Characterization Tests, Open-Circuit Storage Tests, and post storage capacities.

  9. 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.

  10. 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.

  11. Hydroponic phytoremediation of Cd, Cr, Ni, As, and Fe: can Helianthus annuus hyperaccumulate multiple heavy metals?

    PubMed

    January, Mary C; Cutright, Teresa J; Van Keulen, Harry; Wei, Robert

    2008-01-01

    Sundance sunflowers were subjected to contaminated solutions containing 3, 4, or 5 heavy metals, with and without EDTA. The sunflowers exhibited a metal uptake preference of Cd=Cr>Ni, Cr>Cd>Ni>As and Fe>As>Cd>Ni>Cr without EDTA and Cr>Cd>Ni, Fe>As>Cd>Cr>Ni with EDTA. As uptake was not affected by other metals, but it decreased Cd and Ni concentration in the stems. The presence of Fe improved the translocation of the other metals regardless of whether EDTA was present. In general, EDTA served as a hindrance to metal uptake. For the experiment with all five heavy metals, EDTA decreased Cd in the roots and stems from 2.11 to 1.36 and from 2.83 to 2.3 2mg g(-1) biomass, respectively. For the same conditions, Ni in the stems decreased from 1.98 to 0.94 mg g(-1) total metal uptake decreased from 14.95 mg to 13.89 mg, and total biomass decreased from 2.38 g to 1.99 g. These results showed an overall negative effect in addition of EDTA. However it is unknown whether the negative effect was due to toxicity posed by EDTA or the breaking of phytochelatin-metal bonds. The most important finding was the ability of Sundance sunflowers to achieve hyperaccumulator status for both As and Cd under all conditions studied. Ni hyperaccumulator status was only achieved in the presence of three metals without EDTA.

  12. 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.

  13. Bioavailability of adsorbed and coprecipitated Cu, Ni, Pb, and Cd on iron and iron/aluminum hydroxide to Phragmites australis.

    PubMed

    Wang, He; Jia, Yongfeng

    2017-01-01

    The bioavailability of heavy metals strongly depends on their speciation in the environment. Adsorption (ADS) and coprecipitation (CPT) on amorphous metal hydroxides are important processes, controlling the fates of heavy metals in an aqueous environment. This work studied the bioavailability of Cu, Cd, Ni, and Pb adsorbed on and/or coprecipitated with amorphous iron and iron/aluminum mixed hydroxides to the wetland plant Phragmites australis. After a 13-day treatment, there was an apparent uptake of the heavy metals by the plant, and the amount of metal bioaccumulation was measurably different for different association forms (ADS vs. CPT). The bioaccumulation of Cd associated with Fe0.5Al0.5(OH)3 was greater than that with Fe(OH)3; the adsorbed metals were found to be more bioavailable than the coprecipitated forms for most of the treatments while the aging treatment significantly reduced the bioaccumulation of ADS metals. In the single metal treatment, root metal concentrations in the Fe(OH)3 ADS system followed the order Ni (68 mg kg(-1)) > Cu (32 mg kg(-1)) > Cd (28 mg kg(-1)) > Pb (9 mg kg(-1)), while the CPT system followed the order of Cu (30 mg kg(-1)) > Ni (22 mg kg(-1)) > Pb (9 mg kg(-1)) > Cd (7 mg kg(-1)). The order of metal accumulation in a combined metal treatment was similar to that for single metal treatments, but observed Ni concentration declines by 22 and 71 % and Cu and Cd concentrations increase by 30 and 50 % (for CPT and ADS treatments, respectively), while Pb concentrations increased by 30~50 % in both of them. When treated with low-molecular-weight organic acids (LMWOAs), metal desorption, indicative of metal oxide bonding strength and metal bioavailability, was consistent with metal accumulation in the plant.

  14. Cd, Ni, Cr and Pb distribution in biosolid pellets used as soil amendment

    NASA Astrophysics Data System (ADS)

    Jordán, Manuel M.; Rincón-Mora, Beatriz; Belén Almendro-Candel, María; Navarro Pedreño, Jose; Gómez Lucas, Ignacio; Bech, Jaume; Roca, Nuria; Pardo, Francisco

    2016-04-01

    The application of biosolids to a soil is a method that offers important benefits (Navarro et al. 2003). The transport and application costs are quite low (mostly if they are dehydrated biosolids or pellets) if soils are located near a wastewater treatment plant. It is possible to recycle nutrients (N, P, and K) and organic matter by improving the physical and chemical characteristics of the soil and by reducing the fertilizer costs. However, the use of biosolids may also has several problems, such as the presence of quantities of metals that could be toxic for plants or could contaminate ground-waters after being leached. Heavy metals are one of the most serious environmental pollutants because of its high toxicity, abundance and easy accumulation by plant (Soriano-Disla et al. 2014; Rosen and Chen 2014). Contamination of soils by potentially toxic elements (e.g. Cd, Ni, Cr, Pb) from amendments of biosolids is subject to rigorous controls within the European Union. The present study was designed to examine the partition of selected heavy metals in biosolid pellets, and also to relate the distribution patterns of these metals. Samples were collected from the treatment of urban wastewater at the drying grounds of a wastewater processing plant. The samples correspond to biosolids with humidities below 20% and are representative of the three horizons within the pile: the isolation surface (H1), the mesophilous area (H2), and the thermophilous area (H3). Biosolid aggregates were placed in a pellet press and then compacted. Total content of metals was determined following microwave digestion and analysed by ICP/MS. Triplicate samples were weighed in polycarbonate centrifuge tubes and sequentially extracted. The distribution of chemical forms of Cd, Ni, Cr, and Pb in the biosolids was studied using a sequential extraction procedure that fractionates the metal into soluble-exchangeable, specifically sorbed-carbonate bound, oxidizable, reducible, and residual forms. The

  15. 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.

  16. Study of photoconductivity in Ni doped CdS thin films prepared by spray pyrolysis technique

    SciTech Connect

    Patidar, Manju Mishra Gangrade, Mohan; Nath, R.; Ganesan, V.; Ajay, Akhil; Wala, Arwa Dewas; N, Kiran; Panda, Richa

    2014-04-24

    Ni-doped cadmium sulphide [Cd{sub 1−x}Ni{sub x}S, (x=0, 0.03, 0.05 and 0.20)] thin films were investigated for photoconductive properties. The films were prepared by spray Pyrolysis technique (SPT). AFM and two probe resistivity measurements were carried out to analyze the morphological and electrical properties of the films. AFM shows the note worthy changes in the morphology where the nanorod structures in CdS is changed into nano particles with the Ni doping. The presence of persistence photo current is demonstrated and extensive photoconductivity analysis has been studied on these films.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. Ab initio study of W-Al-Co-Ni : An approximant of the decagonal Al-Co-Ni quasicrystal

    NASA Astrophysics Data System (ADS)

    Hassdenteufel, Kai H.; Oganov, Artem R.; Katrych, Sergiy; Steurer, Walter

    2007-04-01

    We have performed ab initio simulations of binary and ternary periodic model structures based on the W phase in order to investigate chemical bonding, its response to pressure, and structural relaxations accompanying the substitution of Co by Ni. Our results support previous conclusions that the maximization of Al-Co and Ni-Ni interactions is favorable for reaching the lowest-energy state. The valence electron localization function (ELF) indicates partially covalent bonding supporting the formation of energetically favorable atomic clusters. The existence of a pseudogap in the calculated electronic density of states close to the Fermi level suggests electronic stabilization according to the Hume-Rothery-type mechanism. High-pressure simulations of binary W-(Al,Co) up to 90GPa reveal increasing puckering of the atomic layers perpendicular to the pseudotenfold b axis. Furthermore, the basic pentagonal columnar clusters become distorted, leading to shorter distances between neighboring Co atoms. The structural changes in the vicinity of the distorted clusters point to local changes in the chemical bonding as reflected in the valence ELF.

  5. Bioaccessibility of As, Cd, Cu, Ni, Pb, and Sb in toys and low-cost jewelry.

    PubMed

    Guney, Mert; Zagury, Gerald J

    2014-01-21

    Children can be exposed to toxic elements in toys and jewelry following ingestion. As, Cd, Cu, Ni, Pb, and Sb bioavailability was assessed (n = 24) via the in vitro gastrointestinal protocol (IVG), the physiologically based extraction test (PBET), and the European Toy Safety Standard protocol (EN 71-3), and health risks were characterized. Cd, Cu, Ni, and Pb were mobilized from 19 metallic toys and jewelry (MJ) and one crayon set. Bioaccessible Cd, Ni, or Pb exceeded EU migratable concentration limits in four to six MJ, depending on the protocol. Using two-phase (gastric + intestinal) IVG or PBET might be preferable over EN 71-3 since they better represent gastrointestinal physiology. Bioaccessible and total metal concentrations were different and not always correlated, indicating that bioaccessibility measurement may provide more accurate risk characterization. More information on impacts of multiple factors affecting metals mobilization from toys and jewelry is needed before recommending specific tests. Hazard index (HI) for Cd, Ni, or Pb were >1 for all six MJ exceeding the EU limits. For infants (6-12 mo old), 10 MJ had HI > 1 for Cd, Cu, Ni, or Pb (up to 75 for Cd and 43 for Pb). Research on prolonged exposure to MJ and comprehensive risk characterization for toys and jewelry exposure is recommended.

  6. Ni/Al Multilayers Produced by Accumulative Roll Bonding and Sputtering

    NASA Astrophysics Data System (ADS)

    Simões, S.; Ramos, A. S.; Viana, F.; Emadinia, O.; Vieira, M. T.; Vieira, M. F.

    2016-10-01

    Ni/Al multilayers are known to transform into NiAl in a highly exothermic and self-sustaining reaction. The fact that this reaction has a high heat release rate and can be triggered by an external impulse, are reasons why it has already attracted much research attention. There is a huge potential in the use of Ni/Al multilayers as a controllable and localized heat source for joining temperature-sensitive materials such as microelectronic components. The heat released and the phases resulting from the reaction of Ni and Al multilayers depend on the production methods, their composition, as well as the bilayer thickness and annealing conditions. The present research aims to explore the influence of these variables on the reaction of different multilayers, namely those produced by accumulative roll bonding (ARB) and sputtering. Structural evolution of Ni/Al multilayers with temperature was studied by differential scanning calorimetry, x-ray diffraction and scanning electron microscopy. Phase evolution, heat release rate and NiAl final grain size are controlled by the ignition method used to trigger the reaction of Ni and Al. The potential use of these multilayers in the diffusion bonding of TiAl was analyzed. The ARB multilayers allow the production of joints with higher strength than the joints produced with commercial multilayers (NanoFoil®) produced by sputtering. However, the formation of brittle intermetallic phases (Ni3Al, Ni2Al3 and NiAl3) compromises the mechanical properties of the joint.

  7. Electronic valence bands in decagonal Al-Ni-Co

    NASA Astrophysics Data System (ADS)

    Theis, W.; Rotenberg, Eli; Franke, K. J.; Gille, P.; Horn, K.

    2003-09-01

    Valence-band photoemission from the s-p region of the tenfold and the two inequivalent twofold surfaces of quasicrystalline decagonal Al71.8Ni14.8Co13.4 reveals strongly dispersing bands. These exhibit a free-electron-like dispersion along quasiperiodic and periodic directions of the decagonal quasicrystal. The experimental photoemission maps are reproduced in detail by a model in which parabolic bands emanate from a set of reciprocal lattice vectors. A parity rule for the principal zone centers is observed.

  8. Lattice dynamics of Ni-Mn-Al Heusler alloys

    SciTech Connect

    Moya, Xavier; Manosa, Lluis; Planes, A.; Krenke, T.; Acet, Mehmet; Wassermann, E. F.; Morin, M.; Garlea, Vasile O; Lograsso, Tom; Zarestky, Jerel L.

    2008-01-01

    We have studied the lattice dynamics of a Ni54Mn23Al23 (at.%) Heusler single-crystalline alloy by means of neutron scattering and ultrasonic techniques. Results show the existence of a number of precursor phenomena. We have found an anomaly (dip) in the low TA2 phonon branch at the wave number 0.33 (in reciprocal lattice units) that becomes more pronounced (phonon softening) with decreasing temperature. We have also observed softening of the associated shear elastic constant (C ) with decreasing temperature. Ultrasonic measurements under applied magnetic field, both isothermally and varying the temperature show that the values of elastic constants depend on magnetic order thus evidencing magnetoelastic coupling.

  9. Process development for Ni-Cr-ThO2 and Ni-Cr-Al-ThO2 sheet

    NASA Technical Reports Server (NTRS)

    Cook, R. C.; Norris, L. F.

    1973-01-01

    A process was developed for the production of thin gauge Ni-Cr-ThO2 sheet. The process was based on the elevated temperature deposition of chromium onto a wrought Ni-2%ThO2 sheet and subsequent high temperature diffusion heat treatments to minimize chromium concentration gradients within the sheet. The mechanical properties of the alloy were found to be critically dependent on those of the Ni-2%ThO2 sheet. A similar process for the production of a Ni-Cr-Al-ThO2 alloy having improved oxidation resistance was investigated but the non-reproducible deposition of aluminum from duplex Cr/Al packs precluded successful scale-up. The mechanical properties of the Ni-Cr-Al-ThO2 alloys were generally equivalent to the best Ni-Cr-ThO2 alloy produced in the programme.

  10. Etude des interdiffusions en phase solide dans le contact Ni/AlAs

    NASA Astrophysics Data System (ADS)

    Députier, S.; Guivarc'h, A.; Caulet, J.; Poudoulec, A.; Guenais, B.; Minier, M.; Guérin, R.

    1995-04-01

    Solid-state interdiffusions between a thin film of nickel deposited under vacuum conditions and a thick layer of epitaxial AlAs on GaAs (001) and (111) substrates were investigated in the temperature range 200-600 ^{circ}C. Complementary analytical methods (RBS, X-ray diffraction, TEM) allow us to point out, according to annealing temperatures, successives steps of the interaction. These steps correspond either to ternary phases which were evidenced by the experimental determination of the Ni-Al-As phase diagram and labelled as A, B and D phases by comparison with the isostructural ternary phases in the Ni-Ga-As diagram or to mixture of ternaries and binaries, more or less strongly textured on the substrate. In fact, the nature of the observed phases is strongly depending on the AlAs substrate orientation, the kinetic of the reaction occurring being slower on AlAs(111) than on AlAs(001). On AlAs(001), a ternary B-phase + NiAl mixture is firstly observed, followed by a second mixture constituted of the ternary A-phase + NiAl and NiAs binaries, and finally, at the end of the interaction, the two binaries NiAl + NiAs appear. On AlAs(111), only two steps of interaction have been found; first of all, the ternary D-phase is obtained, before leading, at the end of the interaction, to the ternary B-phase + NiAl + NiAs mixture. In that case, the 600 ^{circ}C annealing is not sufficient to reach the mixture of the binaries NiAl + NiAs which, according to the ternary phase diagram, is the final stage of the Ni/AlAs interaction. The comparative study of the Ni/AlAs and Ni/GaAs interdiffusions shows that the binary NiAl is the “key” compound around which the Ni/AlAs interaction progresses when NiAs is the one of the Ni/GaAs interaction. The binary NiAl which is thermally stable and strongly textured on AlAs appears as an interesting candidate to prepare epitaxial NiAl/AlAs/GaAs heterostructures. Les interdiffusions en phase solide entre une couche mince de nickel d

  11. Mechanisms of elevated-temperature deformation in the B2 aluminides NiAl and CoAl

    NASA Technical Reports Server (NTRS)

    Yaney, D. L.; Nix, W. D.

    1988-01-01

    A strain rate change technique, developed previously for distinguishing between pure-metal and alloy-type creep behavior, was used to study the elevated-temperature deformation behavior of the intermetallic compounds NiAl and CoAl. Tests on NiAl were conducted at temperatures between 1100 and 1300 K while tests on CoAl were performed at temperatures ranging from 1200 to 1400 K. NiAl exhibits pure-metal type behavior over the entire temperature range studied. CoAl, however, undergoes a transition from pure-metal to alloy-type deformation behavior as the temperature is decreased from 1400 to 1200 K. Slip appears to be inherently more difficult in CoAl than in NiAl, with lattice friction effects limiting the mobility of dislocations at a much higher tmeperature in CoAl than in NiAl. The superior strength of CoAl at elevated temperatures may, therefore, be related to a greater lattice friction strengthening effect in CoAl than in NiAl.

  12. 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.

  13. Observations of Dynamic Strain Aging in Polycrystalline NiAl

    NASA Technical Reports Server (NTRS)

    Weaver, M. L.; Noebe, R. D.; Kaufman, M. J.

    1996-01-01

    Dynamic strain aging has been investigated at temperatures between 77 and 1100 K in eight polycrystalline NiAl alloys. The 0.2% offset yield stress and work hardening rates for these alloys generally decreased with increasing temperature. However, local plateaus or maxima were observed in conventional purity and carbon doped alloys at intermediate temperatures (600-900 K). This anomalous behavior was not observed in low interstitial high-purity, nitrogen doped, or in titanium doped materials. Low or negative strain rate sensitivities (SRS) were also observed in all eight alloys in this intermediate temperature range. Coincident with the occurrence of negative SRS was the occurrence of serrated flow in conventional purity alloys containing high concentrations of Si in addition to C. These phenomena have been attributed to dynamic strain aging (DSA). Chemical analysis of the alloys used in this study suggests that the main species causing strain aging in polycrystalline NiAl is C but indicate that residual Si impurities can enhance the strain aging effect.

  14. Formation of gamma(sup prime)-Ni3Al via the Peritectoid Reaction: gamma + beta (+ Al2O3)=gamma(sup prime)(+ Al2O3)

    NASA Technical Reports Server (NTRS)

    Copeland, Evan

    2008-01-01

    The activities of Al and Ni were measured using multi-cell Knudsen effusion-cell mass spectrometry (multi-cell KEMS), over the composition range 8-32 at.%Al and temperature range T=1400-1750 K in the Ni-Al-O system. These measurements establish that equilibrium solidification of gamma(sup prime)-Ni3Al-containing alloys occurs by the eutectic reaction, L (+ Al2O3)=gamma + Beta(+ Al2O3), at 1640 +/- 1 K and a liquid composition of 24.8 +/- 0.2 at.%al (at an unknown oxygen content). The {gamma + Beta (+Al2O3} phase field is stable over the temperature range 1633-1640 K, and gamma(sup prime)-Ni3Al forms via the peritectoid, gamma + Beta (+ Al2O3)=gamma(sup prime) (+ Al2O3), at 1633 +/- 1 K. This behavior is consistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady-state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma(sup prime)-Ni2Al phase field.

  15. Formation of gamma'-Ni3Al via the Peritectoid Reaction: gamma plus beta (+Al2O3) equals gamma'(+Al2O3)

    NASA Technical Reports Server (NTRS)

    Copland, Evan

    2008-01-01

    The activities of Al and Ni were measured using multi-cell Knudsen effusion-cell mass spectrometry (multi-cell KEMS), over the composition range 8 - 32 at.%Al and temperature range T = 1400 - 1750 K in the Ni-Al-O system. These measurements establish that equilibrium solidification of gamma'-Ni3Al-containing alloys occurs by the eutectic reaction, L (+ Al2O3) = gamma + beta (+ Al2O3), at 1640 plus or minus 1 K and a liquid composition of 24.8 plus or minus 0.2 at.%Al (at an unknown oxygen content). The {gamma + beta + Al2O3} phase field is stable over the temperature range 1633 - 1640 K, and gamma'-Ni3Al forms via the peritectiod, gamma + beta (+ Al2O3) = gamma'(+ Al2O3), at 1633 plus or minus 1 K. This behavior is inconsistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma'-Ni3Al phase field.

  16. NREL Improves Hole Transport in Sensitized CdS-NiO Nanoparticle Photocathodes (Fact Sheet)

    SciTech Connect

    Not Available

    2012-01-01

    Significantly improved charge-collection efficiencies result from a general chemical approach to synthesizing photocathodes. It has been reported that a dye-sensitized nickel oxide (NiO) photocathode, when coupled to a dye-sensitized photoanode, could significantly increase overall solar conversion efficiency. However, the conversion efficiencies of these cells are still low. There has been much effort to improve the conversion efficiency by fabricating films with improved properties and developing more effective sensitizing dyes for p-type NiO. One of the factors limiting the use of NiO for solar cell application is the low hole conductivity in p-NiO. A team of researchers from the National Renewable Energy Laboratory (NREL) developed a general chemical approach to synthesize NiO-cadmium sulfide (CdS) core-shell nanoparticle films as photocathodes for p-type semiconductor-sensitized solar cells. Compared to dye-sensitized NiO photocathodes, the CdS-sensitized NiO cathodes exhibited two orders of magnitude faster hole transport (attributable to the passivation of surface traps by the CdS) and almost 100% charge-collection efficiencies.

  17. Combustion Synthesis Reaction Behavior of Cold-Rolled Ni/Al and Ti/Al Multilayers

    DTIC Science & Technology

    2011-04-01

    6   Figure 4 . Combustion synthesis process of the cold-rolled Ni/Al multilayer foils: (a) reaction front of the displacement of the reaction...Reactive Nanostructured Foil Used as a Heat Source for Joining Titanium . J. Appl. Phys. 2004, 96 ( 4 ), 2336–2342. 16. Wang, J.; Besnoin, E...2011 2. REPORT TYPE Final 3. DATES COVERED (From - To) January 2006–January 2008 4 . TITLE AND SUBTITLE Combustion Synthesis Reaction Behavior of

  18. Influence of Ni silicide phases on effective work function modulation with Al-pileup in the Ni fully silicided gate/HfSiON system

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Yoshinori; Yoshiki, Masahiko; Koga, Junji; Nishiyama, Akira; Koyama, Masato

    2009-08-01

    Influences of Ni silicide phases on the effective work function (Φeff) modulation effect with Al incorporation has been investigated in the Ni silicide/HfSiON systems. We formed metal-insulator-semiconductor capacitors with Al incorporated Ni silicide (NiSi, Ni2Si, and Ni3Si) gates on HfSiON by Al solid-phase diffusion (Al-SPD) process or Al ion implantation (I/I) process. In the Al-SPD process, Al is deposited on Ni silicide gate. In the Al-I/I process, Al ions were doped in the upper part of Ni silicide layer. In both cases, we performed Al drive-in annealing under the condition of 450 °C for 30 min in N2 ambient. It is found that the flat-band voltage (Vfb) values of Al incorporated NiSi and Ni2Si gates shift negatively and identical independent of Al incorporation processes. A highly concentrated Al piled-up layer, which induces Φeff modulation to Al-Φeff value, seems to correspond to the Vfb modulation. On the other hand, Al incorporation has little influence on Φeff at the Ni3Si/HfSiON interface. We revealed that a lower Al diffusion coefficient in Ni3Si phase reduces the Al interface density at the Ni3Si/HfSiON interface. In addition, Al piled-up layer is inherently unstable at the Ni3Si/HfSiON interface, which is confirmed from the detailed investigation about thermal stability of Al piled-up layer by using phase change process from NiSi to Ni3Si phase.

  19. Oxygen-induced changes in electron-energy-loss spectra for Al, Be and Ni. [Al; Be; Ni

    SciTech Connect

    Madden, H.H.; Landers, R.; Kleiman, G.G. , 13081-970 Campinas, Sao Paulo, Brasil); Zehner, D.M. )

    1999-09-01

    Electron-energy-loss spectroscopy (EELS) data are presented to illustrate line shape changes that occur as a result of oxygen interaction with metal surfaces. The metals were aluminum, beryllium and nickel. Core-level EELS data were taken for excitations from Al(2p), Be(1s), Ni(3p/3s) and O(1s) levels to the conduction band (CB) density of states (DOS) of the materials. The primary beam energies for the spectra were 300, 450, 300, and 1135 eV, respectively. The data are presented in both the (as measured) first-derivative and the integral forms. The integral spectra were corrected for coherent background losses and analyzed for CB DOS information. These spectra were found to be in qualitative agreement with published experimental and theoretical studies of these materials. One peak in the spectra for Al oxide is analyzed for its correlation with excitonic screening of the Al(2p) core hole. Similar evidence for exciton formation is found in the Ni(3p) spectra for Ni oxide. Data are also presented showing oxygen-induced changes in the lower-loss-energy EELS curves that, in the pure metal, are dominated by plasmon-loss and interband-transition signals. Single-scattering loss profiles in the integral form of the data were calculated using a procedure of Tougaard and Chorkendorff [S. Tougaard and I. Chorkendorff, Phys. Rev. B. [bold 35], 6570 (1987)]. For all three oxides these profiles are dominated by a feature with a loss energy of around 20[endash]25 eV. Although this feature has been ascribed by other researchers as due to bulk plasmon losses in the oxide, an alternative explanation is that the feature is simply due to O(2s)-to-CB-level excitations. An even stronger feature is found at 7 eV loss energy for Ni oxide. Speculation is given as to its source. The line shapes in both the core-level and noncore-level spectra can also be used simply as [open quotes]fingerprints[close quotes] of the surface chemistry of the materials. Our data were taken using commercially

  20. Processing, physical metallurgy and creep of NiAl + Ta and NiAl + Nb alloys. Ph.D. Thesis. Final Contractor Report

    NASA Technical Reports Server (NTRS)

    Pathare, Viren M.

    1988-01-01

    Powder processed NiAl + Ta alloys containing 1, 2, and 4.5 at percent tantalum and NiAl + Nb alloys containing 1 and 2 at percent niobium were developed for improved creep properties. In addition, a cast alloy with 5 at percent tantalum was also studied. Hot extrusion parameters for processing alloys with 1 and 2 at percent of tantalum or niobium were designed. The NiAl + 4.5 at percent Ta alloy could be vacuum hot pressed successfully, even though it could not be extruded. All the phases in the multiphase alloys were identified and the phase transformations studied. The Ni2AlTa in NiAl + 4.5 at percent Ta alloy transforms into a liquid phase above 1700 K. Solutionizing and annealing below this temperature gives rise to a uniform distribution of fine second phase precipitates. Compressive creep properties were evaluated at 1300 K using constant load and constant velocity tests. In the higher strain rate region single phase NiAl + 1 at percent Ta and NiAl + 1 at percent Nb alloys exhibit a stress exponent of 5 characteristic of climb controlled dislocation creep. In slower strain rate regime diffusional creep becomes important. The two phase alloys containing 2 to 5 at percent Ta and 2 at percent Nb show considerable improvement over binary NiAl and single phase alloys. Loose dislocation networks and tangles stabilized by the precipitates were found in the as crept microstructure. The cast alloy which has larger grains and a distribution of fine precipitates shows the maximum improvement over binary NiAl.

  1. STRESS ANNEALING INDUCED DIFFUSE SCATTERING FROM Ni3(Al,Si) PRECIPITATES

    SciTech Connect

    Barabash, Rozaliya; Ice, Gene E; Karapetrova, Evgenia; Zschack, P.

    2012-01-01

    Diffuse scattering caused by L12 type Ni3 (Al,Si) precipitates after stress annealing of Ni-Al-Si alloys is studied. Experimental reciprocal space maps are compared to the theoretical ones. Oscillations of diffuse scattering due to Ni3 (Al,Sc) precipitates are observed. Peculiarities of diffuse scattering in asymptotic region as compared to Huang scattering region are discussed. Coupling between the stress annealing direction and the precipitate shape is demonstrated.

  2. 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.

  3. Adherent Al2O3 scales produced on undoped NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1986-01-01

    Repeated oxidation and polishing of high purity Ni-15Cr-13Al has dramatically changed its cyclic oxidation behavior from nonadherent to adherent. No apparent change in scale phase, morphology or interface structure occurred during this transition, dismissing any mechanism based on pegging, vacancy sink, or growth stress. The principle change that did occur was a reduction in the sulfur content from 10 ppmw to 3 ppmw after 25 cycles at 1120 C. These observations are used to support the model of Al2O3 scale adherence put forth by Smeggil et al. which claims that Al2O3 scale spallation occurs due to sulfur segregation and bond deterioration at the oxide-metal interface.

  4. 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

  5. Effect of cooling rate on solidification of Al-Ni alloys

    NASA Astrophysics Data System (ADS)

    Ilbagi, A.; Delshad Khatibi, P.; Henein, H.; Lengsdorf, R.; Herlach, D. M.

    2011-12-01

    Particles of Al-Ni alloys with different compositions (Al-50 wt-% Ni and Al-36 wt-% Ni) were produced using a drop tube-impulse system, known as Impulse Atomization. The microstructure of these rapidly solidified particles was compared with those solidified in a DSC at low cooling rates (0.083 and 0.33 K/sec). Also, the microstructure of the sample solidified in microgravity on-board of the TEXUS 44 sounding rocket was analyzed. Neutron diffraction was used to investigate the phases formed during different solidification processes. From SEM micrographs and neutron diffraction it was found that the inner parts of the TEXUS sample and the sample that was cooled at 0.083 K/sec contain almost no eutectic structure. The outer rim of the TEXUS sample showed the highest amount of Al3Ni and lowest amount of Al3Ni2 Increasing the cooling rate from 0.083 to 0.33 K/sec increased the Al3Ni/Al3Ni2 ratio. Opposite trend was observed in the impulse-atomized particles, where increasing the cooling rate decreased the Al3Ni/Al3Ni2 ratio.

  6. Thermodynamic Effect of Platinum Addition to beta-NiAl: An Initial Investigation

    NASA Technical Reports Server (NTRS)

    2005-01-01

    An initial investigation was conducted to determine the effect of platinum addition on the activities of aluminum and nickel in beta-NiAl(Pt) over the temperature range 1354 to 1692 K. These measurements were made with a multiple effusion-cell configured mass spectrometer (multi-cell KEMS). The results of this study show that Pt additions act to decreased alpha(Al) and increased the alpha(Ni) in beta-NiAl(Pt) for constant X(sub Ni)/X(sub Al) approx. = 1.13, while at constant X(sub Al) the affect of Pt on Al is greatly reduced. The measured partial enthalpies of mixing indicate Al-atoms have a strong self interaction while Ni- and Pt-atoms in have similar interactions with Al-atoms. Conversely the binding of Ni-atoms in beta-NiAl decreases with Pt addition independent of Al concentration. These initial results prove the technique can be applied to the Ni-Al-Pt system but more activity measurements are required to fully understand the thermodynamics of this system and how Pt additions improved the scaling behavior of nickel-based superalloys. In addition, with the choice of a suitable oxide material for the effusion-cell, the "closed" isothermal nature of the effusion-cell allows the direct investigation of an alloy-oxide equilibrium which resembles the "local-equilibrium" description of the metal-scale interface observed during high temperature oxidation. It is proposed that with an Al(l) + Al2O3(s) experimental reference state together with the route measurement of the relative partial-pressures of Al(g) and Al2O(g) allows the activities of O and Al2O3 to be determined along with the activities of Ni and Al. These measurements provide a direct method of investigating the thermodynamics of the metal-scale interface of a TGO-scale.

  7. Test summary for advanced H2 cycle NI-CD cell

    NASA Technical Reports Server (NTRS)

    Miller, Lee

    1987-01-01

    To improve operational tolerances and mass, the H2 gas recombination design provisions of the Ni-H2 system were incorporated into the sealed Ni-Cd system. Produced is a cell design capable of operating on the H2 cycle versus the normal O2 cycle. Three test cells have now completed approximately 4,330 LEO (90 minute) cycles at 20 percent depth of discharge (DOD). Performance remains stable although one cell exhibited a temporary pressure anomaly.

  8. Predicting the oxidative lifetime of beta NiAl-Zr alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Vinarcik, E. J.

    1991-01-01

    Nickel aluminides containing 40 to 50 at. pct Al and 0.1 at. pct Zr were studied following cyclic oxidation at 1400 C. The selective oxidation of Al resulted in the formation of protective Al2O3 scales on each alloy composition. However, repeated cycling eventually resulted in the gradual formation of less-protective NiAl2O4, first appearing on the 40Al alloys followed at longer times on the 45Al alloys. The appearance of the NiAl2O4, signaling the end of the protective scale-forming capability of the alloy, was related to the presence of gamma-prime (Ni3Al) which formed as a result of the loss of Al from the sample. A diffusion model, based on finite-difference techniques, was developed to predict the protective life of beta Ni-Al alloys. This model predicts Ni and Al concentration profiles after various oxidation exposures. The model can predict the oxidative lifetime due to Al depletion when the Al concentration decreases to a critical concentration. Measured Al concentration profiles on two alloys after various oxidation exposures are compared to those predicted by the diffusion model. The time to the appearance of the NiAl2O4 and that predicted by the diffusion model are compared and discussed.

  9. 270V Battery Using COTS NiCd Cells For Manned Spacecraft

    NASA Technical Reports Server (NTRS)

    Darcy, Eric; Davies,Frank; Hummer, Leigh; Strangways, Brad

    2002-01-01

    A high power (>35 kW at 215V), low capacity (5.2 Ah), and compact (45L) NiCd battery was developed for the X-38 Crew Return Vehicle (CRV), which is an experimental version of the lifeboat for the International Space Station (ISS). A simple design and innovative approach using a commercial-off-the-shelf (COTS) NiCd cell design enabled the design, qualification, and production of 4 flight units of this highly reliable and safe spacecraft battery to be achieved rapidly (2 years) and cheaply ($13M).

  10. Kinetics of sulfuric acid leaching of cadmium from Cd-Ni zinc plant residues.

    PubMed

    Safarzadeh, Mohammad Sadegh; Moradkhani, Davood; Ojaghi-Ilkhchi, Mehdi

    2009-04-30

    Cd-Ni filtercakes are produced continuously at the third purification step in the electrolytic production of zinc in the National Iranian Lead and Zinc Company (NILZ) in northwestern Iran. In this research, the dissolution kinetics of cadmium from Cd-Ni residues produced in NILZ plant has been investigated. Hence, the effects of temperature, sulfuric acid concentration, particle size and stirring speed on the kinetics of cadmium dissolution in sulfuric acid were studied. The dissolution kinetics at 25-55 degrees C and tCd(5)Ni, Cd(2)Ni(1.9) and Cd(10)Cu(3)) as the rate determining step. This finding is in accordance with the apparent activation energy (E(a)) of 13.363 kJ/mol and a linear relationship between the rate constant and the reciprocal of squared particle size. Arrhenius constant was calculated as 6.3942 min(-1). The order of reaction with respect to sulfuric acid concentration, solid/liquid ratio and particle size were also achieved. The rate of reaction at first 5 min based on diffusion-controlled process can be expressed by a semi-empirical equation as:It was determined that the dissolution rate increased with increasing sulfuric acid concentration and decreasing particle size.

  11. Reactive Ni/Al Nanocomposites: Structural Characteristics and Activation Energy.

    PubMed

    Shuck, Christopher E; Mukasyan, Alexander S

    2017-02-16

    Stochastically structured Ni/Al reactive nanocomposites (RNCs) were prepared using short-term high-energy ball milling. Several milling times were utilized to prepare RNCs with differing internal nanostructures. These internal structures were quantitatively and statistically analyzed by use of serial focused ion beam sectioning coupled with 3D reconstruction techniques. The reaction kinetics were analyzed using the electrothermal explosion technique for each milling condition. It is shown that the effective activation energy (Eef) ranges from 79 to 137 kJ/mol and is directly related to the surface area contact between the reactants. Essentially, the reaction kinetics can be accurately controlled through mechanical processing techniques. Finally, the nature of the reaction is considered; the mechanistic effect of the reactive and three diffusive activation energies on the effective activation energy is examined.

  12. Recrystallization and grain growth in NiAl

    NASA Technical Reports Server (NTRS)

    Haff, G. R.; Schulson, E. M.

    1982-01-01

    Aluminide intermetallics, because of their strength, microstructural stability, and oxidation resistance at elevated temperatures, represent potential structural materials for use in advanced energy conversion systems. This inherent potential of the intermetallics can currently not be realized in connection with the general brittleness of the materials under ambient conditions. It is pointed out, however, that brittleness is not an inherent characteristic. Single crystals are ductile and polycrystals may be, too, if their grains are fine enough. The present investigation is concerned with an approach for reducing material brittleness, taking into account thermal-mechanically induced grain refinement in NiAl, a B2 aluminide which melts at 1638 C and which retains complete order to its melting point. Attention is given to the kinetics of recrystallization and grain growth of warm-worked, nickel-rich material.

  13. Diffusive Interaction Between Ni-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Tkacz-Śmiech, Katarzyna; Danielewski, Marek; Bożek, Bogusław; Berent, Katarzyna; Zientara, Dariusz; Zajusz, Marek

    2017-03-01

    In high-temperature coatings, welded parts, and a range of other applications, components in the contact zone interdiffuse at elevated temperatures and may react to change the phase composition. The diffusion zone can be complex and can consist of sequential layers of intermediate phases, solid solutions, and in the case of multicomponent systems also of multiphase layers. In this work, the interdiffusion in Ni-Cr-Al alloys is studied experimentally and modeled numerically. The diffusion multiples were prepared by hot isostatic pressing and post-annealing at 1473 K (1200 °C). The concentration profiles were measured with wide-line EDS technique which allowed obtaining high-accuracy diffusion paths. The experimental profiles and diffusion paths were compared with numerical results simulated with application of very recent model of interdiffusion in muticomponent-multiphase systems. The calculated and experimental data show good agreement.

  14. 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.

  15. Phase alignment and crystal orientation of Al 3Ni in Al-Ni alloy by imposition of a uniform high magnetic field

    NASA Astrophysics Data System (ADS)

    Wang, Chunjiang; Wang, Qiang; Wang, Zhongying; Li, Hutian; Nakajima, Keiji; He, Jicheng

    2008-03-01

    Solidification experiments of aluminum-nickel binary alloys under uniform high magnetic fields have been conducted. The effects of high magnetic fields on the crystal orientation of Al 3Ni were investigated by XRD and the alignment of primary phases Al 3Ni were also analyzed. Experimental results showed that the easy magnetization axis of Al 3Ni crystal oriented parallel to the imposed magnetic fields and the primary phase Al 3Ni aligned perpendicular to the magnetic fields. Magnetic orientation of crystal was determined by magnetic anisotropy energy. Whereas the phase alignment should be contributed to the combined effects of magnetic orientation, crystal growth and the effects of magnetic fields on mass transport during solidification.

  16. Optical properties of Al-CdO nano-clusters thin films

    NASA Astrophysics Data System (ADS)

    Yahia, I. S.; Salem, G. F.; Abd El-sadek, M. S.; Yakuphanoglu, F.

    2013-12-01

    The aluminum doped cadmium oxide (CdO:Al) thin films were grown onto glass substrates by sol-gel spin-coating method. The structural properties of undoped and Al-doped CdO thin films were studied by atomic force microscopy. AFM results reveal that the studied CdO films were formed from the nano-clusters. The optical transmittance of undoped and Al-doped CdO is decreased with increasing Al contents. The optical band gaps of the CdO films were varied from 2.54 eV to 2.32 eV with increasing Al dopants. The width of localized states in the optical band gap of the films is increased with increasing Al content. The improvement of the optical constant of Al-doped CdO has potential applications as transparent conducting oxide for different optoelectronic device applications.

  17. Preliminary investigation of a NiAl composite prepared by cryomilling

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Arzt, Eduard; Luton, Michael J.

    1990-01-01

    An attempt has been made to improve the high temperature mechanical strength of the B2 cubic crystal structure intermetallic NiAl by dispersion strengthening. Prealloyed Ni-51 at. pct Al was cryomilled with a Y2O3 addition to form an yttria dispersoid within the intermetallic matrix. Following milling, the powder was hot extruded to full density and machined into test coupons. Compression testing between 1200 and 1400 K indicated that the cryogenic process yielded the strongest NiAl based material tested to date. Creep resistance was six times better than NiAl and twice that of a NiAl particulate composite containing 10 vol pct TiB2. Surprisingly, transmission electron microscopy revealed that the second phase was inhomogeneously distributed. Furthermore, X-ray analysis indicated that the second phase was not Y2O3 but rather AlN.

  18. Weak hybridization and isolated localized magnetic moments in the compounds CeT2Cd20 (T = Ni, Pd)

    NASA Astrophysics Data System (ADS)

    White, Benjamin; Yazici, Duygu; Ho, Pei-Chun; Kanchanavatee, Noravee; Pouse, Naveen; Friedman, Aaron; Maple, M. Brian

    2015-03-01

    Large Ce-Ce distances of 6.7-6.8 Åand weak hybridization between Ce 4 f and itinerant electron states act to promote stable localized magnetic moments in the compounds CeT2Cd20 (T = Ni, Pd), but also conspire to severely limit the strength of the Ruderman-Kittel-Kasuya-Yosida (RKKY) magnetic exchange interaction that couples them. As a consequence, measurements of electrical resistivity, performed on single-crystalline samples of these new Cd-based compounds down to 0.138 K, were unable to resolve any evidence for magnetic order. In this presentation, we will compare measurements of the physical properties of CeT2Cd20 (T = Ni, Pd) under ambient and applied pressures with the reported properties of the isostructural compounds CeT2X20 (T = transition metal; X = Al, Zn). We will use these comparisons to discuss the interplay of unit cell volume, hybridization, and the RKKY interaction and its role in establishing the ground states of the Ce-based ``1-2-20'' compounds. Sample synthesis and physical properties measurements were supported by the U.S. DOE under Grant No. DE-FG02-04-ER46105. Measurements of electrical resistivity below 1 K were supported by the NSF under Grants No. DMR-1206553 and No. DMR-1104544.

  19. Giant perpendicular magnetic anisotropy of an Ir monolayer on a NiAl(001) surface

    NASA Astrophysics Data System (ADS)

    Kim, Dongyoo; Yang, Jeonghwa; Hong, Jisang

    2009-08-01

    Using the state-of-the-art full potential linearized augmented plane-wave method, we have investigated the magnetic properties of Os and Ir monolayer (ML) film on NiAl(001) surface. It has been found that the one ML of Os and Ir film can have ferromagnetic ground state with magnetic moment of 0.35 and 0.64μB on Ni terminated surface, whereas both films display no sign of magnetic state on Al terminated surface. In addition, the surface Ni atom has an induced magnetic moment of 0.26μB in Ir/NiAl(001), while only 0.09μB is observed in Os/NiAl(001). We attribute the existence of magnetism to the interaction between 5d of adlayer and 3d of surface Ni. Moreover, we have obtained that the Os/NiAl(001) and Ir/NiAl(001) films show a perpendicular magnetic anisotropy (PMA). Surprisingly, it appears that the Ir/NiAl(001) has a giant PMA energy of 7.18 meV.

  20. Conformal growth of nanocrystalline CdX (X = S, Se) on mesoscopic NiO and their photoelectrochemical properties.

    PubMed

    Safari-Alamuti, Fatemeh; Jennings, James R; Hossain, Md Anower; Yung, Lin Yue Lanry; Wang, Qing

    2013-04-07

    Semiconductor-sensitized NiO photocathodes have been fabricated by successive ionic-layer adsorption and reaction (SILAR) deposition of CdS, CdSe and cascaded CdS/CdSe onto mesoscopic NiO films. Detailed morphological and structural characterization reveals that the growth of CdS and CdSe on mesoscopic NiO electrodes results in the formation of crystalline and conformal layers under ambient conditions. With a polysulfide redox electrolyte and a Pt counter electrode, CdX (X = S and Se)-sensitized p-NiO solar cells operating in a photocathodic mode are unambiguously demonstrated when NiO blocking layers are used, which are critical to prevent anodic photocurrent due to electron injection from CdX into the SnO2:F substrate. To decrease the recombination rate, a CdS barrier layer was deposited between NiO and a CdSe sensitizer which results in much enhanced cell performance. Front and rear spectral incident photon-to-current efficiency (IPCE) measurements were used to investigate charge collection and separation in the cells. The measurements indicate that charge collection in this system is limited by a short hole diffusion length.

  1. Diffusional transport and predicting oxidative failure during cyclic oxidation of beta-NiAl alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Vinarcik, E. J.; Barrett, C. A.; Doychak, J.

    1992-01-01

    Nickel aluminides (NiAl) containing 40-50 at. percent Al and up to 0.1 at. percent Zr have been studied following cyclic oxidation at 1200, 1300, 1350 and 1400 C. The selective oxidation of aluminum resulted in the formation of protective Al2O3 scales on each alloy composition at each temperature. However, repeated cycling eventually resulted in the gradual formation of less protective NiAl2O4. The appearance of the NiAl2O4, signaling the end of the protective scale-forming capability of the alloy, was related to the presence of gamma-prime-(Ni3Al) which formed as a result of the loss of aluminum from the sample. A simple methodology is presented to predict the protective life of beta-NiAl alloys. This method predicts the oxidative lifetime due to aluminum depletion when the aluminum concentration decreases to a critical concentration. The time interval preceding NiAl2O4 formation (i.e., the lifetime based on protective Al2O3 formation) and predicted lifetimes are compared and discussed. Use of the method to predict the maximum use temperature for NiAl-Zr alloys is also discussed.

  2. Method For Making Electronic Circuits Having Nial And Ni3al Substrates

    DOEpatents

    Deevi, Seetharama C.; Sikka, Vinod K.

    2001-01-30

    A method for making electronic circuit component having improved mechanical properties and thermal conductivity comprises steps of providing NiAl and/or Ni.sub.3 Al, and forming an alumina layer thereupon prior to applying the conductive elements. Additional layers of copper-aluminum alloy or copper further improve mechanical strength and thermal conductivity.

  3. A fascinating combination of Co, Ni and Al nanomaterial for oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Khan, Sher Bahadar; Khan, Shahid Ali; Asiri, Abdullah M.

    2016-05-01

    Interesting combination of Co, Ni and Al have been assessed for oxygen evolution reaction (OER). Layered double hydroxide (LDH) nanosheets of NiCoAl, Co-Al oxide nanoparticles and Co-Ni oxide nanoparticles were prepared and studied for the first time as OER catalyst. Among all the subjected catalysts, the binary LDH comprise of NiCoAl showed comparatively high catalytic activity than Co-Al oxide nanoparticles and Co-Ni oxide nanoparticles. The Co-Al and Co-Ni oxide nanoparticles showed current densities of 34.6 and 24.5 mA cm-2, respectively at 1 V in 0.3 M KOH solution. However at the same conditions, NiCoAl-LDH showed comparatively low overpotential, high current density (40.8 mA cm-2) and lower Tafel slope. The low overpotential and high catalytic activity of NiCoAl-LDH stipulate the possibility to reduce the demand of precious, rare earth and expensive transition metal catalyst in electrochemical water splitting for OER.

  4. Development of a high capacity toroidal Ni/Cd cell. Final report

    SciTech Connect

    Holleck, G.L.; Foos, J.S.; Avery, J.W.; Feiman, V.

    1981-07-01

    A nickel cadmium battery design which can offer better thermal management, higher energy density and much lower cost than the state-of-the-art is emphasized. A toroidal Ni/Cd cell concept is described. It was critically reviewed and used to develop two cell designs for practical implementation. One is a double swaged and the other a swaged welded configuration.

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

    NASA Technical Reports Server (NTRS)

    Tausch, Benjamin J., II

    1994-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Tausch, Benjamin J., II

    1994-02-01

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

  7. Review of super Ni/Cd cell designs and performance

    NASA Technical Reports Server (NTRS)

    Abrams-Blakemore, Bruce

    1993-01-01

    Eagle-Picher Industries, Inc., in cooperation with Hughes Aircraft Company, began production of the Super Nickel-Cadmium cell in 1989. Since that time the Super Nickel-Cadmium cell has been deployed in a wide variety of satellites. This paper will review one of those programs and provide a performance update. We will discuss storage requirements and capacity histories for the various Super NiCad Cell designs.

  8. Hydrogen production by thermocatalytic decomposition of methane over Ni-Al and Ni-Cu-Al catalysts: Effect of calcination temperature

    NASA Astrophysics Data System (ADS)

    Echegoyen, Y.; Suelves, I.; Lázaro, M. J.; Moliner, R.; Palacios, J. M.

    Thermo catalytic decomposition of methane using Ni-Al and Ni-Cu-Al catalyst prepared by fusion of the corresponding nitrates is studied. The effects of catalyst calcination temperature on the hydrogen yields and the characteristics of the carbon obtained are studied. The role of copper has been also analyzed. Whatever the calcination temperature, all the catalysts show a high and almost constant hydrogen yield without catalyst deactivation after 8 h on stream, which confirms the good performance of this kind of catalysts. The presence of copper enhances the hydrogen production and the best results were obtained using catalysts calcined at 600 °C. Cu has a strong influence on the dispersion of Ni in the catalysts and inhibits NiO from the formation of nickel aluminate even at high calcinations temperatures, which facilitates the formation of the metallic Ni active phase during the subsequent catalyst reduction step. All catalysts tested promote the formation of very long filaments of carbon a few tens of nanometers in diameter and some micrometers long. The structural properties of these carbon filaments highly depend on the presence of Cu:Ni-Cu-Al catalysts promote the formation of a well-ordered graphitic carbon while Ni-Al catalysts enhance the formation of a rather turbostratic carbon.

  9. Charge optimized many-body (COMB) potential for dynamical simulation of Ni-Al phases

    NASA Astrophysics Data System (ADS)

    Kumar, Aakash; Chernatynskiy, Aleksandr; Liang, Tao; Choudhary, Kamal; Noordhoek, Mark J.; Cheng, Yu-Ting; Phillpot, Simon R.; Sinnott, Susan B.

    2015-08-01

    An interatomic potential for the Ni-Al system is presented within the third-generation charge optimized many-body (COMB3) formalism. The potential has been optimized for Ni3Al, or the γ‧ phase in Ni-based superalloys. The formation energies predicted for other Ni-Al phases are in reasonable agreement with first-principles results. The potential further predicts good mechanical properties for Ni3Al, which includes the values of the complex stacking fault (CSF) and the anti-phase boundary (APB) energies for the (1 1 1) and (1 0 0) planes. It is also used to investigate dislocation propagation across the Ni3Al (1 1 0)-Ni (1 1 0) interface, and the results are consistent with simulation results reported in the literature. The potential is further used in combination with a recent COMB3 potential for Al2O3 to investigate the Ni3Al (1 1 1)-Al2O3 (0 0 01) interface, which has not been modeled previously at the classical atomistic level due to the lack of a reactive potential to describe both Ni3Al and Al2O3 as well as interactions between them. The calculated work of adhesion for this interface is predicted to be 1.85 J m-2, which is in agreement with available experimental data. The predicted interlayer distance is further consistent with the available first-principles results for Ni (1 1 1)-Al2O3 (0 0 0 1).

  10. The 1200 K compressive properties of N-containing NiAl

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Noebe, R. D.; Wheeler, D. R.

    1995-01-01

    As part of a series of experiments to understand the role of N on the strength of NiAl, a heat of NiAl was enriched with N by melting and atomization to powder in a nitrogen atmosphere. Following consolidation of the powder by hot extrusion, 1200 K compressive properties were measured in air. Within the range of strain rates examined, 10(exp -3) to 10(exp -9) s(exp -1), the strength of the N-enriched NiAl was greater than that of a simple 15 micron grain size polycrystalline, binary NiAl alloy. For the most part the overall improvement in strength is ascribed to the fine grain size of the N-doped NiAl rather than the alloy chemistry; however, the alloy displayed a complex behavior exhibiting both weakening effects as well as strengthening ones.

  11. High temperature oxidation resistant coatings for the directionally solidified Ni-Nb-Cr-Al eutectic superalloy

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Ulion, N. E.; Felten, E. J.

    1977-01-01

    Protective coatings required for the Ni-Nb-Cr-Al directionally solidified eutectic superalloy were developed and evaluated on the basis of oxidation resistance, diffusional stability, thermal fatigue, and creep resistance. NiCrAlY+Pt and NiCrAlY physical vapor-deposition coating systems exhibited the best combination of properties. Burner-rig testing indicated that the useful life of a 127-micron-thick NiCrAlY+Pt coating exceeds 1000 h at 1366 K. Eutectic-alloy creep lives at 1311 K and a stress of 151.7 MN/sq m were greater for NiCrAlY+Pt-coated specimens than for uncoated specimens by a factor of two.

  12. Effect of calcination time on NiAl-Al2O3 using gel combustion synthesis method

    NASA Astrophysics Data System (ADS)

    Afandi, N. F.; Manap, A.; Yusof, S. N. A.; Salim, M. A.; Azim, M. Al.; Othman, S. Z.; Pauzi, N. I. M.; Omar, Nooririnah; Misran, H.

    2015-07-01

    This study was conducted in order to investigate the effect of calcination time on phase and microstructural characteristics of intermetallic matric composite (IMC), NiAl-Al2O3 powder. This powder was synthesized using gel combustion method with octyl alcohol as fuel. Upon completion of the combustion process, the loose powder was calcined at 1050°C for 1, 2 and 4 hours and characterized using XRD, FESEM and TEM. The crystallite size was calculated to be in the range of 29-30 nm. It was found that NiAl-Al2O3 exhibits high crystalline structure after calcination for 4 hours. Furthermore, longer calcination time also cause growth of the particle size. Findings indicate that high crystalline nanostructured NiAl-Al2O3 powder consisting of submicron particles can be successfully produced using gel combustion synthesis with longer calcination time.

  13. Microstructure evolution during annealing of TiAl/NiCoCrAl multilayer composite prepared by EB-PVD

    SciTech Connect

    Zhang, Rubing; Zhang, Deming; Chen, Guiqing; Wang, Yuesheng

    2014-07-01

    TiAl/NiCoCrAl laminate composite sheet with a thickness of 0.4–0.6 mm as well as a dimension of 150 mm × 100 mm was fabricated successfully by using electron beam physical vapor deposition (EB-PVD) method. The annealing treatment was processed at 1123 and 1323 K for 3 h in a high vacuum atmosphere, respectively. The phase composition and microstructure of TiAl/NiCoCrAl microlaminated sheet have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Based on the sheet characterization and results of the microstructure evolution during annealing treatment process, the diffusion mechanism of interfacial reaction in TiAl/NiCoCrAl microlaminate was investigated and discussed.

  14. Monolayer dispersion of NiO in NiO/Al2O3 catalysts probed by positronium atom.

    PubMed

    Zhang, H J; Chen, Z Q; Wang, S J

    2012-01-21

    NiO/Al(2)O(3) catalysts with different NiO loadings were prepared by impregnation method. The monolayer dispersion capacity of NiO is determined to be about 9 wt.% through XRD quantitative phase analysis. Positron lifetime spectra measured for NiO/Al(2)O(3) catalysts comprise two long and two short lifetime components, where the long lifetimes τ(3) and τ(4) correspond to ortho-positronium (o-Ps) annihilation in microvoids and large pores, respectively. With increasing loading of NiO from 0 to 9 wt.%, τ(4) drops drastically from 88 to 38 ns. However, when the NiO loading is higher than 9 wt.%, τ(4) shows a slower decrease. Variation of λ(4) (1/τ(4)) as a function of the NiO content can be well fitted by two straight lines with different slopes. The relative intensity of τ(4) also shows a fast decrease followed by a slow decrease for the NiO content lower and higher than 9 wt.%, respectively. The coincidence Doppler broadening measurements reveal a continuous increase of S parameter with increasing NiO loading up to 9 wt.% and then a decrease afterwards. This is due to the variation in intensity of the narrow component contributed by the annihilation of para-positronium (p-Ps). Our results show that the annihilation behavior of positronium is very sensitive to the dispersion state of NiO on the surface of γ-Al(2)O(3). When the NiO loading is lower than monolayer dispersion capacity, spin conversion of positronium induced by NiO is the dominant effect, which causes decrease of the longest lifetime and its intensity but increase of the narrow component intensity. After the NiO loading is higher than monolayer dispersion capacity, the spin conversion effect becomes weaker and inhibition of positronium formation by NiO is strengthened, which results in decrease of both the long lifetime intensity and the narrow component intensity. The reaction rate constant is determined to be (1.50 ± 0.04) × 10(10) g mol(-1) s(-1) and (3.43 ± 0.20) × 10(9) g mol(-1) s(-1

  15. Monolayer dispersion of NiO in NiO/Al2O3 catalysts probed by positronium atom

    NASA Astrophysics Data System (ADS)

    Zhang, H. J.; Chen, Z. Q.; Wang, S. J.

    2012-01-01

    NiO/Al2O3 catalysts with different NiO loadings were prepared by impregnation method. The monolayer dispersion capacity of NiO is determined to be about 9 wt.% through XRD quantitative phase analysis. Positron lifetime spectra measured for NiO/Al2O3 catalysts comprise two long and two short lifetime components, where the long lifetimes τ3 and τ4 correspond to ortho-positronium (o-Ps) annihilation in microvoids and large pores, respectively. With increasing loading of NiO from 0 to 9 wt.%, τ4 drops drastically from 88 to 38 ns. However, when the NiO loading is higher than 9 wt.%, τ4 shows a slower decrease. Variation of λ4 (1/τ4) as a function of the NiO content can be well fitted by two straight lines with different slopes. The relative intensity of τ4 also shows a fast decrease followed by a slow decrease for the NiO content lower and higher than 9 wt.%, respectively. The coincidence Doppler broadening measurements reveal a continuous increase of S parameter with increasing NiO loading up to 9 wt.% and then a decrease afterwards. This is due to the variation in intensity of the narrow component contributed by the annihilation of para-positronium (p-Ps). Our results show that the annihilation behavior of positronium is very sensitive to the dispersion state of NiO on the surface of γ-Al2O3. When the NiO loading is lower than monolayer dispersion capacity, spin conversion of positronium induced by NiO is the dominant effect, which causes decrease of the longest lifetime and its intensity but increase of the narrow component intensity. After the NiO loading is higher than monolayer dispersion capacity, the spin conversion effect becomes weaker and inhibition of positronium formation by NiO is strengthened, which results in decrease of both the long lifetime intensity and the narrow component intensity. The reaction rate constant is determined to be (1.50 ± 0.04) × 1010 g mol-1s-1 and (3.43 ± 0.20) × 109 g mol-1 s-1 for NiO content below and above

  16. 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.

  17. Thermodynamic analysis of compatibility of several reinforcement materials with beta phase NiAl alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1988-01-01

    Chemical compatibility of several reinforcement materials with beta phase NiAl alloys within the concentration range 40 to 50 at. percent Al have been analyzed from thermodynamic considerations at 1373 and 1573 K. The reinforcement materials considered in this study include carbides, borides, oxides, nitrides, beryllides, and silicides. Thermodynamic data for NiAl alloys have been reviewed and activity of Ni and Al in the beta phase have been derived at 1373 and 1573 K. Criteria for chemical compatibility between the reinforcement material and the matrix have been defined and several chemically compatible reinforcement materials have been defined.

  18. Formation and stability of Ni-Al hydroxide phases in soils.

    PubMed

    Peltier, Edward; Lelie, Daniel van der; Sparks, Donald L

    2010-01-01

    The formation of mixed metal-aluminum hydroxide surface precipitates is a potentially significant uptake route for trace metals (including Co, Ni, and Zn) in environmental systems. This paper investigates the effect of mixed Ni-Al hydroxide precipitate formation and aging on Ni solubility and bioavailability in laboratory contaminated soils. Two Delaware agricultural soils were reacted with a 3 mM Ni solution for 12 months at pH's above and below the threshold for mixed Ni-Al hydroxide formation. Ni speciation was determined at 1, 6, and 12 months using X-ray absorption spectroscopy (XAS). Precipitate solubility was examined through desorption experiments using HNO3 and EDTA as desorbing agents, whereas metal bioavailability was assessed using a Ni-specific bacterial biosensor. For both soils, the formation of Ni-Al hydroxide surface precipitates resulted in a reduction in the fraction of desorbed and bioavailable Ni. However, precipitate dissolution was greater, particularly with EDTA, than in published studies on isolated soil clay fractions, and less affected by aging processes. These results suggest that mixed Ni-Al hydroxide phases forming in real world environments may be both longer-lasting and more susceptible to ligand-promoted dissolution than previously expected.

  19. Formation and Stability of Ni-Al Hydroxide Phases in Soils

    SciTech Connect

    Peltier, E.; Van Der Lelie, D; Sparks, D

    2010-01-01

    The formation of mixed metal-aluminum hydroxide surface precipitates is a potentially significant uptake route for trace metals (including Co, Ni, and Zn) in environmental systems. This paper investigates the effect of mixed Ni-Al hydroxide precipitate formation and aging on Ni solubility and bioavailability in laboratory contaminated soils. Two Delaware agricultural soils were reacted with a 3 mM Ni solution for 12 months at pH's above and below the threshold for mixed Ni-Al hydroxide formation. Ni speciation was determined at 1, 6, and 12 months using X-ray absorption spectroscopy (XAS). Precipitate solubility was examined through desorption experiments using HNO{sub 3} and EDTA as desorbing agents, whereas metal bioavailability was assessed using a Ni-specific bacterial biosensor. For both soils, the formation of Ni-Al hydroxide surface precipitates resulted in a reduction in the fraction of desorbed and bioavailable Ni. However, precipitate dissolution was greater, particularly with EDTA, than in published studies on isolated soil clay fractions, and less affected by aging processes. These results suggest that mixed Ni-Al hydroxide phases forming in real world environments may be both longer-lasting and more susceptible to ligand-promoted dissolution than previously expected.

  20. 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.

  1. Growth and characterisation of NiAl and N-doped NiAl films deposited by closed field unbalanced magnetron sputtering ion plating using elemental ni and Al targets.

    PubMed

    Said, R; Ahmed, W; Abuain, T; Abuazza, A; Gracio, J

    2010-04-01

    Closed Field Unbalanced Magnetron Sputtering Ion Plating (CFUBMSIP) has been used to deposit undoped and nitrogen doped NiAI thin films onto glass and stainless steel 316 substrates. These films have potential applications in tribological, electronic media and thermal barrier coatings. The surface characteristics, composition, mechanical and structural properties have been investigated using stylus profilometry, X-ray diffraction (XRD), Energy dispersive spectroscopy (EDAX), Atomic force microscopy (AFM) and nanoindentation. The average thickness of the films was approximately 1 microm. The X-ray diffraction spectra revealed the presence of the beta NiAl phase. The EDAX results revealed that all of the undoped and nitrogen doped NiAl thin films exhibited the near equiatomic NiAl composition with the best results being achieved using 300 Watts DC power for Ni and 400 Watts DC power for Al targets respectively. AFM results of both types of films deposited on glass samples exhibited a surface roughness of less than 100 nm. The nanoindenter results for coatings on glass substrates displayed hardness and elastic modulus of 7.7 GPa and 100 GPa respectively. The hardest coatings obtained were obtained at 10% of nitrogen.

  2. Characteristic losses in metals: Al, Be, and Ni

    SciTech Connect

    Madden, H.H.; Landers, R.; Kleiman, G.G.; Zehner, D.M.

    1998-07-01

    Information about the {ital occupied} portion of the surface density of states of materials can be derived from electron-excited Auger electron spectroscopy (AES), which is a standard experimental technique in most surface science laboratories. Surface sensitive experimental techniques that provide information regarding the {ital unoccupied} portion of the surface density of states are often not standard and are not so readily available. Here we explore the possibility of utilizing the same experimental equipment as in AES to derive information about the unoccupied portion of the surface density of states from a characteristic loss spectroscopy, in particular, from core-level inelastic electron-scattering spectroscopy (CLIESS). An important application of this technique is in comparative studies. CLIESS spectra from clean surfaces of aluminum, beryllium and nickel are presented. These data were taken in the first-derivative mode using the reflection of monoenergetic primary beams of 450 eV energy for Be, and 300 eV for Al and Ni. The Al and Be spectra had to be extracted from overlapping plasmon signals using synthesized plasmon spectra based on the behavior of these spectra between the elastic peak energy and the respective core level threshold energies. After applying loss-deconvolution techniques to remove secondary loss spectral distortions, integral spectra were obtained which compared well to corresponding experimental soft x-ray absorption and transmission electron-energy loss data as well as to theoretical calculations of the unoccupied density-of-states for these materials. Comparison similarities as well as some differences are discussed. Finally, in order to illustrate the potential these signals have in serving as {open_quotes}fingerprints{close_quotes} of surface chemistry, derivative metal-CLIESS curves for the three oxide surfaces of the metals are also presented. {copyright} {ital 1998 American Vacuum Society.}

  3. Diffusional transport during the cyclic oxidation of. gamma. +. beta. , Ni-Cr-Al(Y, Zr) alloys

    SciTech Connect

    Nesbitt, J.A.; Heckel, R.W. )

    1988-02-01

    The cyclic oxidation behavior of several cast {gamma} + {beta}, Ni-Cr-Al(Y, Zr) alloys and one LPPS {gamma} + {beta}, Ni-Co-Cr-Al(Y) alloy was examined ({gamma}, fcc; {beta}, NiAl structure). Cyclic oxidation was performed by cycling between 1200{degree}C and approximately 70{degree}C. Oxide morphologies and microstructural changes during cyclic oxidation were noted. Recession of the high-Al {beta} phase was nonparabolic with time. Kirkendall porosity resulting from diffusional transport within the alloy was observed in the near-surface {gamma}-phase layer of one alloy. Concentration profiles for Ni, Cr, and Al were measured in the {gamma}-phase layer after various cyclic oxidation exposures. It was observed that cyclic oxidation results in a decreasing Al concentration at the oxide-metal interface due to a high demand for Al (a high rate of Al consumption) associated with oxide scale cracking and spalling. In addition, diffusion paths plotted on the ternary phase diagram shifted to higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption, and highest Al content, underwent breakway oxidation after 500 1-hr cycles at 1200{degree}C. Breakaway oxidation occurred when the Al concentration at the oxide-metal interface approached zero. The relationship between the Al transport in the alloy and breakaway oxidation is discussed.

  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. Development of Cu alloy anode and separator coated with Al-Ni intermetallic compound

    SciTech Connect

    Toyokura, K.; Hoshino, K.; Yamamoto, M.

    1996-12-31

    Anode made of Cu alloy and separator coated with Al-Ni intermetallic compound have been developed for VCFC. Anode of Ni alloy is usually used. However, the alternative of cost lower than Ni alloy anode should be needed, because Ni is expensive. Cu is attractive as an anode material for VCFC because it is inexpensive and electrochemically noble. However, the creep resistance of Cu is not sufficient, compared with Ni alloy. In this study, strengthening due to oxide-dispersed microstructure has been developed in Cu-Ni-Al alloy with the two-step sintering process. A wet-seal technique has been widely applied for gas-sealing and supporting of electrolyte in MCFC. Since the wet-seal area is exposed to a severe corrosive environment, corrosion resistance of material for wet sealing is related with the cell performance. Al-Ni plating with post-heat treating for stainless steel has been investigated. Stainless steel substrate was plated with Al after being coated with Ni, then heat-treated at 750 {degrees}C for 1 hour in Ar gas atmosphere. Due to the treatment, Al-Ni intermetallic compound ( mainly Al3Ni2 ) layer is formed on stainless steel surface. The long-term immersion test was carried out till 14,500 hours in 62 mol% Li{sub 2}CO{sub 3}-38 mol% K{sub 2}CO{sub 3} at 650 {degrees}C under air-30%CO{sub 2} atmosphere, for the purpose of evaluating the corrosion resistance and thermal stability of Al-Ni intermetallic compound layer in actual generating with VCFC.

  6. Hexagonal NiS nanobelts as advanced cathode materials for rechargeable Al-ion batteries.

    PubMed

    Yu, Zhijing; Kang, Zepeng; Hu, Zongqian; Lu, Jianhong; Zhou, Zhigang; Jiao, Shuqiang

    2016-08-16

    Hexagonal NiS nanobelts served as novel cathode materials for rechargeable Al-ion batteries based on an AlCl3/[EMIm]Cl ionic liquid electrolyte system. The nano-banded structure of the materials can facilitate the electrolyte immersion and enhance Al(3+) diffusion. The hexagonal NiS nanobelt based cathodes exhibit high storage capacity, good cyclability and low overpotential.

  7. 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.

  8. Study on structural, optical properties of solvothermally synthesized Ni doped CdS nanorods

    SciTech Connect

    Kaur, Kamaldeep Verma, N. K.

    2015-05-15

    Undoped and alkali metal i.e Ni doped CdS nanorods (Cd{sub x}Ni{sub 1-x}S) with (x = 0.0, 0.3,) has been synthesized by using a convenient solvothermal technique. In order to confirm the structure of the synthesized nanorods X-ray diffraction (XRD) has been done which reveals the formation of hexagonal phase of the dilute magnetic semiconducting nanorods having size of undoped 27.79nm and doped 17.49nm. Energy dispersive X-ray analysis depicts the presence of elements Cd, Ni and S in their stoichiometric ratio. Optical behavior of undoped and doped nanorods has been investigated. UV-visible spectra show the blue shift in the band gap, as compared to the bulk CdS which may be due the quantum confinement occurs in the nanostructures. Morphological analysis has been done with the help of Transmission electron microscope which confirms the polycrystalline nature of the synthesized nanorods.

  9. Mechanisms of alleviation of Zn, Cd, V, Ni and Co toxicities by dietary iron

    SciTech Connect

    Blalock, T.L.; Hill, C.H.

    1986-03-01

    Previous studies from this laboratory have demonstrated that supplemental dietary iron (Fe), i.e. 1000 ppm, ameliorated zinc (Zn), cadmium (Cd), vanadium (V), nickel (Ni), and cobalt (Co) toxicities in chicks. Investigations into the mechanisms of this detoxification have been conducted. Chicks were fed diets containing 10, 110 or 1010 ppm iron along with 0 or 4000 ppm Zn, 0 or 40 ppm Cd, 0 or 40 ppm V, 0 or 400 ppm Ni or 0 or 400 ppm Co. In every case the Fe supplemented chicks were less susceptible to the toxicities of these elements as measured by reduction in growth rate than were the iron deficient chicks. The effects of iron on the absorption and distribution of these elements were measured by using radioactive isotopes of the elements. The absorption of Co and Ni was significantly reduced when the diet was adequate in iron. Significantly more vanadium was found in the bone of the iron supplemented chicks and less in liver and kidneys. Significantly more Cd and Zn was found in the liver and less in the blood when dietary iron was adequate. Gel filtration revealed that less Cd and Zn was found on the peak eluting in the volume of metallothionein in those chicks receiving the iron deficient diet. These results suggest the possibility that iron may be essential for the formation of metallothionein. The results also indicate that the protective effect of iron on these toxicities in brought about by several mechanisms.

  10. Shear band blocking in explosively driven collapse of corrugated Ni-Al laminate cylinder

    NASA Astrophysics Data System (ADS)

    Olney, Karl; Chiu, Po-Hsun; Higgins, Andrew; Serge, Matthew; Fritz, Gregory; Stover, Adam; Nesterenko, Vitali; Benson, David

    2013-03-01

    Ni-Al laminate materials have been identified as a possible material system that can be used as a reactive material due to the self-sustaining reaction between Al and Ni layers. Besides traditional ignition methods, shear bands developed during mechanical loading can provide sites where ignition can occur. Corrugated Ni-Al laminate samples were created by swaging alternating layers of Ni (20 micrometers thick) and Al (30 micrometers thick) foils. The thick-walled cylinder (TWC) technique was performed on a corrugated Ni-Al laminate cylinder sample to examine shear band development in this material. Post experiment examination of the corrugated Ni-Al laminate material showed that the development of global shear bands were blocked via mesoscale mechanisms. The collapse of the corrugated laminate cylinder was simulated providing insight into these mesoscale mechanisms that were involved in blocking the development of shear bands during the experiment. Despite the shear band resistance of the material, several regions of the sample had localized reactions of Al and Ni spanning approximately 10-20 layers of laminate. Funding was provided by ONR MURI N00014-07-1-0740 (Program Officer Dr. Clifford Bedford)

  11. Interface Strength in NiAl-Mo Composites from 3D X-ray Microdiffraction

    SciTech Connect

    Barabash, Rozaliya; Bei, Hongbin; Gao, Yanfei; Ice, Gene E

    2011-01-01

    The depth-dependent strain gradients near buried interfaces in a model system of NiAl-Mo composite were nondestructively probed with 3-D X-ray microdiffraction. Coupled with micromechanical analysis, our study shows that the relaxation of the residual thermal strains in the NiAl-Mo composites results in the formation of a near-surface 'slip zone' with large strain gradients in both the reinforcing Mo fibers and NiAl matrix. Based on these results an approach to calculate the fiber-matrix interface strength for composite materials is suggested.

  12. Opto-electrical energy conversion by thin electrolytic CdSe films on Ni substrates

    NASA Astrophysics Data System (ADS)

    Glenis, G. X.; Athanassopoulou, M. D.; Argyropoulos, Th G.; Dervos, C. T.

    2015-02-01

    Thin-films (300 nm) of zinc-blende (cubic structure) CdSe (111) electrolytically deposited on nickel substrates had their surface characteristics investigated by XRD, SEM, and profilometry scans. A metal-CdSe-metal structure was formed by positioning a Au electrode on top of CdSe and the I-V characteristics of the resulting device were investigated in the dark and under low intensities (≤0.2 mW cm-2) of diffused solar radiation. The experimental results show that the illuminated structure is an active device that produces electric power in the 2nd quadrant of the I-V curve. This response may be related to the Ni-to-CdSe interface, where carriers are effectively generated as a result of deep energy level formations, spatially confined in the interfacial region of the depletion layer width of the Ni-CdSe junction. A potential energy diagram is proposed to present the spatially and energetically confined deep-level parameters, the operation principles (carrier generation and transport processes) across the structure and link them to the obtained I-V response. A mathematical modeling based on the Schokley-Read-Hall recombination theory confirms the experimentally obtained current profiles of illuminated junctions. Such opto-electrical tranducers might be implemented in multilayer photovoltaic hetero-structures to enhance their conversion efficiencies and reduce their operating temperatures.

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

    PubMed

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

    2012-09-01

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

  14. Cd and Ni transport and accumulation in the halophyte Sesuvium portulacastrum: implication of organic acids in these processes

    PubMed Central

    Mnasri, Mejda; Ghabriche, Rim; Fourati, Emna; Zaier, Hanen; Sabally, Kebba; Barrington, Suzelle; Lutts, Stanley; Abdelly, Chedly; Ghnaya, Tahar

    2015-01-01

    The implication of organic acids in Cd and Ni translocation was studied in the halophyte species Sesuvium portulacastrum. Citric, fumaric, malic, and ascorbic acids were separated and quantified by HPLC technique in shoots, roots and xylem saps of plants grown on nutrient solutions added with 50 μM Cd, 100 μM Ni and the combination of 50 μM Cd + 100 μM Ni. Results showed that Cd had no significant impact on biomass production while Ni and the combination of both metals drastically affected plant development. Cadmium and Ni concentrations in tissues and xylem sap were higher in plants subjected to individual metal application than those subjected to the combined effect of Cd and Ni suggesting a possible competition between these metals for absorption. Both metals applied separately or in combination induced an increase in citrate concentration in shoots and xylem sap but a decrease of this concentration in the roots. However, a minor relationship was observed between metal application and fumaric, malic, and ascorbic acids. Both observations suggest the implication of citric acid in Cd, Ni translocation and shoot accumulation in S. portulacastrum. The relatively high accumulation of citric acid in xylem sap and shoot of S. portulacastrum could be involved in metal chelation and thus contributes to heavy metal tolerance in this species. PMID:25821455

  15. Source of Scatter in the Creep Lives of NiAl(Hf) Single Crystals Revealed

    NASA Technical Reports Server (NTRS)

    1996-01-01

    In recent years, there has been an increased emphasis in developing NiAl-based alloys for high- temperature applications in aircraft engines. In comparison to commercial superalloys, binary NiAl has a higher melting temperature, lower density, larger thermal conductivity, and better oxidation resistance. These properties make it a desirable material to replace superalloys as blades and vanes in aircraft engines. Despite this attractive combination of properties, binary NiAl cannot be used as a reliable structural material because of its low-temperature brittleness and poor high-temperature creep strength. GE Aircraft Engines in Cincinnati, Ohio, has recently developed NiAl(Hf) alloys that have creep strengths comparable to commercial superalloys while maintaining the other desirable properties of binary NiAl. The microstructures of these alloys consist of finely distributed G-phase (Ni_(16)Hf_(6)Si_(7)) precipitates, which strengthen the NiAl matrix. However, while the creep properties of these alloys were being evaluated, considerable scatter was observed in the creep lives of specimens tested under identical stress and temperature conditions. Although these alloys had nominally the same composition, the test specimens were obtained from four different ingots (A, B, C, and D) that had been heat treated under similar conditions. The NASA Lewis Research Center began the present study at the request of GE Aircraft Engines under a Space Act Agreement to identify the source of this scatter.

  16. Defect Structure of Beta NiAl Using the BFS Method for Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Amador, Carlos; Ferrante, John; Noebe, Ronald D.

    1996-01-01

    The semiempirical BFS method for alloys is generalized by replacing experimental input with first-principles results thus allowing for the study of complex systems. In order to examine trends and behavior of a system in the vicinity of a given point of the phase diagram a search procedure based on a sampling of selected configurations is employed. This new approach is applied to the study of the beta phase of the Ni-Al system, which exists over a range of composition from 45-60 at.% Ni. This methodology results in a straightforward and economical way of reproducing and understanding the basic features of this system. At the stoichiometric composition, NiAl should exist in a perfectly ordered B2 structure. Ni-rich alloys are characterized by antisite point defects (with Ni atoms in the Al sites) with a decrease in lattice parameters. On the Al-rich side of stoichiometry there is a steep decrease in lattice parameter and density with increasing Al content. The presence of vacancies in Ni sites would explain such behavior. Recent X-ray diffraction experiments suggest a richer structure: the evidence, while strongly favoring the presence of vacancies in Ni sites, also suggests the possibility of some vacancies in Al sites in a 3:1 ratio. Moreover, local ordering of vacant sites may be preferred over a random distribution of individual point defects.

  17. Mechanistic insights from DGT and soil solution measurements on the uptake of Ni and Cd by radish.

    PubMed

    Luo, Jun; Cheng, Hao; Ren, Jinghua; Davison, William; Zhang, Hao

    2014-07-01

    This work tests the previously proposed hypothesis that plant uptake of metals is determined dominantly by diffusional controlled or plant limiting uptake mechanisms at, respectively, low and high metal concentrations. Radish (Raphanus sativus) was grown in 13 soils spiked with Ni (10 and 100 mg kg(-1)) and Cd (0.5 and 4 mg kg(-1)) for 4 weeks to investigate the mechanisms affecting plant uptake. Soil solution concentrations, Css, of Ni and Cd were measured, along with the DGT interfacial concentration, CDGT, and the derived effective concentration in soil solution, CE. Free ion activities, aNi(2+) and aCd(2+), were obtained using WHAM 6. Although there was a poor relationship between Ni in radish roots and either Css or aNi(2+) in unamended soils, the distribution of data could be rationalized in terms of the extent of release of Ni from the soil solid phase, as identified by DGT and soil solution measurements. By contrast Ni in radish was linearly related to CE, demonstrating diffusion limited uptake. For soils amended with high concentrations of Ni, linear relationships were obtained for Ni in radish plotted against, Css, aNi(2+), and CE, consistent with the plant controlling uptake. For Ni the hypothesis concerning dominant diffusional and plant limiting uptake mechanisms was demonstrated. Poor relationships between Cd in radish and Css, aCd(2+), and CE, irrespective of amendment by Cd, showed the importance of factors other than diffusional supply, such as rhizosphere and inhibitory processes, and that fulfilment of this hypothesis is plant and metal specific.

  18. 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.

  19. Laser surface heat treatment of electroless Ni-P-SiC coating on Al356 alloy

    NASA Astrophysics Data System (ADS)

    Hashemi, Sayed Hamid; Shoja-Razavi, Reza

    2016-11-01

    Electroless Ni-P-SiC coatings are recognized for their hardness and wear resistance. In the present study, electroless Ni-P coatings containing SiC particles were co-deposited on Al356 substrate. Laser surface heat treatment was performed using 700 W Nd:YAG pulsed laser. Effects of different laser operating parameters, such as laser scan rate, laser average power and defocusing distance on microstructures were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The results of microstructural characterization indicated that the laser treatment under different operating conditions produced composite coating contained nanocrystallined Ni-based matrix with SiC particles Ni3P, Ni12P5, Ni5P2, Ni8P3 precipitates. The microhardness measurements showed that the hardness of the coating was increased up to 60%, due to laser heat treatment, without effect on base metal.

  20. Bioleaching of spent Zn-Mn or Ni-Cd batteries by Aspergillus species.

    PubMed

    Kim, Min-Ji; Seo, Ja-Yeon; Choi, Yong-Seok; Kim, Gyu-Hyeok

    2016-05-01

    This research explores the recovery of metals from spent Zn-Mn or Ni-Cd batteries by a bioleaching using six Aspergillus species. Two different nutrients, malt extract and sucrose, were used to produce different types of organic acids. Oxalic acid and citric acid were shown to be the dominant organic acid in malt extract and sucrose media, respectively. In the bioleaching, the metal removal was higher in sucrose media than malt extract. All species, except A. niger KUC5254, showed more than 90% removal of metals from Zn-Mn battery. For Ni-Cd battery, more than 95% of metals was extracted by A. niger KUC5254 and A. tubingensis KUC5037. As a result, A. tubingensis KUC5037 which is a non-ochratoxigenic fungus was considered to have the greatest potential for improving the safety and efficiency of the bioleaching.

  1. Aqueous synthesis and characterization of Ni, Zn co-doped CdSe QDs

    NASA Astrophysics Data System (ADS)

    Thirugnanam, N.; Govindarajan, D.

    2016-01-01

    Ni, Zn co-doped CdSe quantum dots (QDs) were synthesized by chemical precipitation method through aqueous route. The prepared QDs were characterized by X-ray diffraction (XRD) technique, UV-Vis absorption spectroscopy, photoluminescence (PL) spectroscopy and high resolution transmission electron microscopy (HRTEM). XRD technique results indicate that the prepared samples have a zinc blende cubic phase. From UV-Vis absorption spectroscopy technique, the prepared samples were blue shifted with respect to their bulk counter part due to quantum confinement effect. Among different doping ratios examined, a maximum PL emission intensity was observed for CdSe:Ni(1 %):Zn(1 %) QDs. HRTEM pictures show that the prepared QDs were in spherical shape.

  2. Chemical evaluation of non-woven nylon separators used in Ni/Cd cells

    NASA Technical Reports Server (NTRS)

    Cuddihy, Edward F.

    1991-01-01

    The goals of the chemical analysis was to identify Gates 2505 degradation mechanism, to determine if Eagle-Pitcher 2505 supply suitable for flight, and to assess the 2538 as a candidate replacement, based on chemical findings. Chemical testing strongly indicates that the Gates 2505 stored in Florida had undergone partial chemical deterioration, believed caused by exposure to high humidities and temperature. A suspected role of zinc chloride as a separator concern during storage was not verified in this study (the effect of ZnCl2 on cell/electrode performance was not addressed). No substantial chemical issues or concerns with using EP 2505 as Ni/Cd battery separator for Mars Observer and TOPEX could be found. No chemical issues or concerns with using 2538 as Ni/Cd battery separator were found, in fact, chemical evidence suggest that 2538 may be a better material, as compared to 2505.

  3. Bio-absorption of Ni and Cd on Eichhornia crassipes root thin film.

    PubMed

    Elfeky, Souad A; Imam, Hisham; Alsherbini, Alsayed A

    2013-11-01

    Release of heavy metals into waterways without treatment can cause a significant threat to the environment. In this paper, we present a method of improving the removal of heavy metals by using Eichhornia crassipes roots (ECR) supported on a polymethyl methacrylate (PMMA) thin film. The functional groups of the synthesized PMMA sample were identified by Fourier transform infrared spectroscopy. ECR roots dried fine powder has a small size and large surface area. They contain many polyfunctional metal-binding sites for both cationic and anionic metal complexes. The results show that using 0.1 g of ECR, about 70% of Cd present in the water was removed in 4 h; while under the same conditions, about 55% of Ni was removed. The concentrations of Ni and Cd were measured by laser-induced breakdown spectroscopy, a promising technique for the elemental analysis of heavy metals.

  4. Manifestations of dynamic strain aging in soft-oriented NiAl single crystals

    NASA Astrophysics Data System (ADS)

    Weaver, M. L.; Kaufman, M. J.; Noebe, R. D.

    1996-11-01

    The tensile and compressive properties of six NiAl-base single-crystal alloys have been investigated at temperatures between 77 and 1200 K. The normalized critical resolved shear stresses (CRSS/E) and work-hardening rates ( θ/E) for these alloys generally decreased with increasing temperature. However, anomalous peaks or plateaus for these properties were observed in conventional purity (CPNiAl), Si-doped (NiAl-Si), C-doped low Si (UF-NiAll), and Mo-doped (NiAl-Mo) alloys at intermediate temperatures (600 to 1000 K). This anomalous behavior was not observed in high-purity, low interstitial material (HP-NiAl). Low or negative strain-rate sensitivities (SRS) also were observed in all six alloys in this intermediate temperature range. Coincident with the occurrence of negative strain-rate sensitivities was the observation of serrated stress-strain curves in the CPNiAl and NiAl-Si alloys. These phenomena have been attributed to dynamic strain aging (DSA). Chemical analysis of the alloys used in this study suggests that the main specie responsible for strain aging in NiAl is C but indicate that residual Si impurities can enhance the strain aging effects. The corresponding dislocation microstructures at low temperatures (300 to 600 K) were composed of welldefined cells. At intermediate temperatures (600 to 900 K), either poorly defined cells or coarse bands of localized slip, reminiscent of the vein structures observed in low-cycle fatigue specimens deformed in the DSA regime, were observed in conventional purity, Si-doped, and in Mo-doped alloys. In contrast, a well-defined cell structure persisted in the low interstitial, high-purity alloy. At elevated temperatures (≥1000 K), more uniformly distributed dislocations and sub-boundaries were observed in all alloys. These observations are consistent with the occurrence of DSA in NiAl single-crystal alloys at intermediate temperatures.

  5. Transient Oxidation of a γ-Ni-28Cr-11Al Alloy

    SciTech Connect

    Hu, L; Hovis, D B; Heuer, A H

    2012-04-02

    γ-NiCrAl alloys with relatively low Al contents tend to form a layered oxide scale during the early stages of oxidation, rather than an exclusive α-Al2O3 scale, the so-called 'thermally grown oxide' (TGO). A layered oxide scale was established on a model γ-Ni-28Cr-11Al (at.%) alloy after isothermal oxidation for several minutes at 1100 °C. The layered scale consisted of an NiO layer at the oxide/gas interface, an inner Cr2O3 layer, and an α-Al2O3 layer at the oxide/alloy interface. The evolution of such an NiO/Cr2O3/Al2O3 layered structure on this alloy differs from that proposed in earlier work. During heating, a Cr2O3 outer layer and a discontinuous inner layer of Al2O3 initially formed, with metallic Ni particles dispersed between the two layers. A rapid transformation occurred in the scale shortly after the sample reached maximum temperature (1100°C), when two (possibly coupled) phenomena occurred: (i) the inner transition alumina transformed to α-Al2O3, and (ii) Ni particles oxidized to form the outer NiO layer. Subsequently, NiO reacted with Cr2O3 and Al2O3 to form spinel. Continued growth of the oxide scale and development of the TGO was dominated by growth of the inner α-Al2O3 layer.

  6. Nonprotective Alumina Growth in Sulfur-Doped NiAl(Zr)

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    2000-01-01

    The 1200 C oxidation behavior of NiAl was examined at various levels of sulfur and zirconium dopants to test the possibility of a critical S/Zr ratio required for adhesion. Cyclic furnace testing for 200 1 -hr cycles and interrupted testing for 500 hr were used as screening tests. Pure NiAl and NiAl(Zr) with 0. 14 at.% Zr were chosen as model base compositions; they exhibited normal, slow-growing scales (3 Mg/sq cm) with excellent adhesion for the Zr-doped alloys. NiAl with about 120 ppma S exhibited a substantial weight loss (-20 Mg/sq cm) in cyclic tests and a very large weight gain (+60 Mg/sq cm) in interrupted tests. The major surface phase remained as alpha -Al2O3. Sulfur doping the NiAl(Zr) alloy caused massive weight gains of 80 - 100 Mg/sq cm, swelling, cracking, and nearly complete conversion into NiAl2O4, and alpha- Al2O3. The initial objective of determining critical S/Zr ratios for adhesion was therefore unattainable. Initiation of the catastrophic attack was examined after a 10 hr exposure, revealing a few sites of broad, raised, and cracked ridges. In cross-section, the ridges appeared as modular intrusions, with a complex, fractal, oxide-metal interface. They were primarily alumina (with occasional entrapped islands of NiAl2O4 or pure Ni metal). They possessed a unique microstructure consisting of 0.3 microns lamellae, separated by 0.1 microns open channels. This allowed for rapid growth controlled by gaseous diffusion. The microstructure is discussed in terms of SO2 evolution and a sulfur-driven de-passivation process.

  7. Modification of ZnO Thin Films by Ni, Cu, and Cd Doping*1

    NASA Astrophysics Data System (ADS)

    Jiménez-González, A. E.

    1997-02-01

    With the propose of investigating the effect of transition elements in ZnO thin films prepared by the Successive Ion Layer Adsorption and Reaction (SILAR) technique, the deposition solutions were chemically impurified with Ni, Cu, and Cd, as elements of the Ib, IIb, and VIIIa groups. X-ray fluorescence (XRF) analyses confirm that the impurification with Ni and Cu in fact took place but the impurification with Cd did not, while the XRD analyses show that foras preparedand Ni-impurified annealed films, the crystallites are almost oriented along thecaxis. The electrical properties of the ZnO films were also modified with the impurification. After annealing in air (450°C) the dark conductivity of the films was increased in the case of Ni and Cd impurification up to 1.80×10-3and 1.86×10-2[Ω cm]-1, respectively, but it decreased drastically in the case of Cu to 5.51×10-7[Ω cm]-1, as referred to the dark conductivity (1.86×10-4[Ω cm]-1) of the pure ZnO sample. The measured activation energy for the electrical conductivity of the modified ZnO thin films is 55 meV for the Ni modification, indicating the existence of donor levels. On the other hand, the Cu modification increases the activation energy up to 132 meV, which is higher than the activation energy for pure ZnO thin films (98 meV).

  8. Development of Large Scale Advanced NI-CD Batteries Employing Roll-Bonded Electrodes

    DTIC Science & Technology

    1994-10-17

    LONG-TERM TESTING ..................... TASK 3 - FABRICATION OF SIX ADVANCED 2000-Ah CELLS ........................ METHOD OF...TIME, h TABLE 2-24. 2000-AH NI-CD CELL 2-41 NSWCDD/TR-94/50 METHOD OF TEST A continuous method of testing was used following the formation procedure as...MICHAEL MCKUBRE C/O SRI INTERNATIONAL 333 RAVENSWOOD AVENUE MENLO PARK CA 84025 ATTN SATYAMARAYANA KODALI TACOM WARREN MI 48397-5000 ATTN BRADFORD M

  9. Molecular dynamics simulation of the energetic reaction between Ni and Al nanoparticles

    NASA Astrophysics Data System (ADS)

    Henz, Brian J.; Hawa, Takumi; Zachariah, Michael

    2009-06-01

    Molecular dynamics simulations are used to simulate the energetic reaction of Ni and Al particles at the nanometer scale. The effect of particle size on reaction time and temperature for separate nanoparticles has been considered as a model system for a powder metallurgy system. Coated nanoparticles in the form of Ni-coated Al nanoparticles and Al-coated Ni nanoparticles are also analyzed as a model for nanoparticles embedded within a matrix. The differences in melting temperature and phase change behavior, e.g., the volumetric expansion of Al between Al and Ni, are expected to produce differing results for the coated nanoparticle systems. For instance, the volumetric expansion of Al upon melting is expected to produce large tensile stresses and possibly rupture in the Ni shell for Ni-coated Al. Simulation results show that the sintering time for separate and coated nanoparticles is nearly linearly dependent on the number of atoms or volume of the sintering nanoparticles. We have also found that nanoparticle size and surface energy are important factors in determining the adiabatic reaction temperature for both systems at nanoparticle sizes of less than 10 nm in diameter.

  10. The effects of alloy purity on the mechanical behavior of soft oriented NiAl single crystals

    NASA Technical Reports Server (NTRS)

    Weaver, M. L.; Kaufman, M. J.; Noebe, R. D.

    1993-01-01

    Preliminary results of the effects of alloy purity on the mechanical properties of NiAl single crystals are presented. Two stoichiometric NiAl single crystals with different impurity contents were studied. It is concluded that reductions in the interstitial and substitutional levels cause reduced yield strengths in NiAl. Heat treatment also results in reduced yield and flow stresses in both CP-NiAl and Hp-NiAl which are considered to be due to a reduction in the concentration of thermal vacancies due to vacancy coalescence during heat treatment.

  11. Production of hydrogen by autothermal reforming of propane over Ni/delta-Al2O3.

    PubMed

    Lee, Hae Ri; Lee, Kwi Yeon; Park, Nam Cook; Shin, Jae Soon; Moon, Dong Ju; Lee, Byung Gwon; Kim, Young Chul

    2006-11-01

    The performance of Ni/delta-Al2O3 catalyst in propane autothermal reforming (ATR) for hydrogen production was investigated in the present study. The catalysts were characterized using XRD, TEM, and SEM. The activity of the Ni/delta-Al2O3 catalyst manufactured by the water-alcohol method was better than those of the catalysts manufactured by the impregnation and chemical reduction methods. The Ni/delta-Al2O3 catalysts were modified by the addition of promoters such as Mg, La, Ce, and Co, in order to improve their stability and yield. Hydrogen production was the largest for the Ni-Co-CeO2/Al2O3, catalyst.

  12. 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.

  13. Electrophoretic deposition of double-layer HA/Al composite coating on NiTi.

    PubMed

    Karimi, Esmaeil; Khalil-Allafi, Jafar; Khalili, Vida

    2016-01-01

    In order to improve the bioactivity of NiTi alloys, which are being known as the suitable materials for biomedical applications, numerous NiTi disks were electrophoretically coated by hetero-coagulated hydroxyapatite/aluminum composite coatings in three main voltages from suspensions with different Al concentrations. In this paper, the amount of Ni ions release and bioactivity of prepared samples as well as bonding strength of the coating to substrate were investigated. The surface characterization of the coating by XRD, EDX, SEM, and FTIR showed that HA particles bonded by Al particles. It caused the formation of a free crack coating on NiTi disks. Moreover, the bonding strength of HA/Al coatings to NiTi substrate were improved by two times as compared to that of the pure HA coatings. Immersing of coated samples in SBF for 1 week showed that apatite formation ability was improved on HA/Al composite coating and Ni ions release from the surface of composite coating decreased. These results induce the appropriate bioactivity and biocompatibility of the deposited HA/Al composite coatings on NiTi disks.

  14. Photoelectrochemical performance of NiO-coated ZnO–CdS core-shell photoanode

    NASA Astrophysics Data System (ADS)

    Iyengar, Pranit; Das, Chandan; Balasubramaniam, K. R.

    2017-03-01

    A nano-structured core-shell ZnO–CdS photoanode device with a mesoporous NiO co-catalyst layer was fabricated using solution-processing methods. The growth of the sparse ZnO nano-rod film with a thickness of ca. 930 nm was achieved by optimizing parameters such as the thickness of the ZnO seed layer, choice of Zn precursor salt and the salt concentration. CdS was then coated by a combination of spin coating and spin SILAR (Successive Ionic Layer Adsorption and Reaction) methods to completely fill the interspace of ZnO nano-rods. The uniform CdS surface facilitated the growth of a continuous mesoporous NiO layer. Upon illumination of 100 mW·cm‑2 AM 1.5 G radiation the device exhibits stable photocurrents of 2.15 mA·cm‑2 at 1.23 V and 0.92 mA·cm‑2 at 0.00 V versus RHE, which are significantly higher as compared to the bare ZnO–CdS device. The excellent performance of the device can be ascribed to the higher visible region absorption by CdS, and effective separation of the photogenerated charge carriers due to the suitable band alignment and nanostructuring. Additionally, the mesoporous NiO overlayer offered a larger contact area with the electrolyte and promoted the kinetics enabling higher and stable photocurrent even till the 35th min. of testing.

  15. 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.

  16. Synthesis of Cd/(Al+Fe) layered double hydroxides and characterization of the calcination products

    SciTech Connect

    Perez, M.R.; Barriga, C.; Fernandez, J.M.; Rives, V.; Ulibarri, M.A.

    2007-12-15

    Layered double hydroxides (LDHs) containing Cd(II), Al(III), and Fe(III) in the brucite-like layers with different starting Fe/Al atomic ratios and with nitrate as counteranion have been prepared following the coprecipitation method at a constant pH value of 8. An additional Cd(II),Al(III)-LDH sample interlayered with hexacyanoferrate(III) ions has been prepared by ionic exchange at pH 9. The samples have been characterized by elemental chemical analysis, powder X-ray diffraction (PXRD), and FT-IR spectroscopy. Their thermal stability has been assessed by thermogravimetric and differential thermal analyses (TG-DTA) and mass spectrometric analysis of the evolved gases. The PXRD patterns of the solids calcined at 800 deg. C show diffraction lines corresponding to Cd(Al)O and spinel-type materials, which precise nature (CdAl{sub 2}O{sub 4}, Cd{sub 1-x}Fe{sub 2+x}O{sub 4}, or Cd{sub x}Fe{sub 2.66}O{sub 4}) depends on location and concentration of iron in the parent material or precursor. - Graphical abstract: Layered double hydroxides (LDHs) containing Cd(II), Al(III), and Fe(III) in the brucite-like layers with different starting Fe/Al atomic ratios and with nitrate as counteranion have been prepared following the coprecipitation method. An additional Cd(II),Al(III)-LDH sample interlayered with hexacyanoferrate(III) ions has been prepared by ionic exchange. Calcination at 800 deg. C shows diffraction lines corresponding to CdO and to spinel-type materials. SEM micrograph of sample CdAlFe-N-0.

  17. Effect of grain size on yield strength of Ni/sub 3/Al and other alloys

    SciTech Connect

    Takeyama, M.; Liu, C.T.

    1988-07-01

    This paper analyzes the effect of grain size on yield stress of ordered Ni/sub 3/Al and Zr/sub 3/Al, and mild steels that show Lueders band propagation after yielding, using the Hall--Petch relation, sigma/sub y/ = sigma/sub 0/+k/sub y/ d/sup -1//sup ///sup 2/, and the new relation proposed by Schulson et al., sigma/sub y/ = sigma/sub 0/+kd/sup -(//sup p//sup +1)/2/ (Schulson et al., Acta Metall. 33, 1587 (1985)). The major emphasis is placed on the analysis of Ni/sub 3/Al data obtained from published and new results, with a careful consideration of the alloy stoichiometry effect. All data, except for binary stoichiometric Ni/sub 3/Al prepared by powder extrusion, fit the Hall--Petch relation, whereas the data from boron-doped Ni/sub 3/Al and mild steels do not follow the Schulson relation. However, no conclusion can be made simply from the curve fitting using either relation. The results are also discussed in terms of Lueders strain and alloy preparation methods. On the basis of the Hall--Petch analysis, the small slope k/sub y/ is obtained only for hypostoichiometric Ni/sub 3/Al with boron, which would be related to a stronger segregation of boron in nickel-rich Ni/sub 3/Al. In addition, the potency for the solid solution strengthening effect of boron is found to be much higher for stoichiometric Ni/sub 3/Al than for hypostoichiometric alloys.

  18. Slow strain rate 1200-1400 K compressive properties of NiAl-1Hf

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Nathal, M. V.; Raj, S. V.; Pathare, V. M.

    1991-01-01

    Compression tests are conducted on NiAl-1Hf to assess the elevated-temperature creep behavior of this precipitation-hardened aluminide. While the strength is high under fast strain rates (more than 10 exp -5/s), under slower conditions the alloy is weak. Thus, it is unlikely that effective creep resistance can be obtained in NiAl through small Hf additions.

  19. Sol-gel-derived NiO/NiAl{sub 2}O{sub 4} oxygen carriers for chemical-looping combustion by coal char

    SciTech Connect

    Haibo Zhao; Liming Liu; Baowen Wang; Di Xu; Linlin Jiang; Chuguang Zheng

    2008-03-15

    This paper focuses on the investigation of Ni-based oxygen carriers for CLC by coal char. First, Al(OC{sub 3}H{sub 7}){sub 3} and Ni(NO{sub 3}){sub 2} are selected as the main raw materials to prepare sol-gel-derived NiO/NiAl{sub 2}O{sub 4} oxygen carriers. The oxygen carrier with a mass content of 60% NiO, a sintering temperature of 1300{sup o}C, and a sintering time of 6 h performs comparatively well. Second, the reduction reaction of the NiO/NiAl{sub 2}O{sub 4} oxygen carriers with char and the circular reduction/oxidation reactions of the NiO/NiAl{sub 2}O{sub 4} oxygen carriers with char/air or hydrogen/air are carried out in a thermogravimetric analysis (TGA) instrument to investigate the reactivities and chemical life of the prepared NiO/NiAl{sub 2}O{sub 4} oxygen carriers. The experimental results show that (a) when the TGA temperature is higher than 850{sup o}C, NiO/NiAl{sub 2}O{sub 4} starts to react with coal char rapidly, which indicates that CLC of coal char using NiO/NiAl{sub 2}O{sub 4} as oxygen carriers is a feasible technology of energy utilization in principle; (b) NiO/NiAl{sub 2}O{sub 4}, which maintains its activity over single-cycle reduction/oxidation reactions with char/air or multiple-cycle reduction/oxidation reactions with hydrogen/air, exhibits extremely good recyclablity; (c) the porous beehive structure of the NiO/NiAl{sub 2}O{sub 4} particle is maintained, and the sintering behavior between different particles is not observed during cyclic studies. Those experimental results prove the sol-gel-derived oxygen carrier NiO/NiAl{sub 2}O{sub 4} is capable of being used in chemical-looping combustion fueled by coal char or H{sub 2}. 51 refs., 5 figs., 5 tabs.

  20. Nickel segregation to grain boundaries in Ni sub 3 Al alloys

    SciTech Connect

    Subramanian, R.; Robertson, I.M.; Birnbaum, H.K. )

    1991-12-01

    This paper reports that a considerable research effort has been undertaken to understand the improved ductility of hypo-stoichiometric Ni{sub 3} Al containing B relative to stoichiometric and hyper-stoichiometric alloys. A variety of techniques have shown that in ductile alloys, the level of B at the grain boundary is significantly higher than in the matrix and that the B exhibits equilibrium segregation over distances of the order of 1 nm from the boundaries. The concentration of nickel at the boundaries is less certain. Some measurements have shown somewhat enhanced Ni concentrations within 1 nm of the grain boundaries and correlations between B and Ni segregation, while in others a small amount of Ni segregation was observed but with no correlation to B segregation, and on others no Ni segregation was observed. Baker et al. report the formation of a second phase extending for distances of about 20 nm from the boundaries and having very high Ni concentrations in hypo-stoichiometric Ni{sub 3}Al containing B. These different results may reflect the different material preparation and annealing procedures that have been used. Horton and Liu have shown that the presence of the Ni-rich second phase was not necessary for the ductility of Ni{sub 3}Al. It has been suggested that a disordered fcc layer may exist at B enriched grain boundaries, and that this disorder may enhance Ni{sub 3}Al ductility by making it easier for dislocation to be transmitted through the grain boundaries.

  1. Interface considerations in Al2O3/NiAl composite

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1993-01-01

    The fiber-matrix interface requirements in an Al2O3/NiAl composite were examined from theoretical considerations. Several factors that influence the interface bonding requirements were analyzed. These include: (1) residual stresses due to fiber-matrix coefficient of thermal expansion (CTE) mismatch; (2) matrix cracking stress at room temperature; (3) fracture toughness at room temperature; (4) load transfer from the matrix to the fiber and ultimate tensile strength at the use temperature; and (5) creep resistance at high temperature. A relatively weak fiber-matrix bond, with an interfacial shear strength of approximately 15-20 MPa, might be sufficient for attaining the desired mechanical properties in the fiber direction at the use temperature. A weak fiber-matrix bond is also beneficial for increasing the fracture toughness of the composite at room temperature. In contrast, a strong fiber-matrix bond is required to withstand some of the residual stresses resulting from the fiber-matrix CTE mismatch, which are not likely to be reduced significantly by interface coatings. A relatively strong bond is also beneficial in increasing the matrix cracking stress at room temperature. Various interface coating options to accommodate the conflicting bonding requirements were reviewed. One viable coating option is to incorporate a thick, ductile interface layer well bonded to both the fiber and the matrix.

  2. First principles calculations of the effect of Pt on NiAl surfaceenergy and the site preference of Pt

    SciTech Connect

    Yu, Rong; Hou, Peggy Y.

    2007-03-08

    Pt-modified NiAl is widely used as a coating material in industry. In this study, the surface energies of NiAl with and without Pt are investigated using first-principles calculations. The presence of Pt in NiAl takes the surface electronic states to higher energies, resulting in an increased surface energy, which explains some of the beneficial effects of Pt on the oxidation resistance of NiAl. The electronic structure of NiAl-Pt alloys is also analyzed in terms of the site preference of Pt in NiAl. Results show that Pt bonds strongly to Al, giving its site preference on the Ni site.

  3. Al/CdSe/GaSe/C resonant tunneling thin film transistors

    NASA Astrophysics Data System (ADS)

    Qasrawi, A. F.; Kayed, T. S.; Elsayed, Khaled A.

    2017-02-01

    An Al/CdSe/GaSe/C thin film transistor device was prepared by the physical vapor deposition technique at a vacuum pressure of 10-5 mbar. The x-ray diffraction measurements demonstrated the polycrystalline nature of the surface of the device. The dc current-voltage characteristics recorded for the Al/CdSe/C and Al/CdSe/GaSe/C channels displayed a resonant tunneling diode features during the forward and reverse voltage biasing, respectively. In addition, the switching current ratio of the Al/CdSe/C increased from 18.6 to 9.62×103 as a result of the GaSe deposition on the CdSe surface. Moreover, the alternating electrical signal analyses in the frequency range of 1.0 MHz to 1.8 GHz, showed some remarkable properties of negative resistance and negative capacitance spectra of the Al/CdSe/GaSe/C thin film transistors. Two distinct resonance-antiresonance phenomena in the resistance spectra and one in the capacitance spectra were observed at 0.53, 1.04 and 1.40 GHz for the Al/CdSe/C channel, respectively. The respective resonating peak positions of the resistance spectra shift to 0.38 and 0.95 GHz when GaSe is interfaced with CdSe. These features of the thin film transistors are promising for use in high quality microwave filtering circuits and also for use as ultrafast switches.

  4. Alloying effects on mechanical and metallurgical properties of NiAl

    SciTech Connect

    Liu, C.T.; Horton, J.A.; Lee, E.H.; George, E.P.

    1993-06-01

    Alloying effects were investigated in near-stoichiometric NiAl for improving its mechanical and metallurgical properties. Ternary additions of 19 elements at levels up to 10 at. % were added to NiAl; among them, molybdenum is found to be most effective in improving the room-temperature ductility and high-temperature strength. Alloying with 1.0 {plus_minus} 0.6% molybdenum almost doubles the room-temperature tensile ductility of NiAl and triples its yield strength at 1000C. The creep properties of molybdenum-modified NiAl alloys can be dramatically improved by alloying with up to 1% of niobium or tantalum. Because of the low solubilities of molybdenum and niobium in NiAl, the beneficial effects mainly come from precipitation hardening. Fine and coarse precipitates are revealed by both transmission electron microscopy (TEM) and electron microprobe analyses. Molybdenum-containing alloys possess excellent oxidation resistance and can be fabricated into rod stock by hot extrusion at 900 to 1050C. This study of alloying effects provides a critical input for the alloy design of ductile and strong NiAl aluminide alloys for high-temperature structural applications.

  5. High-rate oxygen evolution reaction on Al-doped LiNiO2.

    PubMed

    Gupta, Asha; Chemelewski, William D; Buddie Mullins, C; Goodenough, John B

    2015-10-21

    LiNi0.8 Al0.2 O2 with a higher Ni(3+) /Li(+) ordering, synthesized by the solution-combustion method, gives oxygen-evolution-reaction (OER) activity in alkaline solution that is comparable to that of IrO2 . This confirms that the octahedral-site Ni(IV) /Ni(III) couple in an oxide is an active redox center for the OER with -redox energy pinned at the top of the O-2p bands.

  6. Constitution of pseudobinary hypoeutectic beta-NiAl + alpha-V alloys

    NASA Technical Reports Server (NTRS)

    Cotton, J. D.; Kaufman, M. J.; Noebe, R. D.

    1991-01-01

    The formation of pseudobinary eutectics between NiAl (beta) and V (alpha) at high temperatures was investigated as a possible way of improving the ductility and toughness of the alloy. It is found that a pseudobinary eutectic, characterized by a large beta+alpha field, is formed in the Ni-Al-V ternary system below about 1370 C. The high-temperature solubility of V in beta is about 14 percent, decreasing markedly with decreasing temperature and increasing Al content above 50 at. pct Al. The pseudobinary hypoeutectic exibits crack resistance under indentation loading.

  7. 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.

  8. Elevated Temperature Compressive Strength Properties of Oxide Dispersion Strengthened NiAl After Cryo-milling and Roasting in Nitrogen

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Grahle, Peter; Arzt, Eduard; Hebsur, Mohan

    1998-01-01

    In an effort to superimpose two different elevated temperature strengthening mechanisms in NiAl, several lots of oxide dispersion strengthened (ODS) NiAl powder have been cryo-milled in liquid nitrogen to introduce AlN particles at the grain boundaries. As an alternative to cryo-milling, one lot of ODS NiAl was roasted in nitrogen to produce AlN. Both techniques resulted in hot extruded AlN-strengthened, ODS NiAl alloys which were stronger than the base ODS NiAl between 1200 and 1400 K. However, neither the cryo-milled nor the N2-roasted ODS NiAl alloys were as strong as cryo-milled binary NiAl containing like amounts of AlN. The reason(s) for the relative weakness of cryo-milled ODS NiAl is not certain; however the lack of superior strength in N2-roasted ODS NiAl is probably due to its relatively large AlN particles.

  9. Crystallography of the NiHfSi Phase in a NiAl (0.5 Hf) Single-Crystal Alloy

    NASA Technical Reports Server (NTRS)

    Garg, A.; Noebe, R. D.; Darolia, R.

    1996-01-01

    Small additions of Hf to conventionally processed NiAl single crystals result in the precipitation of a high density of cuboidal G-phase along with a newly identified silicide phase. Both of these phases form in the presence of Si which is not an intentional alloying addition but is a contaminant resulting from contact with the ceramic shell molds during directional solidification of the single-crystal ingots. The morphology, crystal structure and Orientation Relationship (OR) of the silicide phase in a NiAl (0.5 at.%Hf) single-crystal alloy have been determined using transmission electron microscopy, electron microdiffraction and energy dispersive X-ray spectroscopy. Qualitative elemental analysis and indexing of the electron microdiffraction patterns from the new phase indicate that it is an orthorhombic NiHfSi phase with unit cell parameters, a = 0.639 nm, b = 0.389 nm and c = 0.72 nm, and space group Pnma. The NiHfSi phase forms as thin rectangular plates on NiAl/111/ planes with an OR that is given by NiHfSi(100))(parallel) NiAl(111) and NiHfSi zone axes(010) (parallel) NiAl zone axes (101). Twelve variants of the NiHfSi phase were observed in the alloy and the number of variants and rectangular morphology of NiHfSi plates are consistent with symmetry requirements. Quenching experiments indicate that nucleation of the NiHfSi phase in NiAI(Hf) alloys is aided by the formation of NiAl group of zone axes (111) vacancy loops that form on the NiAl /111/ planes.

  10. Valorization of biosorbent obtained from a forestry waste: Competitive adsorption, desorption and transport of Cd, Cu, Ni, Pb and Zn.

    PubMed

    Cutillas-Barreiro, Laura; Paradelo, Remigio; Igrexas-Soto, Alba; Núñez-Delgado, Avelino; Fernández-Sanjurjo, María José; Álvarez-Rodriguez, Esperanza; Garrote, Gil; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

    2016-09-01

    Bark from Pinus pinaster is one of the most abundant forestry wastes in Europe, and among the proposed technologies for its reutilization, the removal of heavy metals from wastewater has been gaining increasing attention. In this work, we have studied the performance of pine bark for heavy metal biosorption on competitive systems. Pb, Cu, Ni, Zn and Cd sorption and desorption at equilibrium were studied in batch experiments, whereas transport was studied in column experiments. Batch experiments were performed adding simultaneously different concentrations (0.08-3.15mM) of two or more metals in solution to pine bark samples. Column experiments were performed with 10mM solutions of two metals or a 5mM solution of the five metals. In general, the results under competitive conditions were different to those obtained in monoelemental experiments. The multi-metal batch experiments showed the adsorption sequence Pb≈Cu>Cd>Zn>Ni for lower metal doses, Pb>Cu>Cd>Zn>Ni for intermediate doses, and Pb>Cu>Cd≈Zn≈Ni for high metal doses. Desorption followed the sequence Pb<Cd for the lowest metal doses, and PbCd for the highest ones. The bi-metal batch experiments indicated that Cu and Pb suffered the highest retention, with high capacity to displace Cd, Ni and Zn from adsorption sites on pine bark. The transport experiments produced comparable results to those obtained in the batch experiments, with pine bark retention capacity following the sequence Pb>Cu>Zn>Cd>Ni. The presence of a second metal affected the transport of all the elements studied except Pb, and confirmed the strong influence of Pb and Cu on the retention of the other metals. These results can help to appropriately design decontamination systems using this forestry waste.

  11. Hydrothermal Synthesis and Characterization of Ni-Al Montmorillonite-Like Phyllosilicates

    PubMed Central

    Reinholdt, Marc X.; Brendlé, Jocelyne; Tuilier, Marie-Hélène; Kaliaguine, Serge; Ambroise, Emmanuelle

    2013-01-01

    This work describes the first hydrothermal synthesis in fluoride medium of Ni-Al montmorillonite-like phyllosilicates, in which the only metallic elements in the octahedral sheet are Ni and Al. X-ray diffraction , chemical analysis, thermogravimetric and differential thermal analysis, scanning electron microscopy and transmission electron microscopy confirm that the synthesized samples are montmorillonite-like phyllosilicates having the expected chemical composition. The specific surface areas of the samples are relatively large (>100 m2 g−1) compared to naturally occurring montmorillonites. 29Si and 27Al nuclear magnetic resonance (NMR) indicate substitutions of Al for Si in the tetrahedral sheet. 19F NMR and Ni K-edge extended X-ray absorption fine structure (EXAFS) local probes highlight a clustering of the metal elements and of the vacancies in the octahedral sheet of the samples. These Ni-Al phyllosilicates exhibit a higher local order than in previously synthesized Zn-Al phyllosilicates. Unlike natural montmorillonites, where the distribution of transition metal cations ensures a charge equilibrium allowing a stability of the framework, synthetic montmorillonites entail clustering and instability of the lattice when the content of divalent element in the octahedral sheet exceeds ca. 20%. Synthesis of Ni-Al montmorillonite-like phyllosilicates, was successfully achieved for the first time. These new synthetic materials may find potential applications as catalysts or as materials with magnetic, optical or staining properties. PMID:28348321

  12. High thermally stable Ni /Ag(Al) alloy contacts on p-GaN

    NASA Astrophysics Data System (ADS)

    Chou, C. H.; Lin, C. L.; Chuang, Y. C.; Bor, H. Y.; Liu, C. Y.

    2007-01-01

    Ag agglomeration was found to occur at Ni /Ag to p-GaN contacts after annealing at 500°C. This Ag agglomeration led to the poor thermal stability showed by the Ni /Ag contacts in relation to the reflectivity and electrical properties. However, after alloying with 10at.% Al by e-gun deposition, the Ni /Ag(Al) p-GaN contacts were found to effectively retard Ag agglomeration thereby greatly enhancing the thermal stability. Based on the x-ray photoelectron spectroscopy analysis, the authors believe that the key for the retardation of Ag agglomeration was the formation of ternary Al-Ni-O layer at p-GaN interface.

  13. Compositional origin of unusual β-relaxation properties in La-Ni-Al metallic glasses

    SciTech Connect

    Zhu, Z. G.; Li, Y. Z.; Wang, Z.; Gao, X. Q.; Wen, P.; Bai, H. Y.; Wang, W. H.; Ngai, K. L.

    2014-08-28

    The β-relaxation of metallic glasses (MGs) bears nontrivial connections to their microscopic and macroscopic properties. In an effort to elucidate the mechanism of the β-relaxation, we studied by dynamical mechanical measurements the change of its properties on varying the composition of La{sub 60}Ni{sub 15}Al{sub 25} in various ways. The properties of the β-relaxation turn out to be very sensitive to the composition. It is found that the isochronal loss peak temperature of β-relaxation, T{sub β,peak}, is effectively determined by the total (La + Ni) content. When Cu is added into the alloy to replace either La, Ni, or Al, the T{sub β,peak} increases with decrease of the (La + Ni) content. The trend is in accordance with data of binary and ternary MGs formed from La, Ni, Al, and Cu. Binary La-Ni MGs have pronounced β-relaxation loss peaks, well separated from the α-relaxation. In contrast, the β-relaxation is not resolved in La-Al and La-Cu MGs, showing up as an excess wing. For the ternary La-Ni-Al MGs, increase of La or Ni content is crucial to lower the T{sub β,peak}. Keeping the Al content fixed, increase of La content lowers the T{sub β,peak} further, indicating the more important role La plays in lowering T{sub β,peak} than Ni. The observed effects on changing the composition of La{sub 60}Ni{sub 15}Al{sub 25} lead to the conclusion that the properties of the β-relaxation are mainly determined by the interaction between the largest solvent element, La, and the smallest element, Ni. From our data, it is further deduced that La and Ni have high mobility in the MGs, and this explains why the β-relaxation in this La-based MGs is prominent and well resolved from the α-relaxation as opposed to Pd- and Zr-based MGs where the solvent and largest atoms, Pd and Zr, are the least mobile.

  14. Compositional origin of unusual β-relaxation properties in La-Ni-Al metallic glasses.

    PubMed

    Zhu, Z G; Li, Y Z; Wang, Z; Gao, X Q; Wen, P; Bai, H Y; Ngai, K L; Wang, W H

    2014-08-28

    The β-relaxation of metallic glasses (MGs) bears nontrivial connections to their microscopic and macroscopic properties. In an effort to elucidate the mechanism of the β-relaxation, we studied by dynamical mechanical measurements the change of its properties on varying the composition of La60Ni15Al25 in various ways. The properties of the β-relaxation turn out to be very sensitive to the composition. It is found that the isochronal loss peak temperature of β-relaxation, Tβ,peak, is effectively determined by the total (La + Ni) content. When Cu is added into the alloy to replace either La, Ni, or Al, the Tβ,peak increases with decrease of the (La + Ni) content. The trend is in accordance with data of binary and ternary MGs formed from La, Ni, Al, and Cu. Binary La-Ni MGs have pronounced β-relaxation loss peaks, well separated from the α-relaxation. In contrast, the β-relaxation is not resolved in La-Al and La-Cu MGs, showing up as an excess wing. For the ternary La-Ni-Al MGs, increase of La or Ni content is crucial to lower the Tβ,peak. Keeping the Al content fixed, increase of La content lowers the Tβ,peak further, indicating the more important role La plays in lowering Tβ,peak than Ni. The observed effects on changing the composition of La60Ni15Al25 lead to the conclusion that the properties of the β-relaxation are mainly determined by the interaction between the largest solvent element, La, and the smallest element, Ni. From our data, it is further deduced that La and Ni have high mobility in the MGs, and this explains why the β-relaxation in this La-based MGs is prominent and well resolved from the α-relaxation as opposed to Pd- and Zr-based MGs where the solvent and largest atoms, Pd and Zr, are the least mobile.

  15. Oxidation of Al[sub 2]O[sub 3] continuous fiber-reinforced/NiAl composites

    SciTech Connect

    Doychak, J.; Nesbitt, J.A.; Noebe, R.D.; Bowman, R.R. )

    1992-08-01

    The 1,200C and 1,300C isothermal and cyclic oxidation behavior of Al[sub 2]O[sub 3] continuous fiber Saphikon[trademark]-reinforced/NiAl composites were studied. Oxidation resulted in formation of Al[sub 2]O[sub 3] external scales in a similar manner as scales formed on monolithic NiAl. The isothermal oxidation of an Al[sub 2]O[sub 3]/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 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 Al[sub 2]O[sub 3] 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.

  16. Chemical and morphological changes at Al{sub 2}O{sub 3}/NiAl interfaces and their relationship to scale adhesion

    SciTech Connect

    Hou, Peggy Y.

    2003-03-15

    Ni-(40,50)at%Al alloys with different C and S contents were oxidized at 1000-1150 C for various times in oxygen. Auger electron microscopy was used to study the interface chemistry after scale spallation in ultra high vacuum. The interfacial failure stresses were determined with a tensile pull tester and they were related to the interfacial pore density. Results show that sulfur did not segregate to the Al{sub 2}O{sub 3}/Ni50Al interface even after extended oxidation times. Small amounts, however, segregated to the Al{sub 2}O{sub 3}/Ni40Al interface. The difference in behavior may be related to the surface energy difference between Ni50Al and Ni40Al. On the interfacial void faces of Ni50Al, C first segregated, then it was replaced by S after longer oxidation times; the amount of segregants varied with different crystallographic orientation of the void face. On Ni40Al, S segregated much earlier on the void faces due to a faster diffusion rate in the Ni-rich NiAl. The apparent S diffusivity in Ni50Al and Ni40Al at 1000 C was determined to be 10{sup -9} and 6 x 10{sup -9} cm{sup 2}/s respectively. Excess sulfur in Ni40Al greatly increased the interfacial pore density. Preliminary results on interfacial failure stress showed that it decreased with increasing pore density, regardless of whether S was present at the interface, indicating that the major detrimental effect of S on scale adhesion may be to enhance interfacial pore formation.

  17. 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.

  18. 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

  19. Degradation mechanisms of Ti/Al/Ni/Au-based Ohmic contacts on AlGaN/GaN HEMTs

    DOE PAGES

    Hwang, Ya-Hsi; Ahn, Shihyun; Dong, Chen; ...

    2015-04-27

    We investigated the degradation mechanism of Ti/Al/Ni/Au-based Ohmic metallization on AlGaN/GaN high electron mobility transistors upon exposure to buffer oxide etchant (BOE). The major effect of BOE on the Ohmic metal was an increase of sheet resistance from 2.89 to 3.69 Ω/ₜafter 3 min BOE treatment. The alloyed Ohmic metallization consisted 3–5 μm Ni-Al alloy islands surrounded by Au-Al alloy-rings. The morphology of both the islands and ring areas became flatter after BOE etching. Lastly, we used energy dispersive x-ray analysis and Auger electron microscopy to analyze the compositions and metal distributions in the metal alloys prior to and aftermore » BOE exposure.« less

  20. Degradation mechanisms of Ti/Al/Ni/Au-based Ohmic contacts on AlGaN/GaN HEMTs

    SciTech Connect

    Hwang, Ya-Hsi; Ahn, Shihyun; Dong, Chen; Zhu, Weidi; Kim, Byung-Jae; Le, Lingcong; Ren, Fan; Lind, Aaron G.; Dahl, James; Jones, Kevin S.; Pearton, Stephen J.; Kravchenko, Ivan I.; Zhang, Ming-Lan

    2015-04-27

    We investigated the degradation mechanism of Ti/Al/Ni/Au-based Ohmic metallization on AlGaN/GaN high electron mobility transistors upon exposure to buffer oxide etchant (BOE). The major effect of BOE on the Ohmic metal was an increase of sheet resistance from 2.89 to 3.69 Ω/ₜafter 3 min BOE treatment. The alloyed Ohmic metallization consisted 3–5 μm Ni-Al alloy islands surrounded by Au-Al alloy-rings. The morphology of both the islands and ring areas became flatter after BOE etching. Lastly, we used energy dispersive x-ray analysis and Auger electron microscopy to analyze the compositions and metal distributions in the metal alloys prior to and after BOE exposure.

  1. Laser power beaming to extend lives of GSO NiCd satellites

    SciTech Connect

    Monroe, D.K.

    1993-12-31

    It is proposed that a ground-based laser can beam power to commercial communication satellites in geosynchronous orbit and reduce battery depth-of-discharge during eclipses. Two laser system designs are presented which have the capability of reducing battery discharge by 100%. Both utilize a steerable beam director, with a mirror diameter of 4 meters in one case and 8 meters in the other. Both also use an adaptive optics unit within the beam train to provide real-time corrections for wavefront distortions caused by atmospheric turbulence. The required system power output is in the range of 100 to 200 kW for a transmitted wavelength just under 900 nm. Laser power beaming can nearly double the remaining lifetime of a satellite that uses NiCd batteries. However, by the time such lasers become available, nearly all NiCd satellites will be replaced by NiH{sub 2} satellites, which stand to benefit much less from power beaming.

  2. Results of deep DoD life cycle tests at high rates on 12Ah NiCd cells

    NASA Technical Reports Server (NTRS)

    Panneton, Paul E.; Meyer, John R.

    1992-01-01

    A 12 Ah Nickel-Cadmium (NiCd) Low Earth Orbit (LEO) life cycle test that induced 47 percent more deep Depth Of Discharge cycles by mixing them with shallow DOD cycles is discussed. The test showed how aggressive recharging to a C/D ratio of 1.15 nearly doubled performance over cycling below a C/D of 1.11.

  3. Effect of Ni content on microwave absorbing properties of MnAl powder

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-zhong; Lin, Pei-hao; Huang, Wei-chao; Pan, Shun-kang; Liu, Ye; Wang, Lei

    2016-09-01

    MnAlNi powder was prepared by the process of vacuum levitation melting and high-energy ball milling, The morphology and phase structure of the powder were analyzed by Scanning Electron Microscope(SEM), X-ray diffraction(XRD) and the effect of the Ni content on microwave absorbing properties of MnAl powder was investigated by an vector network analyzer. The addition of Ni, which improved the microwave absorbing properties of MnAl powder but not changed the composition of Al8Mn5 alloy. The minimum reflectivity of (Al8Mn5)0.95Ni0.05 powder with a coating thickness (d) of 1.8 mm was about -40.8 dB and has better bandwidth effect, the absorbing mechanism of AlMnNi powders on the electromagnetic was related to the electromagnetic loss within the absorbing coatings and the effect of coating thickness on the interference loss of electromagnetic wave.

  4. The effect of gravity on the combustion synthesis of Ni-Al and Ni3Al-TiB2 composites from elements

    NASA Technical Reports Server (NTRS)

    Varma, Arvind; Yi, Hu Chun; Mcginn, Paul J.

    1995-01-01

    Previous studies on the combustion synthesis of advanced materials indicate that combustion and structure formation mechanisms involve several stages including melting of reactants and products, spreading of the melt, droplet coalescence, diffusion and convection, buoyancy of solid particles, and densification of the liquid product. Most of these processes are affected by gravity. Conducting the combustion synthesis under microgravity conditions is expected to help elucidate the reaction mechanisms. Two systems were examined. The first involves Ni/AI cladded particles, which is an ideal system to examine the individual particle and liquid flow before combustion occurs. For comparison, elemental Ni and Al powders with the same stoichiometry as that of the cladded particles were also used in some experiments. The second system was the Ni3AITiB2 composite in which the Ni3AI (-delta H(sub f) = 153.1 kJ/mol) phase melts during reaction enabling us to examine settling of the liquid phase. The amount of liquid phase was controlled by varying the TiB2 (-delta H(sub f) = 323.8 kJ/mol) content which generates the additional heat. The overall reactions for the two systems can be expressed as follows. System 1: 4Ni + 2AI yields Ni3AI + NiA and System 2: 3Ni + Al + x (Ti + 2B) yields Ni3Al + x(TiB2). For the first system, pellets were pressed directly from the cladded particles, at green densities about 77 +/- 3% of theoretical value. For the second, the pellets were prepared by mixing the elemental reactant powders in the required stoichiometry by ball-milling and then pressing uniaxially at green densities about 70 +/- 3 percent of theoretical. The pellets were cylindrical in shape, 10 mm in diameter and length typically 20-30 mm. The pellet samples were reacted in UHP Argon (1 atm) using the experimental setup and procedure described previously. After reaction, the samples were sectioned axially in order to conduct the microstructural analysis in the longitudinal direction

  5. Hydrometallurgical route to recover nickel, cobalt and cadmium from spent Ni-Cd batteries

    NASA Astrophysics Data System (ADS)

    Fernandes, Aline; Afonso, Julio Carlos; Bourdot Dutra, Achilles Junqueira

    2012-12-01

    In this work a hydrometallurgical route to recover nickel, cobalt and cadmium after leaching spent Ni-Cd batteries with hydrochloric acid was investigated. Co(II) and Cd(II) were both recovered by solvent extraction. Cd(II) was first extracted (99.7 wt.%) with pure tri-n-butylphosphate (TBP), in the original leachate acidity (5.1 mol L-1), in two stages at 25 °C with an aqueous/organic (A/O) phase ratio = 1 v/v. The Co(II) present in the raffinate (free acidity 4.1 mol L-1) was extracted with Alamine 336 or Alamine 304 (10 vol.% in kerosene) at 25 °C with an A/O ratio = 1 in two stages. 97.5 wt.% of Co(II) was extracted using Alamine 336 while only 90.4 wt.% was extracted in the case of Alamine 304. Ni(II) was isolated from the raffinate as oxalate after addition of ammonium oxalate at pH 2.

  6. Structural and optical properties of Ni-doped CdS thin films prepared by chemical bath deposition method

    NASA Astrophysics Data System (ADS)

    Premarani, R.; Saravanakumar, S.; Chandramohan, R.; Mahalingam, T.

    2015-06-01

    The structural and optical behavior of undoped Cadmiun Sulphide (CdS) and Ni-doped CdS thinfilms prepared by Chemical Bath Deposition (CBD) technique is reported. The crystallite sizes of the thinfilms have been characterized by X-ray diffraction pattern (XRD). The particle sizes increase with the increase of Ni content in the CdS thinfilms. Scanning Electron Microscope (SEM) results indicated that CdS thinfilms is made up of aggregate of spherical-like particles. The composition was estimated by Energy Dispersive Analysis of X-ray (EDX) and reported. Spectroscopic studies revealed considerable improvement in transmission and the band gap of the films changes with addition of Ni dopant that is associated with variation in crystallite sizes in the nano regime.

  7. Structural and optical properties of Ni-doped CdS thin films prepared by chemical bath deposition method

    SciTech Connect

    Premarani, R.; Saravanakumar, S. Chandramohan, R.; Mahalingam, T.

    2015-06-24

    The structural and optical behavior of undoped Cadmiun Sulphide (CdS) and Ni-doped CdS thinfilms prepared by Chemical Bath Deposition (CBD) technique is reported. The crystallite sizes of the thinfilms have been characterized by X-ray diffraction pattern (XRD). The particle sizes increase with the increase of Ni content in the CdS thinfilms. Scanning Electron Microscope (SEM) results indicated that CdS thinfilms is made up of aggregate of spherical-like particles. The composition was estimated by Energy Dispersive Analysis of X-ray (EDX) and reported. Spectroscopic studies revealed considerable improvement in transmission and the band gap of the films changes with addition of Ni dopant that is associated with variation in crystallite sizes in the nano regime.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    SciTech Connect

    Alfonso, Dominic R.; Tafen, De Nyago

    2015-04-28

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

  10. 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.

  11. Ni-Ti SMA-reinforced Al composites

    NASA Astrophysics Data System (ADS)

    Porter, G. A.; Liaw, P. K.; Tiegs, T. N.; Wu, K. H.

    2000-10-01

    A shape-memory alloy, nickel-titanium, has been distributed throughout an aluminum matrix, using powder-metallurgy processing, in the hope of using the shape-memory effect to achieve strengthening and improve the fatigue resistance, as compared to the aluminum matrix. The shape-memory effect was activated by cold rolling the samples at -30°C. Upon reheating to the austenite phase, the Ni-Ti was expected to return to its original shape while embedded in the aluminum matrix. It is thought that this action created residual, internal stresses around each particle, which strengthened the material. The yield and ultimate strengths, and the fatigue lives of the Ni-Ti reinforced aluminum composites, have been improved considerably, as compared to the unreinforced material. The cross-sectional microstructures of the composites, as well as the modes of crack growth, have been examined with a scanning electron microscope (SEM) to identify fatigue and fracture mechanisms.

  12. Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transformation temperature

    NASA Technical Reports Server (NTRS)

    Antolovich, Stephen D.; Saxena, Ashok; Cullers, Cheryl

    1992-01-01

    One of the ongoing challenges of the aerospace industry is to develop more efficient turbine engines. Greater efficiency entails reduced specific strength and larger temperature gradients, the latter of which means higher operating temperatures and increased thermal conductivity. Continued development of nickel-based superalloys has provided steady increases in engine efficiency and the limits of superalloys have probably not been realized. However, other material systems are under intense investigation for possible use in high temperature engines. Ceramic, intermetallic, and various composite systems are being explored in an effort to exploit the much higher melting temperatures of these systems. NiAl is considered a potential alternative to conventional superalloys due to its excellent oxidation resistance, low density, and high melting temperature. The fact that NiAl is the most common coating for current superalloy turbine blades is a tribute to its oxidation resistance. Its density is one-third that of typical superalloys and in most temperature ranges its thermal conductivity is twice that of common superalloys. Despite these many advantages, NiAl requires more investigation before it is ready to be used in engines. Binary NiAl in general has poor high-temperature strength and low-temperature ductility. On-going research in alloy design continues to make improvements in the high-temperature strength of NiAl. The factors controlling low temperature ductility have been identified in the last few years. Small, but reproducible ductility can now be achieved at room temperature through careful control of chemical purity and processing. But the mechanisms controlling the transition from brittle to ductile behavior are not fully understood. Research in the area of fatigue deformation can aid the development of the NiAl system in two ways. Fatigue properties must be documented and optimized before NiAl can be applied to engineering systems. More importantly though

  13. Steam Reforming of Glycerol Over Nano Size Ni-Ce/LaAlO3 Catalysts.

    PubMed

    Kim, Seong-Hak; Go, Yoo-Jin; Park, Nam-Cook; Kim, Jong-Ho; Kim, Young-Chul; Moon, Dong-Ju

    2015-01-01

    In this work, hydrogen production from glycerol by Steam Reforming (SR) was studied by Ni-Ce catalysts supported on LaAlO3 perovskite in order to effect of the cerium loading amount and the reaction conditions. Nano size Ni-Ce/LaAlO3 catalysts were prepared by precipitation method. The structure of the catalysts was characterized by XRD analysis. The morphology, dispersion and the reduction properties of catalysts was examined by SEM, TEM, H2-chemisorption and TPR, respectively. It was found that 15 wt% Ni-5 wt% Ce/LaAlO3 catalyst showed the highest glycerol conversion and hydrogen selectivity. In addition, the catalyst also showed the high carbon dioxide selectivity and the lowest methane selectivity. The results indicate that the catalyst promotes methane reforming reaction. The highest activity in the 15 wt% Ni-5 wt% Ce/LaAlO3 was attributed to the proper cerium loading amount. Moreover, the lowest metal crystal size and rise in active site were found to have an effect on catalytic activity and hydrogen selectivity. The 15 wt% Ni-5 wt% Ce/LaAlO3 catalyst exhibited excellent performance with respect to hydrogen production at reaction temperature of 450 degrees C, at atmospheric pressure, 20 wt% glycerol solution and GHSV = 6,000 mL/g-cat x hr.

  14. Kinetics of Static Strain Aging in Polycrystalline NiAl-based Alloys

    NASA Technical Reports Server (NTRS)

    Weaver, M. L.; Kaufman, M. J.; Noebe, R. D.

    1996-01-01

    The kinetics of yield point return have been studied in two NiAl-based alloys as a function of aging time at temperatures between 300 and 700 K. The results indicate that the upper yield stress increment, Delta sigma(sub u) (i.e., stress difference between the upper yield point and the final flow stress achieved during prestraining), in conventional purity (CP-NiAl) and in high purity carbon-doped (NiAl-C) material first increased with a t(exp 2/3) relationship before reaching a plateau. This behavior suggests that a Cottrell locking mechanism is the cause for yield points in NiAl. In addition, positive y-axis intercepts were observed in plots of Delta sigma(sub u) versus t(exp 2/3) suggesting the operation of a Snoek mechanism. Analysis according to the Cottrell Bilby model of atmosphere formation around dislocations yields an activation energy for yield point return in the range 70 to 76 kJ/mol which is comparable to the activation energy for diffusion of interstitial impurities in bcc metals. It is, thus, concluded that the kinetics of static strain aging in NiAl are controlled by the locking of dislocations by Cottrell atmospheres of carbon atoms around dislocations.

  15. 1100 to 1500 K Slow Plastic Compressive Behavior of NiAl-xCr Single Crystals

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Darolia, Ram

    2003-01-01

    The compressive properties of near <001> and <111> oriented NiAl-2Cr single crystals and near <011> oriented NiAl-6Cr samples have been measured between 1100 and 1500 K. The 2Cr addition produced significant solid solution strengthening in NiAl, and the <111> and <001> single crystals possessed similar strengths. The 6Cr crystals were not stronger than the 2Cr versions. At 1100 and 1200 K plastic flow in all three Cr-modified materials was highly dependent on stress with exponents > 10. The <011> oriented 6Cr alloy exhibited a stress exponent of about 8 at 1400 and 1500 K; whereas both <001> and <111> NiAl-2Cr crystals possessed stress exponents near 3 which is indicative of a viscous dislocation glide creep mechanism. While the Cottrell-Jaswon solute drag model predicted creep rates within a factor of 3 at 1500 K for <001>-oriented NiAl-2Cr; this mechanism greatly over predicted creep rates for other orientations and at 1400 K for <001> crystals.

  16. Deformation and fracture of a directionally solidified NiAl-28Cr-6Mo eutectic alloy

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    A directionally solidified alloy based on the NiAl-(Cr, Mo) eutectic was examined by transmission and scanning electron microscopy to characterize the microstructure and room temperature deformation and fracture behavior. The microstructure consisted of a lamellar morphology with a group of zone axes (111) growth direction for both the NiAl and (Cr, Mo) phases. The interphase boundary between the eutectic phases was semicoherent and composed of a well-defined dislocation network. In addition, a fine array of coherent NiAl precipitates was dispersed throughout the (Cr, Mo) phase. The eutectic morphology was stable at 1300 K with only coarsening of the NiAl precipitates occurring after heat treatment for 1.8 ks (500 h). Fracture of the aligned eutectic is characterized primarily by a crack bridging/renucleation mechanism and is controlled by the strength of the semicoherent interface between the two phases. However, contributions to the toughness of the eutectic may arise from plastic deformation of the NiAl phase and the geometry associated with the fracture surface.

  17. Thermal explosion in Al-Ni system: influence of mechanical activation.

    PubMed

    White, Jeremiah D E; Reeves, Robert V; Son, Steven F; Mukasyan, Alexander S

    2009-12-03

    The influence of short-term (5-15 min) highly energetic ball milling on the ignition characteristics of a gasless heterogeneous Ni-Al reactive system has been investigated. By using Al-Ni clad particles (30-40 microm diameter Al spheres coated by a 3-3.5 microm layer of Ni, that corresponds to a 1:1 Ni/Al atomic ratio), it was shown that such mechanical treatment leads to a significant decrease in the self-ignition temperature of the system. For example, after 15 min of ball milling, the ignition temperature appears to be approximately 600 K, well below the eutectic (913 K) in the considered binary system, which is the ignition temperature for the initial clad particles. Thus, it was demonstrated that the thermal explosion process for mechanically treated reactive media can be solely defined by solid-state reactions. Additionally, thermal analysis measurements revealed that mechanical activation results in a substantial decrease in the effective activation energy (from 84 to 28 kcal/mol) of interaction between Al and Ni. This effect, that is, mechanical activation of chemical reaction, is connected to a substantial increase of contact area between reactive particles and fresh interphase boundaries formed in an inert atmosphere during ball milling. It is also important that by varying the time of mechanical activation one can precisely control the ignition temperature in high-density energetic heterogeneous systems.

  18. Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transition temperature

    NASA Technical Reports Server (NTRS)

    Cullers, Cheryl L.; Antolovich, Stephen D.

    1993-01-01

    The intermetallic compound NiAl is one of many advanced materials which is being scrutinized for possible use in high temperature, structural applications. Stoichiometric NiAl has a high melting temperature, excellent oxidation resistance, and good thermal conductivity. Past research has concentrated on improving monotonic properties. The encouraging results obtained on binary and micro-alloyed NiAl over the past ten years have led to the broadening of NiAl experimental programs. The purpose of this research project was to determine the low cycle fatigue properties and dislocation mechanisms of stoichiometric NiAl at temperatures near the monotonic brittle-to-ductile transition. The fatigue properties were found to change only slightly in the temperature range of 600 to 700 K; a temperature range over which monotonic ductility and fracture strength increase markedly. The shape of the cyclic hardening curves coincided with the changes observed in the dislocation structures. The evolution of dislocation structures did not appear to change with temperature.

  19. Distribution of Cd, Ni, Cr and Pb in sewage sludge amended soils

    NASA Astrophysics Data System (ADS)

    Sanfeliu, Teófilo

    2010-05-01

    Restoration of degraded soils with organic wastes could be a feasible practice to minimise erosion in the Mediterranean area. Today the use of sewage sludge to improve the nutrient contents of a soil is a common practice. Contamination of soils by potentially toxic elements (e.g. Cd, Ni, Cr, Pb) from amendments of sewage sludge is subject to strict controls within the European Community in relation to total permissible metal concentrations, soil properties and intended use. This study is aimed at ascertaining the chemical partitioning of Cd, Ni, Cr and Pb in agricultural soils repeatedly amended with sludge. Five surface soils (0-15 cm) that were polluted as a result of agricultural activities were used in this experiment. The sewage sludge amended soils were selected for diversity of physicochemical properties, especially pH and carbonate content. The soils are classified as non-calcareous and calcareous soils. The distribution of chemical forms of Cd, Ni, Cr and Pb in five sewage sludge amended soils was studied using a sequential extraction procedure that fractionates the metal into soluble-exchangeable, specifically sorbed-carbonate bound, oxidizable, reducible and residual forms. With regard to the mineralogical composition of the soil clay fraction, the mineralogical association found was: illite, kaolinite and chlorite. This paper provides quantitative evidence regarding the form of the association of metals and indirectly of their bioavailability. It can help to explain the process by which metals are eliminated from sewage sludge and also indicate the impact of the use of sludge on agricultural soils, as amendments. Data obtained showed different metal distribution trend among the fractions in sludge-amended soils. Comparison of distribution pattern of metals in sludge-applied soils shows that there is possible redistribution of metals among the different phases. Detailed knowledge of the soil at the application site, especially pH, CEC, buffering capacity

  20. Design, development, performance, and reconditioning of Ni-Cd batteries using polyropylene separators

    NASA Technical Reports Server (NTRS)

    Britting, A. O., Jr.

    1984-01-01

    A performance assessment is made for the Viking Mars Lander Program's sealed, sterilizable, 8-ampere hour Ni-Cd batteries, which use a nonwoven polypropylene separator material. Attention is given to separator wettability, the optimization of electrolyte quantity, and the reduction of plate carbonate, in view of thermal considerations and other environmental design and test requirements generated by mission characteristics. Life data based on mission experience identify, in addition to performance and degradation behavior, a series of shallow discharge reconditioning cycles and an intensive program of deep discharge reconditioning.

  1. Behavior of a cycled Ni-Cd battery during pulse discharge

    SciTech Connect

    Rao, G.; Vaidyanathan, H.; Nakhleh, W.

    1997-12-01

    The pulse discharge behavior of a 9-Ah, 12-V nickel-cadmium (Ni-Cd) battery fabricated for the FAST program was studied. The response of the battery voltage to a pulse with a current of 60 A and duration of 10 to 200 ms was measured, along with the capacity remaining at the end of pulse discharge. The maximum drop in voltage at the beginning of the pulse was 505 to 1,049 mV, and battery capacity remained stable.

  2. An evaluation of potentially useful separator materials for nickel-cadmium (Ni-Cd] satellite batteries

    NASA Technical Reports Server (NTRS)

    Baker, H. A.; Toner, S. D.; Cuthrell, W. F.

    1974-01-01

    An evaluation intended to determine the potential suitability and probable efficacy of a group of separator materials for use in nickel-cadmium (Ni-Cd) satellite batteries was carried out. These results were obtained using test procedures established in an earlier evaluation of other separator materials, some of which were used in experimental battery cells subjected to simulated use conditions. The properties that appear to be most important are: high electrolyte absorptivity, good electrolyte retention, low specific resistivity, rapid wettability and low resistance to air permeation. Wicking characteristics and wet-out time seem to be more important with respect to the initial filling of the battery with the electrolyte.

  3. Simultaneous removal of As, Cd, Cr, Cu, Ni and Zn from stormwater: experimental comparison of 11 different sorbents.

    PubMed

    Genç-Fuhrman, Hülya; Mikkelsen, Peter S; Ledin, Anna

    2007-02-01

    The potential of using alumina, activated bauxsol-coated sand (ABCS), bark, bauxsol-coated sand (BCS), fly ash (FA), granulated activated carbon (GAC), granulated ferric hydroxide (GFH), iron oxide-coated sand (IOCS), natural zeolite (NZ), sand, and spinel (MgAl(2)O(4)) as sorbents for removing heavy metals from stormwater are investigated in the present study. The ability of the sorbents to remove a mixture of As, Cd, Cr, Cu, Ni and Zn from synthetic stormwater samples were evaluated in batch tests at a starting pH of 6.5. The metal speciation and saturation data is obtained using the PHREEQ-C geochemical model and used to elucidate the sorption data. It is found that BCS, FA, and spinel have significantly higher affinity towards heavy metals mainly present as cationic or non-charged species (i.e. Cd, Cu, Ni and Zn) compared to those present as anionic species (i.e. As and Cr). However, IOCS, NZ and sand have higher affinity towards As and Cr, while alumina has equally high affinity to all tested heavy metals. The Freundlich isotherm model is found to fit the data in many cases, but ill fitted results are also observed, especially for FA, BCS and GAC, possibly due to leaching of some metals from the sorbents (i.e. for FA) and oversaturated conditions making precipitation the dominant removal mechanism over sorption in batches with high heavy metal concentrations and pH. Calculated sorption constants (i.e. K(d)) are used to compare the overall heavy metal removal efficiency of the sorbents, which in a decreasing order are found to be: alumina, BCS, GFH, FA, GAC, spinel, ABCS, IOCS, NZ, bark, and sand. These findings are significant for future development of secondary filters for removal of dissolved heavy metals from stormwater runoff under realistic competitive conditions in terms of initial heavy metal concentrations, pH and ionic strength.

  4. Manifestations of Dynamic Strain Aging in Soft-Oriented NiAl Single Crystals

    NASA Technical Reports Server (NTRS)

    Weaver, M. L.; Kaufman, M. J.; Noebe, R. D.

    1996-01-01

    The tensile and compressive properties of six NiAl-base single-crystal alloys have been investigated at temperatures between 77 and 1200 K. The normalized critical resolved shear stresses (CRSS/E) and work-hardening rates (Theta/E) for these alloys generally decreased with increasing temperature. However, anomalous peaks or plateaus for these properties were observed in conventional purity (CPNiAl), Si-doped (NiAl-Si), C-doped low Si (UF-NiAl1), and Mo-doped (NiAl-Mo) alloys at intermediate temperatures (600 to 1000 K). This anomalous behavior was not observed in high-purity, low interstitial material (HP-NiAl). Low or negative strain-rate sensitivities (SRS) also were observed in all six alloys in this intermediate temperature range. Coincident with the occurrence of negative strain-rate sensitivities was the observation of serrated stress-strain curves in the CPNiAl and NiAl-Si alloys. These phenomena have been attributed to dynamic strain aging (DSA). Chemical analysis of the alloys used in this study suggests that the main specie responsible for strain aging in NiAl is C but indicate that residual Si impurities can enhance the strain aging effects. The corresponding dislocation microstructures at low temperatures (300 to 600 K) were composed of well-defined cells. At intermediate temperatures (600 to 900 K), either poorly defined cells or coarse bands of localized slip, reminiscent of the vein structures observed in low-cycle fatigue specimens deformed in the DSA regime, were observed in conventional purity, Si-doped, and in Mo-doped alloys. In contrast, a well-defined cell structure persisted in the low interstitial, high-purity alloy. At elevated temperatures (greater than or equal to 1000 K), more uniformly distributed dislocations and sub-boundaries were observed in all alloys. These observations are consistent with the occurrence of DSA in NiAl single-crystal alloys at intermediate temperatures.

  5. A study of the oxide dispersion and recrystallization in NiCrAl prepared from preoxidized powder

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1975-01-01

    The SAP technique of dispersion strengthening (formation of an oxide dispersion by preoxidation of metal powders) was applied to atomized powder of the alloy Ni-17Cr-5Al-0.2 Y. SAP-NiCrAl was worked by extrusion and rod rolling at 1205 C and by swaging at 760 C. A variety of annealing treatments were applied after working to determine the recrystallization response. NiCrAlY, similarly prepared from atomized powder, but without a preoxidation treatment, was examined for comparison. The SAP-NiCrAl of this study exhibited oxide particle size and spacing much larger than that usually observed in oxide dispersion strengthened alloys; nonetheless, it was possible to achieve abnormal (secondary) recrystallization in the SAP-NiCrAl as has been reported for other oxide dispersion strengthened alloys. In contrast, unoxidized NiCrAlY exhibited only primary recrystallization.

  6. Cadmium Stabilization Efficiency and Leachability by CdAl4O7 Monoclinic Structure.

    PubMed

    Su, Minhua; Liao, Changzhong; Chuang, Kui-Hao; Wey, Ming-Yen; Shih, Kaimin

    2015-12-15

    This study investigated the stabilization efficiencies of using an aluminum-rich precursor to incorporate simulated cadmium-bearing waste sludge and evaluated the leaching performance of the product phase. Cadmium oxide and γ-alumina mixtures with various Cd/Al molar ratios were fired at 800-1000 °C for 3 h. Cadmium could be crystallochemically incorporated by γ-alumina into CdAl4O7 monoclinic phase and the reaction was strongly controlled by the treatment temperature. The crystal structure details of CdAl4O7 were solved and refined with the Rietveld refinement method. According to the structural refinement results, the stabilization efficiencies were quantified and expressed as a transformation ratio (TR) with optimized processing parameters. The preferred treatment temperature was found to be 950 °C for mixtures with a Cd/Al molar ratio of 1/4, as its TR value indicated the cadmium incorporation was nearly completed after a 3 h treatment scheme. Constant-pH leaching tests (CPLT) were conducted by comparing the leachability of the CdO and CdAl4O7 phases in a pH 4.0 environment. A remarkable reduction in cadmium leachability could be achieved via monoclinic CdAl4O7 structure formation to effectively stabilize hazardous cadmium in the waste stream. The CPLT and X-ray photoelectron spectroscopy (XPS) results suggested incongruent dissolution behavior during the leaching of the CdAl4O7 phase.

  7. 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

  8. INVESTIGATION OF NOVEL ALLOY TiC-Ni-Ni3Al FOR SOLID OXIDE FUEL CELL INTERCONNECT APPLICATIONS

    SciTech Connect

    Rasit Koc; Geoffrey Swift; Hua Xie

    2005-01-25

    Solid oxide fuel cell interconnect materials must meet stringent requirements. Such interconnects must operate at temperatures approaching 800 C while resisting oxidation and reduction, which can occur from the anode and cathode materials and the operating environment. They also must retain their electrical conductivity under these conditions and possess compatible coefficients of thermal expansion as the anode and cathode. Results are presented in this report for fuel cell interconnect candidate materials currently under investigation based upon nano-size titanium carbide (TiC) powders. The TiC is liquid phase sintered with either nickel (Ni) or nickel-aluminide (Ni{sub 3}Al) in varying concentrations. The oxidation resistance of the submicron grain TiC-metal materials is presented as a function weight change versus time at 700 C and 800 C for varying content of metal/intermetallic in the system. Electrical conductivity at 800 C as a function of time is also presented for TiC-Ni to demonstrate the vitality of these materials for interconnect applications. TGA studies showed that the weight gain was 0.8 mg/cm{sup 2} for TiC(30)-Ni(30wt.%) after 100 hours in wet air at 800 C and the weight gain was calculated to be 0.5205 mg/cm{sup 2} for TiC(30)- Ni(10 wt.%) after 100 hours at 700 C and 100 hours at 800 C. At room temperature the electrical conductivity was measured to be 2444 1/[ohm.cm] for TiC-Ni compositions. The electrical conductivities at 800 C in air was recorded to be 19 1/[ohm.cm] after 125 hours. Two identical samples were supplied to PNNL (Dr. Jeff Stevenson) for ASR testing during the pre-decision period and currently they are being tested there. Fabrication, oxidation resistance and electrical conductivity studies indicate that TiC-Ni-Ni{sub 3}Al ternary appears to be a very important system for the development of interconnect composition for solid oxide fuel cells.

  9. Effects on Ni and Cd speciation in sewage sludge during composting and co-composting with steel slag.

    PubMed

    Zeng, Zheng-Zhong; Wang, Xiao-Li; Gou, Jian-Feng; Zhang, He-Fei; Wang, Hou-Cheng; Nan, Zhong-Ren

    2014-03-01

    Sewage sludge and industrial steel slag (SS) pose threats of serious pollution to the environment. The experiments aimed to improve the stabilizing effects of heavy metal Ni and Cd morphology in composting sludge. The total Ni and Cd species distribution and chemical forms in the compost sewage sludge were investigated with the use of compost and co-compost with SS, including degradation. The carbon/nitrogen ratio of piles was regulated with the use of sawdust prior to batch aerobic composting experiments. Results indicated that the co-composting with SS and organic matter humification can contribute to the formation of Fe and Mn hydroxides and that the humus colloid significantly changed Ni and Cd species distribution. The decreased content of Ni and Cd in an unstable state inhibited their biological activity. Conclusions were drawn that an SS amount equal to 7% of the dry sludge mass was optimal value to guarantee the lowest amount of Cd in an unstable state, whereas the amount was 14% for Ni.

  10. Sorption, desorption, and speciation of Cd, Ni, and Fe by four calcareous soils as affected by pH.

    PubMed

    Tahervand, Samaneh; Jalali, Mohsen

    2016-06-01

    The sorption, desorption, and speciation of cadmium (Cd), nickel (Ni), and iron (Fe) in four calcareous soils were investigated at the pH range of 2-9. The results indicated that sorption of Fe by four soils was higher than 80 % at pH 2, while in the case of Cd and Ni was less than 30 %. The most common sequence of metal sorption at pH 2-9 for four soils was in the order of Fe ≫ Ni > Cd. Cadmium and Ni sorption as a function of pH showed the predictable trend of increasing metal sorption with increase in equilibrium pH, while the Fe sorption trend was different and characterized by three phases. With regard to the order of Cd, Ni, and Fe sorption on soils, Cd and Ni showed high affinity for organic matter (OM), whereas Fe had high tendency for calcium carbonate (CaCO3). Results of metal desorption using 0.01 M NaCl demonstrated that metal sorption on soils containing high amounts of CaCO3 was less reversible in comparison to soils containing high OM. In general, Cd and Ni desorption curves were characterized by three phases; (1) the greatest desorption at pH 2, (2) the low desorption at pH 3-7, and (3) the least desorption at pH > 7. The MINTEQ speciation solubility program showed that the percentage of free metals declined markedly with increase of pH, while the percentage of carbonate and hydroxyl species increased. Furthermore, MINTEQ predicted that saturation index (SI) of metals increased with increasing pH.

  11. 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.

  12. Ni{sub x}Cd{sub 1−x}O: Semiconducting alloys with extreme type III band offsets

    SciTech Connect

    Francis, Christopher A.; Detert, Douglas M.; Dubon, Oscar D.; Chen, Guibin; Yu, Kin M.; Walukiewicz, Wladek

    2015-01-12

    We have synthesized alloys of NiO and CdO that exhibit an extreme type III band offset and have studied the structural, electrical, and optical properties of Ni{sub x}Cd{sub 1−x}O over the entire composition range. The alloys are rocksalt structured and exhibit a monotonic shift of the (220) diffraction peak to higher 2θ angles with increasing Ni concentration. The electron mobility and electron concentration decrease with increasing x, and samples become insulating for Ni content x > 0.44. This decrease in n-type conductivity is consistent with the movement of the conduction band minimum from below to above the Fermi stabilization energy with increasing Ni content. The optical absorption edge of the alloys can be tuned continuously from CdO to NiO. The intrinsic gap of the alloys was calculated with the electrical and optical measurements and accounting for Burstein-Moss carrier filling and carrier-induced bandgap renormalization effects. We observe an uncommon composition dependence of the intrinsic bandgap on the alloy composition. The effect is tentatively attributed to an interaction between extended states of the conduction band and localized d-states of Ni.

  13. Facile preparation of NiS/CdS-t composite photocatalyst for hydrogen evolution from aqueous solution of sulphide/sulphite under visible light

    SciTech Connect

    Meng, Jianling; Li, Fengyan; Hu, Yiming; Xu, Lin; Sun, Zhixia; Liu, Jian

    2013-06-01

    Highlights: ► The nanostructured NiS/CdS photocatalyst was prepared by a facile two-step method. ► After aged for six days, the photocatalyst achieved a maximal rate of H{sub 2} evolution. ► The rate of H{sub 2} evolution on NiS(0.14)/CdS-6 is about 33 times that of CdS-6. - Abstract: The nanostructured NiS/CdS-t (t = aging period in day number) composite photocatalysts were prepared by a facile two-step synthesis method. The photocatalytic activity of H{sub 2} evolution over NiS/CdS could be greatly enhanced by changing the aging period of CdS. The NiS/CdS achieved a maximal rate of H{sub 2} evolution when CdS was aged for 6 days before hydrothermal treatment. It was demonstrated that the composite NiS(0.14)/CdS-6 could achieve a H{sub 2} evolution rate up to 1517 μmol h{sup −1} and show high photocatalytic stability for H{sub 2} evolution under long-term light irradiation. The rate of H{sub 2} evolution on NiS(0.14)/CdS-6 is about 7.5 times that of NiS(0.14)/CdS-3 and 33 times that of CdS-6. The notable improvement can be attributed to the fast electron transfer from CdS to NiS, which is proved by the surface photovoltage spectroscopy and photoluminescent measurements, as well as the increasing percentage of hexagonal-CdS in the mixture of cubic and hexagonal CdS.

  14. Raman spectroscopic study of Ni/Al 2O 3 catalyst

    NASA Astrophysics Data System (ADS)

    Aminzadeh, A.; Sarikhani-fard, H.

    1999-07-01

    In this article a preliminary Raman spectroscopic study of Ni/Al 2O 3 catalyst of the type used for the steam reformation of methane is reported. With several prepared samples of this catalyst and using FT-Raman and conventional dispersive Raman technique, it is shown how Raman spectroscopy can be used to monitor the exact conditions during the preparation of the catalyst. Raman data shows that despite a strong fluorescence background, some useful information can be obtained. According to these data, when the calcination temperature is raised above 1000°C, the gamma alumina ( γ-Al 2O 3) is converted to alpha alumina ( α-Al 2O 3) as it is expected. It further shows that Ni is not present as NiO: it is probably embedded in the crystal structure of γ-Al 2O 3 as NiAl 2O 4 (the spinel structure) or constituted as a solid solution with Al 2O 3.

  15. Physical and mechanical properties of the B2 compound NiAl

    NASA Technical Reports Server (NTRS)

    Noebe, R. D.; Bowman, R. R.; Nathal, M. V.

    1993-01-01

    Considerable work has been performed on NiAl over the last three decades, with an extremely rapid growth in research on this intermetallic occurring in the last few years due to recent interest in this material for electronic and high temperature structural applications. However, many physical properties and the controlling fracture and deformation mechanisms over certain temperature regimes are still in question. Part of this problem lies in the incomplete characterization of many of the alloys previously investigated. Fragmentary data on processing conditions, chemistry, microstructure and the apparent difficulty in accurately measuring composition has made direct comparison between individual studies sometimes tenuous. Therefore, the purpose of this review is to summarize all available mechanical and pertinent physical properties on NiAl, stressing the most recent investigations, in an attempt to understand the behavior of NiAl and its alloys over a broad temperature range.

  16. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approx. 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  17. Origin of Ferromagnetism in Al and Ni Co-doped ZnO Based DMS Materials

    NASA Astrophysics Data System (ADS)

    Murtaza, Saleem; Saadat, A. Siddiqi; Shahid, M. Ramay; Shahid, Atiq; Shahzad, Naseem

    2012-10-01

    Zn0.95Ni0.05O and Zn0.90Ni0.05Al0.05O compositions of nanocrystallites are synthesised using the well recognised auto-combustion technique. The x-ray diffraction patterns demonstrate the phase pure characteristic wurtzite-type crystal structure with space group P63mc in both the compositions. The elemental incorporation of Ni and Al contents into the ZnO structure is confirmed by energy dispersive x-ray analysis. The micrographs of scanning electron microscopy show an approximate ordered morphology. The electrical resistivity is observed to decrease with the rising temperature, depicting the characteristic semiconductor behaviour of the samples. The lower values of resistivity and ferromagnetic interactions in the Al-doped sample correspond to an increase of carrier's density. It is observed that the carrier mediated mechanism is mainly responsible for ferromagnetism in ZnO-based diluted magnetic semiconductors.

  18. Advances in processing of NiAl intermetallic alloys and composites for high temperature aerospace applications

    NASA Astrophysics Data System (ADS)

    Bochenek, Kamil; Basista, Michal

    2015-11-01

    Over the last few decades intermetallic compounds such as NiAl have been considered as potential high temperature structural materials for aerospace industry. A large number of investigations have been reported describing complex fabrication routes, introducing various reinforcing/alloying elements along with theoretical analyses. These research works were mainly focused on the overcoming of main disadvantage of nickel aluminides that still restricts their application range, i.e. brittleness at room temperature. In this paper we present an overview of research on NiAl processing and indicate methods that are promising in solving the low fracture toughness issue at room temperature. Other material properties relevant for high temperature applications are also addressed. The analysis is primarily done from the perspective of NiAl application in aero engines in temperature regimes from room up to the operating temperature (over 1150 °C) of turbine blades.

  19. Molecular Dynamics Simulation Of The Energetic Reaction Between Ni And Al Nanoparticle Aggregates

    NASA Astrophysics Data System (ADS)

    Sparks, Jacob; Hawa, Takumi

    2013-03-01

    Molecular Dynamics simulations are used to simulate the energetic reaction of Ni and Al particles at the nanometer scale. The effect of particle size and structures on reaction time and temperature for Ni and Al separate nanoparticles has been considered. The differences in melting temperature and phase change behavior between Al and Ni are expected to produce differing results for the nanoparticle aggregates systems. Simulation results show that the sintering time increases with increasing mass of the aggregates and with decreasing the fractal dimension of the aggregate. The final temperature of the systems increases with decreasing the primary particle sizes when mass of the aggregates remains unchanged. The phenomenological model is a power law including a dependence on the number of particles in an aggregates and fractal dimension is also developed.

  20. Fabrication of NiAl intermetallic reactors for microtechnology-based energy chemical systems (MECS)

    SciTech Connect

    Alman, D.A.; Wilson, R.D.; Paul, B.K.

    2001-01-01

    Microtechnology-based energy chemical systems (MECS) offer opportunities for portable power 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 micrometer) dimensions. It has been recognized that materials with limited formability, like ceramics and intermetallics, may be required for high temperature applications. In this paper, a method for forming an array of internal microchannels in a NiAl device is presented. Microchannels are precision machined (via laser ablation) into elemental Ni and Al foils. During bonding, these foils are converted into NiAl. Results show that this is a viable method for producing aluminide-based structure containing complex, internal features.

  1. Structure-property relationships in directionally solidified single crystal NiAl

    NASA Technical Reports Server (NTRS)

    Noebe, R. D.; Kim, J. T.; Gibala, R.

    1987-01-01

    The ordered intermetallic alloy NiAl is being considered as a potential high temperature structural material, but lack of ductility at ambient temperatures, especially in polycrystalline form, is presently a major obstacle in achieving this goal. Even general agreement of the intrinsic ductility that can be achieved in monocrystals is in dispute. In order to understand this problem, two directionally solidified ingots of NiAl which displayed known differences in ductility were characterized in sufficient detail to identify the corresponding microstructural differences. It was found that the type and size of casting defects, i.e., porosity, present in the material were the major factors in controlling ductility of NiAl single crystals and could explain the order of magnitude variance in fracture strains reported in the literature.

  2. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33 Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approximately 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  3. Interdiffusion and Diffusion Mobility for fcc Ni-Co-Al Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Zhu, Naqiong; Wang, Hao; Lu, Xiao-Gang

    2016-12-01

    Ternary fcc Ni-Co-Al diffusion couples annealed at 1173 K (900 °C), 1373 K (1100 °C), and 1573 K (1300 °C) have been studied by using electron probe microanalysis. The interdiffusion coefficients were extracted using the Sauer-Freise and Whittle-Green methods from the measured concentration profiles of binary and ternary diffusion couples, respectively. Based on the diffusion coefficients reported in the literature and those determined in the present work, the diffusion mobilities for fcc Ni-Co-Al alloys were assessed. In general, reasonable agreements were reached and the resulted mobility database can be used to study the diffusion behavior of the ternary fcc Ni-Co-Al alloys in a wide composition range.

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

    NASA Technical Reports Server (NTRS)

    Raj, Sai V. (Inventor)

    2005-01-01

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

  5. Interdiffusion and Diffusion Mobility for fcc Ni-Co-Al Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Zhu, Naqiong; Wang, Hao; Lu, Xiao-Gang

    2017-03-01

    Ternary fcc Ni-Co-Al diffusion couples annealed at 1173 K (900 °C), 1373 K (1100 °C), and 1573 K (1300 °C) have been studied by using electron probe microanalysis. The interdiffusion coefficients were extracted using the Sauer-Freise and Whittle-Green methods from the measured concentration profiles of binary and ternary diffusion couples, respectively. Based on the diffusion coefficients reported in the literature and those determined in the present work, the diffusion mobilities for fcc Ni-Co-Al alloys were assessed. In general, reasonable agreements were reached and the resulted mobility database can be used to study the diffusion behavior of the ternary fcc Ni-Co-Al alloys in a wide composition range.

  6. 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.

  7. 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.

  8. Rippled Surface Structure and Electronic and Magnetic Properties of Ni_3Al(001)

    NASA Astrophysics Data System (ADS)

    Lee, Jae Il; Hong, S. C.; Mannstadt, W.; Freeman, A. J.

    1998-03-01

    LEED experiments on the composite Ni-Al surface of Ni_3Al(001) revealed a very small amount of ripplingfootnote D. Sondericker, F. Jona and P. M. Marcus, Phys. Rev. B33, 900 (1986). Challenged by this observation, structural, electronic and magnetic properties of Ni_3Al(001) were investigated by the local density full-potential linearized augmented plane wave (FLAPW) methodfootnote E. Wimmer, H. Krakauer, M. Weinert and A. J. Freeman, Phys. Rev. B24, 864 (1981).. A stable rippled surface atomic geometry was determined by atomic force calculations, with both surface Ni and Al atoms contracting down to the bulk region-consistent with experiment. The amount of rippling found by calculation (0.054 Åis almost within the experimental error bar (0.02 ± 0.03 ÅCharge densities, calculated work functions, and density of states for the rippled surfaces are reported. The spin polarized calculation shows that the magnetic moments for the Ni atoms decrease from 0.2 μB for the center layer to ~ 0.03 μB for the surface layer, which is essentially "magnetically dead". * Work in Korea supported by KOSEF through SNU-CTP and work at Northwestern U. supported by ONR

  9. EPR study of the formation of Ni/sup +/ ions by photoreduction in hydrogen of Ni/Al/sub 2/O/sub 3/ catalysts

    SciTech Connect

    Bonneviot, L.; Che, M.; Dyrek, K.; Schoellner, R.; Wendt, G.

    1986-05-22

    Photoreduction in H/sub 2/ at low temperatures of Ni/Al/sub 2/O/sub 3/ catalysts leads to the formation of Ni/sup +/ species in nonequivalent sites and in concentrations which depend on the pretreatment temperature. Upon adsorption of CO, several carbonyl-Ni/sup +/ species can be formed. Mono-, di-, tri-, and tetracarbonyl-Ni/sup +/ species are observed successively when the CO pressure is increased. At the same time, the Al/sub 2/O/sub 3/ surface can act as a tri-, di-, or monodentate ligand. The results obtained with the Ni/Al/sub 2/O/sub 3/ catalysts appear to be very similar to those observed for the Ni/SiO/sub 2/ and NiCa-X systems. The possibility of monitoring the changes occurring in the coordination sphere upon adsorption indicates that the Ni/sup +/ ions are accessible to gas-phase molecules and isolated on the Al/sub 2/O/sub 3/ surface. This study also indicates that there are several types of Ni/sup 2 +/ ions and some appear to be located in more or less distorted tetrahedral or octahedral sites in a spinel-like structure on the Al/sub 2/O/sub 3/ surface in agreement with literature data.

  10. The effect of NaCl/g/ on the oxidation of NiAl

    NASA Technical Reports Server (NTRS)

    Smeggil, J. G.; Bornstein, N. S.

    1978-01-01

    NaCl is ingested into operating gas turbines. The effect of this salt on the high temperature surface stability properties of turbine hardware is not well understood. The involvement of gaseous NaCl in the high temperature oxidation of NiAl, a principal component in many high temperature environmental coatings, is herein examined. The results of this work indicate that gaseous NaCl present in an oxidizing atmosphere affects the formation of Al2O3 whiskers on a dense Al2O3 layer. Such whisker growth, attributed to vapor transport processes through an otherwise dense Al2O3 scale, increases the aluminum depletion of the NiAl substrate.

  11. 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.

  12. Correlation of deformation mechanisms with the tensile and compressive behavior of NiAl and NiAl(Zr) intermetallic alloys

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    To identify the mechanisms controlling strength and ductility in powder-extruded NiAl and NiAl + 0.05 at. pct Zr, tensile and compressive testing was performed from 300 to 1300 K for several grain sizes. Grain size refinement significantly increased yield stress in both alloys and, in some cases, slightly lowered the ductile-to-brittle transition temperature (DBTT), although no room-temperature tensile ductility was observed even in the finest grain size specimens. The small Zr addition increased the DBTT and changed the low-temperature fracture mode from intergranular in NiAl to a combination of intergranular and transgranular in the Zr-doped alloy. Scanning electron microscopy of compression specimens deformed at room temperature revealed the presence of grain-boundary cracks in both alloys. These cracks were due to the incompatibility of strain in the polycrystalline material, owing to the lack of five independent slip systems. The tendency to form grain-boundary cracks, in addition to the low fracture stress of these alloys, contributed to the lack of tensile ductility at low temperatures.

  13. A Study of Pack Aluminizing Process for NiCrAlY Coatings Using Response Surface Methodology

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Huang, Xiao; Liu, Rong; Yang, Qi

    2014-01-01

    Aluminizing process is widely used to provide additional Al deposition onto superalloy surface for enhanced oxidation and corrosion resistance. In this research, an aluminizing process—pack cementation process, is used to deposit Al onto the surface of NiCrAlY coatings for increasing environmental protection. The experiment is designed using Box-Behnken approach, in which three parameters, the Al content, Ni content of the pack powder, and the temperature of the process, are selected as factors; and the thickness and Al/Ni ratio of the coatings are selected as responses. The effects of the factors on the responses are analyzed and modeled empirically. It is found that these empirical models correlate well with the results from additional sets of experiment. These models can be used to produce aluminized NiCrAlY coatings with specific thicknesses and Al/Ni ratios.

  14. 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.

  15. 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.

  16. 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.

  17. Modeling degradation and failure of Ni-Cr-Al overlay coatings

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1984-01-01

    Degradation of a Ni-16Cr-25Al-0.06Zr overlay coating on a Ni-22Cr substrate was examined after oxidation accompanied by thermal cycling. Concentration/distance profiles were measured in the coating and substrate after various one-hour cycles at 1150 C. A numerical model was developed to simulate coating degradation by simultaneous oxidation and coating/substrate interdiffusion. The validity of the model was confirmed by comparison of predicted and measured concentration/distance profiles. The ability of the model to identify critical system parameters was demonstrated for the case of the initial Al and Cr content of the coating and substrate.

  18. An Introduction to the BFS Method and Its Use to Model Binary NiAl Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Ferrante, J.; Amador, C.

    1998-01-01

    We introduce the Bozzolo-Ferrante-Smith (BFS) method for alloys as a computationally efficient tool for aiding in the process of alloy design. An intuitive description of the BFS method is provided, followed by a formal discussion of its implementation. The method is applied to the study of the defect structure of NiAl binary alloys. The groundwork is laid for a detailed progression to higher order NiAl-based alloys linking theoretical calculations and computer simulations based on the BFS method and experimental work validating each step of the alloy design process.

  19. 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.

  20. 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.

  1. The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Douglass, D. L.; Nasrallah, M.

    1974-01-01

    The investigation reported included a determination of the optimum composition of a Ni-Cr-Al ternary alloy with respect to oxidation resistance and minimum film-spalling tendencies. Yttrium and thorium in small amounts were added to the ternary alloy and an investigation of the oxidation mechanism and the oxide scale adherence was conducted. It was found that the oxidation mechanism of Ni-Cr-Al ternary alloys depends upon the composition of the alloy as well as the time, oxygen pressure, and temperature of oxidation.

  2. Interdiffusion of Al-Ni system enhanced by ultrasonic vibration at ambient temperature.

    PubMed

    Li, Mingyu; Ji, Hongjun; Wang, Chunqing; Bang, Han Sur; Bang, Hee Seon

    2006-12-01

    At ambient temperature, Al-1%Si wire of 25 microm diameter was bonded successfully onto the Au/Ni/Cu pad by ultrasonic wedge bonding technology. Physical process of the bond formation and the interface joining essence were investigated. It is found that the wire was softened by ultrasonic vibration, at the same time, pressure was loaded on the wire and plastic flow was generated in the bonding wire, which promoted the diffusion for Ni into Al. Ultrasonic vibration enhanced the interdiffusion that resulted from the inner defects such as dislocations, vacancies, voids and so on, which ascribed to short circuit diffusion.

  3. Shock compression response of highly reactive Ni + Al multilayered thin foils

    NASA Astrophysics Data System (ADS)

    Kelly, Sean C.; Thadhani, Naresh N.

    2016-03-01

    The shock-compression response of Ni + Al multilayered thin foils is investigated using laser-accelerated thin-foil plate-impact experiments over the pressure range of 2 to 11 GPa. The foils contain alternating Ni and Al layers (parallel but not flat) of nominally 50 nm bilayer spacing. The goal is to determine the equation of state and shock-induced reactivity of these highly reactive fully dense thin-foil materials. The laser-accelerated thin-foil impact set-up involved combined use of photon-doppler-velocimetry to monitor the acceleration and impact velocity of an aluminum flyer, and VISAR interferometry was used to monitor the back free-surface velocity of the impacted Ni + Al multilayered target. The shock-compression response of the Ni + Al target foils was determined using experimentally measured parameters and impedance matching approach, with error bars identified considering systematic and experimental errors. Meso-scale CTH shock simulations were performed using real imported microstructures of the cross-sections of the multilayered Ni + Al foils to compute the Hugoniot response (assuming no reaction) for correlation with their experimentally determined equation of state. It was observed that at particle velocities below ˜150 m/s, the experimentally determined equation of state trend matches the CTH-predicted inert response and is consistent with the observed unreacted state of the recovered Ni + Al target foils from this velocity regime. At higher particle velocities, the experimentally determined equation of state deviates from the CTH-predicted inert response. A complete and self-sustained reaction is also seen in targets recovered from experiments performed at these higher particle velocities. The deviation in the measured equation of state, to higher shock speeds and expanded volumes, combined with the observation of complete reaction in the recovered multilayered foils, confirmed via microstructure characterization, is indicative of the occurrence

  4. Interdiffusion in Ni-rich, Ni-Cr-Al alloys at 1100 and 1200 C. I - Diffusion paths and microstructures. II - Diffusion coefficients and predicted concentration profiles

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1987-01-01

    Interdiffusion in Ni-rich Ni-Cr-Al alloys is investigated experimentally after annealing at 1100 and 1200 C using gamma/gamma, gamma/gamma+beta, gamma/gamma+gamma prime, and gamma/gamma+alpha diffusion couples. The amount and location of Kirkendall porosity suggests that Al diffuses more rapidly than Cr which diffuses more rapidly than Ni in the gamma phase of Ni-Cr-Al alloys. The location and extent of maxima and minima in the concentration profiles of the diffusion couples indicate that both cross-term diffusion coefficients are positive. Measurements are also presented of the ternary interdiffusion coefficients of the gamma phase in the Ni-Cr-Al system. It is shown that the interdiffusion coefficients can be accurately predicted by using a ternary finite-difference interdiffusion model.

  5. 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.

  6. 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.

  7. Chromium and Tantalum Site Substitution Patterns in Ni3Al (L1(sub 2))gamma(prime)- Precipitates

    NASA Technical Reports Server (NTRS)

    Booth-Morrison, Christopher; Mao, Zugang; Seidman, David N.; Noebe, Ronald D.

    2008-01-01

    The site substitution behavior of Cr and Ta in the Ni3Al (Ll2)-type gamma'-precipitates of a Ni-Al-Cr-Ta alloy is investigated by atom-probe tomography (APT) and first-principles calculations. Measurements of the gamma'-phase composition by APT suggest that Al, Cr, and Ta share the Al sublattice sites of the gamma'-precipitates. The calculated substitutional energies of the solute atoms at the Ni and Al sublattice sites indicate that Ta has a strong preference for the Al sites, while Cr has a weak Al site preference. Furthermore, Ta is shown to replace Cr at the Al sublattice sites of the gamma'-precipitates, altering the elemental phase partitioning behavior of the Ni-Al-Cr-Ta alloy.

  8. Certain aspects of the melting, casting and welding of Ni{sub 3}Al alloys

    SciTech Connect

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

    1994-06-01

    Two alloys under development for castings are IC221M, (nominal composition Ni-8Al-7.7Cr-1.4Mo-1.7Zr wt %), and IC396M (nominal composition Ni-8Al-7.7Cr-3Mo-0.85Zr wt %). These alloys can be melted and cast using the techniques normally used for Ni-based materials. Oxidation of the liquid alloys can be controlled by vacuum processing or inert gas cover during processing. The liquid alloys can react with silica and zircon sands during casting, but this can be controlled through the use of appropriate mold washes like carbon-based materials. Welding studies showed that these alloys are susceptible to solidification cracking in weld fusion zones; the cracks are generally associated with occurrence of Ni-Ni{sub 5}Zr eutectic in interdendritic regions of the weld. Amount of eutectic in the weld microstructures increases with Zr concentration in weld filler metal. Weld filler metal Zr concentrations of 3 wt % and higher prevented solidification cracking of weld deposits on the base casting alloys; This is consistent with accepted phenomonological theory of this process. A weld filler metal with a composition of Ni-8Al-7.7Cr-1.5Mo-3.0Zr wt % was prepared and used to gas tungsten arc weld together 15-mm-thick plates of the IC221M alloy. This weldment was free of cracks. Weldment tensile specimens were machined from the plate and tested at 21, 800, and 900 C. Weldment yield strength at elevated temperatures was higher than room temperature and nearly comparable with that of the base IC221M alloy. Evaluation of the cast Ni{sub 3}Al alloys for furnace furniture, turbocharger rotors, and manufacturing tooling is also briefly discussed.

  9. Eutectic superalloys strengthened by aligned delta, Ni3Cb lamellae, gamma-prime, Ni3Al precipitates and reduced interlamellar spacing.

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    Monovariant eutectic alloys, located on the liquidus trough between the binary eutectic gamma, Ni - delta, Ni3Cb and the ternary eutectic gamma, Ni - gamma-prime, Ni3Al - delta, Ni3Cb, were identified which permitted the production of aligned lamellae within a nickel solid solution matrix containing the precipitate gamma-prime. These alloys exhibited great insensitivity in their composite microstructures to solidification parameters such as growth rate temperature gradient, and were found to be remarkably uniform in composition along their length.

  10. Anomalous hexagonal superstructure of aluminum oxide layer grown on NiAl(110) surface.

    PubMed

    Krukowski, Pawel; Chaunchaiyakul, Songpol; Minagawa, Yuto; Yajima, Nami; Akai-Kasaya, Megumi; Saito, Akira; Kuwahara, Yuji

    2016-11-11

    A modified method for the fabrication of a highly crystallized layer of aluminum oxide on a NiAl(110) surface is reported. The fabrication method involves the multistep selective oxidation of aluminum atoms on a NiAl(110) surface resulting from successive oxygen deposition and annealing. The surface morphology and local electronic structure of the novel aluminum oxide layer were investigated by high-resolution imaging using scanning tunneling microscopy (STM) and current imaging tunneling spectroscopy. In contrast to the standard fabrication method of aluminum oxide on a NiAl(110) surface, the proposed method produces an atomically flat surface exhibiting a hexagonal superstructure. The superstructure exhibits a slightly distorted hexagonal array of close-packed bright protrusions with a periodicity of 4.5 ± 0.2 nm. Atomically resolved STM imaging of the aluminum oxide layer reveals a hexagonal arrangement of dark contrast spots with a periodicity of 0.27 ± 0.02 nm. On the basis of the atomic structure of the fabricated layer, the formation of α-Al2O3(0001) on the NiAl(110) surface is suggested.

  11. 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.

  12. Single-Crystal NiAl-X Alloys Tested for Hot Corrosion

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.

    1999-01-01

    Single-crystal nickel aluminide (NiAl) has been investigated extensively throughout the last several years as a potential structural material in aero-gas turbine engines. The attractive features of NiAl in comparison to Ni-base superalloys include a higher melting point, lower density, higher thermal conductivity, and excellent oxidation resistance. However, NiAl suffers from a lack of ductility and fracture toughness at low temperatures and a low creep strength at high temperatures. Alloying additions of hafnium (Hf), gallium (Ga), titanium (Ti), and chromium (Cr) have each shown some benefit to the mechanical properties over that of the binary alloy. However, the collective effect of these alloying additions on the environmental resistance of NiAl-X was unclear. Hence, the present study was undertaken to examine the hot corrosion behavior of these alloys. A companion study examined the cyclic oxidation resistance of these alloys. Several single-crystal NiAl-X alloys (where X is Hf, Ti, Cr, or Ga) underwent hot corrosion testing in a Mach 0.3 burner rig at the NASA Lewis Research Center. Samples were tested for up to 300 1-hr cycles at a temperature of 900 C. It was found that increasing the Ti content from 1 to 5 at.% degraded the hot corrosion behavior. This decline in the behavior was reflected in high weight gains and large corrosion mound formation during testing (see the figures). However, the addition of 1 to 2 at.% Cr to alloys containing 4 to 5 at.% Ti appeared to greatly reduce the susceptibility of these alloys to hot corrosion attack and negated the deleterious effect of the increased Ti addition.

  13. Processing and Characterization of Mechanically Alloyed NiAl-Based Alloys

    DTIC Science & Technology

    1994-07-20

    50.1 49.9 - - - 0.007 * 5 00 0E 4 CD C o E * 0 0 L 00000i,_ 0 • 4- -. 0 * CCL 6.2 6- Three types of alloys were produced, NiAI with a brittle, Heusler ...16): -e - h where 7’ is the Orowan stress, h is particle height (usually, particle radius), and X is half the mean interparticle spacing. By

  14. Interfacial Reactions Between ZnAl(Ge) Solders on Cu and Ni Substrates

    NASA Astrophysics Data System (ADS)

    Rautiainen, Antti; Vuorinen, Vesa; Paulasto-Kröckel, Mervi

    2017-04-01

    Reactions between zinc-aluminum-germanium solder and copper/nickel substrates were investigated after 30 min of soldering at 420°C that simulates a wafer-level bonding process, and the results were compared to a eutectic zinc-aluminum solder. The ZnAlGe system (81.4 at.% Zn, 13.1 at.% Al, 5.5 at.% Ge) was selected in order to decrease the eutectic temperature of the ZnAleut (88.7 at.% Zn, 11.3 at.% Al) for high-temperature lead-free solder applications. In addition, a standard high temperature storage test at 150°C was performed up to 3000 h in order to investigate the evolution of the interconnection microstructures. Extensive copper dissolution was discovered during the soldering process. Germanium did not participate in any of the interfacial reactions on a copper substrate. On a nickel substrate, rapid formation of intermetallic compounds was discovered with both solders, and all the aluminum from the 500 μm thick solder was consumed by the formation of the Al3Ni2 phase during bonding. Germanium was observed to dissolve in the Al3Ni2 phase, but the addition of germanium to the solder was not found to affect markedly the interfacial microstructure. Based on the results, isothermal sections at 150°C of Al-Cu-Zn and Al-Ni-Zn systems are presented with superimposed diffusion paths.

  15. Microstructure and erosive wear behaviors of Ti6Al4V alloy treated by plasma Ni alloying

    NASA Astrophysics Data System (ADS)

    Wang, Z. X.; Wu, H. R.; Shan, X. L.; Lin, N. M.; He, Z. Y.; Liu, X. P.

    2016-12-01

    The Ni modified layers were prepared on the surface of Ti6Al4V substrate by the plasma surface alloying technique. The surface and cross-section morphology, element concentration and phase composition were investigated by thermal field emission scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy (GDOES), X-ray diffraction (XRD), respectively. The cross-section nano-scale hardness of the Ni modified layer was measured by nanoindenter. The results showed that the Ni modified layers exhibited triple-layer structure and continuous gradient distribution of the concentration. From the surface to the matrix, they were 2 μm Ni deposition layer, 8 μm Ni-rich alloying layer including the phases of Ni3Ti, NiTi, Ti2Ni, AlNi3 and 24 μm Ni-poor alloying layer forming the solid solution of nickel. With increasing of the thickness of the Ni modified layer, the microhardness increased first, reached the climax, then gradient decreased. The erosion tests were performed on the surfaces of the untreated and treated Ti6Al4V samples using MSE (Micro-slurry-jet Erosion) method. The experiment results showed that the wear rate of every layer showed different values, and the Ni-rich alloying layer was the lowest. The strengthening mechanism of the Ni modified layer showed micro-cutting wearing.

  16. 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.

  17. High-purity Ni electroless plating on screen-printed anodized Al substrates

    NASA Astrophysics Data System (ADS)

    Park, Sang-Geon; Lee, Youn-Seoung; Rha, Sa-Kyun

    2016-07-01

    By using an electroless plating process with a Ni source solution including dimethylamine borane (DMAB) at pH 6.5 and 65 ◦ C, we obtained a higher purity Ni film (< 1 at.% boron) without damage to the anodized Al substrate. With increasing plating time, the thickness of the film increased gradually, although the average deposition rate of the Ni films decreased steadily. We can infer that the abrupt decrease in sheet resistance (Rs) at the interface region is due to the change in the boron concentration caused by surface reactions, and the gradual decrease in Rs in the bulk region is due mainly to the effect of the saturation of boron's concentration on the thickness. From a boron-distribution viewpoint, this result indicates that the B concentration in the Ni film increases gradually with increasing plating time for plating times ≤ 60 s as a kind of initial stage (that is, interface region), and then saturates uniformly for plating times ≥ 300 s as a kind of bulk region. On the other hand, from an electronic structure viewpoint, this result implies that Ni gains 3d electrons with respect to elemental Ni. The increase in the number of electrons gained by the Ni 3d states may result in an enhancement of the electrical conductivity.

  18. 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.

  19. Rare-earth metals (REMs) in nickel aluminide-based alloys: I. Physicochemical laws of interaction in the Ni-Al-REM and Ni x Al y -REM-AE (alloying element) systems

    NASA Astrophysics Data System (ADS)

    Povarova, K. B.; Kazanskaya, N. K.; Drozdov, A. A.; Morozov, A. E.

    2008-02-01

    The data on the Ni-Al- R ( R = REM Sc, Y, La, lanthanides) binary and ternary systems and the interactions of three rare-earth metals (yttrium, lanthanum, cerium) with the main alloying elements (Ti (Zr, Hf), Cr (Mo, W) that are introduced into Ni3Al-based VKNA alloys are analyzed. The binary aluminides of REMs in the Ni-Al- R ternary systems are shown to be in equilibrium with neither NiAl nor Ni3Al. The solid solution of aluminum in RNi5, which penetrates deep into these ternary systems, is the most stable phase in equilibrium with Ni3Al. In the NiAl (Ni3Al)-AE- R systems, REM precipitation (segregation) on various defects and interfaces in nickel aluminides is likely to be the most probable, and REMs are thought to interact with the most active impurities in real alloys (C, O, N), since REMs have a large atomic radius and, thus, are virtually undissolved in nickel, aluminum, and nickel aluminides.

  20. Thermal evolution of Mg-Al and Ni-Al layered double hydroxides: the structure of the dehydrated phase.

    PubMed

    Cherepanova, Svetlana; Leont'eva, Natalya; Drozdov, Vladimir; Doronin, Vladimir

    2016-11-01

    Simulation of X-ray diffraction patterns on the basis of the models of one-dimensional disordered crystals was used to investigate the structure of the dehydrated phase produced by dehydration of Mg-Al and Ni-Al layered double hydroxides at a temperature of ∼473-498 K. It was found that the removal of water molecules transforms the initial structure, which is a mixture of 3R1 and 2H1 polytypes, into a structure that comprises preferentially fragments of 3R2 and 1H polytypes and has some turbostratic disorder.

  1. Synthesis and analysis of nanocrystalline β1-Cu3Al and β2-NiAl intermetallic-reinforced aluminum matrix composite by high energy ball milling

    NASA Astrophysics Data System (ADS)

    Nguyen, Hong-Hai; Nguyen, Minh-Thuyet; Kim, Won Joo; Kim, Jin-Chun

    2017-01-01

    Nanocrystalline β1-Cu3Al and β2-NiAl intermetallic compounds were in-situ reinforced in the aluminum matrix with the atomic composition of Al67Cu20Ni13 by the mechanical alloying of elemental powders. Both β1-Cu3Al, β2-NiAl phases that can be only co-synthesized in Cu base alloys have been obtained after 15h milling in this study. The phase evolution during milling process was investigated by X-ray diffraction. The β1-Cu3Al, β2-NiAl phases were metastable with further milling time up to 40 h. Specially, unreacted Al matrix has been totally transformed to amorphous state in the final powder. A remarkable crystalline size of 6.5 nm was reached after 15 h milling time. Thermal stability of the milled powder was also studied by differential thermal analysis. It is shown that β1-Cu3Al, β2-NiAl phases were stable up to higher than 550 °C. Moreover, the inter-diffusion between Al matrix and Cu3Al within the temperature range of 620-740 °C led to the formation of superstructure ζ1-Al3Cu4 phase.

  2. Microstructure and Phase Stability of Single Crystal NiAl Alloyed with Hf and Zr

    NASA Technical Reports Server (NTRS)

    Locci, I. E.; Dickerson, R. M.; Garg, A.; Noebe, R. D.; Whittenberger, J. D.; Nathal, M. V.; Darolia, R.

    1996-01-01

    Six near stoichiometric, NiAl single-crystal alloys, with 0.05-1.5 at.% of Hf and Zr additions plus Si impurities, were microstructurally analyzed in the as-cast, homogenized, and aged conditions. Hafnium-rich interdendritic regions, containing the Heusler phase (Ni2AlHf), were found in all the as-cast alloys containing Hf. Homogenization heat treatments partially reduced these interdendritic segregated regions. Transmission electron microscopy (TEM) observations of the as-cast and homogenized microstructures revealed the presence of a high density of fine Hf (or Zr) and Si-rich precipitates. These were identified as G-phase, Nil6X6Si7, or as an orthorhombic NiXSi phase, where X is Hf or Zr. Under these conditions the expected Heusler phase (beta') was almost completely absent. The Si responsible for the formation of the G and NiHfSi phases is the result of molten metal reacting with the Si-containing crucible used during the casting process. Varying the cooling rates after homogenization resulted in the refinement or complete suppression of the G and NiHfSi phases. In some of the alloys studied, long-term aging heat treatments resulted in the formation of Heusler precipitates, which were more stable at the aging temperature and coarsened at the expense of the G-phase. In other alloys, long-term aging resulted in the formation of the NiXSi phase. The stability of the Heusler or NiXSi phases can be traced to the reactive element (Hf or Zr) to silicon ratio. If the ratio is high, then the Heusler phase appears stable after long time aging. If the ratio is low, then the NiHfSi phase appears to be the stable phase.

  3. Burner Rig Hot Corrosion of a Single Crystal Ni-48Al-Ti-Hf-Ga Alloy

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Darolia, Ram; Cuy, Michael D.

    1998-01-01

    The hot corrosion resistance of a single crystal Ni-48Al-1Ti-0.5Hf-0.2Ga alloy was examined in a Mach 0.3 burner rig at 900 C for 300 hours. The combustion chamber was doped with 2 ppmw synthetic sea salt. The hot corrosion attack produced a random mound morphology on the surface. Microstructurally, the hot corrosion attack appeared to initiate with oxide-filled pits which were often broad and shallow. At an intermediate stage, the pits increased in size to incorporate unoxidized Ni islands in the corrosion product. The rampant attack stage, which was observed only at sharp sample corners, was characterized by rapid inward growth of alumina in finger-like protrusions incorporating significant amounts of Al-depleted Ni islands. Aluminum consumption in the oxide fingers resulted in the growth of a gamma' layer ahead of the advancing oxide fingers.

  4. Electrical properties of the amorphous interfacial layer between Al electrodes and epitaxial NiO films

    SciTech Connect

    Hyuck Jang, Jae; Kwon, Ji-Hwan; Kim, Miyoung; Ran Lee, Seung; Char, Kookrin

    2012-04-23

    The amorphous interfacial layer (a-IL) between Al electrode and epitaxial NiO films were studied using electron energy-loss spectroscopy (EELS) and energy-dispersive x-ray spectroscopy. Two distinct properties were found in the a-IL, i.e., a lower metallic and an upper insulating layer. EELS results revealed that the metallic Ni atoms were responsible for the conducting nature of the lower oxide amorphous layer. The resistance behavior of Al/a-IL/epi-NiO was changed from a high to a low resistance state after forming process. The resistance change could be explained by the formation of a nanocrystalline metal alloy in the insulating amorphous layer.

  5. Burner rig hot corrosion of a single crystal Ni-48Al-Ti-Hf-Ga alloy

    SciTech Connect

    Nesbitt, J.A.; Darolia, R.; Cuy, M.D.

    1999-07-01

    The hot corrosion resistance of a single crystal Ni-48Al-1Ti-0.5Hf-0.2Ga alloy was examined in a Mach 0.3 burner rig at 900 C for 300 hours. The combustion chamber was doped with 2 ppmw synthetic sea salt. The hot corrosion attack produced a random mound morphology on the surface. Microstructurally, the hot corrosion attack appeared to initiate with oxide-filled pits which were often broad and shallow. At an intermediate stage, the pits increased in size to incorporate unoxidized Ni islands in the corrosion product. The rampant attack stage, which was observed only at sharp sample corners, was characterized by rapid inward growth of alumina in finger-like protrusions incorporating significant amounts of Al-depleted Ni islands. Aluminum consumption in the oxide fingers resulted in the growth of a {gamma}{prime} layer ahead of the advancing oxide fingers.

  6. Progress in the Modeling of NiAl-Based Alloys Using the BFS Method

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Ferrante, John; Garg, Anita

    1997-01-01

    The BFS method has been applied to the study of NiAl-based materials to assess the effect of alloying additions on structure. Ternary, quaternary and even pent-alloys based on Ni-rich NiAl with additions of Ti, Cr and Cu were studied. Two approaches were used, Monte Carlo simulations to determine ground state structures and analytical calculations of high symmetry configurations which give physical insight into preferred bonding. Site occupancy energetics for ternary and the more complicated case of quaternary additions were determined, and solubility limits and precipitate formation with corresponding information concerning structure and lattice parameter were also 'observed' computationally. The method was also applied to determine the composition of alloy surfaces and interfaces. Overall, the results demonstrate that the BFS method for alloys is a powerful tool for alloy design and with its simplicity and obvious advantages can be used to complement any experimental alloy design program.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  8. Deformation and annealing study of NiCrAlY

    NASA Technical Reports Server (NTRS)

    Ebert, L. J.; Trela, D. M.

    1978-01-01

    The elevated temperature properties (tensile and creep) of NiCrALY, a nickel base alloy containing nominally 16% chromium, 4% aluminum, and 2 to 3% yttria (Y2O3) were evaluated and the optimal combination of thermomechanical treatments for maximum creep resistance was determined. Stored strain energy in as-extruded bars (14:1 extrusion ratio) permitted the development of a large grain size in the material when it was annealed at the maximum safe temperature 2450 F (1343 C). With a one-hour anneal at this temperature, the relatively fine grain size of the as-extruded material was changed to one in which the average grain diameter approached 1 mm, and the aspect ratio was about 10. The material was capable of being cold worked (by rolling) in amounts greater than 30% reduction in area. When the cold worked material was given a relaxation treatment, consisting of heating one hour at 1600 F(871 C), and then a high temperature anneal at 2450 F (1343 C) for one hour, both the high temperature strength and the high temperature creep resistance of the material was further enhanced.

  9. Al-doping influence on crystal growth of Ni-Al alloy: Experimental testing of a theoretical model

    NASA Astrophysics Data System (ADS)

    Rong, Xi-Ming; Chen, Jun; Li, Jing-Tian; Zhuang, Jun; Ning, Xi-Jing

    2015-12-01

    Recently, a condensing potential model was developed to evaluate the crystallization ability of bulk materials [Ye X X, Ming C, Hu Y C and Ning X J 2009 J. Chem. Phys. 130 164711 and Peng K, Ming C, Ye X X, Zhang W X, Zhuang J and Ning X J 2011 Chem. Phys. Lett. 501 330], showing that the best temperature for single crystal growth is about 0.6Tm, where Tm is the melting temperature, and for Ni-Al alloy, more than 6 wt% of Al-doping will badly reduce the crystallization ability. In order to verify these predictions, we fabricated Ni-Al films with different concentrations of Al on Si substrates at room temperature by pulsed laser deposition, and post-annealed the films at 833, 933, 1033 (˜ 0.6Tm), 1133, and 1233 K in vacuum furnace, respectively. The x-ray diffraction spectra show that annealing at 0.6Tm is indeed best for larger crystal grain formation, and the film crystallization ability remarkably declines with more than 6-wt% Al doping. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education, China (Grant No. 20130071110018) and the National Natural Science Foundation of China (Grant No. 11274073).

  10. Oxidation and microstructure evolution of Al-Si coated Ni3Al based single crystal superalloy with high Mo content

    NASA Astrophysics Data System (ADS)

    Tu, Xiaolu; Peng, Hui; Zheng, Lei; Qi, Wenyan; He, Jian; Guo, Hongbo; Gong, Shengkai

    2015-01-01

    A Si modified aluminide (Al-Si) coating was prepared on a Ni3Al based single crystal superalloy with high Mo content by high-activity pack cementation. Cyclic oxidation test at 1150 °C was carried out and the microstructure evolution of the coating was investigated. The results show that the oxidation resistance of the substrate was greatly increased by applying an Al-Si coating. During oxidation, outward diffusion of Mo was effectively blocked due to its high affinity with Si. Besides, a layered structure was formed as a result of the elements inter-diffusion. An obvious degradation of the Al-Si coating was observed after 100 h oxidation. Possible mechanisms related to the oxidation and elements inter-diffusion behaviours were also discussed.

  11. Annealing effect on the electrical properties and composition of a NiCrAl thin film resistor

    NASA Astrophysics Data System (ADS)

    Chuang, Nai-Chuan; Lin, Jyi-Tsong; Chen, Huey-Ru

    2015-12-01

    The composition of NiCrAl thin film resistors, under different annealing conditions in a N2 atmosphere, was investigated. The Auger electron spectrum (AES) has been used in studying the composition of NiCrAl thin films. The concentration ratio of Cr to Ni decreases when the annealing temperature increases. The electrical properties of a NiCrAl thin film resistor are affected by the concentrations of Cr and Ni, which lead to a higher temperature coefficient of resistance (TCR) and a lower sheet resistivity. The TCR of a NiCrAl thin film resistor is -5 ppm/°C at a 250 °C annealing temperature.

  12. Microstructure and Mechanical Properties of Dissimilar Welded Ti3Al/Ni-Based Superalloy Joint Using a Ni-Cu Filler Alloy

    NASA Astrophysics Data System (ADS)

    Chen, Bing-Qing; Xiong, Hua-Ping; Guo, Shao-Qing; Sun, Bing-Bing; Chen, Bo; Tang, Si-Yi

    2015-02-01

    Dissimilar welding of a Ti3Al-based alloy and a Ni-based superalloy (Inconel 718) was successfully carried out using gas tungsten arc welding technology in this study. With a Ni-Cu alloy as filler material, sound joints have been obtained. The microstructure evolution along the cross section of the dissimilar joint has been revealed based on the results of scanning electron microscopy and X-ray energy dispersive spectroscopy as well as X-ray diffractometer. It is found that the weld/Ti3Al interface is composed of Ti2AlNb matrix dissolved with Ni and Cu, Al(Cu, Ni)2Ti, (Cu, Ni)2Ti, (Nb, Ti) solid solution, and so on. The weld and In718/weld interface mainly consist of (Cu, Ni) solid solutions. The weld exhibits higher microhardness than the two base materials. The average room-temperature tensile strength of the joints reaches 242 MPa and up to 73.6 pct of the value can be maintained at 873 K (600 °C). The brittle intermetallic phase of Ti2AlNb matrix dissolved with Ni and Cu at the weld/Ti3Al interface is the weak link of the joint.

  13. Effects of Cd, Cu, Ni, and Zn on brown tide alga Aureococcus anophagefferens growth and metal accumulation.

    PubMed

    Wang, Bin; Axe, Lisa; Michalopoulou, Zoi-Heleni; Wei, Liping

    2012-01-03

    Trace metals play important roles in regulating phytoplankton growth and could influence algal bloom development. Laboratory studies were conducted to evaluate the influence of environmentally relevant concentrations of Cd, Cu, Ni, and Zn on Aureococcus anophagefferens bloom (brown tide) development. Results show that the elevated Ni(2+) concentrations, e.g. those of brown tide waters in the northeastern US, greatly stimulated A. anophagefferens growth (as compared to the control without Ni addition), yet, only low amounts of dissolved Ni were sequestered, thus leaving excessive Ni directly promoting A. anophagefferens blooms. The medium effective concentration EC(50) (Me(2+)) suggests A. anophagefferens has similar Cd sensitivity but much greater Cu tolerance as compared to cyanobacteria, as such, excessive Cu could indirectly promote A. anophagefferens blooms by inhibiting competitors such as Synechococcus sp. The effects of Ni and Cu promoting growth are consistent with the recent genomic study of this alga. In addition, Zn(2+) concentrations lower than those in brown tide waters enhance A. anophagefferens growth, but Zn sequestration in A. anophagefferens would not substantially reduce total dissolved Zn in these waters. Overall, this study, showing that excessive Cu and Ni likely promote brown tides, provides evidence for trace metal linkages in algal bloom development.

  14. Recent advances in alloy design of Ni{sub 3}Al alloys for structural use

    SciTech Connect

    Liu, C.T.; George, E.P.

    1996-12-31

    This is a comprehensive review of recent advances in R&D of Ni{sub 3}Al-based alloys for structural use at elevated temperatures in hostile environments. Recent studies indicate that polycrystalline Ni{sub 3}Al is intrinsically quite ductile at ambient temperatures, and its poor tensile ductility and brittle grain-boundary fracture are caused mainly by moisture-induced hydrogen embrittlement when the aluminide is tested in moisture- or hydrogen-containing environments. Tensile ductility is improved by alloying with substitutional and interstitial elements. Among these additives, B is most effective in suppressing environmental embrittlement and enhancing grain-boundary cohesion, resulting in a dramatic increase of tensile ductility at room temperature. Both B-doped and B-free Ni{sub 3}Al alloys exhibit brittle intergranular fracture and low ductility at intermediate temperatures (300-850 C) because of oxygen-induced embrittlement in oxidizing environments. Cr is found to be most effective in alleviating elevated-temperature embrittlement. Parallel efforts on alloy development using physical metallurgy principles have led to development of several Ni{sub 3}Al alloys for industrial use. The unique properties of these alloys are briefly discussed. 56 refs, 15 figs, 3 tabs.

  15. Aging effects in palladium and LaNi sub 4. 25 Al sub 0. 75 tritides

    SciTech Connect

    Nobile, A.; Wermer, J.R.; Walters, R.T.

    1991-01-01

    Palladium and LaNi{sub 5-x}Al{sub x} (x=0.30, 0.75, 0.85), which form reversible hydrides, are used for tritium processing and storage in the Savannah River Site (SRS) tritium facilities. As part of a program to develop technology based on the use of reversible metal hydrides for tritium processing and storage, the effects of aging on the thermodynamic behavior of palladium and LaNi{sub 4.25}Al{sub 0. 75} tritides are under investigation. During aging, the {sup 3}He tritium decay product remains in the tritide lattice and changes the thermodynamics of the tritium-metal tritide system. Aging effects in 755-day-aged palladium and 1423-day-aged LaNi{sub 4.25}Al{sub 0.75} tritides will be reported. Changes in the thermodynamics were determined by measuring tritium desorption isotherms on aging samples. In palladium, aging decreases the desorption isotherm plateau pressure and changes the {alpha}-phase portion of the isotherm. Aging-induced changes in desorption isotherms are more drastic in LaNi{sub 4.25}Al{sub 0.75}. Among the changes noted are: (1) decreased isotherm plateau pressure, (2) increased isotherm plateau slope, and (3) appearance of deep-trapped tritium, removable only by exchange with deuterium.

  16. Ni3Al-based alloys for die and tool application

    DOEpatents

    Liu, Chain T.; Bloom, Everett E.

    2001-01-01

    A novel Ni.sub.3 Al-based alloy exhibits strengths and hardness in excess of the standard base alloy IC-221M at temperatures of up to about 1000.degree. C. The alloy is useful in tool and die applications requiring such temperatures, and for structural elements in engineering systems exposed to such temperatures.

  17. 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.

  18. Solute transport during the cyclic oxidation of Ni-Cr-Al alloys. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.

    1982-01-01

    Important requirements for protective coatings of Ni-Cr-Al alloys for gas turbine superalloys are resistance to oxidation accompanied by thermal cycling, resistance to thermal fatigue cracking. The resistance to oxidation accompanied by thermal cycling is discussed. The resistance to thermal fatigue cracking is also considered.

  19. 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

  20. Containerless drop tube solidification and grain refinement of NiAl3

    NASA Technical Reports Server (NTRS)

    Ethridge, E. C.; Curreri, P. A.; Kelly, M.; Workman, G.; Smith, A. M.; Bond, R.

    1984-01-01

    The possibility of undercooling Ni-Al alloys below the liquidus in order to produce a single phase peritectic structure by containerless drop tube solidification was studied. Containerless process is a technique for both high purity contamination free studies as well as for investigating the undercooling and rapid solidification of alloys by suppression of heterogeneous nucleation on container walls. In order to achieve large undercoolings one must avoid heterogeneous nucleation of crystallization. It was shown that the Marshall Space Flight Center drop tubes ae unique facilities for containerless solidification experiments and large undercoolings are possible with some alloys. The original goal of undercooling the liquid metal well below the liquidus to the peritectic temperature during containerless free to form primarily NiAl3 was achieved. The microstructures were interesting from another point of view. The microstructure from small diameter samples is greatly refined. Small dendrite arm spacings such as these could greatly facilitate the annealing and solid state transformation of the alloy to nearly 10% NiAl3 by reducing the distance over which diffusion needs to occur. This could minimize annealing time and might make it economically feasible to produce NiAl3 alloy.

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

    DOEpatents

    Liu, Chain T.

    2000-01-01

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

  2. Study of the Ni NiAl2O4 YSZ cermet for its possible application as an anode in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Reyes-Rojas, A.; Esparza-Ponce, H. E.; Reyes-Gasga, J.

    2006-05-01

    Nanocrystalline Ni-NiAl2O4-YSZ cermet with a possible application as anode in solid oxide fuel cells (SOFCs) has been developed. The powders were prepared by using an alternative solid-state method that includes the use of nickel acetylacetonate as an inorganic precursor to obtain a highly porous material after sintering at 1400 °C and oxide reduction ({\\mathrm {NiO\\mbox {--}Al_{2}O_{3}\\mbox {--}YSZ}} \\to {\\mathrm {Ni\\mbox {--}NiAl_{2}O_{4}\\mbox {--}YSZ}} ) at 800 °C for 8 h in a tubular reactor furnace using 10% H2/N2. Eight samples with 45% Ni and 55% Al2O3-YSZ in concentrations of Al2O3 oxides from 10 to 80 wt% of were mixed to obtain the cermets. The obtained material was compressed using unidirectional axial pressing and calcinations from room temperature to 800 °C. Good results were registered using a heating rate of 1 °C min-1 and a special ramp to avoid anode cracking. Thermal expansion, electrical conductivity, and structural characterization by thermo-mechanical analyser (TMA) techniques/methods, the four-point probe method for conductivity, scanning electron microscopy (SEM), x-ray energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), and the Rietveld method were carried out. Cermets in the range 5.5 to 11% Al2O3 present a crystal size around 200 nm. An inversion degree (I) in the NiAl2O4 spinel structure of the cermets Ni-NiAl2O4-YSZ was found after the sintering and reduction processes. Good electrical conductivity and thermal expansion coefficient were obtained for the cermet with 12 wt% of spinel structure formation.

  3. Bio-active trace elements (cd, cu, fe, ni) in the oligotrophic south china sea

    NASA Astrophysics Data System (ADS)

    Wen, L.-S.; Jiann, K.-T.; Liu, K.-K.

    2003-04-01

    Bio-active trace elements (Cu, Ni, Cd, Fe) in seawater play a critical role in regulating oceanic phytoplankton growth and, hence, may influence global carbon cycle. However, their in-situ speciation and bio-reactivity are poorly understood. Dissolved copper and nickel are believed to be present in seawater predominantly as low molecular weight soluble organic complexes which are readily available to marine organism and immune from particle scavenging. Dissolved iron is believed to exist predominantly as high molecular weight colloidal species. Using ultraclean ultrafiltration and ion exchange/affinity chelating chemistry, we demonstrate that in the oligotrophic ocean waters, these four bio-active elements have distinctive characteristics of speciation and reactivity, even though they display similar nutrient-type distributions. For dissolved Cu, the concentration increased from 0.9 nM in the surface water to 3 nM at depths below 500 m; for dissolved Ni, 2˜9 nM; for dissolved Cd, 0.01˜0.9 nM; for dissolved Fe, 0.1˜0.6 nM. All four elements showed a subsurface minimum around 60 m deep, which corresponded to the subsurface Chl a maximum, indicating strong biological interactions with these elements. Detailed analysis revealed distinct size distribution and chemical reactivity for each element. For Cu, more than 50% in surface water was in smaller than 1kDa labile forms; the strongly complexed inert form increased from 28% at surface to 50% below 500 meter; the colloidal form Cu decreased from 12% at surface to a minimum of 6% at 60 meter, and then gradually increased to 16% in deeper water. For Ni, more than 80% was in smaller than 1kDa labile form, and very small fraction (˜5%) in colloidal from. For Cd, almost all dissolved fraction was in smaller than 1kDa labile form. As for Fe, its dynamic nature in water column caused by complicated bio-interactions was evident. This study indicated that, with preferential uptake of trace elements by different phytoplankton

  4. Low cycle fatigue behavior of polycrystalline NiAl at 300 and 1000 K

    NASA Technical Reports Server (NTRS)

    Lerch, Bradley A.; Noebe, Ronald D.

    1993-01-01

    The low cycle fatigue behavior of polycrystalline NiAl was determined at 300 and 1000 K - temperatures below and above the brittle- to-ductile transition temperature (BDTT). Fully reversed, plastic strain-controlled fatigue tests were conducted on two differently fabricated alloy samples: hot isostatically pressed (HIP'ed) prealloyed powder and hot extruded castings. HIP'ed powder (HP) samples were tested only at 1000 K, whereas the more ductile cast-and-extruded (C+E) NiAl samples were tested at both 1000 and 300 K. Plastic strain ranges of 0.06 to 0.2 percent were used. The C+E NiAl cyclically hardened until fracture, reaching stress levels approximately 60 percent greater than the ultimate tensile strength of the alloy. Compared on a strain basis, NiAl had a much longer fatigue life than other B2 ordered compounds in which fracture initiated at processing-related defects. These defects controlled fatigue life at 300 K, with fracture occurring rapidly once a critical stress level was reached. At 1000 K, above the BDTT, both the C+E and HP samples cyclically softened during most of the fatigue tests in air and were insensitive to processing defects. The processing method did not have a major effect on fatigue life; the lives of the HP samples were about a factor of three shorter than the C+E NiAl, but this was attributed to the lower stress response of the C+E material. The C+E NiAl underwent dynamic grain growth, whereas the HP material maintained a constant grain size during testing. In both materials, fatigue life was controlled by intergranular cavitation and creep processes, which led to fatigue crack growth that was primarily intergranular in nature. Final fracture by overload was transgranular in nature. Also, HP samples tested in vacuum had a life three times longer than their counterparts tested in air and, in contrast to those tested in air, hardened continuously over half of the sample life, thereby indicating an environmentally assisted fatigue damage

  5. NiCo nanoalloy encapsulated in graphene layers for improving hydrogen storage properties of LiAlH4

    PubMed Central

    Jiao, Chengli; Sun, Lixian; Xu, Fen; Liu, Shu-Sheng; Zhang, Jian; Jiang, Xia; Yang, Lini

    2016-01-01

    NiCo nanoalloy (4–6 nm) encapsulated in grapheme layers (NiCo@G) has been prepared by thermolysis of a 3D bimetallic complex CoCo[Ni(EDTA)]2·4H2O and successfully employed as a catalyst to improve the dehydrogenation performances of LiAlH4 by solid ball-milling. NiCo@G presents a superior catalytic effect on the dehydrogenation of LiAlH4. For LiAlH4 doped with 1 wt% NiCo@G (LiAlH4-1 wt% NiCo@G), the onset dehydrogenation temperature of LiAlH4 is as low as 43 °C, which is 109 °C lower than that of pristine LiAlH4. 7.3 wt% of hydrogen can be released from LiAlH4-1 wt% NiCo@G at 150 °C within 60 min. The activation energies of LiAlH4 dehydrogenation are extremely reduced by 1 wt% NiCo@G doping. PMID:27270633

  6. NiCo nanoalloy encapsulated in graphene layers for improving hydrogen storage properties of LiAlH4

    NASA Astrophysics Data System (ADS)

    Jiao, Chengli; Sun, Lixian; Xu, Fen; Liu, Shu-Sheng; Zhang, Jian; Jiang, Xia; Yang, Lini

    2016-06-01

    NiCo nanoalloy (4–6 nm) encapsulated in grapheme layers (NiCo@G) has been prepared by thermolysis of a 3D bimetallic complex CoCo[Ni(EDTA)]2·4H2O and successfully employed as a catalyst to improve the dehydrogenation performances of LiAlH4 by solid ball-milling. NiCo@G presents a superior catalytic effect on the dehydrogenation of LiAlH4. For LiAlH4 doped with 1 wt% NiCo@G (LiAlH4-1 wt% NiCo@G), the onset dehydrogenation temperature of LiAlH4 is as low as 43 °C, which is 109 °C lower than that of pristine LiAlH4. 7.3 wt% of hydrogen can be released from LiAlH4-1 wt% NiCo@G at 150 °C within 60 min. The activation energies of LiAlH4 dehydrogenation are extremely reduced by 1 wt% NiCo@G doping.

  7. Relationship between microstructure, cytotoxicity and corrosion properties of a Cu-Al-Ni shape memory alloy.

    PubMed

    Colić, Miodrag; Rudolf, Rebeka; Stamenković, Dragoslav; Anzel, Ivan; Vucević, Dragana; Jenko, Monika; Lazić, Vojkan; Lojen, Gorazd

    2010-01-01

    Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but their biomedical application is still limited. The aim of this work was to compare the microstructure, corrosion and cytotoxicity in vitro of a Cu-Al-Ni SMA. Rapidly solidified (RS) thin ribbons, manufactured via melt spinning, were used for the tests. The control alloy was a permanent mould casting of the same composition, but without shape memory effect. The results show that RS ribbons are significantly more resistant to corrosion compared with the control alloy, as judged by the lesser release of Cu and Ni into the conditioning medium. These results correlate with the finding that RS ribbons were not cytotoxic to L929 mouse fibroblasts and rat thymocytes. In addition, the RS ribbon conditioning medium inhibited cellular proliferation and IL-2 production by activated rat splenocytes to a much lesser extent. The inhibitory effects were almost completely abolished by conditioning the RS ribbons in culture medium for 4 weeks. Microstructural analysis showed that RS ribbons are martensitic, with boron particles as a minor phase. In contrast, the control Cu-Al-Ni alloy had a complex multiphase microstructure. Examination of the alloy surfaces after conditioning by energy dispersive X-ray and Auger electron spectroscopy showed the formation of Cu and Al oxide layers and confirmed that the metals in RS ribbons are less susceptible to oxidation and corrosion compared with the control alloy. In conclusion, these results suggest that rapid solidification significantly improves the corrosion stability and biocompatibility in vitro of Cu-Al-Ni SMA ribbons.

  8. First-principles studies of effects of interstitial boron and carbon on the structural, elastic, and electronic properties of Ni solution and Ni3Al intermetallics

    NASA Astrophysics Data System (ADS)

    Huang, Meng-Li; Wang, Chong-Yu

    2016-10-01

    The effects of boron and carbon on the structural, elastic, and electronic properties of both Ni solution and Ni3Al intermetallics are investigated using first-principles calculations. The results agree well with theoretical and experimental data from previous studies and are analyzed based on the density of states and charge density. It is found that both boron and carbon are inclined to occupy the Ni-rich interstices in Ni3Al, which gives rise to a cubic interstitial phase. In addition, the interstitial boron and carbon have different effects on the elastic moduli of Ni and Ni3Al. The calculation results for the G/B and Poisson’s ratios further demonstrate that interstitial boron and carbon can both reduce the brittleness of Ni, thereby increasing its ductility. Meanwhile, boron can also enhance the ductility of the Ni3Al while carbon hardly has an effect on its brittleness or ductility. Project supported by the National Basic Research Program of China (Grant No. 2011CB606402).

  9. 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.

  10. Influence of Al doping on optical properties of CdS/PVA nanocomposites: Theory and experiment

    SciTech Connect

    Bala, Vaneeta Tripathi, S. K. Kumar, Ranjan

    2014-04-24

    In the present work theoretical and experimental studies of aluminium doped cadmium sulphide polyvinyl alcohol (Al:CdS/PVA) nanocomposites have been carried out. Tetrahedral cluster AlCd{sub 9}S{sub 2}(SH){sub 18}]{sup 1−} has been encapsulated by small segments of polyvinyl alcohol (PVA) chains in order to simulate experimental environment of nanocomposites. Density functional theory (DFT) using local density approximation (LDA) functionals is employed to study the broadening of band gap upon ligation of nanoclusters. We have used in situ chemical route to synthesize nanocomposites. Optical band gap has been calculated from both experimental and theoretical approach.

  11. Changes in impedance of Ni/Cd cells with voltage and cycle life

    NASA Astrophysics Data System (ADS)

    Reid, Margaret A.

    1992-07-01

    Impedances of aerospace design Super Ni/Cd cells are being measured as functions of voltage and number of cycles. The cells have been cycled over 4400 cycles to date. Analysis of the impedance data has been made using a number of equivalent circuits. The model giving the best fit over the whole range of voltage has a parallel circuit of a kinetic resistance and a constant phase element in series with the ohmic resistance. The values for the circuit elements have been treated as empirical parameters, and no attempt has been made as yet to correlate them with physical and chemical changes in the electrode. No significant changes have been seen as yet with the exception of a decrease in kinetic resistance at low states of charge in the first 500 cycles.

  12. Design and Performance of Tropical Rainfall Measuring Mission (TRMM) Super NiCd Batteries

    NASA Technical Reports Server (NTRS)

    Ahmad, Anisa J.; Rao, Gopalakrishna M.; Jallice, Doris E.; Moran Vickie E.

    1999-01-01

    The Tropical Rainfall Measuring Mission (TRMM) is a joint mission between NASA and the National Space Development Agency (NASDA) of Japan. The observatory is designed to monitor and study tropical rainfall and the associated release of energy that helps to power the global atmospheric circulation shaping both weather and climate around the globe. The spacecraft was launched from Japan on November 27,1997 via the NASDA H-2 launch vehicle. The TRMM Power Subsystem is a Peak Power Tracking system that can support the maximum TRMM load of 815 watts at the end of its three year life. The Power Subsystem consists of two 50 Ampere Hour Super NiCd batteries, Gallium Arsenide Solar Array and the Power System Electronics. This paper describes the TRMM Power Subsystem, battery design, cell and battery ground test performance, and in-orbit battery operations and performance.

  13. A Ni-Cd battery model considering state of charge and hysteresis effects

    NASA Astrophysics Data System (ADS)

    García-Plaza, M.; Serrano-Jiménez, D.; Eloy-García Carrasco, J.; Alonso-Martínez, J.

    2015-02-01

    This paper introduces an electrical battery model. Based on a Thévenin circuit with two RC parallel branches, it includes an ampère-hour counting method to estimate the state of charge (SOC) and a novel model for the hysteresis. The presented model can consider variations in its parameters under changes in all of its internal and external variables, although only SOC and hysteresis are considered. Hysteresis consideration does not only allow distinguishing the parameters during charging and discharging, but also during transients between them. The model was designed to be capable of being implemented in online and offline systems. Finally the proposed model was validated for a single Ni-Cd cell, characterized by current interruption method, in an offline system. The validation was also extended to a stack of 210 cells of the same technology.

  14. Long life and low weight Ni/Cd cells for spacecraft

    SciTech Connect

    Lim, H.S.; Knechtli, R.C.; Margerum, J.D.; Pickett, D.F.; Rogers, M.M.; Verzwyvelt, S.A.

    1984-08-01

    Nickel-cadmium cells of various designs, containing polymer reinforced inorganic separators and either chemically deposited or electrochemically deposited nickel and cadmium electrodes, have been studied for their cycle life performance. The performance goal of these Ni/Cd cells is more than 10 years of cycle life at 80% depth of discharge operation in a geosynchronous orbit. Three alternate cycle regimes, including one with a high rate (0.4C) charging (HGEO regime), were used to test the cells. In all cycle regimes, the performance goal appears to be feasible with selected cell designs. The cycle life, in general, was longer in the HGEO cycling regime. However, in practice this HGEO cycling requires a sequential charging system which results in a tradeoff to a standard low rate charge for GEO cycling because of the extra charge control equipment needed for an HGEO regime.

  15. Changes in impedance of Ni/Cd cells with voltage and cycle life

    NASA Technical Reports Server (NTRS)

    Reid, Margaret A.

    1992-01-01

    Impedances of aerospace design Super Ni/Cd cells are being measured as functions of voltage and number of cycles. The cells have been cycled over 4400 cycles to date. Analysis of the impedance data has been made using a number of equivalent circuits. The model giving the best fit over the whole range of voltage has a parallel circuit of a kinetic resistance and a constant phase element in series with the ohmic resistance. The values for the circuit elements have been treated as empirical parameters, and no attempt has been made as yet to correlate them with physical and chemical changes in the electrode. No significant changes have been seen as yet with the exception of a decrease in kinetic resistance at low states of charge in the first 500 cycles.

  16. CdS-pillared CoAl-layered double hydroxide nanosheets with superior photocatalytic activity

    SciTech Connect

    Qiu, Yanqiang; Lin, Bizhou Jia, Fangcao; Chen, Yilin; Gao, Bifen; Liu, Peide

    2015-12-15

    Graphical abstract: - Highlights: • CdS nanocrystals were intercalated into CoAl-LDH interlayer. • The nanohybrid display superior visible-light photocatalytic activity. • A photoexcitation model for the pillared heterostructured system was proposed. - Abstract: A new nanohybrid was synthesized by mixing the positively charged 2D nanosheets of CoAl-layered double hydroxide (CoAl-LDH) and the negatively charged CdS nanosol suspensions. It was revealed that the CdS nanoparticles were intercalated into the interlayer region of CoAl-LDH with a spacing of 2.62 nm. The obtained nanohybrid exhibited a mesoporous texture with an expanded specific surface area of 62 m{sup 2} g{sup −1} and a superior photocatalytic activity in the degradation of acid red with a reaction constant of 1.26 × 10{sup −2} min{sup −1} under visible-light radiation, which is more than 2 times those of his parents CoAl-LDH and CdS.

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

    DOE PAGES

    Alfonso, Dominic R.; Tafen, De Nyago

    2015-04-28

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

  18. Large perpendicular magnetic anisotropy of ultrathin Ru and Rh films on a NiAl(001) surface.

    PubMed

    Kim, DongYoo; Yang, JeongHwa; Hong, Jisang

    2010-10-27

    Using the full potential linearized augmented plane wave (FLAPW) method, the magnetic properties of two-dimensional Ru and Rh monolayers (MLs) on a NiAl(001) surface have been investigated. It has been found that free standing one monolayer Ru and Rh films have ferromagnetic ground state with magnetic moments of 2.21 and 1.48 μ(B), respectively. The ferromagnetism is still observed even on a Ni terminated NiAl(001) surface, while no magnetic state is found on an Al terminated surface. The calculated magnetic moments of Ru and Rh atoms are 1.56 and 0.88 μ(B), respectively. In addition, an induced magnetic moment in surface Ni is observed. It has been found that the free standing Ru film has perpendicular magnetization to the film surface with a magnetocrystalline anisotropy (MCA) energy of 0.66 meV/atom, while an in-plane MCA energy of 0.37 meV/atom is achieved in Rh film. Very interestingly, we find that both Ru/NiAl(001) and Rh/NiAl(001) films have perpendicular magnetic anisotropy and the calculated MCA energies are 0.66 and 1.11 meV in Ru/NiAl(001) and Rh/NiAl(001), respectively. Along with the magnetic anisotropy, we have presented theoretically calculated x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) results.

  19. Large perpendicular magnetic anisotropy of ultrathin Ru and Rh films on a NiAl(001) surface

    NASA Astrophysics Data System (ADS)

    Kim, Dongyoo; Yang, JeongHwa; Hong, Jisang

    2010-10-01

    Using the full potential linearized augmented plane wave (FLAPW) method, the magnetic properties of two-dimensional Ru and Rh monolayers (MLs) on a NiAl(001) surface have been investigated. It has been found that free standing one monolayer Ru and Rh films have ferromagnetic ground state with magnetic moments of 2.21 and 1.48 μB, respectively. The ferromagnetism is still observed even on a Ni terminated NiAl(001) surface, while no magnetic state is found on an Al terminated surface. The calculated magnetic moments of Ru and Rh atoms are 1.56 and 0.88 μB, respectively. In addition, an induced magnetic moment in surface Ni is observed. It has been found that the free standing Ru film has perpendicular magnetization to the film surface with a magnetocrystalline anisotropy (MCA) energy of 0.66 meV/atom, while an in-plane MCA energy of 0.37 meV/atom is achieved in Rh film. Very interestingly, we find that both Ru/NiAl(001) and Rh/NiAl(001) films have perpendicular magnetic anisotropy and the calculated MCA energies are 0.66 and 1.11 meV in Ru/NiAl(001) and Rh/NiAl(001), respectively. Along with the magnetic anisotropy, we have presented theoretically calculated x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) results.

  20. Cu-Al-Ni Shape Memory Single Crystal Wires with High Transformation Temperature

    NASA Technical Reports Server (NTRS)

    Hautcoeur, Alain; Fouché, Florian; Sicre, Jacques

    2016-01-01

    CN-250X is a new material with higher performance than Nickel-Titanium Shape Memory Alloy (SMA). For space mechanisms, the main disadvantage of Nickel-Titanium Shape Memory Alloy is the limited transformation temperature. The new CN-250X Nimesis alloy is a Cu-Al-Ni single crystal wire available in large quantity because of a new industrial process. The triggering of actuators made with this Cu-Al-Ni single crystal wire can range from ambient temperature to 200 C in cycling and even to 250 C in one-shot mode. Another advantage of CN-250X is a better shape recovery (8 to 10%) than Ni-Ti (6 to 7%). Nimesis is the first company able to produce this type of material with its new special industrial process. A characterization study is presented in this work, including the two main solicitation modes for this material: tensile and torsion. Different tests measure the shape recovery of Cu-Al-Ni single crystals wires during heating from room temperature to a temperature higher than temperature of end of martensitic transformation.

  1. Phase and structural stability in Ni-Al systems from first principles

    NASA Astrophysics Data System (ADS)

    Goiri, Jon Gabriel; Van der Ven, Anton

    2016-09-01

    We report on a comprehensive first-principles study of phase stability in the Ni-Al binary, both at zero Kelvin and at finite temperature. First-principles density functional theory calculations of the energies of enumerated orderings on fcc and the sublattices of B2 not only predict the stability of known phases, but also reveal the stability of a family of ordered phases that combine features of L 12 and L 10 in different ratios to adjust their overall composition. The calculations also confirm the stability of vacancy ordered B2 derivatives that are stable in the Al-rich half of the phase diagram. We introduce strain order parameters to systematically analyze instabilities with respect to the Bain path connecting the fcc and bcc lattices. Many unstable orderings on both fcc and bcc are predicted around compositions of xNi=0.625 , where a martensitic phase transformation is known to occur. Cluster expansion techniques together with Monte Carlo simulations were used to calculate a finite-temperature-composition phase diagram of the Ni-Al binary. The calculated phase diagram together with an analysis of Bain instabilities reveals the importance of anharmonicity in determining the phase bounds between the B2 based β phase and the L 12 based γ' phase, as well as properties related to martensitic transformations that are observed upon quenching Ni-rich β .

  2. The response of macrophages to a Cu-Al-Ni shape memory alloy.

    PubMed

    Colić, Miodrag; Tomić, Sergej; Rudolf, Rebeka; Anzel, Ivan; Lojen, Gorazd

    2010-09-01

    Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but little is known about their biocompatibility. The aim of this work was to study the response of rat peritoneal macrophages (PMØ) to a Cu-Al-Ni SMA in vitro, by measuring the functional activity of mitochondria, necrosis, apoptosis, and production of proinflammatory cytokines. Rapidly solidified (RS) thin ribbons were used for the tests. The control alloy was a permanent mold casting of the same composition, but without the shape memory effect. Our results showed that the control alloy was severely cytotoxic, whereas RS ribbons induced neither necrosis nor apoptosis of PMØ. These findings correlated with the data that RS ribbons are significantly more resistant to corrosion compared to the control alloy, as judged by the lesser release of Cu and Ni in the conditioning medium. However, the ribbons generated intracellular reactive oxygen species and upregulated the production of IL-6 by PMØ. These effects were almost completely abolished by conditioning the RS ribbons for 5 weeks. In conclusion, RS significantly improves the corrosion stability and biocompatibility of Cu-Al-Ni SMA. The biocompatibility of this functional material could be additionally enhanced by conditioning the ribbons in cell culture medium.

  3. Solution-based thermodynamic modeling of the Ni-Al-Mo system using first-principles calculations

    SciTech Connect

    Zhou, S H; Wang, Y; Chen, L -Q; Liu, Z -K; Napolitano, R E

    2014-09-01

    A solution-based thermodynamic description of the ternary Ni–Al–Mo system is developed here, incorporating first-principles calculations and reported modeling of the binary Ni–Al, Ni–Mo and Al–Mo systems. To search for the configurations with the lowest energies of the N phase, the Alloy Theoretic Automated Toolkit (ATAT) was employed and combined with VASP. The liquid, bcc and γ-fcc phases are modeled as random atomic solutions, and the γ'-Ni3Al phase is modeled by describing the ordering within the fcc structure using two sublattices, summarized as (Al,Mo,Ni)0.75(Al,Mo,Ni)0.25. Thus, γ-fcc and γ'-Ni3Al are modeled with a single Gibbs free energy function with appropriate treatment of the chemical ordering contribution. In addition, notable improvements are the following: first, the ternary effects of Mo and Al in the B2-NiAl and D0a-Ni3Mo phases, respectively, are considered; second, the N-NiAl8Mo3 phase is described as a solid solution using a three-sublattice model; third, the X-Ni14Al75Mo11 phase is treated as a stoichiometric compound. Model parameters are evaluated using first-principles calculations of zero-Kelvin formation enthalpies and reported experimental data. In comparison with the enthalpies of formation for the compounds ψ-AlMo, θ-Al8Mo3 and B2-NiAl, the first-principles results indicate that the N-NiAl8Mo3 phase, which is stable at high temperatures, decomposes into other phases at low temperature. Resulting phase equilibria are summarized in the form of isothermal sections and liquidus projections. To clearly identify the relationship between the γ-fcc and γ'-Ni3Al phases in the ternary Ni–Al–Mo system, the specific γ-fcc and γ'-Ni3Al phase fields are plotted in x(Al)–x(Mo)–T space for a temperature range 1200–1800 K.

  4. Nickel self-diffusion along grain boundaries in Ni{sub 3}Al-base intermetallic alloys

    SciTech Connect

    Zulina, N.P.; Bolberova, E.V.; Razumovskii, I.M.

    1996-09-01

    {sup 63}Ni self-diffusion along grain boundaries (GBs) in intermetallic alloys Ni-25.2Al, Ni-24.9Al-4.8W, Ni-24.2Al-4.7Cr, Ni-19.3Al-4.5Hf and Ni-27.6Al-4.9Co (at.%) has been investigated by the radiotracer technique. The usual darkening in the positions of GBs on the autoradiographs obtained on the parallel and inclined sections of the specimens was observed. The diffusion penetration profiles were measured by the serial sectioning technique. Using the near-surface parts of the profiles which characterize lattice diffusion, the volume diffusion coefficients D were estimated. For pure Ni{sub 3}Al the agreement of the measured high temperature values of D with those of Bronfin et al. is good. By using the D-values and processing the tails of the measured profiles the GB diffusivity P (P = D{prime}{delta}, where D{prime} is the GB diffusion coefficient, {delta} the GB width) was calculated. The obtained P values followed an Arrhenius dependence at high temperatures: Ni-Al, T = 1,273--1,073 K, Q{prime} = 195 kJ/mol, P{sub 0} = 1 {times} 10{sup {minus}12}m{sup 3}/s; Ni-Al-Hf, T = 1,373--1,023 K, Q{prime} = 219 kJ/mol, P{sub 0} = 6.4 {times} 10{sup {minus}12}m{sup 3}/s; Ni-Al-W, T = 1,373--1,023 K, Q{prime} = 217 kJ/mol, P{sub 0} = 3.3 {times} 10{sup {minus}12}m{sup 3}/s; Ni-Al-Co, T = 1,273--1,023 K, Q{prime} = 189 kJ/mol, P{sub 0} = 6.8 {times} 10{sup {minus}13}m{sup 3}/s; Ni-Al-Cr, T = 1,323--1,023 K, Q{prime} = 265 kJ/mol, P{sub 0} = 1.8 {times} 10{sup {minus}9}m{sup 3}/s. By using the obtained D and P values the GB energy {gamma} in Ni{sub 3}Al and its alloys was estimated by the Borisov et al. semiempirical relationship. The {gamma}-values calculated exhibit a strong positive temperature dependence, which is usually revealed in metallic alloys containing elements with a strong tendency to GB segregation.

  5. O-18 tracer studies of Al2O3 scale formation on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Reddy, K. P. R.; Cooper, A. R.; Smialek, J. L.

    1982-01-01

    Diffusion processes in Al2O3 scales formed on NiCrAl + Zr alloys were studied by the proton activation technique employing the O-18 isotope as a tracer. The O-18 profiles identified a zone of oxide penetration beneath the external scale. Both this subscale formation and the outer Al2O3 scale thickness were shown by this technique to increase with Zr content in the alloy. Estimated kp's from scale thicknesses were in agreement with gravimetric measurements for various Zr levels. Alternate exposures in O-16 and O-18 revealed that oxygen inward transport was the primary growth mechanism. A qualitative analysis of these O-18 profiles indicated that the oxygen transport was primarily via short-circuit paths, such as grain boundaries.

  6. Unique coordination of pyrazine in T[Ni(CN){sub 4}].2pyz with T=Mn, Zn, Cd

    SciTech Connect

    Lemus-Santana, A.A.; Rodriguez-Hernandez, J.; Castillo, L.F. del; Basterrechea, M.; Reguera, E.

    2009-04-15

    The materials under study, T[Ni(CN){sub 4}].2pyz with T=Mn, Zn, Cd, were prepared by separation of T[Ni(CN){sub 4}] layers in citrate aqueous solution to allow the intercalation of the pyrazine molecules. The obtained solids were characterized from chemical analyses, X-ray diffraction, infrared, Raman, thermogravimetry, UV-Vis, magnetic and adsorption data. Their crystal structure was solved from ab initio using direct methods and then refined by the Rietveld method. A unique coordination for pyrazine to metal centers at neighboring layers was observed. The pyrazine molecule is found forming a bridge between Ni and T atoms, quite different from the proposed structures for T=Fe, Ni where it remains coordinated to two T atoms to form a vertical pillar between neighboring layers. The coordination of pyrazine to both Ni and T atoms minimizes the material free volume and leads to form a hydrophobic framework. On heating the solids remain stable up to 140 deg. C. No CO{sub 2} and H{sub 2} adsorption was observed in the small free spaces of their frameworks. - Graphical abstract: Framework for T[Ni(CN){sub 4}].2pyz with T=Mn, Zn, Cd.

  7. Interlaboratory comparison exercise for the determination of As, Cd, Ni and Pb in PM 10 in Europe

    NASA Astrophysics Data System (ADS)

    Gerboles, M.; Buzica, D.; Brown, R. J. C.; Yardley, R. E.; Hanus-Illnar, A.; Salfinger, M.; Vallant, B.; Adriaenssens, E.; Claeys, N.; Roekens, E.; Sega, K.; Jurasović, J.; Rychlik, S.; Rabinak, E.; Tanet, G.; Passarella, R.; Pedroni, V.; Karlsson, V.; Alleman, L.; Pfeffer, U.; Gladtke, D.; Olschewski, A.; O'Leary, B.; O'Dwyer, M.; Pockeviciute, D.; Biel-Ćwikowska, J.; Turšič, J.

    2011-07-01

    This paper presents the results of an intercomparison exercise for the determination of arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb) in PM 10, which are regulated by the European Directives for ambient air quality. Thirteen laboratories participated, generally using the European reference methods of measurement which consist of a microwave digestion followed by analysis with either ICP-MS or GFAAS. Each participant was asked to analyse five test samples: a liquid Certified Reference Material (CRM), two sub-samples of a NIST dust CRM (one already-digested and one to be digested by the participants) and two loaded filters (one already-digested and one to be digested by the participants). Participants were able to meet the Data Quality Objectives (DQOs) of the European Directives (expanded uncertainties of 25% for Pb and 40% for As, Cd and Ni) for 93% of all test samples, except for the loaded filter that were digested by the participants. In fact, only 76% of DQOs were met for this test sample, the closest to a routine sample analysis in the laboratory. The difficulties in analysing this test sample came mainly from digestion and contamination processes. Satisfactory results were also obtained using other digestion techniques (Soxhlet extraction and high pressure methods) and analytical methods (ICP-OES for Cd, Ni and Pb, EDXRF for Pb and Ni and Voltammetry for As, Ni, and Pb). Participants claimed uncertainties of about 10% for Pb and between 15 and 20% for As, Cd and Ni. These uncertainties were confirmed for 77% of results. The reproducibility of the methods of measurement was between 41 and 54% while repeatability remained between 5 and 12% except for the analysis of As on filters which was up to 20%. The majority of participant results showed higher between-day variability (14 ± 11%) than within-day variability (6.0 ± 5.3%).

  8. The transient oxidation of single crystal NiAl+Zr. M.S. Thesis. Final Report

    NASA Technical Reports Server (NTRS)

    Doychak, J. K.

    1983-01-01

    The 800 C oxidation of oriented single crystals of Zr doped beta-NiAl was studied using transmission electron microscopy. The oxide phases and metal-oxide orientation relationships were determined to characterize the transient stages of oxidation prior to the transformation to or formation of alpha-Al2O3. On (001) and (012) metal orientations, NiAl2O4 was the first oxide to form followed by delta-Al2O3 which becomes the predominant oxide phase. All oxides were highly epitaxially related to the metal; the orientation relationships being function of parallel cation close-packed directions in the meta and oxide. On (011) and (111) metal orientations, gamma-Al2O3 became the predominant oxide phase rather than delta-Al2O3, indicating a structural stability from the highly epitaxial oxides. The relative concentration of aluminum in the oxide scales increased with time indicating preferential gamma-or delta-Al2O3 growth. The striking feature common to the orientation relationships is the alignment of 100 m and 110 ox directions, believed to result from the minimal 3 percent mismatch between the corresponding (100)m and (110)ox planes.

  9. Oxidation Behavior of NiAl-TiB2 Coatings Prepared by Electrothermal Explosion Ultrahigh Speed Spraying

    NASA Astrophysics Data System (ADS)

    Hou, Shixiang; Liu, Zongde; Liu, Dongyu; Ma, Yimin

    The electro-thermal explosion ultrahigh speed spraying technology was employed to prepare the NiAl coatings with 0, 10, and 20 wt.% TiB2 on the Ni-based super-alloy substrate. The Microstructure, phase structure, and hardness of coatings were analyzed by scanning electron microscopy with energy dispersive X-ray spectrometry, X-ray diffraction, and Vickers micro-hardness tester, respectively. The results showed that the coatings had dense microstructure with submicron grains. The addition of TiB2 as a particulate reinforcement increased the hardness of NiAl. The isothermal oxidation test of coatings at 1000 °C for 140 h in air was investigated. The results showed that the oxidation resistance of NiAl coatings was higher than that of NiAl-TiB2 coatings at high temperature. The oxides and morphologies of the above coatings were investigated. The Al2O3 was formed on NiAl coating surface, while Al2O3 and TiO2 were formed on NiAl-TiB2 coating surface after oxidation.

  10. Effects of Fabrication Parameters on Interface of Zirconia and Ti-6Al-4V Joints Using Zr55Cu30Al10Ni5 Amorphous Filler

    NASA Astrophysics Data System (ADS)

    Liu, Yuhua; Hu, Jiandong; Shen, Ping; Guo, Zuoxing; Liu, Huijie

    2013-09-01

    ZrO2 was brazed to Ti-6Al-4V using a Zr55Cu30Al10Ni5 (at.%) amorphous filler in a high vacuum at 1173-1273 K. The influences of brazing temperature, holding time, and cooling rate on the microstructure and shear strength of the joints were investigated. The interfacial microstructures can be characterized as ZrO2/ZrO2- x + TiO/(Zr,Ti)2(Cu,Ni)/(Zr,Ti)2(Cu,Ni,Al)/acicular Widmanstäten structure/Ti-6Al-4V. With the increase in the brazing temperature, both the thickness of the ZrO2- x + TiO layer and the content of the (Zr,Ti)2(Cu,Ni) phase decreased. However, the acicular Widmanstäten structure gradually increased. With the increase in the holding time, the (Zr,Ti)2(Cu,Ni) phase decreased, and the thickness of the (Zr,Ti)2(Cu,Ni) + (Zr,Ti)2(Cu,Ni,Al) layer decreased. In addition, cracks formed adjacent to the ZrO2 side under rapid cooling. The microstructures produced under various fabrication parameters directly influence the shear strength of the joints. When ZrO2 and Ti-6Al-4V couples were brazed at 1173 K for 10 min and then cooled at a rate of 5 K/min, the maximum shear strength of 95 MPa was obtained.

  11. Anomalous magnetic configuration of Mn{sub 2}NiAl ribbon and the role of hybridization in the martensitic transformation of Mn{sub 50}Ni{sub 50−x}Al{sub x} ribbons

    SciTech Connect

    Zhao, R. B.; Zhao, D. W.; Li, G. K.; Ma, L. E-mail: houdenglu@mail.hebtu.edu.cn; Zhen, C. M.; Hou, D. L. E-mail: houdenglu@mail.hebtu.edu.cn; Wang, W. H.; Liu, E. K.; Chen, J. L.; Wu, G. H.

    2014-12-08

    The magnetic configuration of Mn{sub 2}NiAl ribbon has been investigated. In contrast to Ni{sub 2}MnAl, the compound Mn{sub 2}NiAl with considerable disorder does exhibit ferromagnetism and, due to exchange interaction competition, both ferromagnetic and antiferromagnetic moment orientations can coexist between nearest neighbor Mn atoms. This is unexpected in Heusler alloys. Regarding the mechanism of the martensitic transformation in Mn{sub 50}Ni{sub 50−x}Al{sub x}, it is found that increasing the Al content results in an unusual change in the lattice constant, a decrease of the transformation entropy change, and enhancement of the calculated electron localization. These results indicate that the p-d covalent hybridization between Mn (or Ni) and Al atoms gradually increases at the expense of the d-d hybridization between Ni and Mn atoms. This leads to an increased stability of the austenite phase and a decrease of the martensitic transformation temperature. For 11 ≤ x ≤ 14, Mn{sub 50}Ni{sub 50−x}Al{sub x} ferromagnetic shape memory alloys are obtained.

  12. In-situ studies of the TGO growth stresses and the martensitic transformation in the B2 phase in commercial Pt-modified NiAl and NiCoCrAlY bond coat alloys.

    SciTech Connect

    Hovis, D.; Hu, L.; Reddy, A.; Heuer, A. H.; Paulikas, A. P.; Veal, B. W.

    2007-12-01

    Oxide growth stresses were measured in situ at 1100 C on commercial Pt-modified NiAl and NiCoCrAlY bond coat alloys using synchrotron X-rays. Measurements were taken on samples that had no preoxidation, as well as on samples that had experienced 24 one-hour thermal exposures at 1150 C, a condition known to induce rumpling in the Pt-modified NiAl alloy, but not in the NiCoCrAlY alloy. The NiCoCrAlY alloy showed continuous stress relaxation under all conditions, whereas the Pt-modified NiAl alloys would typically stabilize at a fixed (often non-zero) stress suggesting a higher creep strength in the 'Thermally Grown Oxide' on the latter alloy, though the precise behavior was dependent on initial surface preparation. The formation of martensite in the Pt-modified NiAl alloys was also observed upon cooling and occurred at temperatures below 200 C for all of the samples observed. Based on existing models, this M{sub s} temperature is too low to account for the rumpling observed in these alloys.

  13. Moderate temperature sodium cells. V - Discharge reactions and rechargeability of NiS and NiS2 positive electrodes in molten NaAlCl4

    NASA Technical Reports Server (NTRS)

    Abraham, K. M.; Elliot, J. E.

    1984-01-01

    NiS2 and NiS have been characterized as high energy density rechargeable positive electrodes for moderate-temperature Na batteries of the configuration, Na(1)/beta double prime-Al2O3/NaAlCl4(1), NiSx. The batteries operate in the temperature range 170 - 190 C. Positive electrode reactions during discharge/charge cycles have been characterized. Excellent rechargeability of the batteries has been demonstrated by extended cell cycling. A Na/NiS2 cell, operating at 190 C, exceeded 600 deep discharge/charge cycles with practically no capacity deterioration. The feasibility of secondary Na/NiSx batteries with specific energies equal to or greater than 50 Wh/lb and cycle lifes exceeding 1000 deep discharge/charge cycles has been demonstrated.

  14. Electroless Ni-P-PTFE-Al2O3 Dispersion Nanocomposite Coating for Corrosion and Wear Resistance

    NASA Astrophysics Data System (ADS)

    Sharma, Ankita; Singh, A. K.

    2014-01-01

    With the aim to produce a coating having good corrosion and wear resistance alongside hardness but lesser friction coefficient, Ni-P-PTFE-Al2O3 (NiPPA) dispersion coating was developed. This was achieved by introducing nanosized polytetrafluoroethylene (PTFE) and alumina (Al2O3) in the Ni-P matrix deposited on mild steel substrate. The coating was characterized using scanning electron microscopy, energy dispersive analysis of x-ray, and x-ray diffractrometry. Microhardness and wear resistance of the coating was measured using Vicker's hardness tester and Pin-on-Disc method, respectively. The corrosion behavior was measured using electrochemical polarization and immersion tests with and without exposure in 3.5% NaCl solution. It is observed that codeposition of Al2O3 and PTFE particles with Ni-P coating results in comparatively smooth surface with nodular grains. The NiPPA coating was observed to have moderate hardness between electroless Ni-P-PTFE and Ni-P-Al2O3 coating and good wear resistance with lubricating effect. Addition of both PTFE and Al2O3 is observed to enhance corrosion resistance of the Ni-P coating. However, improvement in corrosion resistance is more due to addition of Al2O3 than PTFE. Continuous exposure for 10-20 days in corrosive solution is found to deteriorate corrosion protection properties of the coating.

  15. Predicting minimum Al concentrations for protective scale fromation on Ni-base alloys. I - Isothermal oxidation. II - Cyclic oxidation

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.

    1989-01-01

    Criteria proposed to predict the minimum bulk Al concentration for the formation of protective Al2O3 scales on Ni-based alloys during isothermal oxidation (two criteria proposed by Wagner, 1952 and 1959) and cyclic oxidation (the criteria proposed by Wahl, 1983, and Whittle, 1972/Wahl, 1983) were applied to Ni-Al and Ni-Cr-Al(Zr) alloys, respectively. It is shown that the first Wagner (1952) criterion underpredicted, by a factor of 3, the experimentally observed minimum Al concentration for the formation of an external Al2O3 scale on Ni-Al alloys at 1200 C; the second Wagner criterion predicted a transition from internal oxidation to continuous Al2O3 formation in good agreement with experimentally observed concentrations. It was also found that the two criteria for an Al2O3 scale formation during cyclic oxidation of Ni-Cr-Al(Zr) alloys were inadequate to predict the minimum Al concentration necessary for repeated formation of an Al2O3 scale, regardless of the adherence of the scale.

  16. Influence of Al content on non-equilibrium solidification behavior of Ni-Al-Ta model single crystal alloys

    NASA Astrophysics Data System (ADS)

    Ai, Cheng; Zhou, Jian; Zhang, Heng; Zhao, Xinbao; Pei, Yanling; Li, Shusuo; Gong, Shengkai

    2016-01-01

    The non-equilibrium solidification behaviors of five Ni-Al-Ta ternary model single crystal alloys with different Al contents were investigated by experimental analysis and theoretical calculation (by JMatPro) in this study. These model alloys respectively represented the γ' phase with various volume fractions (100%, 75%, 50%, 25% and 0%) at 900 °C. It was found that with decreasing Al content, liquidus temperature of experimental alloys first decreased and then increased. Meanwhile, the solidification range showed a continued downward trend. In addition, with decreasing Al content, the primary phases of non-equilibrium solidified model alloys gradually transformed from γ' phase to γ phase, and the area fraction of which first decreased and then increased. Moreover, the interdendritic/intercellular precipitation of model alloys changed from β phase (for 100% γ') to (γ+γ')Eutectic (for 75% γ'), (γ+γ')Eutectic+γ' (for 50% γ' and 25% γ') and none interdendritic precipitation (for 0% γ'), and the last stage non-equilibrium solidification sequence of model alloys was determined by the nominal Al content and different microsegregation behaviors of Al element.

  17. Effect of composition on antiphase boundary energy in Ni3Al based alloys: Ab initio calculations

    NASA Astrophysics Data System (ADS)

    Gorbatov, O. I.; Lomaev, I. L.; Gornostyrev, Yu. N.; Ruban, A. V.; Furrer, D.; Venkatesh, V.; Novikov, D. L.; Burlatsky, S. F.

    2016-06-01

    The effect of composition on the antiphase boundary (APB) energy of Ni-based L 12-ordered alloys is investigated by ab initio calculations employing the coherent potential approximation. The calculated APB energies for the {111} and {001} planes reproduce experimental values of the APB energy. The APB energies for the nonstoichiometric γ' phase increase with Al concentration and are in line with the experiment. The magnitude of the alloying effect on the APB energy correlates with the variation of the ordering energy of the alloy according to the alloying element's position in the 3 d row. The elements from the left side of the 3 d row increase the APB energy of the Ni-based L 12-ordered alloys, while the elements from the right side slightly affect it except Ni. The way to predict the effect of an addition on the {111} APB energy in a multicomponent alloy is discussed.

  18. A study on the structure and electrochemical characteristics of a Ni/Al double hydroxide

    NASA Astrophysics Data System (ADS)

    Zhen, Fu Zhong; Quan, Jiang Wen; Min, Yu Li; Peng, Zhang; Jun, Jiang Li

    2004-10-01

    Aluminium-substituted nickel based layered double hydroxides (LDHs), Ni0.78Zn0.04Co0.04Co0.02Al0.16(OH)2(CO3)0.08· 1.0H2O, were synthesized by a chemical co-precipitating process. It was shown that the structure of the LDHs is similar with that of α-Ni(OH)2 investigated by X-ray diffraction and transmission electron microscopy. The electrode comprising the LDHs was charged/discharged according to a galvanostatic model, and displayed better discharge capacity than the common β-Ni(OH)2 electrode. In addition, the effects of losing structure water on structure and electrochemical performance were investigated.

  19. A comparative scanning tunneling spectroscopy investigation of the (12110)-surface of decagonal Al-Ni-Co and the (100)-surface of its approximant Y-Al-Ni-Co

    NASA Astrophysics Data System (ADS)

    Mäder, Ruben; Widmer, Roland; Gröning, Pierangelo; Ruffieux, Pascal; Steurer, Walter; Gröning, Oliver

    2010-07-01

    We present a low-temperature scanning tunneling spectroscopy study of the local density of states (LDOS) on the (12110)-surface of the decagonal quasicrystal d-Al-Ni-Co and the (100)-surface of its structurally closely related approximant Y-Al-Ni-Co in the range of ±1 eV around the Fermi energy. The LDOS of both surfaces are dominated by a large parabolic pseudogap centered at the Fermi energy, which can be attributed to the Hume-Rothery stabilization mechanism or to an orbital hybridization. Superimposed on this large pseudogap, a spatially varying fine structure is revealed, whose spatial distribution correlates with the structures of both of the surfaces. This fine structure shows narrow peaks and pseudogaps exhibiting typical energy widths between 50 and 150 meV. The spatial extent of these localized states is of the order of the width of the topographic features, which is about 0.45 nm. Our findings show that specific electronic states are localized on equivalent topographic features regardless of the presence of periodic or quasiperiodic long-range order. We interpret this result as an indication that the fine structure in the LDOS is dominated much more by the complex short-range order than by the presence of the quasiperiodic long-range order.

  20. Aqueous-phase reforming of n-BuOH over Ni/Al 2O 3 and Ni/CeO 2 catalysts

    NASA Astrophysics Data System (ADS)

    Roy, B.; Sullivan, H.; Leclerc, C. A.

    The aqueous-phase reforming (APR) of n-butanol (n-BuOH) over Ni(20 wt%) loaded Al 2O 3 and CeO 2 catalysts has been studied in this paper. Over 100 h of run time, the Ni/Al 2O 3 catalyst showed significant deactivation compared to the Ni/CeO 2 catalyst, both in terms of production rates and the selectivity to H 2 and CO 2. The Ni/CeO 2 catalyst demonstrated higher selectivity for H 2 and CO 2, lower selectivity to alkanes, and a lower amount of C in the liquid phase compared to the Ni/Al 2O 3 sample. For the Ni/Al 2O 3 catalyst, the selectivity to CO increased with temperature, while the Ni/CeO 2 catalyst produced no CO. For the Ni/CeO 2 catalyst, the activation energies for H 2 and CO 2 production were 146 and 169 kJ mol -1, while for the Ni/Al 2O 3 catalyst these activation energies were 158 and 175 kJ mol -1, respectively. The difference of the active metal dispersion on Al 2O 3 and CeO 2 supports, as measured from H 2-pulse chemisorption was not significant. This indicates deposition of carbon on the catalyst as a likely cause of lower activity of the Ni/Al 2O 3 catalyst. It is unlikely that carbon would build up on the Ni/CeO 2 catalyst due to higher oxygen mobility in the Ni doped non-stoichiometric CeO 2 lattice. Based on the products formed, the proposed primary reaction pathway is the dehydrogenation of n-BuOH to butaldehyde followed by decarbonylation to propane. The propane then partially breaks down to hydrogen and carbon monoxide through steam reforming, while CO converts to CO 2 mostly through water gas shift. Ethane and methane are formed via Fischer-Tropsch reactions of CO/CO 2 with H 2.

  1. Microstructure and mechanical properties of zirconium doped NiAl/Cr(Mo) hypoeutectic alloy prepared by injection casting

    NASA Astrophysics Data System (ADS)

    Sheng, L. Y.; Du, B. N.; Guo, J. T.

    2017-01-01

    NiAl based materials has been considered as most potential candidate of turbine blade, due to its excellent high-temperature properties. However the bad room-temperature properties handicap its application. In the present paper, the zirconium doped NiAl/Cr(Mo) hypoeutectic alloy is fabricated by conventional casting and injection casting technology to improve its room-temperature properties. The microstructure and compressive properties at different temperatures of the conventionally-cast and injection-cast were investigated. The results exhibit that the conventionally-cast alloy comprises coarse primary NiAl phase and eutectic cell, which is dotted with irregular Ni2AlZr Heusler phase. Compared with the conventionally-cast alloy, the injection-cast alloy possesses refined the primary NiAl, eutectic cell and eutectic lamella. In addition, the Ni2AlZr Heusler phase become smaller and distribute uniformly. Moreover, the injection casting decrease the area fraction of primary NiAl phase at the cell interior or cell boundaries. The compressive ductility and yield strength of the injection-cast alloy at room temperature increase by about 100% and 35% over those of conventionally-cast alloy, which should be ascribed to the microstructure optimization.

  2. Initial oxidation behavior of Ni3Al (210) surface induced by supersonic oxygen molecular beam at room temperature

    NASA Astrophysics Data System (ADS)

    Xu, Ya; Sakurai, Junya; Teraoka, Yuden; Yoshigoe, Akitaka; Demura, Masahiko; Hirano, Toshiyuki

    2017-01-01

    The initial oxidation behavior of a clean Ni3Al (210) surface was studied at 300 K using a supersonic O2 molecular beam (O2 SSMB) having an O2 translational energy of 2.3 eV, and real-time photoemission spectroscopy performed with high-brilliance synchrotron radiation. The evolution behaviors of the O 1s, Ni 2p, Al 2p, and Ni 3p spectra were examined during irradiation with the O2 SSMB. The spectral analysis revealed that both the Al atoms and the Ni atoms on the surface were oxidized; however, the oxidation of Al progressed much faster than that of Ni. The oxidation of Al began to occur and AlOx was formed at an oxygen coverage of 0.26 monolayer (ML) (1 ML was defined as the atomic density of the Ni3Al (210) surface) and saturated at an oxygen coverage of 2.5 ML. In contrast, the oxidation of Ni commenced a little late at an oxygen coverage of 1.6 ML and slowly progressed to saturation, which occurred at an oxygen coverage of 4.89 ML.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  4. PLASMA SPRAYED Ni-Al COATINGS FOR SAFE ENDING HEAT EXCHANGER TUBES

    SciTech Connect

    ALLAN,M.L.; OTTERSON,D.; BERNDT,C.C.

    1998-11-01

    Brookhaven National Laboratory (BNL) has developed thermally conductive composite liners for corrosion and scale protection in heat exchanger tubes exposed to geothermal brine. The liners cannot withstand roller expansion to connect the tubes to the tubesheet. It is not possible to line the ends of the tubes with the same material after roller expansion due to the nature of the current liner application process. It was requested that BNL evaluate plasma sprayed Ni-Al coatings for safe ending heat exchanger tubes exposed to geothermal brine. The tubes of interest had an internal diameter of 0.875 inches. It is not typical to thermal spray small diameter components or use such small standoff distances. In this project a nozzle extension was developed by Zatorski Coating Company to spray the tube ends as well as flat coupons for testing. Four different Ni-Al coatings were investigated. One of these was a ductilized Ni-AIB material developed at Oak Ridge National Laboratory. The coatings were examined by optical and scanning electron microscopy. In addition, the coatings were analyzed by X-ray diffraction and subjected to corrosion, tensile adhesion, microhardness and field tests in a volcanic pool in New Zealand. It was determined that the Ni-Al coatings could be applied to a depth of two inches on the tube ends. When sprayed on flat coupons the coatings exhibited relatively high adhesion strength and microhardness. Polarization curves showed that the coating performance was variable. Measured corrosion potentials indicated that the Ni-Al coatings are active towards steel coated with thermally conductive polymers, thereby suggesting preferential corrosion. Corrosion also occurred on the coated coupons tested in the volcanic pool. This may have been exacerbated by the difficulty in applying a uniform coating to the coupon edges. The Ni-Al coatings applied to the tubes had significant porosity and did not provide adequate corrosion protection. This is associated with

  5. Removal of As, Cd, Cu, Ni, Pb, and Zn from a highly contaminated industrial soil using surfactant enhanced soil washing

    NASA Astrophysics Data System (ADS)

    Torres, Luis G.; Lopez, Rosario B.; Beltran, Margarita

    Surfactant enhanced soil washing (SESW) was applied to an industrial contaminated soil. A preliminary characterization of the soil regarding the alkaline-earth metals, Na, K, Ca and Mg took values of 2866, 2036, 2783 and 4149 mg/kg. The heavy metals As, Cd, Cu, Pb, Ni and Zn, had values of 4019, 14, 35582, 70, 2603, and 261 mg/kg, respectively. When using different surfactants, high removal of Cu, Ni and Zn were found, and medium removals for Pb, As and Cd. In the case of these three metals, tap water removed more than the surfactant solutions, except for the case of As. There were surfactants with average removals (this is, the removal for all the metals studied) of 67.1% (Tween 80), 64.9% (Surfacpol 14104) and 61.2% (Emulgin W600). There were exceptional removals using Texapon N-40 (83.2%, 82.8% and 86.6% for Cu, Ni and Zn), Tween 80 (85.9, 85.4 and 81.5 for Cd, Zn and Cu), Polafix CAPB (79%, 83.2% and 49.7% for Ni, Zn and As). The worst results were obtained with POLAFIX LO with a global removal of 45%, well below of the average removal with tap water (50.2%).All removal efficiencies are reported for a one step washing using 0.5% surfactant solutions, except for the case of mezquite gum, where a 0.1% solution was employed.

  6. Effects of diffusion on aluminum depletion and degradation of NiAl coatings

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.; Lowell, C. E.

    1973-01-01

    Experiments were performed to critically demonstrate the effects of diffusion on the aluminum depletion and degradation of NiAl coatings on superalloys. Pack aluminized IN 100 and Mar-M200 were diffusion annealed in 0.0005 torr vacuum at 1100 C for 300 hours. Aluminum losses due to oxidation and vaporization were minimal. Metallographic and electron microprobe analyses showed considerable interdiffusion of the coating with the substrate, which caused a large decrease in the original aluminum level of the coating. Subsequent cyclic furnace oxidation tests were performed at 1100 C using 1 hour cycles on pre-diffused and as-coated specimens. The pre-diffusion treatment decreased the oxidation protection for both alloys, but more dramatically for IN 100. Identical oxidation tests of bulk NiAl, where such diffusion effects are precluded, showed no signs of degradation at twice the time needed to degrade the coated superalloys.

  7. 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.

  8. 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.

  9. 1300 K compressive properties of several dispersion strengthened NiAl materials

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    To examine the potential of rapid solidification technology (RST) as a means to fabricate dispersion-strengthened aluminides, cylindrical compression samples were machined from the gauge section of their tensile specimens and tested in air at 1300 K. While microscopy indicates that RST can produce fine dispersions of TiB2, TiC and HfC in a NiAl matrix, the mechanical property data reveal that only HfC successfully strengthens the intermetallic matrix. The high stress exponents (above 10) and/or independence of strain rate on stress for NiAl-HfC materials suggest elevated temperature mechanical behavior similar to that found in oxide dispersion-strengthened alloys. Furthermore, an apparent example of departure side pinning has been observed, and as such, it is indicative of a threshold stress for creep.

  10. Alloying propagation in nanometric Ni/Al multilayers: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Turlo, V.; Politano, O.; Baras, F.

    2017-02-01

    In nanometric metallic multilayers such as Ni/Al, the alloying reaction proceeds in the form of a propagating wave. We studied the different phase transformations involved in the reactive wave propagation by means of molecular dynamics. The focus was on a specific regime that involves melting of reactants, intermixing of reactants, and formation of an intermetallic compound. We found that the wave consists of two stages. The first front is associated with a dissolution process and propagates at several meters per second, while the second front is due to the crystallization of the final product and is slower, leading to a specific microstructure with alternated large grains of NiAl and liquid regions in the front propagation direction. Three main exothermic processes were identified, including grain coarsening. Their respective contributions were evaluated. We developed a new texture analysis tool that allowed us to follow the evolution of the microstructure and the dynamics of the grain orientation.

  11. Sessile dislocations by reactions in NiAl severely deformed at room temperature

    SciTech Connect

    Geist, D.; Gammer, C.; Rentenberger, C.; Karnthaler, H. P.

    2015-02-05

    B2 ordered NiAl is known for its poor room temperature (RT) ductility; failure occurs in a brittle like manner even in ductile single crystals deforming by single slip. In the present study NiAl was severely deformed at RT using the method of high pressure torsion (HPT) enabling the hitherto impossible investigation of multiple slip deformation. Methods of transmission electron microscopy were used to analyze the dislocations formed by the plastic deformation showing that as expected dislocations with Burgers vector a(100) carry the plasticity during HPT deformation at RT. In addition, we observe that they often form a(110) dislocations by dislocation reactions; the a(110) dislocations are considered to be sessile based on calculations found in the literature. It is therefore concluded that the frequently encountered 3D dislocation networks containing sessile a(110) dislocations are pinned and lead to deformation-induced embrittlement. In spite of the severe deformation, the chemical order remains unchanged.

  12. 1300 K Compressive Properties of Directionally Solidified Ni-33Al-33Cr-1Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, Ivan E.

    2000-01-01

    The Ni-33Al-33Cr-1Mo eutectic has been directionally solidified by a modified Bridgeman technique at growth rates ranging from 7.6 to 508 mm/h to produce grain/cellular microstructures, containing alternating plates of NiAl and Cr alloyed with Mo. The grains had sharp boundaries for slower growth rates (< 12.7 mm/h), while faster growth rates (> 25.4 mm/h) lead to cells bounded by intercellular regions. Compressive testing at 1300 K indicated that alloys DS'ed at rates between 25.4 to 254 mm/h possessed the best strengths which exceed that for the as-cast alloy.

  13. Processing, properties, and applications of Ni{sub 3}Al-based alloys

    SciTech Connect

    Sikka, V.K.; Santella, M.L.; Liu, C.T.

    1997-06-01

    The Ni{sub 3}Al-based alloys represent a quantum jump in advanced alloys for structural applications at elevated temperatures. These alloys offer benefits of oxidation, carburization, and chlorination resistance, and significantly higher strength than many commercially used alloys. The commercial applications of the Ni{sub 3}Al-based alloys have begun to occur because of their comprehensive development This paper is to provide a review of. (1) alloy development, (2) melting, casting, and processing of alloys, (3) property data, (4) welding process and weldment properties, and (5) case histories of current applications. It is concluded that the cast alloy IC-221M is on its way to commercialization. 22 refs., 8 figs., 2 tabs.

  14. Extended solubility and stability in vapor quenched Ni3Al-X intermetallics

    NASA Technical Reports Server (NTRS)

    Wang, Rong

    1989-01-01

    A series of fine-grain and amorphous Ni3Al-X alloys, where X is a solute of 1 to 45 at. pct hf, C, or Hf+C in continuously graded compositions, was formed simultaneously into a 0.2 mm-thick disk by high-rate sputter codeposition. The as-deposited Ni3Al-X alloys exhibited a disordered L1(2) structure and extended solid solubility limits beyond which amorphous phases were formed. Heat-treatment of the alloys at 900 C resulted in fine grain size of 0.5 micron to 1.5 microns. Ultra fine dispersoids less than 500 A in size were observed, and they seemed resistant to coarsening.

  15. Assessment of microalloying effects on the high temperature fatigue behavior of NiAl

    NASA Technical Reports Server (NTRS)

    Noebe, R. D.; Lerch, B. A.; Rao, K. B. S.

    1995-01-01

    Binary NiAl suffers from a lack of strength and poor creep properties at and above 1000 K. Poor creep resistance in turn affects low cycle fatigue (LCF) lives at low strain ranges due to the additional interactions of creep damage. One approach for improving these properties involved microalloying with either Zr or N. As an integral part of a much larger alloying program the low cycle fatigue behavior of Zr and N doped nickel aluminides produced by extrusion of prealloyed powders has been investigated. Strain controlled LCF tests were performed in air at 1000 K. The influence of these microalloying additions on the fatigue life and cyclic stress response of polycrystalline NiAl are discussed.

  16. Microstructure and Pitting Corrosion of Plasma-Sprayed Ni-Al Nanocomposite Coating

    NASA Astrophysics Data System (ADS)

    Shi, X.; Zhong, Q. D.

    2016-06-01

    Ni-Al nanoparticles coating (NAN) was manufactured via atmospheric plasma spraying (APS) and thermal treated under hydrogen atmosphere at 1300∘C (TNAN) remained 1 h, and NiAl microparticles coating (NAM) was manufactured as a reference. Nanoscale particles were observed in NAN by TEM, and these nanoscale particles disappeared in TNAN. Many pores and cracks were observed in NAM. Few pores and cracks were observed in NAN, and no pores and cracks were found in TNAN with SEM. A scanning electrochemical microscopy (SECM) testing in 3.5% (wt.) NaCl solution for 3 h revealed that NAM underwent several pitting corrosion, NAN pitting corrosion was relatively minor, and TNAN had no pitting corrosion.

  17. Improving the phase stability and oxidation resistance of β-NiAl

    SciTech Connect

    Brammer, Travis

    2011-01-01

    High temperature alloys are essential to many industries that require a stable material to perform in harsh oxidative environments. Many of these alloys are suited for specific applications such as jet engine turbine blades where most other materials would either melt or oxidize and crumble (1). These alloys must have a high melting temperature, excellent oxidation resistance, good creep resistance, and decent fracture toughness to be successfully used in such environments. The discovery of Ni based superalloys in the 1940s revolutionized the high temperature alloy industry and there has been continued development of these alloys since their advent (2). These materials are capable of operating in oxidative environments in the presence of combustion gases, water vapor and at temperatures around 1050 C. Demands for increased f uel efficiency, however, has highlighted the need for materials that can be used under similar atmospheres and at temperatures in excess of 1200 C. The current Ni based superalloys are restricted to lower temperatures due to the presence of a number of low melting phases that result in softening of the alloys above 1000 C. Therefore, recent research has been aimed at exploring and developing newer alloy systems that can meet the escalating requirements. This thesis comprises a part of such an effort. The motivation of this work is to develop a novel high temperature alloy system that shows improved performance at higher temperatures than the currently employed alloys. The desired alloy should be in accordance with the requirements established in the National Energy Technology Laboratory (NETL) FutureGen program having an operating temperature around 1300 C. Alloys based on NiAl offer significant potential payoffs as structural materials in gas turbine applications due to a unique range of physical and mechanical properties. Alloying additions to NiAl could be used to further improve the pertinent properties that currently limit this system from

  18. Stress Development and Relaxation in Al2O3 during Early StageOxidation of beta-NiAl

    SciTech Connect

    Hou, P.Y.; Paulikas, A.P.; Veal, B.W.

    2005-04-20

    Using a glancing synchrotron X-ray beam (Advanced Photon Source, Beamline 12BM, Argonne National Laboratory), Debye-Scherrer diffraction patterns from thermally grown oxides on NiAl samples were recorded during oxidation at 1000 or 1100 C in air. The diffraction patterns were analyzed to determine strain and phase changes in the oxide scale as it developed and evolved. Strain was obtained from measurements of the elliptical distortion of the Debye-Scherrer rings, where data from several rings of a single phase were used. Results were obtained from {alpha}-Al{sub 2}O{sub 3} as well as from the transition alumina, in this case {theta}-Al{sub 2}O{sub 3}, which formed during the early stage. Compressive stress was found in the first-formed transition alumina, but the initial stress in {alpha}-Al{sub 2}O{sub 3} was tensile, with a magnitude high enough to cause Al{sub 2}O{sub 3} fracture. New {alpha}-Al{sub 2}O{sub 3} patches nucleated at the scale/alloy interface and spread laterally and upward. This transformation not only puts the alpha alumina in tension, but can also cause the transition alumina to be in tension. After a complete {alpha}-Al{sub 2}O{sub 3} layer formed at the interface, the strain level in {alpha}-Al{sub 2}O{sub 3} became compressive, reaching a steady state level around -75 MPa at 1100 C. To study a specimen's response to stress perturbation, samples with different thickness, after several hours of oxidation at 1100 C, were quickly cooled to 950 C to impose a compressive thermal stress in the scale. The rate of stress relaxation was the same for 1 and 3.5 mm thick samples, having a strain rate of {approx} 1 x 10{sup -8}/s. This behavior indicates that oxide creep is the major stress relaxation mechanism.

  19. 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.

  20. 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.

  1. Moisture-Induced Delayed Alumina Scale Spallation on a Ni(Pt)Al Coating (Preprint)

    DTIC Science & Technology

    2009-04-01

    crystal superalloys . But it is less widely appreciated that such phenomena may also occur for commercial platinum aluminide coatings . This has...examined for samples of a Ni(Pt)Al- coated CMSX4 single crystal superalloy , cyclically oxidized at 1150oC for 2000 hr. One sample exhibited... coated CMSX4 single crystal superalloy , cyclically oxidized at 1150oC for 2000 hr. One sample exhibited accentuated coating grain boundary wrinkling

  2. A study of Ni-5wt. pct Al coatings produced from different feedstock powder

    SciTech Connect

    Svantesson, J.; Wigren, J. )

    1992-03-01

    Ten different Ni-5 wt pct Al powders, three clad, one sintered, three water atomized, and three gas atomized, have been evaluated and plasma sprayed. The study focuses on how the manufacturing method, chemical composition, and particle size distribution of the powders affect the quality of the coating. Properties such as microstructure and mechanical behavior, as well as oxidation and corrosion resistance, are discussed. In conclusion, recommendations concerning the selection of powders for different applications are presented. 10 refs.

  3. Strengthening and Plastic Flow of Ni3Al Alloy Microcrystals (Preprint)

    DTIC Science & Technology

    2012-08-01

    Finally, the Ni3Al alloys exhibit a greater strengthening as a function of microcrystal diameter when com - pared to other materials for at least...2007) p. 4777. [56] M. Denura, D. Golberg and T. Hirano, Intermetallics 15 (2007) p. 1322 .   27 Approved for public release; distribution...dashed line shows the nominal shear strain-hardening rate (SHR) for the largest microcrystals as a fraction of the anisotropic shear modulus Ks. (b) Com

  4. 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.

  5. Effect of prestress on tensile yield strength of a Ni/sub 3/Al alloy

    SciTech Connect

    Yoo, M.H.; Liu, C.T.

    1988-09-01

    An experimental technique of prestressing and quenching was employed in order to elucidate the nature of pinning points responsible for the anomalous yield strength of Ni/sub 3/Al. The apparent number density of pinning points at room temperature was found to be unaffected by the prestressing and quenching from elevated temperatures. This result is consistent with the cross-slip-pinning (CSP) model in that cross-slipped segments act as pinning points on the leading superpartial dislocations.

  6. 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.

  7. Bulk Properties of Ni3Al(gamma') With Cu and Au Additions

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John

    1995-01-01

    The BFS method for alloys is applied to the study of 200 alloys obtained from adding Cu and Au impurities to a Ni3Al matrix. We analyze the trends in the bulk properties of these alloys (heat of formation, lattice parameter, and bulk modulus) and detect specific alloy compositions for which these quantities have particular values. A detailed analysis of the atomic interactions that lead to the preferred ordering patterns is presented.

  8. Structure and Properties of Detonation Coatings of Mechanocomposite Based on Bazalt-NiAl

    NASA Astrophysics Data System (ADS)

    Yakovlev, V. I.; Sitnikov, A. A.; Ovcharebko, A. G.; Golovina, T. A.; Sitnikova, T. A.

    2017-01-01

    The chemical composition, structure and microhardness of detonation coatings based on mechanically activated mixture of basalt powder and NiAl have been studied. It has been shown that the application of mechanomixture by detonation method results in the formation of composite coating similar to the composition of starting mixture. It has high microhardness and temperature resistance that will increase the wear resistance of parts coated with basalt at elevated temperatures.

  9. The effect of zirconium on the cyclic oxidation of NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Khan, A. S.; Lowell, C. E.

    1981-01-01

    This paper examines results with cyclic oxidation tests of Ni(9-20) Cr(15-30) Al-(x)Zr alloys carried out at 1100 C and 1200 C in static air. The concentration of zirconium varies from 0 to 0.63 atomic percent. Significant aluminum penetration is found in metallographic and electron microscopic examination of oxidized surfaces. Small amounts of zirconium lead to minimal penetration, and with increased zirconium content pronounced oxide penetration is observed.

  10. Removal of Cu, Cr, Ni, Zn, and Cd from electroplating wastes and synthetic solutions by vermicompost of cattle manure.

    PubMed

    Jordão, Cláudio Pereira; Pereira, Madson de Godoi; Einloft, Rosilene; Santana, Marlete Bastos; Bellato, Carlos Roberto; de Mello, Jaime Wilson Vargas

    2002-01-01

    This study was undertaken to evaluate the retention of Cu, Cr, Ni, Zn, and Cd under laboratory conditions from synthetic solution and electroplating wastes by vermicompost. A glass column was loaded with vermicompost, and metal solutions were passed through it. Metal concentrations were then measured in the eluate in order to evaluate the amounts retained by the vermicompost. Measurements of pH, metal concentrations, moistness, organic matter and ash contents, and infrared and XRD spectroscopy were used for vermicompost characterisation. Vermicompost residues obtained from this process were used for plant nutrition in eroded soil collected from a talus near a highway. Metal retention (in g of metal/kg of vermicompost) from effluents ranged from 2 for Cr and Zn to 4 in the case of Ni. In synthetic solutions, the values for metal retention were 4 for Cd and Zn, 6 for Cu and Ni, and 9 for Cr. The results also showed that metal concentrations in the purified effluents were below the maximum values established for waste discharges into rivers by the Brazilian Environmental Standards. The relatively high available Cd concentration of the vermicompost residue resulted in plant damage. This effect was attributed to the presence of Cd in the synthetic solution passed through the vermicompost. The data obtained do not give a complete picture of using vermicompost in cultivated lands, but such values as are determined do show that it can be suitable to remove heavy metals from industrial effluents.

  11. Tensile Creep Fracture of Polycrystalline Near-Stoichiometric NiAl

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2004-01-01

    Tensile creep fracture behavior of polycrystalline near-stoichiometric NiAl has been studied between 700 and 1200 K under initial applied stresses varying between 10 and 200 MPa. The stress exponent for fracture varied between 5.0 and 10.7 while the activation energy for fracture was 250 +/- 22 kJ/mol. The fracture life was inversely proportional to the secondary creep rate in accordance with the Monkman-Grant relation although there was extensive scatter in the data. This observation suggests that the fracture life for near-stoichiometric NiAl was influenced by creep under these stress and temperature conditions. Several different fracture morphologies were observed. Transgranular ductile cleavage fracture occurs at 700 K and at the higher stresses at 800 K. The fracture mode transitions to transgranular creep fracture at 900 and 1000 K and at lower stresses at 800 K, while plastic rupture and grain boundary cavitation occur at 1100 and 1200 K. An experimental fracture mechanism map is constructed for near-stoichiometric NiAl.

  12. Warm Spraying of High-Strength Ni-Al-Bronze: Cavitation Characteristics and Property Prediction

    NASA Astrophysics Data System (ADS)

    Krebs, Sebastian; Kuroda, Seiji; Katanoda, Hiroshi; Gaertner, Frank; Klassen, Thomas; Araki, Hiroshi; Frede, Simon

    2017-01-01

    Bronze materials such as Ni-Al-bronze show exceptional performances against cavitation erosion, due to their high fatigue strength and high strength. These materials are used for ship propellers, pump systems or for applications with alternating stresses. Usually, the respective parts are cast. With the aim to use resources more efficiently and to reduce costs, this study aimed to evaluate opportunities to apply bronze as a coating to critical areas of respective parts. The coatings should have least amounts of pores and non-bonded areas and any contaminations that might act as crack nuclei and contribute to material damages. Processes with low oxidation and high kinetic impacts fulfill these criteria. Especially warm spraying, a nitrogen-cooled HVOF process, with similar impact velocities as cold gas spraying but enhanced process temperature, allows for depositing high-strength Ni-Al-bronze. This study systematically simulates and evaluates the formation and performance of warm-sprayed Ni-Al-bronze coatings for different combustion pressures and nitrogen flow rates. Substrate preheating was used to improve coating adhesion for lower spray parameter sets. Furthermore, this study introduces an energy-based concept to compare spray parameter sets and to predict coating properties. Coatings with low porosities and high mechanical strengths are obtained, allowing for a cavitation resistance similar to bulk material.

  13. Molecular dynamics simulations of the melting curve of NiAl alloy under pressure

    SciTech Connect

    Zhang, Wenjin; Peng, Yufeng; Liu, Zhongli

    2014-05-15

    The melting curve of B2-NiAl alloy under pressure has been investigated using molecular dynamics technique and the embedded atom method (EAM) potential. The melting temperatures were determined with two approaches, the one-phase and the two-phase methods. The first one simulates a homogeneous melting, while the second one involves a heterogeneous melting of materials. Both approaches reduce the superheating effectively and their results are close to each other at the applied pressures. By fitting the well-known Simon equation to our melting data, we yielded the melting curves for NiAl: 1783(1 + P/9.801){sup 0.298} (one-phase approach), 1850(1 + P/12.806){sup 0.357} (two-phase approach). The good agreement of the resulting equation of states and the zero-pressure melting point (calc., 1850 ± 25 K, exp., 1911 K) with experiment proved the correctness of these results. These melting data complemented the absence of experimental high-pressure melting of NiAl. To check the transferability of this EAM potential, we have also predicted the melting curves of pure nickel and pure aluminum. Results show the calculated melting point of Nickel agrees well with experiment at zero pressure, while the melting point of aluminum is slightly higher than experiment.

  14. Tribological Characterization of NiAl Self-Lubricating Composites Containing V2O5 Nanowires

    NASA Astrophysics Data System (ADS)

    Huang, Yuchun; Ibrahim, Ahmed Mohamed Mahmoud; Shi, Xiaoliang; Radwan, Amr Rady; Zhai, Wenzheng; Yang, Kang; Xue, Bing

    2016-11-01

    In order to improve the tribological properties of NiAl self-lubricating composites, V2O5 nanowires with average width of 39 nm were synthesized by hydrothermal method. Furthermore, NiAl self-lubricating composites containing V2O5 nanowires (NAV) were successfully fabricated using spark plasma sintering technique. The tribological characteristics and wear mechanisms of NAV were evaluated at different sliding speeds, counterface ball materials and elevated temperatures. The results revealed that the frictional properties of NAV improved slightly with adding V2O5 nanowires at room temperature if compared to NiAl self-lubricating composites without solid lubricant as investigated in previous studies, while the wear mechanisms of NAV change widely with the change of the counterface ball materials and sliding velocities. V2O5 nanowires showed a beneficial effect on tribological performance of NAV at high temperatures owing to the formation of the V2O5-enriched glaze film at temperatures above 700 °C, which acts as the lubricous and protective mask against the severe wear.

  15. Effects of Solute Concentrations on Kinetic Pathways in Ni-Al-Cr Alloys

    NASA Technical Reports Server (NTRS)

    Booth-Morrison, Christopher; Weninger, Jessica; Sudbrack, Chantal K.; Mao, Zugang; Seidman, David N.; Noebe, Ronald D.

    2008-01-01

    The kinetic pathways resulting from the formation of coherent gamma'-precipitates from the gamma-matrix are studied for two Ni-Al-Cr alloys with similar gamma'-precipitate volume fractions at 873 K. The details of the phase decompositions of Ni-7.5Al-8.5Cr at.% and Ni-5.2Al-14.2Cr at.% for aging times from 1/6 to 1024 h are investigated by atom-probe tomography, and are found to differ significantly from a mean-field description of coarsening. The morphologies of the gamma'-precipitates of the alloys are similar, though the degrees of gamma'-precipitate coagulation and coalescence differ. Quantification within the framework of classical nucleation theory reveals that differences in the chemical driving forces for phase decomposition result in differences in the nucleation behavior of the two alloys. The temporal evolution of the gamma'-precipitate average radii and the gamma-matrix supersaturations follow the predictions of classical coarsening models. The compositional trajectories of the gamma-matrix phases of the alloys are found to follow approximately the equilibrium tie-lines, while the trajectories of the gamma'-precipitates do not, resulting in significant differences in the partitioning ratios of the solute elements.

  16. Plasma Sprayed Ni-Al Coatings for Safe Ending Heat Exchanger Tubes

    SciTech Connect

    Allen, M.L.; Berndt, C.C.; Otterson, D.

    1998-11-01

    Brookhaven National Laboratory (BNL) has developed thermally conductive composite liners for corrosion and scale protection in heat exchanger tubes exposed to geothermal brine. The liners cannot withstand roller expansion to connect the tubes to the tubesheet. It is not possible to line the ends of the tubes with the same material after roller expansion due to the nature of the current liner application process. It was requested that BNL evaluate plasma sprayed Ni-Al coatings for safe ending heat exchanger tubes exposed to geothermal brine. The tubes of interest had an internal diameter of 0.875 inches. It is not typical to thermal spray small diameter components or use such small standoff distances. In this project a nozzle extension was developed by Zatorski Coating Company to spray the tube ends as well as flat coupons for testing. Four different Ni-Al coatings were investigated. One of these was a ductilized Ni-AlB material developed at Oak Ridge National Laboratory. The coatings were examined by optical and scanning electron microscopy. In addition, the coatings were analyzed by X-ray diffraction and subjected to corrosion, tensile adhesion, microhardness and field tests in a volcanic pool in New Zealand.

  17. Kinetic Spraying Deposition of Reactive-Enhanced Al-Ni Composite for Shaped Charge Liner Applications

    NASA Astrophysics Data System (ADS)

    Byun, Gyeongjun; Kim, Jaeick; Lee, Changhee; Kim, See Jo; Lee, Seong

    2016-02-01

    Liners used in shaped charges (SC) must possess good penetration ability and explosive power. Producing the reactive layer (i.e., the Al-Ni composite) on a well-penetrating liner (i.e., Cu) via spray coating is a novel method; the exothermic reaction of this reactive layer can be enhanced by controlling the structure of the feedstock material. However, preceding studies have been unable to completely succeed in achieving this goal. There is still an opportunity to improve the performance of reactive layers in SC liner applications. In order to address this problem, a reactive Al-Ni composite powder was produced via arrested reactive milling (ARM) and deposited by a kinetic spray process. Afterward, the deposition state and self-propagating high-temperature synthesis (SHS) reaction behavior of the ARMed Al-Ni deposit were investigated. The deposition state was degraded by the ARM process due to the remaining solid lubricant and the strain-hardening effect, but the practically estimated bond strength was not poor (~40 MPa). No SHS reactions were induced by the ARM and kinetic spray process, which resulted in the quantitative maximization of the exothermic reaction. It is noteworthy that the initiation temperature of the SHS reaction was highly advanced (~300 °C) relative to preceding studies (~500 °C); this change is due to the additional mechanical activation initiated by the kinetic spray deposition.

  18. Impact Ignition of Low Density Mechanically Activated and Multilayer Foil Ni/Al

    NASA Astrophysics Data System (ADS)

    Beason, Matthew; Mason, B.; Son, Steven; Groven, Lori

    2013-06-01

    Mechanical activation (MA) via milling of reactive materials provides a means of lowering the ignition threshold of shock initiated reactions. This treatment provides a finely mixed microstructure with wide variation in the resulting scales of the intraparticle microstructure that makes model validation difficult. In this work we consider nanofoils produced through vapor deposition with well defined periodicity and a similar degree of fine scale mixing. This allows experiments that may be easier to compare with computational models. To achieve this, both equimolar Ni/Al powder that has undergone MA using high energy ball milling and nanofoils milled into a powder using low energy ball milling were used. The Asay Shear impact experiment was conducted on both MA Ni/Al and Ni/Al nanofoil-based powders at low densities (<60%) to examine their impact response and reaction behavior. Scanning electron microscopy and energy-dispersive x-ray spectroscopy were used to verify the microstructure of the materials. The materials' mechanical properties were evaluated using nano-indentation. Onset temperatures were evaluated using differential thermal analysis/differential scanning calorimetry. Impact ignition thresholds, burning rates, temperature field, and ignition delays are reported. Funding from the Defense Threat Reduction Agency (DTRA) Grant Number HDTRA1-10-1-0119. Counter-WMD basic research program, Dr. Suhithi M. Peiris, program director is gratefully acknowledged.

  19. Structural and electronic properties of the graphene/Al/Ni(111) intercalation system

    NASA Astrophysics Data System (ADS)

    Voloshina, E. N.; Generalov, A.; Weser, M.; Böttcher, S.; Horn, K.; Dedkov, Yu S.

    2011-11-01

    Decoupling of the graphene layer from the ferromagnetic substrate via intercalation of sp metal has recently been proposed as an effective way to realize a single-layer graphene-based spin-filter. Here, the structural and electronic properties of the prototype system, graphene/Al/Ni(111), are investigated via a combination of electron diffraction and spectroscopic methods. These studies are accompanied by state-of-the-art electronic structure calculations. The properties of this prospective Al-intercalation-like system and its possible implementations in future graphene-based devices are discussed.

  20. Study of the feasibility of producing Al-Ni intermetallic compounds by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Mohammed, Kahtan S.; Naeem, Haider T.; Iskak, Siti Nadira

    2016-08-01

    Mechanical alloying (MA) was employed to synthesize Al-Zn-Mg-Cu alloys of high weight percentage of the nickel component from the elemental powders of constituents via high-energy ball milling. The mixed powders underwent 15 h of milling time at 350 rpm speed and 10: 1 balls/powder weight ratio. The samples were cold-compacted and sintered thereafter. The sintered compacts underwent homogenization treatments at various temperatures conditions and were aged at 120°C for 24 h (T6). The milled powders and heat-treated Al alloy products were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The crystallite sizes and microstrains of the alloyed powder were estimated via measuring the broadening of XRD peaks using the Williamson-Hall equation. The results have revealed that optimum MA time of 15 h has led to the formation of Al-based solid solutions of Zn, Mg, Cu, and Ni. The outcomes showed that the Vickers hardness of the sintered Al-Zn-Mg-Cu compacts of Ni alloys was enhanced following aging at T6 tempering treatments. Higher compression strength of Al-alloys with the addition of 15% nickel was obtained next to the aging treatment.

  1. Microstructural changes to AlCu6Ni1 alloy after prolonged annealing at elevated temperature.

    PubMed

    Wierzbińska, M; Sieniawski, J

    2010-03-01

    This work presents results of microstructure examination of AlCu(6)Ni(1) aluminium alloy. The commercial AlCu(4)Ni(2)Mg(2) (M-309) alloy is widely used for elements of aircraft and automotive engines. Modification its chemical composition was aimed at improving the stability of mechanical properties of the alloy subjected to long-term exposure to high temperature. The alloy after standard T6 heat treatment (solution heat treated at 818 K/10 h/water quenched followed by ageing at 498 K/8 h/air cooled) was annealed for 150 h at elevated temperature of 573 K corresponding to the maximum value at which structural elements of jet piston engines made of aluminium alloys operate. It was found that applied heat treatment caused an increasing in the particles of hardening phase (theta'-Al(2)Cu) size. The significant growth of the length of theta'-Al(2)Cu precipitations was observed in particularly. Nevertheless, it did not strongly result in change of its shape - the 'crystallites' and 'rods' were still characteristic of hardening phase morphology. The phenomena of the growth of theta'-Al(2)Cu precipitates caused decreasing the mechanical properties of the alloy, what is the subject of further investigations by the authors.

  2. Electrical properties of pure and (Al, Ga and In) doped CdS/PVA nanocomposites

    NASA Astrophysics Data System (ADS)

    Bala, Vaneeta; Rani, Mamta; Tripathi, S. K.; Kumar, Ranjan

    2015-09-01

    (Al, Ga and In) doped CdS/PVA nanocomposites have been prepared by an in situ chemical method. dc conductivity (σd) measurements of thin films have been done at different temperatures from 288-333 K. The variation of current with voltage is found to be symmetric and linear up to the operating range of the applied voltage. At low temperatures (below 300 K), the conduction mechanism is based on the Davis-Mott model, which involve the presence of localized states originating from a lack of long-range order. In this regime, σ varies exponentially with T-1/4. For high temperatures, conduction is through regular band-type conduction in extended states. From the slope of lnσT1/2 versus T-1/4, we have calculated various Mott’s parameters such as degree of disorder (To), density of states N (Ef), hopping distance (R), and hopping energy (W). The doping of group III elements in CdS/PVA thin films results in a decrease in photoconductivity. Further, n-type conduction behaviour is confirmed in pure and (Al, Ga and In) doped CdS/PVA thin films with Hall measurements. Hall mobility increases with the doping of Ga and In, while it remains almost the same with Al doping in CdS/PVA. Dielectric measurements have also been done to see the effect of frequency at different temperatures (293 K, 313 K and 333 K) and at different applied fields (1 Volt and 3 Volt) on pure and (Al, Ga and In) doped CdS/PVA nanocomposites.

  3. Heavy metal content (Cd, Ni, Cr and Pb) in soil amendment with a low polluted biosolid

    NASA Astrophysics Data System (ADS)

    Gomez Lucas, Ignacio; Lag Brotons, Alfonso; Navarro-Pedreño, Jose; Belén Almendro-Candel, Maria; Jordán, Manuel M.; Bech, Jaume; Roca, Nuria

    2016-04-01

    The progressively higher water quality standards in Europe has led to the generation of large quantities of sewage sludge derived from wastewater treatment (Fytili and Zabaniotou 2008). Composting is an effective method to minimize these risks, as pathogens are biodegraded and heavy metals are stabilized as a result of organic matter transformations (Barker and Bryson 2002; Noble and Roberts 2004). Most of the studies about sewage sludge pollution are centred in medium and high polluted wastes. However, the aim of this study was to assess the effects on soil heavy metal content of a low polluted sewage sludge compost in order to identify an optimal application rate based in heavy metal concentration under a period of cultivation of a Mediterranean horticultural plant (Cynara carducnculus). The experiment was done between January to June: rainfall was 71 mm, the volume of water supplied every week was 10.5 mm, mean air temperatures was 14.2, 20.4 (maximum), and 9.2◦C (minimum). The soil was a clay-loam anthrosol (WRB 2006). The experimental plot (60 m2) was divided into five subplots with five treatments corresponding to 0, 2, 4, 6, and 8 kg compost/m2. Three top-soil (first 20 cm) samples from each treatment were taken (January, April and June) and these parameters were analysed: pH, electrical conductivity, organic matter and total content of heavy metals (microwave acid digestion followed by AAS-spectrometry determination). The results show that sewage sludge compost treatments increase the organic matter content and salinity (electrical conductivity of the soils) and diminish the pH. Cd and Ni total content in top-soil was affected and both slightly reduce their concentration. Pb and Cr show minor changes. In general, the application of this low polluted compost may affect the mobility of Cd and Ni due to the pH modification and the water added by irrigation along time but Pb and Cr remain their content in the top-soil. References Barker, A.V., and G.M. Bryson

  4. Modelling the concentrations of dissolved contaminants (Cd, Cu, Ni, Pb, Zn) in floodplain soils.

    PubMed

    Rennert, Thilo; Rabus, Widar; Rinklebe, Jörg

    2016-07-29

    Central European floodplain soils are often contaminated with potentially toxic metals. The prediction of their aqueous concentrations is a prerequisite for an assessment of environmental concerns. We tested the aqueous concentrations of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) derived from multi-surface adsorption modelling (on hydrous iron, aluminum and manganese oxides, clay and soil organic matter) against those analyzed in situ in the soil solution of four horizons of floodplain soils at the Elbe River, Germany. The input data for the reactive metals were derived from a seven-step sequential extraction scheme or from extraction with 0.43 M nitric acid (HNO3) and evaluated in four modelling scenarios. In all scenarios, measured and modelled concentrations were positively related, except partially for Pb. Close reproduction of the measured data was obtained using measured data of accompanying cations and anions together with amounts of reactive metals from both the sequential extraction or from 0.43 M HNO3 extraction, except for Cu, which was often strongly overestimated, and partially Cd. We recommend extraction with 0.43 M HNO3 to quantify reactive metals in soil because the modelling results were metal-specific with better or equal results using the single extractant, the application of which is also less laborious. Approximations of ion concentrations and water contents yielded similar results. Modelled solid-phase speciation of metals varied with pH and differed from that from sequential extraction. Multi-surface modelling may be an effective tool to predict both aqueous concentrations and solid-phase speciation of metals in soil.

  5. High Temperature Oxidation Behavior of gamma-Ni+gamma'-Ni3Al Alloys and Coatings Modified with Pt and Reactive Elements

    SciTech Connect

    Mu, Nan

    2007-12-01

    Materials for high-pressure turbine blades must be able to operate in the high-temperature gases (above 1000 C) emerging from the combustion chamber. Accordingly, the development of nickel-based superalloys has been constantly motivated by the need to have improved engine efficiency, reliability and service lifetime under the harsh conditions imposed by the turbine environment. However, the melting point of nickel (1455 C) provides a natural ceiling for the temperature capability of nickel-based superalloys. Thus, surface-engineered turbine components with modified diffusion coatings and overlay coatings are used. Theses coatings are capable of forming a compact and adherent oxide scale, which greatly impedes the further transport of reactants between the high-temperature gases and the underlying metal and thus reducing attack by the atmosphere. Typically, these coatings contain β-NiAl as a principal constituent phase in order to have sufficient aluminum content to form an Al2O3 scale at elevated temperatures. The drawbacks to the currently-used {beta}-based coatings, such as phase instabilities, associated stresses induced by such phase instabilities, and extensive coating/substrate interdiffusion, are major motivations in this study to seek next-generation coatings. The high-temperature oxidation resistance of novel Pt + Hf-modified γ-Ni + γ-Ni3Al-based alloys and coatings were investigated in this study. Both early-stage and 4-days isothermal oxidation behavior of single-phase γ-Ni and γ'-Ni3Al alloys were assessed by examining the weight changes, oxide-scale structures, and elemental concentration profiles through the scales and subsurface alloy regions. It was found that Pt promotes Al2O3 formation by suppressing the NiO growth on both γ-Ni and γ'Ni3Al single-phase alloys. This effect increases with increasing Pt content. Moreover, Pt exhibits this effect even at lower

  6. Preparation of Ni/Pt catalysts supported on spinel (MgAl 2O 4) for methane reforming

    NASA Astrophysics Data System (ADS)

    Foletto, Edson L.; Alves, Ricardo W.; Jahn, Sérgio L.

    MgAl 2O 4 was synthesized through hydrolysis of metallic alkoxides of Mg 2+ and Al 3+. The formed spinel precursor phase was calcined at temperatures between 600 and 1100 °C, for 4 h. The spinel was utilized as a Ni/Pt catalyst support. The Ni/MgAl 2O 4 catalysts (15% Ni, w/w) containing small amounts of Pt were tested for methane steam reforming. The solids were analyzed by X-ray diffraction (XRD), temperature programmed reduction (TPR) with H 2 and catalytic tests. The spinel phase was formed at temperatures above 700 °C. The addition of small amounts of Pt to Ni/MgAl 2O 4 promoted an increase in surface area. This probably caused the considerable increase in methane conversion.

  7. The effect of platinum on diffusion kinetics in beta-NiAl: implications for thermal barrier coating lifetimes.

    PubMed

    Marino, Kristen A; Carter, Emily A

    2009-01-12

    Platinum is added to thermal barrier coatings (TBCs) as it is observed empirically to extend their lifetime, but the mechanism by which Pt acts is unknown. Since Pt has been proposed to alter diffusivities in NiAl, a key component of TBCs, we use first-principles quantum mechanics calculations to investigate atomic level diffusion mechanisms. Here, we examine the effect of Pt on five previously proposed mechanisms for Ni diffusion in NiAl: next-nearest-neighbor jumps, the triple defect mechanism, and three variants of the six jump cycle. We predict that Pt increases the rate of Ni diffusion by stabilizing point defects and defect clusters that are diffusion intermediates. Previously, we predicted the triple defect mechanism to be a dominant Ni diffusion mechanism; it simultaneously results in long-range Al diffusion in the opposite direction. Since Pt increases the rate of Ni diffusion, it also increases Al diffusion in NiAl, which may be key to extending the coating lifetime.

  8. Kaolinite sorption of Cd, Ni and Cu from landfill leachates: influence of leachate composition.

    PubMed

    Petrangeli Papini, M; Majone, M; Rolle, E

    2001-01-01

    Heavy metal speciation in landfill leachates plays a significant role in determining the mobility during the percolation through soils. The complexation characteristics of landfill leachate directly affects heavy metal solubility and the extent of the interaction with soils, lowering or raising the sorbed amount depending on the relative affinity of the complexed metal and uncomplexed form to soil adsorption sites. In this paper, the adsorption of Cd, Ni and Cu onto kaolinite from three leachates (collected from landfill at different fermentation stage) is studied, also in comparison with metal speciation by two different operative procedures. The heavy metals, at their natural concentration, were divided into operational classes according to an exchange-based procedure and by fractionation on the basis of molecular weight (exchange onto Chelex100 resin and ultrafiltration, respectively). All the experiments were performed also on synthetic solutions designed according to leachate composition and theoretical speciation. The experimental results have shown leachate complexing capacity is strongly dependent on landfill age, and that broad parameters such as COD, DOC, pH, ionic strength and VFA concentration are not able to predict it. It is notheworthy that the strong complexing capacity of leachate can cause extraction of metals from the solid phase instead of adsorption from the liquid one.

  9. 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.

  10. Closed field unbalanced magnetron sputtering ion plating of Ni/Al thin films: influence of the magnetron power.

    PubMed

    Said, R; Ahmed, W; Gracio, J

    2010-04-01

    In this study NiAl thin films have been deposited using closed field unbalanced magnetron sputtering Ion plating (CFUBMSIP). The influence of magnetron power has been investigated using dense and humongous NiAl compound targets onto stainless steel and glass substrates. Potential applications include tribological, electronic media and bond coatings in thermal barrier coatings system. Several techniques has been used to characterise the films including surface stylus profilometry, energy dispersive spectroscopy (EDAX), X-Ray diffraction (XRD) Composition analysis of the samples was carried out using VGTOF SIMS (IX23LS) and Atomic force microscopy (AFM). Scratch tester (CSM) combined with acoustic emission singles during loading in order to compare the coating adhesion. The acoustic emission signals emitted during the indentation process were used to determine the critical load, under which the film begins to crack and/or break off the substrate. The average thickness of the films was approximately 1 um. EDAX results of NiAl thin films coating with various magnetron power exhibited the near equal atomic% Ni:Al. The best result being obtained using 300 W and 400 W DC power for Ni and Al targets respectively. XRD revealed the presence of beta NiAl phase for all the films coatings. AFM analysis of the films deposited on glass substrates exhibited quite a smooth surface with surface roughness values in the nanometre range. CSM results indicate that best adhesion was achieved at 300 W for Ni, and 400 W for Al targets compared to sample other power values. SIMS depth profile showed a uniform distribution of the Ni and Al component from the surface of the film to the interface.

  11. Evolution of Dislocation Structure in a Ni3Al Single Crystal Under the Conditions of High-Temperature Superplasticity

    NASA Astrophysics Data System (ADS)

    Kazantseva, N. V.; Stepanova, N. N.; Vinogradova, N. I.

    2017-01-01

    The evolution of defective structure in a single crystal of a Ni3Al-base intermetallic with iron and chromium additives under the conditions of superplasticity (δ = 140%) is studied by transmission electron microscopy. The tensile deformation is performed a 1150°C. Planar flaws and recrystallized grains are detected in the fractured zone of the metal. The mechanisms of high-temperature superplasticity of alloys based on Ni3Al intermetallic are discussed.

  12. Structure and composition of higher-rhenium-content superalloy based on La-alloyed Ni-Al-Cr

    SciTech Connect

    Kozlov, Eduard V.; Koneva, Nina A.; Nikonenko, Elena L.; Popova, Natalya A.; Fedorischeva, Marina V.

    2015-10-27

    The paper presents the transmission and scanning electronic microscope investigations of Ni-Al-Cr superalloy alloyed with additional Re and La elements. This superalloy is obtained by a directional solidification method. It is shown that such additional elements as Re and La result in formation of new phases in Ni-Al-Cr accompanied by considerable modifications of quasi-cuboid structure in its γ’-phase.

  13. Initial biochar properties related to the removal of As, Se, Pb, Cd, Cu, Ni, and Zn from an acidic suspension.

    PubMed

    Clemente, Joyce S; Beauchemin, Suzanne; MacKinnon, Ted; Martin, Joseph; Johnston, Cliff T; Joern, Brad

    2017-03-01

    This study tests the influence of a diverse set of biochar properties on As(V), Se(IV), Cd(II), Cu(II), Ni(II), Pb(II), or Zn(II) removal from solution at pH 4.5. Six commercial biochars produced using different feedstock and pyrolysis conditions were extensively characterized using physical, chemical, and spectroscopic techniques, and their properties were correlated to anion and cation removal using multiple linear regression. H/total organic C (TOC) ratio and volatile matter were positively correlated to cation removal from solution, which indicate interactions between metals and non-aromatic C. Defining the correlation of ion removal with specific OC functional groups was hindered by the inherent limitations of the spectroscopic techniques, which was exacerbated by the heterogeneity of the biochars. Ash was negatively correlated to Se(IV) and positively correlated to Cd(II), Cu(II), and Ni(II) removal from solution. Interference from soluble P in biochars may partly explain the low Se(IV) removal from solution; and Ca-, P-, and Fe- containing compounds likely sorbed or precipitated Pb(II), Cd(II), Cu(II), Ni(II) and Zn(II). Furthermore, Ca-oxalate identified using X-ray diffraction in willow, may be responsible for willow's increased ability to remove Cd(II), Ni(II), and Zn(II) compared to the other 5 biochars. It was clear that both OC and inorganic biochar components influenced metal(loid) and Se(IV) removal from solution. The non-aromatic and volatile OC correlated to removal from solution may be readily available for microbial degradation, while Mg, N, P, and S are required for biological growth. Biological metabolism and uptake of these compounds may inhibit or destabilize their interaction with contaminants.

  14. Influence of Cr and W alloying on the fiber-matrix interfacial shear strength in cast and directionally solidified sapphire NiAl composites

    NASA Technical Reports Server (NTRS)

    Asthana, R.; Tiwari, R.; Tewari, S. N.

    1995-01-01

    Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr) than in sapphire-NiAl(W) due to interface enrichment with chromium particles. The matrix microhardness progressively decreased with increasing distance from the interface in both DS NiAl and NiAl(Cr) specimens. The study highlights the potential of casting and DS techniques to improve the toughness and strength of NiAl by designing dual-phase microstructures in NiAl alloys reinforced with sapphire fibers.

  15. Cold-Sprayed Ni-Al2O3 Coatings for Applications in Power Generation Industry

    NASA Astrophysics Data System (ADS)

    Sevillano, F.; Poza, P.; Múnez, C. J.; Vezzù, S.; Rech, S.; Trentin, A.

    2013-06-01

    Cermets coatings are extensively used in energy applications both because of their high wear resistance as required, for example, in components like gas turbine sealants, and because of their specific functionality as required in solar absorbers. So far, high-temperature thermal spraying and physical vapor deposition have traditionally been used to deposit this kind of coatings. In this study, Ni-Al2O3 coatings have been deposited using a Kinetic®3000 cold-spray system starting from Ni and Al2O3 powders blend; five blends have been prepared setting the alumina content in the feedstock to 10, 25, 50, 75, and 90 wt.%. The embedded alumina ranges between a few percent weight up to 16 and 31 wt.%, while the microhardness shows a deep increase from 175 Vickers in the case of pure Ni coatings up to 338 Vickers. The spray and coating growth mechanism have been discussed, with special attention to the fragmentation of the ceramic particles during the impact. Finally, the coating behavior at high temperature was analyzed by oxidation tests performed in air at 520 °C emphasizing a good oxidation resistance that could represent a very promising basis for application in power generation systems.

  16. Electrodeposition of Ni-Al2O3 nano composite coating and evaluation of wear characteristics

    NASA Astrophysics Data System (ADS)

    Raghavendra, C. R.; Basavarajappa, S.; Sogalad, Irappa

    2016-09-01

    Electrodeposition is one of the most technologically feasible and economically superior technique for producing metallic coating. The advancement in the application of nano particles has grabbed the attention in all fields of engineering. In this present study an attempt has been made on the nano particle composite coating on aluminium substrate by electrodeposition process. The aluminium surface requires a specific pre-treatment for better adherence of coating. In light of this a thin zinc layer is coated on the aluminium substrate by electroless process. This layer offers protection against oxidation thus prevents the formation of a native oxide layer. In this work Ni-Al2O3 composite coating were successfully coated by varying the process parameters such as bath temperature, current density and particle loading. The experimentation was performed using central composite design based 20 trials of experiments. The effect of process parameters on surface morphology and wear behavior was studied. The results shown a better wear resistance of Ni-Al2O3 composite electrodeposited coating compared to Ni coating. The particle loading and interaction effect of current density with temperature has greater significant effect on wear rate followed by the bath temperature. The decrease in wear rate was observed with the increased current density and temperature.

  17. Electrokinetic recovery of Cd, Cr, As, Ni, Zn and Mn from waste printed circuit boards: effect of assisting agents.

    PubMed

    Xiu, Fu-Rong; Zhang, Fu-Shen

    2009-10-15

    The printed circuit boards (PCBs) contains large number of heavy metal such as Cd, Cr, As, Ni, Zn and Mn. In this study, the use of electrokinetic (EK) treatment with different assisting agents has been investigated to recover the heavy metals from waste PCBs, and the effectiveness of different assisting agents (HNO(3), HCl, citric acid) was evaluated. The PCBs were first pre-treated by supercritical water oxidation (SCWO) process, then subjected to EK process. The heavy metal speciation, migration and recovery efficiency in the presence of different assisting agents during EK process were discussed. The mass loss of Cd, Cr, As and Zn during the SCWO process was negligible, but approximately 52% of Ni and 56% of Mn were lost in such a process. Experimental results showed that different assisting agents have significant effect on the behavior and recovery efficiency of different heavy metals. HCl was highly efficient for the recovery of Cd in waste PCBs due to the low pH and the stable complexation of Cl(-). Citric acid was highly efficient for the recovery of Cr, Zn and Mn. HNO(3) was low efficient for recovery of most heavy metals except for Ni.

  18. Effect of synthesis route on the uptake of Ni and Cd by MgFe2O4 nanopowders

    NASA Astrophysics Data System (ADS)

    Al-Najar, B.; Khezami, L.; Judith Vijaya, J.; Lemine, O. M.; Bououdina, M.

    2017-01-01

    In this study, MgFe2O4 nanopowders were synthesized through two different methods, sol-gel method (SG) and modified sol-gel with Ammonia (MSG-A). The influence of synthesis route was investigated in terms of phase stability, pores size and surface area, magnetic properties and uptake of Ni and Cd metals from aqueous solution. Rietveld refinements of x-ray diffraction patterns confirmed the formation of single spinel phase for SG sample, while minor impurity was detected for SGM-A sample (few amount of MgO). The crystallite size was found to be sensitive to the preparation method; it ranges from 4 nm for SG to 15 nm for MSG-A. Magnetization experiment at room temperature showed ferromagnetic behavior with a saturation magnetization ( M s) ranging from 5.39 emu/g for SG to 9.93 emu/g for MSG-A. Preliminary results showed that SG and MSG-A samples are efficient adsorbent for Ni and Cd metal ions from aqueous solution. Maximum quantity of 62.67 and 61.2 mg of Ni(II) and 36.49 and 32.84 mg of Cd(II) was adsorbed per gram of MgFe2O4 synthesized by SG and MSG-A, respectively.

  19. BFS Simulation and Experimental Analysis of the Effect of Ti Additions on the Structure of NiAl

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Ferrante,John; Garg, Anita; Honecy, Frank S.; Amador, Carlos

    1999-01-01

    The Bozzolo-Ferrante-Smith (BFS) method for alloy energetics is applied to the study of ternary additions to NiAl. A description of the method and its application to alloy design is given. Two different approaches are used in the analysis of the effect of Ti additions to NiAl. First, a thorough analytical study is performed, where the energy of formation, lattice parameter and bulk modulus are calculated for a large number of possible atomic distributions of Ni, Al and Ti. Substitutional site preference schemes and formation of precipitates are thus predicted and analyzed. The second approach used consists of the determination of temperature effects on the final results, as obtained by performing a number of large scale numerical simulations using the Monte Carlo-Metropolis procedure and BFS for the calculation of the energy at every step in the simulation. The results indicate a sharp preference of Ti for Al sites in Ni-rich NiAl alloys and the formation of ternary Heusler precipitates beyond the predicted solubility limit of 5 at. % Ti. Experimental analysis of three Ni-Al-Ti alloys confirms the theoretical predictions.

  20. Atomistic Simulations and Experimental Analysis of the Effect of Ti Additions on the Structure of NiAl

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Ferrante, John; Garg, Anita; Amador, Carlos

    1997-01-01

    The Bozzolo-Ferrante-Smith (BFS) semiempirical method for alloy energetics is applied to the study of ternary additions to NiAl alloys. A detailed description of the method and its application to alloy design is given. Two different approaches are used in the analysis of the effect of Ti additions to NiAl. First, a thorough analytical study is performed, where the energy of formation, lattice parameter and bulk modulus are calculated for hundreds of possible atomic distributions of Ni, Al and Ti. Substitutional site preference schemes and formation of precipitates are thus predicted and analyzed. The second approach used consists of the determination of temperature effects on the final results, as obtained by performing a number of large scale numerical simulations using the Monte Carlo - Metropolis procedure and BFS for the calculation of the energy at every step in the simulation. The results indicate a sharp preference of Ti for Al sites in Ni-rich NiAl alloys and the formation of ternary Heusler precipitates beyond the predicted solubility limit of 5 at. % Ti. Experimental analysis of three NiAl+Ti alloys confirms the theoretical predictions.

  1. Ion irradiation induced element-enriched and depleted nanostructures in Zr-Al-Cu-Ni metallic glass

    SciTech Connect

    Chen, H. C.; Liu, R. D.; Yan, L. E-mail: zhouxingtai@sinap.ac.cn; Zhou, X. T. E-mail: zhouxingtai@sinap.ac.cn; Cao, G. Q.; Wang, G.

    2015-07-21

    The microstructural evolution of a Zr-Al-Cu-Ni metallic glass induced by irradiation with Ar ions was investigated. Under ion irradiation, the Cu- and Ni-enriched nanostructures (diameter of 30–50 nm) consisted of crystalline and amorphous structures were formed. Further, Cu- and Ni-depleted nanostructures with diameters of 5–20 nm were also observed. The formation of these nanostructures can be ascribed to the migration of Cu and Ni atoms in the irradiated metallic glass.

  2. Cyclic Oxidation of Single-Crystal NiAl-X Alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Barrett, Charles A.; Darolia, Ram

    1999-01-01

    Several single-crystal NiAl-X alloys (X = Hf, Ti, Cr, Ga) were cyclically oxidized at 1000 C for up to 1000 1-hr cycles. The alloys all showed protective, adherent alpha-Al2O3 scale formation with positive weight change behavior throughout the test. There was no clear correlation between the composition of the various alloys and the specific weight gain although the ranking by weight change was relatively consistent for two duplicate series of samples. The presence of Hf (0.5 - 0.8 at.%) resulted in the internal formation of Al2O3/HfO2 "stringers." Diffusion of Hf to the growing oxide stringers resulted in the development of a near-surface layer depleted of these precipitates.

  3. Structure and atomic vibrations in bimetallic Ni13 - n Al n clusters

    NASA Astrophysics Data System (ADS)

    Rusina, G. G.; Borisova, S. D.; Chulkov, E. V.

    2015-04-01

    The binding energy, equilibrium geometry, and vibration frequencies in bimetallic clusters Ni13 - n Al n ( n = 0-13) have been calculated using the embedded atom method potentials. It has been shown that the icosahedral structure is the most stable in monoatomic and bimetallic clusters. A tendency of Al atoms to segregate on the cluster surface has been revealed in agreement with the experimental data. The calculations of the atomic vibrations have shown the nonmonotonic dependence of the minimum and maximum vibration frequencies of cluster atoms on its composition and the coupling of their extreme values with the most stable atomic configuration. The increase in the number of Al atoms leads to the shift of the frequency spectrum and the substantial redistribution of the localization of vibrations on the cluster atoms.

  4. Tribological Properties of Ni3Al Matrix Composite Sliding Against Si3N4, SiC and Al2O3 at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Yan, Chengqi; Kang, Yonghai; Kong, Lingqian; Zhu, Shengyu

    2017-01-01

    The Ni3Al matrix self-lubricating composite was fabricated by powder metallurgy technique. The tribological behavior of the composite sliding against commercial Si3N4, SiC and Al2O3 ceramic balls was investigated from 20 to 1000 °C. It was found that the composite demonstrated excellent lubricating properties with different friction pairs at a wide temperature range, which can be attributed to the synergetic effect of Ag, fluorides, and molybdates formed by oxidations. The Ni3Al matrix self-lubricating composite/Si3N4 couple possessed the stable friction coefficient and wear rate.

  5. Tribological Properties of Ni3Al Matrix Composite Sliding Against Si3N4, SiC and Al2O3 at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Yan, Chengqi; Kang, Yonghai; Kong, Lingqian; Zhu, Shengyu

    2016-12-01

    The Ni3Al matrix self-lubricating composite was fabricated by powder metallurgy technique. The tribological behavior of the composite sliding against commercial Si3N4, SiC and Al2O3 ceramic balls was investigated from 20 to 1000 °C. It was found that the composite demonstrated excellent lubricating properties with different friction pairs at a wide temperature range, which can be attributed to the synergetic effect of Ag, fluorides, and molybdates formed by oxidations. The Ni3Al matrix self-lubricating composite/Si3N4 couple possessed the stable friction coefficient and wear rate.

  6. Molecular dynamics simulation of the martensitic phase transformation in NiAl alloys.

    PubMed

    Pun, G P Purja; Mishin, Y

    2010-10-06

    Using molecular dynamics simulations with an embedded-atom interatomic potential, we study the effect of chemical composition and uniaxial mechanical stresses on the martensitic phase transformation in Ni-rich NiAl alloys. The martensitic phase has a tetragonal crystal structure and can contain multiple twins arranged in domains and plates. The transformation is reversible and is characterized by a significant temperature hysteresis. The magnitude of the hysteresis depends on the chemical composition and stress. We show that applied compressive and tensile stresses reduce and can even eliminate the hysteresis. Crystalline defects such as free surfaces, dislocations and anti-phase boundaries reduce the martensitic transformation temperature and affect the microstructure of the martensite. Their effect can be explained by heterogeneous nucleation of the new phase in defected regions.

  7. Investigation on compressive behavior of Cu-35Ni-15Al alloy at high temperatures

    NASA Astrophysics Data System (ADS)

    Li, Cong; Chen, Jian; Li, Wei; Hu, Yongle; Ren, Yanjie; Qiu, Wei; He, Jianjun; Chen, Jianlin

    2014-09-01

    Microstructures and mechanical properties of Cu-35Ni-15Al alloy in cast and porous states were studied by scanning electron microscopy and compression tests. The influence of porosity, deformation temperature and loading rate on mechanical properties of the two kinds of alloys was investigated. The results show that the as cast alloy and porous alloys have almost the same phase constitution: Cu rich phase, Ni rich phase and K intermetallics. The yield strength of porous alloys increases continuously with decreasing porosity, the relationship between porosity and yield stress follows Gibson-Ashby equation. With decreasing deformation temperature, the yield strength of as cast alloy and porous alloy increase. With the increase of loading rate, the yield strength of these alloys shows an increasing trend. After compression, the microstructure of as cast alloy is more uniform, and porous alloys are more prone to have localized deformations.

  8. Interdiffusion in (fcc) Ni-Cr-X (X = Al, Si, Ge or Pd) Alloys at 700?aC

    SciTech Connect

    Garimella, N; Brady, Michael P; Sohn, Yong Ho

    2007-01-01

    Interdiffusion at 700 aC for Ni-22at.%Cr (fcc ^ phase) alloys with small additions of Al, Si, Ge, or Pd was examined using solid-to-solid diffusion couples. Rods of Ni-22at.%Cr, Ni-21at.%Cr-6.2at.%Al, Ni-22at.%Cr-4.0at.%Si, Ni-22at.%Cr-1.6at.%Ge and Ni-22at.%Cr-1.6at.%Pd alloys were cast using arc-melt and homogenized at 900 aC for 168 hours. The diffusion couples were assembled with alloy disks in Invar steel jig, encapsulated in Argon after several hydrogen flushes, and annealed at 700 XC for 720 hours. Experimental concentration profiles were determined from polished cross-sections by using electron probe microanalysis with pure standards of Ni, Cr, Al, Si, Ge and Pd. Interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the moments of interdiffusion fluxes were examined to determine average ternary interdiffusion coefficients. Effects of ternary alloying additions on the interdiffusional behavior of Ni-Cr-X alloys at 700 XC are presented in the light of the diffusional interactions and the formation of protective Cr2O3 scale.

  9. Thermodynamic Descriptions of NI Alloys Containing AL, CR, and RU: A Computational Thermodynamic Approach Coupled with Experiments

    DTIC Science & Technology

    2006-09-03

    the present study is to adopt the Calphad approach to develop thermodynamic descriptions of Ni alloys containing elements such as Al, Cr , Ru, etc and...Fig. 2(b), the agreement between calculated 0.0 Al 0 cr three phases SLiquidus o two phases 0.2 0.2 bcc 02 02 O . O 0.2 040. 08 000 0.2 0406 O . 10 44 40...experimentation is achieved. 8 0.7, 0.7, U_. 0.01 0.01 - yphase Y phase Miyazaki 1994 Miyazaki 1994 •Ni, 0 AI, -V Cr , XRe & Ni, o AI, Cr , X Re IE-3 I

  10. 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

  11. Low temperature structural transformation in T[Ni(CN){sub 4}].xpyz with x=1,2; T=Mn,Co,Ni,Zn,Cd; pyz=pyrazine

    SciTech Connect

    Rodriguez-Hernandez, J.; Lemus-Santana, A.A.; Ortiz-Lopez, J.; Jimenez-Sandoval, S.; Reguera, E.

    2010-01-15

    The materials under study are pillared solids T[Ni(CN){sub 4}].xpyz with one and two (x=1,2) pyrazine (pyz) molecules and where T=Mn, Co, Ni, Zn, Cd. Stimulated by their structural features and potential role as prototype of porous solids for hydrogen storage, the structural stability under cryogenic conditions for this series of pillared solids was studied. At low temperature, in the 100-200 K range, the occurrence of a reversible structural transformation was found. For T=Mn, Co, Zn, Cd, with x=2, the structural transformation was observed to occur around 185 K, and the low temperature phase crystallizes with a monoclinic unit cell (space group Pc). This structure change results from certain charge redistribution on cooling within the involved ligands. For T=Ni with x=1, both the low and high temperature phases crystallize with unit cells of tetragonal symmetry, within the same space group but with a different unit cell volume. In this case the structure change is observed around 120 K. Above that temperature the rotational states for the pyrazine molecule are thermally excited and all the pyrazine molecules in the structure become equivalent. Under this condition the material structure is described using a smaller structural unit. The structural study using X-ray powder diffraction data was complemented with calorimetric and Raman spectroscopy measurements. For the low temperature phases the crystal structures were solved from Patterson methods and then refined using the Rietveld method. - Graphical abstract: Low temperature ordered structure for pyrazine in T[Ni(CN){sub 4}].pyz.

  12. Adsorption of Cd(II), Cu(II) and Ni(II) ions by cross-linking chitosan/rectorite nano-hybrid composite microspheres.

    PubMed

    Zeng, Lixuan; Chen, Yufei; Zhang, Qiuyun; Guo, Xingmei; Peng, Yanni; Xiao, Huijuan; Chen, Xiaocheng; Luo, Jiwen

    2015-10-05

    Chitosan/rectorie (CTS/REC) nano-hybrid composite microsphere was prepared by changing the proportion of CTS/REC with 2:1, 3:1 and 4:1. Compared with the pure cross-linking chitosan microsphere, the nano-hybrid composite microsphere was proved to have better sorption capacity of Cd(II), Cu(II) and Ni(II), especially 2:1(CTS/REC-1). The adsorption behavior of the microsphere of Cd(II), Cu(II) and Ni(II) was investigated in single and binary metal systems. In single system, the equilibrium studies showed that the adsorption of Cd(II), Cu(II) and Ni(II) followed the Langmuir model and the pseudo-second-order kinetic model. The negative values of (ΔG) suggested that the adsorption process was spontaneous. In binary system, the combined action of the metals was found to be antagonistic and the metal sorption followed the order of Cu(II)>Cd(II)>Ni(II). The regeneration studies indicated that EDTA desorbed Cd(II), Cu(II) and Ni(II) from cross-linking microspheres better than HCl. The FT-IR and XPS spectra showed that coordination bonds were formed between Cd(II), Cu(II) and Ni(II) and the nitrogen atoms of cross-linking CTS/REC nano-hybrid composite microspheres.

  13. Thermal stability of Ni/Ti/Al ohmic contacts to p-type 4H-SiC

    SciTech Connect

    Yu, Hailong; Shen, Huajun Tang, Yidan; Bai, Yun; Liu, Xinyu; Zhang, Xufang; Wu, Yudong; Liu, Kean

    2015-01-14

    Low resistivity Ni/Ti/Al ohmic contacts on p-type 4H-SiC epilayer were developed, and their thermal stabilities were also experimentally investigated through high temperature storage at 600 °C for 100 h. The contact resistance of the Al/Ti/Ni/SiC contacts degraded in different degrees, and the contact morphology deteriorated with the increases of the average surface roughness and interface voids. X-ray spectra showed that Ni{sub 2}Si and Ti{sub 3}SiC{sub 2}, which were formed during ohmic contact annealing and contributed to low contact resistivity, were stable under high temperature storage. The existence of the TiAl{sub 3} and NiAl{sub 3} intermetallic phases was helpful to prevent Al agglomeration on the interface and make the contacts thermally stable. Auger electron spectroscopy indicated that the incorporation of oxygen at the surface and interface led to the oxidation of Al or Ti resulting in increased contact resistance. Also, the formation of these oxides roughened the surface and interface. The temperature-dependence of the specific contact resistance indicated that a thermionic field emission mechanism dominates the current transport for contacts before and after the thermal treatment. It suggests that the Ni/Ti/Al composite ohmic contacts are promising for SiC devices to be used in high temperature applications.

  14. Al3+ ions dependent structural and magnetic properties of Co-Ni nano-alloys.

    PubMed

    Kadam, R H; Alone, Suresh T; Gaikwad, Anil S; Birajdar, A P; Shirsath, Sagar E

    2014-06-01

    Ferrite samples with a chemical formula Co0.5Ni0.5Al(x)Fe(2-x)O4 (where x = 0.0, 0.25, 0.5, 0.75 and 1.0) were synthesized by sol-gel auto-combustion method. The synthesized samples were annealed at 600 degrees C for 4 h. An analysis of X-ray diffraction (XRD) patterns reveals the formation of single phase cubic spinel structure. The lattice parameter decreased linearly with the increasing Al content x. Nano size of the powders were confirmed by the transmission electron micrographs (TEM). Particle size, bulk density decreased whereas specific surface area and porosity of the samples increased with the Al substitution. Cation distribution of constituent ions shows linear dependence of Al substitution. Based on the cation distribution obtained from XRD data, structural parameters such as lattice parameters, ionic radii of available sites and the oxygen parameter 'u' is calculated. Saturation magnetization (M(s)), magneton number (n(B)) and coercivity (H(c)) decreased with the Al substitution. Possible explanation for the observed structural and magnetic behavior with various Al content are discussed.

  15. 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.

  16. Fermi states and anisotropy of Brillouin zone scattering in the decagonal Al-Ni-Co quasicrystal

    NASA Astrophysics Data System (ADS)

    Rogalev, V. A.; Gröning, O.; Widmer, R.; Dil, J. H.; Bisti, F.; Lev, L. L.; Schmitt, T.; Strocov, V. N.

    2015-10-01

    Quasicrystals (QCs) are intermetallic alloys that have excellent long-range order but lack translational symmetry in at least one dimension. The valence band electronic structure near the Fermi energy EF in such materials is of special interest since it has a direct relation to their unusual physical properties. However, the Fermi surface (FS) topology as well as the mechanism of QC structure stabilization are still under debate. Here we report the first observation of the three-dimensional FS and valence band dispersions near EF in decagonal Al70Ni20Co10 (d-AlNiCo) QCs using soft X-ray angle-resolved photoemission spectroscopy. We show that the FS, formed by dispersive Al sp-states, has a multicomponent character due to a large contribution from high-order bands. Moreover, we discover that the magnitude of the gap at the FS related to the interaction with Brillouin zone boundary (Hume-Rothery gap) critically differs for the periodic and quasiperiodic directions.

  17. Elevated temperature creep properties of NiAl cryomilled with and without Y2O3

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Luton, Michael J.

    1995-01-01

    The creep properties of lots of NiAl cryomilled with and without Y2O3 have been determined in compression and tension. Although identical cryomilling procedures were used, differences in composition were found between the lot ground with 0.5 vol% yttria and the lot ground without Y2O3. Compression testing between 1000 and 1300 K yielded similar creep strengths for both materials, while tensile creep rupture testing indicated that the yttria-containing alloy was slightly stronger than the Y2O3-free version. Both compression and tensile testing showed two deformation regimes; whereas the stress state did not affect the high stress exponent (n approximately equals 10) mechanism, the low stress exponent regime n was approximately 6 in tension and approximately 2 in compression. The strengths in tension were somewhat less than those measured in compression, but the estimated activation energies (Q) of approximately 600 kJ/mol for tensile testing were closer to the previously measured values (approximately 700 kJ/mol) for NiAl-AlN and very different from the Q's of 400 and 200 kJ/mol for compression tests in the high and low stress exponent regimes, respectively. A Larson-Miller comparison indicated that cryomilling can produce an alloy with long-term, high-temperature strength at least equal to conventional superalloys.

  18. N-doped carbon@Ni-Al2O3 nanosheet array@graphene oxide composite as an electrocatalyst for hydrogen evolution reaction in alkaline medium

    NASA Astrophysics Data System (ADS)

    Wang, Juan; Qiu, Tian; Chen, Xu; Lu, Yanluo; Yang, Wensheng

    2015-10-01

    An NiAl-layered double-hydroxide (NiAl-LDH) nanosheet array is grown on a graphene oxide (GO) substrate (NiAl-LDH@GO) by the hydrothermal method. The NiAl-LDH@GO is used as the precursor to synthetize an N-doped carbon@Ni-Al2O3 nanosheet array@GO composite (N-C@Ni-Al2O3@GO) by coating with dopamine followed by calcination. The N-C@Ni-Al2O3@GO is used as a non-noble metal electrocatalyst for hydrogen evolution reaction in alkaline medium, and exhibits high electrocatalytic activity with low onset overpotential (-75 mV). The improved electrocatalytic performance of N-C@Ni-Al2O3@GO arises from its intrinsic features. First, it has a high specific surface area with the Ni nanoparticles in the composite dispersed well and the sizes of Ni nanoparticles are small, which lead to the exposure of more active sites for electrocatalysis. Second, there is a synergistic effect between the Ni nanoparticles and the N-C coating layer, which is beneficial to reduce the activation energy of the Volmer step and improve the electrocatalytic activity. Third, the N-C coating layer and the XC-72 additive can form an electrically conductive network, which serves as a bridge for the transfer of electrons from the electrode to the Ni nanoparticles.

  19. CdS/CdSe-sensitized solar cell based on Al-doped ZnO nanoparticles prepared by the decomposition of zinc acetate solid solution

    NASA Astrophysics Data System (ADS)

    Deng, Jianping; Wang, Minqiang; Ye, Wei; Fang, Junfei; Zhang, Pengchao; Yang, Yongping; Yang, Zhi

    2017-01-01

    In the study, Al-doped ZnO nanoparticles (Al-ZnO NPs) were prepared by the decomposition of zinc acetate solid solution. The X-ray diffraction results showed that Al3+ was successfully doped without the formation of Al and Al2O3 impurity phases. The less Al-doping did not change the hexagonal wurtzite crystal structure of ZnO. The ratio of Al to Al + Zn (9.05%) measured by the energy dispersive X-ray also confirmed the formation of Al-ZnO. The Al-ZnO NPs were used as the photoanode material to prepare CdS/CdSe-sensitized solar cell. Compared with the cell based on commercial ZnO NPs (C-ZnO), the short-circuit current density and the fill factor of the cell were increased from 5.8 mA/cm2 and 34.1% (C-ZnO) to 7.78 mA/cm2 and 48.7% (Al-ZnO), respectively. The cell efficiency was increased from 1.01% (C-ZnO) to (1.9%) (Al-ZnO) and the increase percentage reached 88.1%. The results of electrochemical impedance spectroscopy and open-circuit voltage-decay suggested the lower carrier transport resistance and the longer electron lifetime of Al-ZnO-based cell.

  20. Development of Ni-Mo/Al2O3 catalyst for reverse water gas shift (RWGS) reaction.

    PubMed

    Kharaji, Abolfazl Gharibi; Shariati, Ahmad; Ostadi, Mohammad

    2014-09-01

    In the present study, Mo/Al2O3 catalyst was prepared using impregnation method. Then it was promoted with Ni ions to produce Ni-Mo/Al2O3 catalyst. The structures of the catalysts were studied using X-ray diffraction (XRD), Energy dispersive X-ray (EDAX), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), CO chemisorption, temperature programmed reduction of hydrogen (H2-TPR) and scanning electron microscope (SEM) techniques. Catalytic performances of the two catalysts were investigated in a fixed-bed reactor for RWGS reaction. The results indicated that addition of nickel promoter to Mo/Al2O3 catalyst enhances its activity. It is reasonable for the electron deficient state of the Ni species and existence of NiMoO4 phase to possess high activity in RWGS reaction. Stability test of Ni-Mo/Al2O3 catalyst was carried out in a fixed bed reactor and a high CO2 conversion for 60 h time on stream was demonstrated. This study introduces a new catalyst, Ni-Mo/Al2O3, with high activity and stability for RWGS reaction.

  1. Temperature-dependent phase-specific deformation mechanisms in a directionally solidified NiAl-Cr(Mo) lamellar composite

    SciTech Connect

    Yu, Dunji; An, Ke; Chen, Xu; Bei, Hongbin

    2015-10-09

    Phase-specific thermal expansion and mechanical deformation behaviors of a directionally solidified NiAl–Cr(Mo) lamellar in situ composite were investigated by using real-time in situ neutron diffraction during compression at elevated temperatures up to 800 °C. Tensile and compressive thermal residual stresses were found to exist in the NiAl phase and Crss (solid solution) phase, respectively. Then, based on the evolution of lattice spacings and phase stresses, the phase-specific deformation behavior was analyzed qualitatively and quantitatively. Moreover, estimates of phase stresses were derived by Hooke's law on the basis of a simple method for the determination of stress-free lattice spacing in in situ composites. During compressive loading, the NiAl phase yields earlier than the Crss phase. The Crss phase carries much higher stress than the NiAl phase, and displays consistent strain hardening at all temperatures. The NiAl phase exhibits strain hardening at relatively low temperatures and softening at high temperatures. During unloading, the NiAl phase yields in tension whereas the Crss phase unloads elastically. Additionally, post-test microstructural observations show phase-through cracks at room temperature, micro cracks along phase interfaces at 600 °C and intact lamellae kinks at 800 °C, which is due to the increasing deformability of both phases as temperature rises.

  2. Temperature-dependent phase-specific deformation mechanisms in a directionally solidified NiAl-Cr(Mo) lamellar composite

    DOE PAGES

    Yu, Dunji; An, Ke; Chen, Xu; ...

    2015-10-09

    Phase-specific thermal expansion and mechanical deformation behaviors of a directionally solidified NiAl–Cr(Mo) lamellar in situ composite were investigated by using real-time in situ neutron diffraction during compression at elevated temperatures up to 800 °C. Tensile and compressive thermal residual stresses were found to exist in the NiAl phase and Crss (solid solution) phase, respectively. Then, based on the evolution of lattice spacings and phase stresses, the phase-specific deformation behavior was analyzed qualitatively and quantitatively. Moreover, estimates of phase stresses were derived by Hooke's law on the basis of a simple method for the determination of stress-free lattice spacing in inmore » situ composites. During compressive loading, the NiAl phase yields earlier than the Crss phase. The Crss phase carries much higher stress than the NiAl phase, and displays consistent strain hardening at all temperatures. The NiAl phase exhibits strain hardening at relatively low temperatures and softening at high temperatures. During unloading, the NiAl phase yields in tension whereas the Crss phase unloads elastically. Additionally, post-test microstructural observations show phase-through cracks at room temperature, micro cracks along phase interfaces at 600 °C and intact lamellae kinks at 800 °C, which is due to the increasing deformability of both phases as temperature rises.« less

  3. Nanostructured Al-ZnO/CdSe/Cu2O ETA solar cells on Al-ZnO film/quartz glass templates

    PubMed Central

    2011-01-01

    The quartz/Al-ZnO film/nanostructured Al-ZnO/CdSe/Cu2O extremely thin absorber solar cell has been successfully realized. The Al-doped ZnO one-dimensional nanostructures on quartz templates covered by a sputtering Al-doped ZnO film was used as the n-type electrode. A 19- to 35-nm-thin layer of CdSe absorber was deposited by radio frequency magnetron sputtering, coating the ZnO nanostructures. The voids between the Al-ZnO/CdSe nanostructures were filled with p-type Cu2O, and therefore, the entire assembly formed a p-i-n junction. The cell shows the energy conversion efficiency as high as 3.16%, which is an interesting option for developing new solar cell devices. PACS: 88.40.jp; 73.40.Lq; 73.50.Pz. PMID:22136081

  4. Nanostructured Al-ZnO/CdSe/Cu2O ETA solar cells on Al-ZnO film/quartz glass templates

    NASA Astrophysics Data System (ADS)

    Wang, Xianghu; Li, Rongbin; Fan, Donghua

    2011-12-01

    The quartz/Al-ZnO film/nanostructured Al-ZnO/CdSe/Cu2O extremely thin absorber solar cell has been successfully realized. The Al-doped ZnO one-dimensional nanostructures on quartz templates covered by a sputtering Al-doped ZnO film was used as the n-type electrode. A 19- to 35-nm-thin layer of CdSe absorber was deposited by radio frequency magnetron sputtering, coating the ZnO nanostructures. The voids between the Al-ZnO/CdSe nanostructures were filled with p-type Cu2O, and therefore, the entire assembly formed a p-i-n junction. The cell shows the energy conversion efficiency as high as 3.16%, which is an interesting option for developing new solar cell devices. PACS: 88.40.jp; 73.40.Lq; 73.50.Pz.

  5. Strain Aging Behavior in NiAl Microalloyed with Interstitial and Substitutional Solutes

    NASA Technical Reports Server (NTRS)

    Weaver, M. L.; Noebe R. D.; Kaufman, M. J.

    1997-01-01

    Dynamic strain aging has been investigated in polycrystalline NiAl alloys containing combined additions of interstitial and substitutional impurities. The results indicate that strain aging can be enhanced in polycrystalline alloys containing concentrations of silicon or iron in excess of 0.15 at.% in addition to conventional levels of carbon. This co-doping leads to very dramatic strain aging events, comparable to those typically observed in single crystals. This effect will be discussed with respect to conventional theories of strain aging.

  6. The study of the thermal stability of Ni3Al nanoneedles using computer simulation

    NASA Astrophysics Data System (ADS)

    Poletaev, G. M.; Starostenkov, M. D.; Novoselova, D. V.; Tsellermaer, V. Y.

    2016-02-01

    The study of the thermal stability of Ni3Al nanoneedles in the dependence on the sharpness and crystallography orientation of the needle axis was held using molecular dynamics method. It is shown that the most stability nanoneedles in the conditions of thermal influence are the nanoneedles with the axis along [111] direction. Violation of the nanoneedles stability associated with their blunting, which is caused by surface diffusion. Stable radius of curvature of the needles depends on the angle of the tip and orientation of the needle axis. It is 0.6-1 nm at low temperatures.

  7. Mobile Interfacial Microstructures in Single Crystals of Cu-Al-Ni Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Seiner, Hanuš

    2015-06-01

    This paper summarizes the main properties of the microstructures formed during reverse (austenite → martensite) transitions in single crystals of the Cu-Al-Ni shape memory alloy, and discusses the relation between these properties and the mechanical stabilization effect. It is shown that all experimentally observed interfacial microstructures ( X- and λ-interfaces and their non-classical equivalents) are not local minimizers of the quasi-static energy, and their formation is probably governed by requirements on mobility and dissipation. This conclusion is supported by finite elements models, and acoustic emission measurements.

  8. Superelasticity of Cu-Ni-Al shape-memory fibers prepared by melt extraction technique

    NASA Astrophysics Data System (ADS)

    Li, Dong-yue; Zhang, Shu-ling; Liao, Wei-bing; Geng, Gui-hong; Zhang, Yong

    2016-08-01

    In the paper, a melt extraction method was used to fabricate Cu-4Ni-14Al (wt%) fiber materials with diameters between 50 and 200 μm. The fibers exhibited superelasticity and temperature-induced martensitic transformation. The microstructures and superelasticity behavior of the fibers were studied via scanning electron microscopy (SEM) and a dynamic mechanical analyzer (DMA), respectively. Appropriate heat treatment further improves the plasticity of Cu-based alloys. The serration behavior observed during the loading process is due to the multiple martensite phase transformation.

  9. 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.

  10. Microstructure characterization and room temperature deformation of a rapidly solidified NiAl-based eutectic alloy containing trace Dy

    NASA Astrophysics Data System (ADS)

    Li, Hutian; Guo, Jianting; Huai, Kaiwen; Ye, Hengqiang

    2006-04-01

    The microstructure and room temperature compressive deformation behavior of a rapidly solidified NiAl-Cr(Mo)-Dy eutectic alloy fabricated by water-cooled copper mold method were studied by a combination of SEM, EDS and compressive tests. The morphology stability after hot isostatic pressing (HIP) treatment was evaluated. Rapid solidification resulted in a shift in the coupled zone for the eutectic growth towards the Cr(Mo) phase, indicating a hypoeutectic composition, hence increasing the volume fraction of primary dendritic NiAl. Meanwhile, significantly refined microstructure and lamellar/rod-like Cr(Mo) transition were observed due to trace rare earth (RE) element Dy addition and rapid solidification effects. Compared with the results in literature [H.E. Cline, J.L. Walter, Metall. Trans. 1(1970)2907-2917; P. Ferrandini, W.W. Batista, R. Caram, J. Alloys Comp. 381(2004)91-98], an interesting phenomenon, viz., NiAl halos around the primary Cr(Mo) dendrites in solidified NiAl-Cr(Mo) hypereutectic alloy, was not observed in this study. This difference was interpreted in terms of their different reciprocal nucleation ability. In addition, it was proposed that the localized destabilization of morphology after HIP treatment is closely related to the presence of primary NiAl dendrites. The improved mechanical properties can be attributed to the synergistic effects of rapid solidification and Dy addition, which included refined microstructure, suppression of the crack development along eutectic grain boundaries, enhancement of density of geometrically necessary dislocations located at NiAl/Cr(Mo) interfaces and the Cr solubility extension in NiAl.

  11. Kinetics for Steam and CO2 Reforming of Methane Over Ni/La/Al2O3 Catalyst.

    PubMed

    Park, Myung Hee; Choi, Bong Kwan; Park, Yoon Hwa; Moon, Dong Ju; Park, Nam Cook; Kim, Young Chul

    2015-07-01

    Kinetic studies of mixed (steam and dry) reforming of methane on Ni/La/Al2O3 and Ni/La-Co (1, 3 wt%)/Al2O3 catalysts were performed in an atmospheric fixed-bed reactor. Kinetic parameters for the mixed reforming over these catalysts were obtained under reaction conditions free from heat and mass transfer limitations. Variables for the mixed reforming were the reaction temperature and partial pressure of reactants. The fitting of the experimental data for the rate of methane conversion, rCH4, using the power law rate equation rCH4 = k(PrCH4)α(PCO2)β(PH2O)γ showed that the reaction orders α, β, and γ are steady and obtained values equal to α = 1, β = 0, and γ = 0. In other words, among CH4, CO2, H2O, and H2, only CH4 reaction orders were not zero and they were affected by the promoters. The apparent activation energy on catalysts Ni/La/Al2O3, Ni/La-Co (1)/Al2O3 and Ni/La-Co (3)/Al2O3 is 85.2, 93.8, and 99.4 kJ/mol, respectively. The addition of Co to Ni/La/Al2O3 was increased the apparent activation energy of the mixed reforming reaction. And the Ni/La-Co (3 wt%)/Al2O3 catalyst showed the highest reforming activity and apparent activation energy. The Co promoters can increase the apparent activation energy of mixed reforming of methane.

  12. A study of the oxide dispersion and recrystallization in NiCrAl prepared from preoxidized powder

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1975-01-01

    The sintered aluminum powder (SAP) technique of dispersion strengthening (formation of an oxide dispersion by preoxidation of metal powders) was applied to atomized powder of a nickel alloy containing, by weight, 17% Cr, 5% Al, and 0.2% Y. The SAP-NiCrAl alloy (without the ytterbium removed by oxdation) was worked by extrusion and rod rolling at 1205 C and by swaging at 760 C. Annealing treatments were applied after working to determine the recrystallization response. The NiCrAlY alloy, similarly prepared from atomized powder, but without a preoxidation treatment, was examined for comparison. The SAP-NiCrAl alloy exhibited oxide particle size and spacing much larger than that usually observed in oxide dispersion strengthened alloys; nonetheless, it was possible to achieve abnormal (secondary) recrystallization in the SAP-NiCrAl alloy as has been reported for other oxide dispersion strengthened alloys. In contrast, the unoxidized NiCrAlY alloy exhibited only primary recrystallization.

  13. Ion irradiation induced nanocrystal formation in amorphous Zr 55Cu 30Al 10Ni 5 alloy

    NASA Astrophysics Data System (ADS)

    Carter, Jesse; Fu, E. G.; Martin, Michael; Xie, Guoqiang; Zhang, X.; Wang, Y. Q.; Wijesundera, D.; Wang, X. M.; Chu, Wei-Kan; McDeavitt, Sean M.; Shao, Lin

    2009-09-01

    Ion irradiation can be used to induce partial crystallization in metallic glasses to improve their surface properties. We investigated the microstructural changes in ribbon Zr 55Cu 30Al 10Ni 5 metallic glass after 1 MeV Cu-ion irradiation at room temperature, to a fluence of 1.0 × 10 16 cm -2. In contrast to a recent report by others that there was no irradiation induced crystallization in the same alloy [S. Nagata, S. Higashi, B. Tsuchiya, K. Toh, T. Shikama, K. Takahiro, K. Ozaki, K. Kawatusra, S. Yamamoto, A. Inouye, Nucl. Instr. and Meth. B 257 (2007) 420], we have observed nanocrystals in the as-irradiated samples. Two groups of nanocrystals, one with diameters of 5-10 nm and another with diameters of 50-100 nm are observed by using high resolution transmission electron microscopy. Experimentally measured planar spacings ( d-values) agree with the expectations for Cu 10Zr 7, NiZr 2 and CuZr 2 phases. We further discussed the possibility to form a substitutional intermetallic (Ni xCu 1-x)Zr 2 phase.

  14. Interdiffusion in ? (fcc) Ni-Cr-X (X=Al, Si, Ge or Pd) Alloys at 900?C

    SciTech Connect

    Garimella, N; Brady, Michael P; Sohn, Yong Ho

    2006-01-01

    Interdiffusion in Ni-Cr (fcc phase) alloys with small additions of Al, Si, Ge, or Pd was investigated using solid-to-solid diffusion couples. Ni-Cr-X alloys having compositions of Ni- 22at.%Cr, Ni-21at.%Cr-6.2at.%Al, Ni-22at.%Cr-4.0at.%Si, Ni-22at.%Cr-1.6at.%Ge and Ni- 22at.%Cr-1.6at.%Pd were manufactured by arc-casting. The diffusion couples were assembled in an Invar steel jig, encapsulated in Ar after several hydrogen purges, and annealed at 900 C in a three-zone tube furnace for 168 hours. Experimental concentration profiles were determined from polished cross-section of these couples by using electron probe microanalysis with pure element standards. Interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the moments of interdiffusion fluxes were examined to determine average ternary interdiffusion coefficients. Effects of ternary alloying additions on the diffusional behavior of Ni-Cr-X alloys are presented in the light of the diffusional interactions and the formation of a protective Cr2O3 scale

  15. The effect of Pt content on NiPtAl coatings

    SciTech Connect

    Haynes, James A; Pint, Bruce A; Zhang, Ying; Wright, Ian G

    2008-01-01

    This study investigated the impact of Pt content on the coating composition and subsequent oxidation behavior of gamma/gamma-prime NiPtAl coatings. Gamma/gamma-prime diffusion coatings were fabricated by vacuum annealing electroplated Pt on single-crystal and directionally-solidified superalloy substrates. Specimens with 7 and 12 m thickness Pt were annealed at 1100 or 1175oC. Coating compositions were characterized to evaluate distribution of Pt and Al as a function of annealing temperature and Pt thickness. Selected coatings fabricated from 7 and 12 m Pt were evaluated in cyclic oxidation at 1100 and 1150oC. Coatings with higher Pt contents showed improvements in spallation resistance at both 1100 and 1150oC, particularly on superalloys with higher Hf and S contents.

  16. Moebius inversion and mechanical properties of Ni{sub 3}Al

    SciTech Connect

    Chen, N.X.; Li, M.; Liu, S.J.; Chen, Z.D.

    1995-08-01

    Recently, Chen et al. have applied the Moebius inversion formula to a variety of inversion problems with very concise expressions in analysis and with very fast convergence in calculation. The so-called inverse cohesion problem is to determine the pair potentials between atoms from the cohesive energy curve of the crystal. Carlsson, Gelatt and Ehrenreich were the first to solve this problem by using an operational method. In the present work, the authors deduce a new and concise Moebius inversion formula for some real three-dimensional structures, such as the simple cubic, face-centered and L1{sub 2} structures. Then the calculation of the elastic constants for the intermetallic compound Ni{sub 3}Al is performed based on the new Moebius inversion formula. The calculated result is in good agreement with the experiments.

  17. 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)

  18. The Temporal Evolution of the Nanostructure of a Model Ni-Al-Cr Superalloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2004-01-01

    The early to the later stages of precipitation of ordered gamma'-precipitates (L1(sub 2)) in Ni-5.2 Al-14.2 Cr (at.%) are studied at 873 K. Precipitates with radii as small as 0.45 nm are characterized fully by three-dimensional atom-probe (3DAP) microscopy. Contrary to what is often assumed by theory or in models, the average precipitate composition is shown to evolve with time, such that solute concentrations decrease toward an equilibrium value given by the solvus lines. Power-law time dependencies of the number density, mean radius, and supersaturations of Al and Cr are discussed in light of theoretical predictions for Ostwald ripening.

  19. The effects of alloying elements Al and In on Ni-Mn-Ga shape memory alloys, from first principles.

    PubMed

    Chen, Jie; Li, Yan; Shang, Jia-Xiang; Xu, Hui-Bin

    2009-01-28

    The electronic structures and formation energies of the Ni(9)Mn(4)Ga(3-x)Al(x) and Ni(9)Mn(4)Ga(3-x)In(x) alloys have been investigated using the first-principles pseudopotential plane-wave method based on density functional theory. The results show that both the austenite and martensite phases of Ni(9)Mn(4)Ga(3) alloy are stabilized by Al alloying, while they become unstable with In alloying. According to the partial density of states and structural energy analysis, different effects of Al and In alloying on the phase stability are mainly attributed to their chemical effects. The formation energy difference between the austenite and martensite phases decreases with Al or In alloying, correlating with the experimentally reported changes in martensitic transformation temperature. The shape factor plays an important role in the decrease of the formation energy difference.

  20. Predicting diffusion paths and interface motion in gamma/gamma + beta, Ni-Cr-Al diffusion couples

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1987-01-01

    A simplified model has been developed to predict Beta recession and diffusion paths in ternary gamma/gamma + beta diffusion couples (gamma:fcc, beta: NiAl structure). The model was tested by predicting beta recession and diffusion paths for four gamma/gamma + beta, Ni-Cr-Al couples annealed for 100 hours at 1200 C. The model predicted beta recession within 20 percent of that measured for each of the couples. The model also predicted shifts in the concentration of the gamma phase at the gamma/gamma + beta interface within 2 at. pct Al and 6 at. pct Cr of that measured in each of the couples. A qualitative explanation based on simple kinetic and mass balance arguments has been given which demonstrates the necessity for diffusion in the two-phase region of certain gamma/gamma + beta, Ni-Cr-Al couples.

  1. Pinning effect of reactive elements on adhesion energy and adhesive strength of incoherent Al2O3/NiAl interface.

    PubMed

    Zhang, Z; Zhang, R F; Legut, D; Li, D Q; Zhang, S H; Fu, Z H; Guo, H B

    2016-08-17

    The profound effects of reactive elements (REs) on the adhesion energy and adhesive strength of the α-Al2O3/β-NiAl interface in thermal barrier coating (TBC) systems have attracted increasing attention because RE-doping has played a significant role in improving the thermal cycling lifetime of TBCs. However, the fundamental mechanism is, so far, not well understood due to the experimental difficulty and theoretical complexity in interface modelling. For this purpose, in the present study we have performed comprehensive density functional theory calculations and information targeted experiments to underline the origin of the surprising enhancement of interface adhesion, stability and mechanical strength of the α-Al2O3/β-NiAl interface by different RE doping levels. Our results suggest that the interface failure firstly appears within the NiAl layer adjacent to the Al-terminated oxide under mechanical loading, while the formation of O-RE-Ni bond pairs at the interface can effectively hinder the interface de-cohesion, providing a higher mechanical strength. By comparing several typical REs, it is observed that Hf can emerge not only with the highest interface adhesion energy, but also the highest mechanical strength; in agreement with our experimental results. By continuously increasing the dopant concentration, the strengthening effect may increase correspondingly, but is limited by the solute solubility. These results shed light into the effect of REs on the stability and strength of the α-Al2O3/β-NiAl interface, providing theoretical guidance for interface design via a combinational analysis of bond topology and electronic structure.

  2. Pyridine adsorption on NiSn/MgO-Al2O3: An FTIR spectroscopic study of surface acidity

    NASA Astrophysics Data System (ADS)

    Penkova, Anna; Bobadilla, Luis F.; Romero-Sarria, Francisca; Centeno, Miguel A.; Odriozola, José A.

    2014-10-01

    The acid-base properties of MgO-Al2O3 supports and NiSn/MgO-Al2O3 catalysts were evaluated by IR spectroscopy using pyridine as a probe molecule. The results indicate that only Lewis acid sites were detected on the surface of the supports as well as on the catalysts. Nevertheless, Brønsted acid sites were not detected. In the support without MgO three kinds of coordinatively unsaturated acid sites were detected: Al3+ cations occupying octahedral, tetrahedral and tetrahedral with cationic vacancy in the neighbourhood. The last sites appear as the strongest. Moreover, they are able to activate the pyridine molecules leading to the formation of an intermediate α-pyridone complex. When MgO or NiO were added to the alumina, the number and strength of the Lewis acid sites decreased and significant changes were observed in the tetrahedral sites with adjoining cation vacancies. The incorporation of the Mg2+ cations into the alumina's structure takes place on the vacant tetrahedral positions, forming spinel MgAl2O4. As a result, the fraction of tetrahedral sites with adjoining cationic vacancy diminished and the intermediate α-pyridone complex in the support with the highest MgO loading was hardly detected. The addition of Ni2+ cations leads to the filling of the free octahedral positions, resulting in the formation of a NiAl2O4 spinel structure and the thermal stability of the α-pyridone species decreases. In the catalysts, the progressive reduction of the number and strength of the Lewis acid sites is due to a competitive formation of the two types of MgAl2O4 and NiAl2O4 spinels. In the catalyst NiSn/30MgO-Al2O3 no cationic vacancies were detected and the surface reaction with α-pyridone formation did not occur.

  3. Advanced image analysis of the surface pattern emerging in Ni3Al intermetallic alloys on anodization

    NASA Astrophysics Data System (ADS)

    Salerno, Marco; Stępniowski, Wojciech; Cieślak, Grzegorz; Norek, Małgorzata; Michalska-Domańska, Marta; Karczewski, Krzysztof; Chilimoniuk, Paulina; Polkowski, Wojciech; Jóźwik, Paweł; Bojar, Zbigniew

    2016-07-01

    Anodization of Ni3Al alloy is of interest in the field of industrial manufacturing, thanks to the formation of protective oxide layer on the materials working in corrosive environments and high temperatures. However, homogeneous surface treatment is paramount for technological applications of this material. The anodization conditions have to be set outside the ranges of corrosion and “burning”, which is the electric field enhanced anodic dissolution of the metal. In order to check against occurrence of these events, proper quantitative means for assessing the surface quality have to be developed and established. We approached this task by advanced analysis of scanning electron microscope images of anodized Ni3Al plates. The anodization was carried out in 0.3 M citric acid at two temperatures of 0 and 30°C and at voltages in the range of 2 12 V. Different figures can be used to characterize the quality of the surface, in terms of uniformity. Here, the concept of regularity ratio spread is used for the first time on surfaces of technological interest. Additionally, the Minkowski parameters have been calculated and their meaning is discussed.

  4. Precipitation Effects on the Martensitic Transformation in a Cu-Al-Ni Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Suru, Marius-Gabriel; Lohan, Nicoleta-Monica; Pricop, Bogdan; Mihalache, Elena; Mocanu, Mihai; Bujoreanu, Leandru-Gheorghe

    2016-04-01

    This paper describes the effects of precipitation of α-phase on a Cu-Al-Ni shape memory alloy (SMA) with chemical composition bordering on β region. By differential scanning calorimetry, a series of reproducible heat flow fluctuations was determined on heating a hot-rolled martensitic Cu-Al-Ni SMA, which was associated with the precipitation of α-phase. Two heat treatments were given to the SMA so as to "freeze" its states before and after the thermal range for precipitation, respectively. The corresponding microstructures of the two heat-treated states were observed by optical and scanning electron microscopy and were compared with the initial martensitic state. Energy dispersive spectroscopy experiments were carried out to determine the chemical compositions of the different phases formed in heat-treated specimens. The initial as well as the heat-treated specimens with a lamellar shape were further comparatively investigated by dynamic mechanical analysis and two-way shape memory effect (TWSME) tests comprising heating-cooling cycles under a bending load. Temperature scans were applied to the three types of specimens (initial and heat-treated states), so as to bring out the effects of heat treatment. The storage modulus increased, corresponding to the reversion of thermoelastic martensite and disappeared with the formation of precipitates. These features are finally discussed in association with TWSME under bending.

  5. Shock Loading of Granular Ni/Al Composites. Part 1. Mechanics of Loading

    SciTech Connect

    Cherukara, Mathew J.; Germann, Timothy C.; Kober, Edward M.; Strachan, Alejandro

    2014-10-16

    We present molecular dynamics simulations of the thermomechanical response under shock loading of a granular material consisting of laminated Ni/Al grains. We observe two regimes: At low piston velocities (up ≲ 1km/s), the shock wave is diffuse, and the width of the shock front decreases with increasing piston velocity. Beyond a critical shock strength, however, the width remains relatively constant at approximately the mean grain radius. This change in behavior follows from an evolution of the mechanism of compaction with increasing insult strength. Furthermore, the mechanism evolves from plastic deformation-mediated pore collapse for relatively weak shocks, to solid extrusion and fluid ejecta filling pores ahead of the shock front at intermediate strengths, and finally to atomic jetting into the pore for very strong shocks (up ≳ 2 km/s). High-energy fluid ejecta into pores leads to the formation of flow vorticity and can result in a large fraction of the input energy localizing into translational kinetic energy components including the formation of hot spots. This has implications for the mechanical mixing of Ni and Al in these reactive composites.

  6. Development of biogas reforming Ni-La-Al catalysts for fuel cells

    NASA Astrophysics Data System (ADS)

    Benito, M.; García, S.; Ferreira-Aparicio, P.; Serrano, L. García; Daza, L.

    In this work, the results obtained for Ni-La-Al catalysts developed in our laboratory for biogas reforming are presented. The catalyst 5% Ni/5% La 2O 3-γ-Al 2O 3 has operated under kinetic control conditions for more than 40 h at 700 °C and feeding CH 4/CO 2 ratio 1/1, similar to the composition presented in biogas streams, being observed a stable behaviour. Reaction parameters studied to evaluate the catalyst activity were H 2/CO and CH 4/CO 2 conversion ratio obtained. On the basis of a CH 4 conversion of 6.5%, CH 4/CO 2 conversion ratio achieved 0.48 and H 2/CO ratio obtained was 0.43. By comparison of experimental results to equilibrium prediction for such conditions, is detectable a lower progress of reverse water gas shift reaction. This fact increases the H 2/CO ratio obtained and therefore the hydrogen production. The higher H 2/CO and a CH 4/CO 2 conversion ratio in comparison to CH 4 one close to equilibrium is due to the carbon deposits gasification which avoids catalyst deactivation. A thermodynamic analysis about the application of dry and combined methane reforming to hydrogen production for fuel cells application is presented. Data obtained by process simulation considering a Peng-Robinson thermodynamic model, allows optimizing process conditions depending on biogas composition.

  7. Adsorption and reactions of NO on NiAl(111) at 75 K

    NASA Astrophysics Data System (ADS)

    Schmitz, G.; Bartolucci, F.; Gassmann, P.; Masuch, J.; Franchy, R.

    1997-11-01

    The adsorption and reactions of NO on NiAl(111) at 75 K were studied by high resolution electron energy loss spectroscopy, temperature programmed desorption, Auger electron spectroscopy, and low energy electron diffraction. At low exposure (⩽1 L), NO mainly adsorbs molecularly on top in an upright geometry on Ni atoms. Simultaneously, a small amount of NO dissociates. Higher exposures (⩾2 L up to saturation) lead to the formation of a thin amorphous Al-oxynitride (am-ALON) film. In the presence of am-ALON, a molecular adsorption of NO on am-ALON sites and/or in the neighborhood of ALON islands is observed. Besides the upright geometry, NO molecules are adsorbed in disarranged (bent or tilted) configurations. The growing am-ALON film acts as a catalyst for the reduction of NO to N2O. Substantial amounts of N2O are formed for NO exposures higher than 5 L, and are coadsorbed molecularly. The main thermal desorption products are N2O, N2, and NO. For an exposure of 20 L NO, the ratios of the amounts of desorbing molecules are: N2O:N2:NO=1:0.43:0.36. It could be shown that the N2 signal is due to a recombinative desorption of adsorbed nitrogen atoms.

  8. Shock Loading of Granular Ni/Al Composites. Part 1. Mechanics of Loading

    DOE PAGES

    Cherukara, Mathew J.; Germann, Timothy C.; Kober, Edward M.; ...

    2014-10-16

    We present molecular dynamics simulations of the thermomechanical response under shock loading of a granular material consisting of laminated Ni/Al grains. We observe two regimes: At low piston velocities (up ≲ 1km/s), the shock wave is diffuse, and the width of the shock front decreases with increasing piston velocity. Beyond a critical shock strength, however, the width remains relatively constant at approximately the mean grain radius. This change in behavior follows from an evolution of the mechanism of compaction with increasing insult strength. Furthermore, the mechanism evolves from plastic deformation-mediated pore collapse for relatively weak shocks, to solid extrusion andmore » fluid ejecta filling pores ahead of the shock front at intermediate strengths, and finally to atomic jetting into the pore for very strong shocks (up ≳ 2 km/s). High-energy fluid ejecta into pores leads to the formation of flow vorticity and can result in a large fraction of the input energy localizing into translational kinetic energy components including the formation of hot spots. This has implications for the mechanical mixing of Ni and Al in these reactive composites.« less

  9. Use of Ni{sub 3}Al-based alloys for walking-beam furnaces

    SciTech Connect

    Sikka, V.K.; Dailey, R.E.

    1996-02-01

    This report summarizes the joint work performed by the Oak Ridge National Laboratory (ORNL) and Rapid Technologies, Inc. (the CRADA partner) to determine the potential of Ni{sub 3}Al-based alloys for use in gas-fired walking-beam furnace components. The report identifies tasks to be performed as part of the CRADA and the organization responsible for each task. The work required under each task was completed and is described. The CRADA accomplished the primary goal of utilizing cast Ni{sub 3}Al-based alloy as rails and other components for walking-beam furnaces manufactured by Rapid Technologies. Rapid Technologies, a small business, is implementing on a commercial basis a highly energy efficient rapid-heating technology for use in the metal manufacturing industry. The rapid heating process allows energy savings of up to 95%. Although goals of all of the tasks of this CRADA were met, there is still a need for a material to work in the rapid heating furnaces at temperatures in the range of 1,350 to 1,400 C. Future effort should be focused in fulfilling this need.

  10. Shock response of Ni/Al reactive inter-metallic composites

    NASA Astrophysics Data System (ADS)

    Cherukara, Mathew; Germann, Timothy; Kober, Edward; Strachan, Alejandro

    2014-03-01

    Intermolecular reactive composites find diverse applications in defense, microelectronics and medicine, where strong, localized sources of heat are required. Motivated by experimental work which has shown that high-energy ball milling can significantly improve the reactivity as well as the ease of ignition of Ni/Al inter-metallic composites, we present large scale (~41 million atom) molecular dynamics simulations of shock-induced chemistry in porous, polycrystalline, lamellar Ni/Al nano-composites, which are designed to capture the microstructure that is obtained post milling. Shock propagation in these porous, lamellar materials is observed to be extremely diffuse, leading to substantial inhomogeneity in the local stress states of the material. We describe the importance of pores as sites of initiation, where local temperatures can rise to several thousands of degrees, and chemical mixing is accelerated by vortex formation and jetting in the pore. We also follow the evolution of the chemistry after the shock passage by allowing the sample to ``cook'' under the shock induced pressures and temperatures for up to 0.5 ns. Multiple ``tendril-like'' reaction fronts, born in the cauldron of the pores, propagate rapidly through the sample, consuming it within a nanosecond. US Defense Threat Reduction Agency, Contract No. HDTRA1-10-1-0119.

  11. Sessile dislocations by reactions in NiAl severely deformed at room temperature

    DOE PAGES

    Geist, D.; Gammer, C.; Rentenberger, C.; ...

    2015-02-05

    B2 ordered NiAl is known for its poor room temperature (RT) ductility; failure occurs in a brittle like manner even in ductile single crystals deforming by single slip. In the present study NiAl was severely deformed at RT using the method of high pressure torsion (HPT) enabling the hitherto impossible investigation of multiple slip deformation. Methods of transmission electron microscopy were used to analyze the dislocations formed by the plastic deformation showing that as expected dislocations with Burgers vector a(100) carry the plasticity during HPT deformation at RT. In addition, we observe that they often form a(110) dislocations by dislocationmore » reactions; the a(110) dislocations are considered to be sessile based on calculations found in the literature. It is therefore concluded that the frequently encountered 3D dislocation networks containing sessile a(110) dislocations are pinned and lead to deformation-induced embrittlement. In spite of the severe deformation, the chemical order remains unchanged.« less

  12. Dislocation-grain boundary interactions in Ni sub 3 Al; Effects of structure and chemistry

    SciTech Connect

    Lee, T.C.; Subramanian, R.; Robertson, I.M.; Birnbaum, H.K. . Materials Research Lab.)

    1991-06-01

    This paper reports that one of the critical issues in developing an understanding of the response of Ni{sub 3}Al to stress is the interaction between dislocations and grain boundaries. Even in simple metals this issue is complex, depending as it does on the nature and orientation of the grain boundary and the character of the interacting dislocations. In the case of intermetallic alloys, the issue is even more complex, as the additional factors of grain boundary chemistry, local order, etc. play an important role. This si clearly illustrated in the specific case of Ni{sub 3}Al which exhibits brittle intergranular fracture at low temperatures, except for hypo-stoichiometric alloys containing small amounts of Boron. The B-doped alloy exhibits extensive plastic deformation before undergoing ductile rupture. The effect of B is clearly on the response of grain boundaries to the stresses caused by slip dislocations as both ductile and brittle alloys show extensive slip within the grains prior to fracture. Two mechanism have been proposed to account for this effect of B on the fracture process. In one, it is postulated that B segregation to the grain boundaries increases the cohesive energy of the grain boundaries to the extent that stress concentrations at the boundaries are relieved by initiation of slip rather than fracture. This is consistent with the thermodynamic treatment of fracture as it has been observed that B does segregate more strongly to grain boundaries than to external surfaces.

  13. Experimental results from Al/p-CdTe/Pt X-ray detectors

    NASA Astrophysics Data System (ADS)

    Abbene, L.; Gerardi, G.; Turturici, A. A.; Del Sordo, S.; Principato, F.

    2013-12-01

    Recently, Al/CdTe/Pt detectors have been proposed for the development of high resolution X-ray spectrometers. Due to the low leakage currents, these detectors allow high electric fields and the pixellization of anodes with the possibility to realize single charge carrier sensing detectors. In this work, we report on the results of electrical and spectroscopic investigations on CdTe diode detectors with Al/CdTe/Pt electrode configuration (4.1×4.1×0.75 and 4.1×4.1×2 mm3). The detectors are characterized by very low leakage currents in the reverse bias operation: 0.3 nA at 25 °C and 2.4 pA at -25 °C under a bias voltage of -1000 V. The spectroscopic performance of the detectors at both low and high photon counting rates were also investigated with a focus on the minimization of time instability, generally termed as polarization, looking for the optimum bias voltage and temperature. Good time stability, during a long-term operation of 10 h, was observed for both detectors at -25 °C and by using an electric field of 5000 V/cm. The 2 mm thick detector exhibited good energy resolution of 6.1%, 2.5% and 2.0% (FWHM) at 22.1 keV, 59.5 and 122.1 keV, respectively. Performance enhancements were obtained by using digital pulse processing techniques, especially at high photon counting rates (300 kcps). The 2 mm thick detector, after a digital pulse shape correction (PSC), is characterized by similar performance to the thin detector ones, opening up to the use of thick CdTe detectors without excessive performance degradations. This work was carried out in the framework of the development of portable X-ray spectrometers for both laboratory research and medical applications.

  14. Directionally Solidified NiAl-Based Alloys Studied for Improved Elevated-Temperature Strength and Room-Temperature Fracture Toughness

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

    2000-01-01

    Efforts are underway to replace superalloys used in the hot sections of gas turbine engines with materials possessing better mechanical and physical properties. Alloys based on the intermetallic NiAl have demonstrated potential; however, they generally suffer from low fracture resistance (toughness) at room temperature and from poor strength at elevated temperatures. Directional solidification of NiAl alloyed with both Cr and Mo has yielded materials with useful toughness and elevated-temperature strength values. The intermetallic alloy NiAl has been proposed as an advanced material to extend the maximum operational temperature of gas turbine engines by several hundred degrees centigrade. This intermetallic alloy displays a lower density (approximately 30-percent less) and a higher thermal conductivity (4 to 8 times greater) than conventional superalloys as well as good high-temperature oxidation resistance. Unfortunately, unalloyed NiAl has poor elevated temperature strength (approximately 50 MPa at 1027 C) and low room-temperature fracture toughness (about 5 MPa). Directionally solidified NiAl eutectic alloys are known to possess a combination of high elevated-temperature strength and good room-temperature fracture toughness. Research has demonstrated that a NiAl matrix containing a uniform distribution of very thin Cr plates alloyed with Mo possessed both increased fracture toughness and elevated-temperature creep strength. Although attractive properties were obtained, these alloys were formed at low growth rates (greater than 19 mm/hr), which are considered to be economically unviable. Hence, an investigation was warranted of the strength and toughness behavior of NiAl-(Cr,Mo) directionally solidified at faster growth rates. If the mechanical properties did not deteriorate with increased growth rates, directional solidification could offer an economical means to produce NiAl-based alloys commercially for gas turbine engines. An investigation at the NASA Glenn

  15. Characteristics of the Energetic Micro-initiator Through Integrating Al/Ni Nano-multilayers with Cu Film Bridge

    NASA Astrophysics Data System (ADS)

    Zhang, Yuxin; Jiang, Hongchuan; Zhao, Xiaohui; Yan, Yichao; Zhang, Wanli; Li, Yanrong

    2017-01-01

    An energetic micro-initiator through integrating Al/Ni nano-multilayers with Cu film bridge was investigated in this study. The Cu film bridge was initially fabricated with wet etching, and Al/Ni nano-multilayers were alternately deposited on the surface of Cu film bridge by magnetron sputtering. The periodic layer structure of Al/Ni nano-multilayers was verified by scanning electron microscopy. The exothermic reaction in Al/Ni nano-multilayers can be initiated with onset reaction temperature as low as 503 K, and the total reaction heat is about 774.6 J/g. This energetic micro-initiator exhibited improved performances with lower threshold voltage, smaller initiation energy, and higher explosion temperature compared with Cu film bridge. An extra violent explosion phenomenon with longer duration time and larger quantities of ejected product particles was detected on this energetic micro-initiator by high-speed camera. Overall, the electric explosion performances of Cu film bridge can be improved evidently with the integration of Al/Ni nano-multilayers.

  16. Characterization and oxidation behavior of NiCoCrAlY coating fabricated by electrophoretic deposition and vacuum heat treatment

    NASA Astrophysics Data System (ADS)

    Li, Zhiming; Qian, Shiqiang; Wang, Wei

    2011-03-01

    Electrophoretic deposition (EPD) was showed to be a feasible and convenient method to fabricate NiCoCrAlY coatings on nickel based supperalloys. The microstructure and composition of the NiCoCrAlY coatings after vacuum heat treatment were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). Isothermal-oxidation test was performed at 1100 °C in static air for 100 h. The results show that the major phases in electrophoretic deposited and vacuum heat treated NiCoCrAlY coating are γ-Ni and γ‧-Ni3Al phases, also there is an extremely small quantity of Al2O3 in the coating. Composition fluctuations occur in the coating and a certain amount of titanium diffuse from the superalloy substrate to the top of the coating during vacuum heat treatment. The oxidation test results exhibit that the oxidation kinetics of this coating has two typical stages. The protective oxide layer is mainly formed in the initial linear growth stage and then the oxide layer hinders further oxidation of the coating in the subsequent parabolic growth stage. The coating can effectively protect the superalloy substrate from oxidation. A certain amount of rutile TiO2 is formed in the coating during oxidation and it is adverse to the oxidation resistance of the coating.

  17. Facile synthesis of NiAl-layered double hydroxide/graphene hybrid with enhanced electrochemical properties for detection of dopamine.

    PubMed

    Li, Meixia; Zhu, Jun E; Zhang, Lili; Chen, Xu; Zhang, Huimin; Zhang, Fazhi; Xu, Sailong; Evans, David G

    2011-10-05

    Layered double hydroxides (LDHs), also known as hydrotalcite-like anionic clays, have been investigated widely as promising electrochemical active materials. Due to the inherently weak conductivity, the electrochemical properties of LDHs were improved typically by utilization of either functional molecules intercalated between LDH interlayer galleries, or proteins confined between exfoliated LDH nanosheets. Here, we report a facile protocol to prepare NiAl-LDH/graphene (NiAl-LDH/G) nanocomposites using a conventional coprecipitation process under low-temperature conditions and subsequent reduction of the supporting graphene oxide. Electrochemical tests showed that the NiAl-LDH/G modified electrode exhibited highly enhanced electrochemical performance of dopamine electrooxidation in comparison with the pristine NiAl-LDH modified electrode. Results of high-resolution transmission electron microscopy and Raman spectra provide convincing information on the nanostructure and composition underlying the enhancement. Our results of the NiAl-LDH/G modified electrodes with the enhanced electrochemical performance may allow designing a variety of promising hybrid sensors via a simple and feasible approach.

  18. Characteristics of the Energetic Micro-initiator Through Integrating Al/Ni Nano-multilayers with Cu Film Bridge.

    PubMed

    Zhang, Yuxin; Jiang, Hongchuan; Zhao, Xiaohui; Yan, Yichao; Zhang, Wanli; Li, Yanrong

    2017-12-01

    An energetic micro-initiator through integrating Al/Ni nano-multilayers with Cu film bridge was investigated in this study. The Cu film bridge was initially fabricated with wet etching, and Al/Ni nano-multilayers were alternately deposited on the surface of Cu film bridge by magnetron sputtering. The periodic layer structure of Al/Ni nano-multilayers was verified by scanning electron microscopy. The exothermic reaction in Al/Ni nano-multilayers can be initiated with onset reaction temperature as low as 503 K, and the total reaction heat is about 774.6 J/g. This energetic micro-initiator exhibited improved performances with lower threshold voltage, smaller initiation energy, and higher explosion temperature compared with Cu film bridge. An extra violent explosion phenomenon with longer duration time and larger quantities of ejected product particles was detected on this energetic micro-initiator by high-speed camera. Overall, the electric explosion performances of Cu film bridge can be improved evidently with the integration of Al/Ni nano-multilayers.

  19. Microstructure Investigation of Cu-Ni Base Al2O3 Nanocomposites: From Nanoparticles Synthesis to Consolidation

    NASA Astrophysics Data System (ADS)

    Ramos, M. I.; Suguihiro, N. M.; Brocchi, E. A.; Navarro, R.; Solorzano, I. G.

    2017-02-01

    Different compositions of Cu-Ni/Al2O3 nanocomposites were prepared by a chemical-based synthesis of co-formed oxides (CuO-NiO-Al2O3) nanoparticles followed by selective hydrogen reduction of the Cu and Ni oxides and finally by consolidation into pellets. The synthesized composites with both phases (metallic and oxide) containing nanoparticles in the 5 to 60 nm range have been systematically produced. Micro- and nanoscale characterization techniques were extensively employed in all stages of the process. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses have shown a heterogeneous distribution of chemical elements resulting in the formation of Cu- and Ni-rich nanoparticles containing Al2O3 phase in a controlled low volume fraction, which later mostly dispersed between the metallic particle and, to a lesser extent, within metallic particles. After consolidation, under uniaxial pressure followed by sintering, the compacted nanocomposite observed in the transmission electron microscope (TEM) revealed that the Al2O3 have been more homogeneously distributed as such: the majority of it at the newly formed grain boundaries of the consolidated pellet and a small part of it within the metallic Cu-Ni matrix. Microhardness measurements demonstrate that dispersion of Al2O3 was successfully achieved as reinforcement phase, yielding up to 100 pct increase in hardness.

  20. The influence of grain size and composition on 1000 to 1400 K slow plastic flow properties of NiAl

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel

    1988-01-01

    The compressive slow plastic flow behavior of several B2 crystal structure NiAl intermetallics has been studied in air between 1000 and 1400 K. Small grain-sized Ni-48.25 at. pct Al (of about 10 microns) was found to be stronger than the previously studied 17 microns diameter material. While grain refinement improved the strength at all test temperatures, the exact mechanism is not clear. Experiments at lower temperature revealed that composition as well as grain size can be an important factor, since Ni-49.2Al was weaker than Ni-48.25Al. Pronounced yield points were found during slow strain-rate testing at 1000 K; however, continued deformation appears to take place by the same mechanism(s) as found at high temperatures. Small changes in thermomechanical processing (TMP) schedules to fabricate Ni-49.2Al indicated that basic deformation characteristics (stress exponent and activation energy) are not affected; however, the preexponential term could be modified if TMP alters the grain structure.

  1. Temporal variability of bioavailable Cd, Hg, Zn, Mn and Al in an upwelling regime.

    PubMed

    Lares, M Lucila; Flores, Muñoz Gilberto; Lara-Lara, Ruben

    2002-01-01

    Monthly variability of Cd, Hg, Zn, Mn and Al concentrations in mussels (Mytilus californianus) soft tissue and brown seaweed (Macrocystis pyrifera) was studied at a pristine rocky shore off San Quintin Bay, Baja California, México. The results were related to climatic and hydrographic conditions and to the physiological state of the mussels (condition index) by correlation analysis and principal component analysis (PCA). A "normalization" to account for the variability induced by the physiological state of the mussel was performed. The PCA was performed in two ways to relate the environmental variables and the condition index to: (1) the metal concentrations in mussels, and (2) the "normalized" mussel concentrations. The association of the variability of Cd with the upwelling season was revealed in both PCAs. The temporal variability of this metal in mussels was highly correlated to that in seaweed, suggesting that the dissolved phase determined the variability of Cd in mussels. However, for Hg, Zn, Mn and Al the results from both PCAs were different. The first PCA showed the relationship of these metals to pluvial precipitation and to the condition index. The PCA for the normalized mussel concentrations showed that, after eliminating the effect of the condition index, only Al was related to pluvial precipitation. Manganese, and to a less degree Zn, were related to these metals in seaweed. Because zinc is an essential element in mussels, some regulation of their internal concentrations is likely. Mercury was not detected in seaweed, but because of its reactive nature, it is not expected that the dissolved fraction could be a significant pathway; therefore, it can be concluded that its temporal variability was determined by the variability in the condition index only.

  2. Structure of Al87Y8Ni5 Amorphous Alloy Analyzed by Anomalous X-ray Scattering

    NASA Astrophysics Data System (ADS)

    Arima, Hiroshi; Kawamata, Toru; Yokoyama, Yoshihiko; Sugiyama, Kazumasa

    The structure of Al87Y8Ni5 amorphous alloy was investigated by the anomalous X-ray scattering (AXS) coupled with a model calculation using reverse Monte Carlo (RMC) simulation, and a three-dimensional structural model was obtained. The model showed the existence of a pre-peak on the small-Q side of the first main peak for the structure factor, and the geometrical origin of this peak is discussed. Partial structure factors indicated that pre-peaks for environmental structure factors around Ni and Y were caused by pair correlations associated with Ni atoms. Further, Voronoi analysis of the nearest-neighbor region suggested that the structure around Ni atoms was dominated by a tetragonal dodecahedron. The origin of the pre-peak would be attributed to the unique local atomic arrangement of prism-like polyhedra around Ni atoms.

  3. 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.

  4. 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.

  5. Hydrodésazotation de la pyridine sous pression atmosphérique catalysée par des oxynitrures de Ni, Mo, et des oxynitrures mixtes MoNi, MoPNi, AlNi et AlPNi

    NASA Astrophysics Data System (ADS)

    Elkamel, K.; Elidrissi, M.; Yacoubi, A.; Nadiri, A.; Abouarnadasse, S.

    1998-11-01

    Hydrodenitrogenation of pyridine has been realised, under atmospheric pressure, in the presence of oxynitride catalysts of molybdenum, nickel and their solid solutions as well as on mixed catalysts MoNi, MoPNi, AlNi and AlPNi. In all cases, the main reaction products are n-pentane and N-pentylpiperidine, at any conversion. Kinetic results suggest that the conversion of pyridine, on nickel oxynitride, proceeds through successive steps with hydrogenation as rate-limiting. Molybdenum oxynitride and Mo-Ni-N solid solutions tested in the temperature range 500 circC-450 circC, showed a good structural and catalytic stability, but a low catalytic activity. On the other hand, nickel oxynitride catalyst yielded higher activity at much lower temperatures (190 circC-250 circC). X-rays analysis indicates that the used catalyst was entirely reduced to metallic nickel, which is the active phase. Under the same experimental conditions, mixed catalysts are relatively less active but more selective than nickel oxynitride into n-pentane formation. La réaction d'hydrodésazotation de la pyridine a été réalisée, sous pression atmosphérique, en présence de catalyseurs oxynitrures de molybdène, de nickel et leurs solutions solides ainsi que sur les catalyseurs mixtes MoNi, MoPNi, AlNi et AlPNi. Dans tous les cas, les principaux produits de réaction observés sont le n-pentane et la N- pentylpipéridine, quel que soit le taux de conversion. Les résultats cinétiques obtenus en régime intégral, en présence de l'oxynitrure de nickel, suggèrent un schéma réactionnel successif où l'hydrogénation de la pyridine serait l'étape limitante. L'oxynitrure de molybdène et les solutions solides Mo-Ni-N, testés à des températures supérieures ou égales à 500 circC, ont montré une bonne stabilité catalytique et structurale mais une faible activité catalytique. En revanche, l'oxynitrure de nickel présente une activité catalytique plus importante à des températures de r

  6. Effect of Pt promotion on Ni/Al2O3 for the selective catalytic reduction of NO with hydrogen

    NASA Astrophysics Data System (ADS)

    Mihet, Maria; Lazar, Mihaela D.; Borodi, G.; Almasan, V.

    2013-11-01

    Ni/Al2O3 (10 wt.% Ni) and Ni-Pt/Al2O3 (10 wt.% Ni, 0.5 wt.% Pt) were comparatively tested in the hydrogen selective catalytic reduction process (H2-SCR), at reaction temperatures below 350°C. Catalytic activity tests consisted in temperature programmed reactions (TPRea) under plug flow conditions from 50 to 350°C, with a temperature rate of 5°C/min, using a feed stream with a reactant ratio NO:H2 = 1:1.3 and a GHSV of 4500 h-1. Promotion with Pt increases the catalytic performances of the Ni based catalyst, in respect to NO conversion, N2 selectivity and N2 yield. The reaction temperatures for NO conversion above 95% decrease significantly due to Pt addition, from 250°C for Ni/Al2O3 to 125°C for Ni-Pt/Al2O3. Characterization of catalysts was performed by: X ray powder diffraction (XRD) for the estimation of Ni crystallite size, temperature programmed reduction (TPR) for the catalyst reducibility, temperature programmed desorption of hydrogen (H2-TPD) for the investigation of active sites and metal dispersion on the support, N2 adsorption-desorption isotherms at -196°C for the determination of total specific surface area and pore size distribution, and H/D isotopic exchange on the catalyst surface. At the request of the Proceedings Editor, and all authors of the paper, an updated version of this article was published on 14 January 2014. Data presented in Table 1 of the original paper contained errors which have been corrected in the updated and re-published article. The Corrigendum attached to the corrected article PDF file explains the errors in more detail.

  7. Interaction of oxygen with samarium on Al{sub 2}O{sub 3} thin film grown on Ni{sub 3}Al(111)

    SciTech Connect

    Cheng, Dingling; Xu, Qian E-mail: jfzhu@ustc.edu.cn; Han, Yong; Ye, Yifan; Pan, Haibin; Zhu, Junfa E-mail: jfzhu@ustc.edu.cn

    2014-03-07

    The interaction between oxygen and samarium (Sm) on the well-ordered thin Al{sub 2}O{sub 3} film grown on Ni{sub 3}Al(111) has been investigated by X-ray photoelectron spectroscopy and synchrotron radiation photoemission spectroscopy. At Sm coverage higher than one monolayer, exposure of oxygen to the Sm films at room temperature leads to the formation of both samarium peroxide (O{sub 2}{sup 2−}) states and regular samarium oxide (O{sup 2−}) states. By contrast, when exposing O{sub 2} to Sm film less than one monolayer on Al{sub 2}O{sub 3}, no O{sub 2}{sup 2−} can be observed. Upon heating to higher temperatures, these metastable O{sub 2}{sup 2−} states dissociate, supplying active O atoms which can diffuse through the Al{sub 2}O{sub 3} thin film to further oxidize the underlying Ni{sub 3}Al(111) substrate, leading to the significant increase of the Al{sub 2}O{sub 3} thin film thickness. Therefore, it can be concluded that Sm, presumably in its peroxide form, acts as a catalyst for the further oxidation of the Ni{sub 3}Al substrate by supplying the active oxygen species at elevated temperatures.

  8. 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.

  9. Effects of a Tantalum Addition on the Morphological and Compositional Evolutions of a Model Ni-AL-Cr Superalloy

    NASA Technical Reports Server (NTRS)

    Booth-Morrison, Christopher; Seidman, David N.; Noebe, Ronald D.

    2008-01-01

    The effects of a 2.0 at.% addition of Ta to a model Ni-Al-Cr superalloy aged at 1073 K are assessed using scanning electron microscopy and atom-probe tomography. The addition of Ta results in appreciable strengthening, and the morphology is found to evolve from a bimodal distribution of spheroidal precipitates, to cuboidal precipitates aligned along the elastically soft <001>-type directions. Tantalum is observed to partition preferentially to the gamma -precipitate phase and decreases the mobility of Ni in the gamma- matrix sufficiently to cause an accumulation of Ni on the gamma-matrix side of the gamma -precipitate/gamma-matrix heterophase interface.

  10. Preliminary tests for Salix sp. tolerance to heavy metals (Cd, Ni, Pb)

    NASA Astrophysics Data System (ADS)

    Corneanu, Mihaela; Hernea, Cornelia; Butnariu, Monica; Corneanu, Gabriel; Sărac, Ioan; Hollerbach, Wilhelm; Neţoiu, Constantin; Petcov, Andreea Adriana

    2014-05-01

    spectrometry). The analysis of variance proved the significant role of the genotype in all analyzed features. The percent of shooting was significant higher in Salix alba (81.90 - 96.26%) in comparison with Salix viminalis (50.43 - 62.67%). The best results for all treatment variants were registered in hybrid 892. Clone 202, hybrid 892 and Inger are sensitive to highest concentration of lead (450.0 ppm) and tolerant to all other treatment variants, while Gudrun is sensitive to Ni, but all the concentrations of Cd and Pb presented a stimulative effect on shoots development. The content of heavy metals in plant was also dependent by the organ (root or shoot) and by the genotype.

  11. As, Cd, Cr, Ni and Pb pressurized liquid extraction with acetic acid from marine sediment and soil samples

    NASA Astrophysics Data System (ADS)

    Moreda-Piñeiro, Jorge; Alonso-Rodríguez, Elia; López-Mahía, Purificación; Muniategui-Lorenzo, Soledad; Prada-Rodríguez, Darío; Moreda-Piñeiro, Antonio; Bermejo-Barrera, Adela; Bermejo-Barrera, Pilar

    2006-12-01

    Rapid leaching procedures by Pressurized Liquid Extraction (PLE) have been developed for As, Cd, Cr, Ni and Pb leaching from environmental matrices (marine sediment and soil samples). The Pressurized Liquid Extraction is completed after 16 min. The released elements by acetic acid Pressurized Liquid Extraction have been evaluated by inductively coupled plasma-optical emission spectrometry. The optimum multi-element leaching conditions when using 5.0 ml stainless steel extraction cells, were: acetic acid concentration 8.0 M, extraction temperature 100 °C, pressure 1500 psi, static time 5 min, flush solvent 60%, two extraction steps and 0.50 g of diatomaceous earth as dispersing agent (diatomaceous earth mass/sample mass ratio of 2). Results have showed that high acetic acid concentrations and high extraction temperatures increase the metal leaching efficiency. Limits of detection (between 0.12 and 0.5 μg g - 1 ) and repeatability of the over-all procedure (around 6.0%) were assessed. Finally, accuracy was studied by analyzing PACS-2 (marine sediment), GBW-07409 (soil), IRANT-12-1-07 (cambisol soil) and IRANT-12-1-08 (luvisol soil) certified reference materials (CRMs). These certified reference materials offer certified concentrations ranges between 2.9 and 26.2 μg g - 1 for As, from 0.068 to 2.85 μg g - 1 for Cd, between 26.4 and 90.7 μg g - 1 for Cr, from 9.3 to 40.0 μg g - 1 for Ni and between 16.3 and 183.0 μg g - 1 for Pb. Recoveries after analysis were between 95.7 and 105.1% for As, 96.2% for Cd, 95.2 and 100.6% for Cr, 95.7 and 103% for Ni and 94.2 and 105.5% for Pb.

  12. Laser Shock Compression and Spalling of Reactive Ni-Al Laminate Composites

    NASA Astrophysics Data System (ADS)

    Wei, C. T.; Maddox, B. R.; Weihs, T. P.; Stover, A. K.; Nesterenko, V. F.; Meyers, M. A.

    2009-12-01

    Reactive laminates produced by successive rolling and consisting of alternate layers of Ni and Al (with bi-layer thicknesses of 5 and 30 μm) were investigated by subjecting them to laser shock-wave loading. The laser intensity was varied between ˜2.68×1011 W/cm2 (providing an initial estimated pressure P˜25 GPa) and ˜1.28×1013 W/cm2 (P˜333 GPa) with two distinct initial pulse durations: 3 ns and 8 ns. Hydrodynamic calculations (using commercial code HYADES) were conducted to simulate the behavior of shock-wave propagation in the laminate structures. SEM, and XRD were carried out on the samples to study the reaction initiation, and the intermetallic compounds. It was found that the thinner bilayer thickness (5 μm) laminate exhibited the most intensive localized interfacial reaction at the higher laser intensity (1.28×1013 W/cm2); the reaction products were identified as NiAl and other Al-rich intermetallic compounds. The reaction front and the formation of intermetallic compounds extend into the sample with a thinner bilayer thickness (5 μm) to a depth of about 50 μm. Increase in the duration of laser shock wave induces increased reaction, which occurs also in the thicker bilayer laminate samples (30 μm bi-layer thickness). It is demonstrated that the methodology of laser shock is well suited to investigate the threshold conditions for dynamic mechanical reaction initiation caused by high intensity laser irradiation.

  13. Simultaneous determination of Ca, Cu, Ni, Zn and Cd binding strengths with fulvic acid fractions by Schubert's method

    USGS Publications Warehouse

    Brown, G.K.; MacCarthy, P.; Leenheer, J.A.

    1999-01-01

    The equilibrium binding of Ca2+, Ni2+, Cd2+, Cu2+ and Zn2+ with unfractionated Suwannee river fulvic acid (SRFA) and an enhanced metal binding subfraction of SRFA was measured using Schubert's ion-exchange method at pH 6.0 and at an ionic strength (??) of 0.1 (NaNO3). The fractionation and subfractionation were directed towards obtaining an isolate with an elevated metal binding capacity or binding strength as estimated by Cu2+ potentiometry (ISE). Fractions were obtained by stepwise eluting an XAD-8 column loaded with SRFA with water eluents of pH 1.0 to pH 12.0. Subfractions were obtained by loading the fraction eluted from XAD-8 at pH 5.0 onto a silica gel column and eluting with solvents of increasing polarity. Schuberts ion exchange method was rigorously tested by measuring simultaneously the conditional stability constants (K) of citric acid complexed with the five metals at pH 3.5 and 6.0. The logK of SRFA with Ca2+, Ni2+, Cd2+, Cu2+ and Zn2+ determined simultaneously at pH 6.0 follow the sequence of Cu2+>Cd2+>Ni2+>Zn2+>Ca2+ while all logK values increased for the enhanced metal binding subfraction and followed a different sequence of Cu2+>Cd2+>Ca2+>Ni2+>Zn2+. Both fulvic acid samples and citric acid exhibited a 1:1 metal to ligand stochiometry under the relatively low metal loading conditions used here. Quantitative 13C nuclear magnetic resonance spectroscopy showed increases in aromaticity and ketone content and decreases in aliphatic carbon for the elevated metal binding fraction while the carboxyl carbon, and elemental nitrogen, phosphorus, and sulfur content did not change. The more polar, elevated metal binding fraction did show a significant increase in molecular weight over the unfractionated SRFA. Copyright (C) 1999 Elsevier Science B.V.

  14. 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.

  15. 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.

  16. 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.

  17. Investigation of Ni/. gamma. -Al/sub 2/O/sub 3/ catalyst modified by Sb and Pb

    SciTech Connect

    Thoang, H.S.; Lanh, H.D.; Khoai, N.

    1986-09-01

    Ni/..gamma..-Al/sub 2/O/sub 3/ catalysts have a very strong dehydrogenation function; however, they also show strong hydrogenolysis activity. The addition of inactive metal such as Cu or Sn inhibits the hydrogenolysis activity, but improves the hydrogenation selectivity of Ni/..gamma..-Al/sub 2/O/sub 3/. In several cases, reforming properties of modified catalysts have also been observed, i.e., combined dehydrogenation and aromatization catalytic properties of the catalysts. In this paper, the authors present the results of a study of Ni/..gamma..-Al/sub 2/O/sub 3/ catalysts modified by Sb and Pb. these metals are generally inactive and have not been extensively investigated as modifying agents for catalysts. They used hydrogen adsorption methods to study the influence of catalysts preparation (oxidation and reduction) on the surface states of the metals as well as the metal-metal interactions on the catalyst surfaces.

  18. Nature of slip during Knoop indentation on {l_brace}100{r_brace} surface of NiAl

    SciTech Connect

    Ebrahimi, F.; Gomez, A.; Hicks, T.G.

    1996-01-15

    The intermetallic NiAl, because of its excellent thermal conductivity, high temperature oxidation resistance, and low density, is a candidate material for high temperature application in jet engines. Stoichiometric NiAl single crystal is a semibrittle material, in which plasticity always precedes fracture. Contrary to tensile testing, during hardness indentation on a {l_brace}100{r_brace}<001> slip systems may not be zero everywhere. For a given indentation plane, the variation in hardness with indentation direction has been shown to reflect the anisotropy in slip and the nature of dislocation interactions. One method to study slip is by analysis of slip lines. The purpose of this study was to investigate the nature of slip and the anisotropy of plastic deformation during Knoop microhardness indentation of a {l_brace}100{r_brace} face in NiAl single crystals using slip trace analysis.

  19. The effect of Zr on the low-cycle fatigue behavior of NiAl at 1000 K

    NASA Astrophysics Data System (ADS)

    Lerch, B. A.; Noebe, R. D.; Rao, K. B. S.

    1998-04-01

    The effect of a 0.1 at. % alloying addition of Zr on the low-cycle fatigue behavior of polycrystalline NiAl was determined at 1000 K and compared to that of binary NiAl. Samples of binary NiAl and the Zr-doped alloy were processed by either HIP consolidation or extrusion of prealloyed intermetallic powders. The cyclic stress response, cyclic stress-strain behavior, and strain-life relationships were all significantly influenced by the microalloying addition of Zr, regardless of the processing technique. A detailed examination of the post-tested low-cycle fatigue (LCF) samples was conducted by optical and electron microscopy to determine variations in fracture and deformation modes and to characterize any microstructural changes that occurred during LCF testing. Differences in LCF behavior due to the Zr addition are attributed to the strong effect that Zr has on modifying the deformation behavior of the intermetallic.

  20. Laser operation by dissociation of metal complexes. II - New transitions in Cd, Fe, Ni, Se, Sn, Te, V, and Zn

    NASA Technical Reports Server (NTRS)

    Chou, M. S.; Cool, T. A.

    1977-01-01

    The reported investigation is a continuation of a study conducted by Chou and Cool (1976). The experimental results discussed are partly related to laser transitions in Cd(I), Cd(II), and Zn(II). Laser transitions in Fe(I), Ni(I), Sn(I), Te(I), and V(I) are also considered along with the observation of a laser pulse with two peaks in connection with the study of laser transitions in Se(I). Experiments related to prospective visible laser operation in thallium at 6550 and 6714 are also discussed, giving attention to spontaneous emission measurements at 6550 and 5350 A, the effects of additive molecules, and laser cavity experiments at 6550 and 6714 A.