Showing papers on "Nickel published in 1990"

Rhenium-containing protective coating with high corrosion and oxidation resistance

Abstract: The present invention relates to a corrosion-resistant or oxidation-resistant coating for metallic components, in particular gas turbine components of superalloys based on nickel or cobalt. By adding rhenium, the life of protective coatings, in particular of the MCrAlY type, under corrosive or oxidising conditions can be increased. The protective coating according to the invention contains, in addition to certain selected components and impurities, the following components (in percent by weight): 1 - 20%, prefeably 4 - 10%, of rhenium, 22 - 50% of chromium, 0 - 15% of aluminium, the amount of chromium and aluminium together being at least 25% and not more than 53%, 0.3 - 2% of yttrium and 0 - 3% of silicon, the remainder mainly being at least one of the elements selected from iron, nickel and cobalt, preferably one of the elements selected from nickel and cobalt. Protective coatings qualified for certain applications can be considerably improved with regard to the life under corrosive conditions by adding even smaller amounts of rhenium.

Transition metal-based hydrogen electrodes in alkaline solution — electrocatalysis on nickel based binary alloy coatings

Abstract: Nickel-molybdenum, nickel-zinc, nickel-cobalt, nickel-tungsten, nickel-iron and nickel chromium binary alloy codeposits, obtained through electrodeposition methods on mild steel strips, have been characterized with the objective of qualitatively comparing and assessing their electrocatalytic activities as hydrogen electrodes in alkaline solution. It has been concluded that their electrocatalytic effects for the hydrogen evolution reaction rank in the following order: Ni-Mo > Ni-Zn (after leaching Zn in KOH) > Ni-Co > Ni-W > Ni-Fe > Ni-Cr > Ni plated steel. Further investigations on the alloy electrocatalysts have revealed that the cathodic overpotential contribution to the electrolysis voltage can be brought down by 0.3 V when compared with conventional cathodes. The best and most stable hydrogen evolving cathode, based on nickel-molybdenum alloy, exhibited an overpotential of about 0.18 V for over 1500 h of continuous electrolysis in 6m KOH at 300 mA cm−2 and 353 K. The salient features of the coatings, such as physical characteristics, chemical composition, crystal structure of the alloy phases and the varying effects of the catalytic activation method were analysed with a view to correlating the micro-structural characteristics of the coatings with the hydrogen adsorption process. The stability under open-circuit conditions, the tolerance to electrochemical corrosion and the long term stability of nickel-molybdenum alloy cathodes were very encouraging. An attempt to identify the pathway for the hydrogen evolution reaction on these alloy coatings was made, in view of the very low apparent activation energy values obtained experimentally.

Microstructures and crystallization of electroless Ni-P deposits

Abstract: A study has been made of microstructures and crystallization of the electroless Ni-P deposits containing 11.3 to 23.0 at% P obtained from acidic nickel sulphate baths with sodium hypophosphite as a reducing agent by means of differential scanning calorimetry, X-ray diffractometry and hot stage transmission electron microscopy. The deposits containing low phosphorus content of 11.3 at% could be represented as an fcc Ni-P solid solution of 5 to 10 nm microcrystallites, whereas the deposits containing high phosphorus content were amorphous. The crystallization process of amorphous Ni-P solution involved more than one intermediate phases; precrystallized nickel or off-stoichiometric Ni3(P, Ni) or Ni5(P, Ni)2 phase in which some phosphorus sites are replaced by nickel atoms. The final equilibrium phases were bct Ni3P and fcc nickel crystals regardless of phosphorus content. The amorphous phase containing 20 to 22 at% phosphorus was the most stable among the amorphous Ni-P alloys.

Characteristics of Slurry‐Coated Nickel Zirconia Cermet Anodes for Solid Oxide Fuel Cells

Abstract: Polarization characteristics were studied in nickel and yttria stabilized zirconia cermet (Ni-YSZ cermet) electrodes in order to search for an adequate fabrication condition of a planar solid oxide fuel cell. Several electrodes were prepared by the slurry coating method, and dc and ac polarization behaviors were investigated at 1273 K in H 2 -H 2 O atmosphere. An experimental equation was derived to describe a typical dc polarization curve of a Ni-YSZ cermet electrode. Effects of fabrication temperature, nickel content, and material powder were investigated in terms of deviation from this equation. Anodic overvoltage with a carefully prepared electrode was decreased to about 0.12 V at 1 A/cm 2

Catalytic dimerization of alkenes by nickel complexes in organochloroaluminate molten salts

Abstract: Organochloroaluminate molten salts based on aluminium trichloride or ethylaluminium dichloride and 1-methyl-3-butylimidazolium chloride, 1-butylpyridinium chloride or tetrabutylphosphonium chloride can be used as solvents for the catalytic dimerization of propene to hexenes isomers by nickel complexes.

The toughening of alumina with nickel inclusions

Abstract: Brittle solids can be toughened by the introduction of ductile metallic inclusions. In the present study, the mechanical properties and oxidation resistance of Al2O3/Ni composites are investigated. The oxidation resistance of the ceramic/metal composite (8 × 10−11 g2 cm−4 s−1 at 1300° C) is comparable to that of many silicon nitrides. The fracture toughness of the composite containing 13 vol.% nickel is twice that of alumina alone. The square of the toughness enhancement for composites containing various amounts of nickel exhibits a linear relationship with the product of volume fraction and inclusion size, as predicted in theoretical models. For the alumina/nickel composite system, it is demonstrated that dissolved oxygen in the nickel increases the yield strength of nickel and enhances the toughness of the composite.

Sound speed and thermophysical properties of liquid iron and nickel

Abstract: An electrical-pulse-heating technique has been used to heat iron and nickel to high temperatures to measure thermophysical properties in the liquid state. A dynamic technique was used because static techniques, which are capable of greater precision, fail at a relatively low temperature. Measurements have been made, and results are shown for enthalpy, temperature, density, electrical resistivity, and sound speed up to 3950 K in iron and 4250 K in nickel.

Comparison of two serpentine species with different nickel tolerance strategies.

Abstract: The effects of nickel were studied in two serpentine species with different metal tolerance strategies:Silene italica L., which limits nickel uptake and translocation, andAlyssum bertolonii Desv., a serpentine endemic, which accumulates nickel mostly in the leaves. InS. italica, nickel 7.5 μM inhibited root growth and depressed mitotic activity in root tips. Peroxidase activity and phenol concentration both in roots and shoots were increased; under the same conditions nickel did not produce any relevant effect onA. bertolonii.

Extended X-ray absorption fine structure investigations of nickel hydroxides

Abstract: Etude de Ni(OH) 2 en phases α et β, a la temperature ambiante et a la temperature de l'azote liquide. Comparaison des longueurs des liaisons

Nucleation‐limited phase selection during reactions in nickel/amorphous‐silicon multilayer thin films

Abstract: Isothermal and constant‐heating‐rate differential scanning calorimetry, cross‐sectional transmission electron microscopy, thin‐film x‐ray diffraction, and thermodynamic and kinetic analyses have been used to investigate silicide phase selection in nickel/amorphous‐silicon multilayer thin‐film reactions. The atomic concentration ratio of the films was two Ni atoms to one Si atom and the layer thickness ratio was one to one. During deposition, a thin layer of amorphous nickel silicide formed between the nickel and amorphous‐silicon layers. Upon heating, this amorphous nickel silicide thickened slightly, until crystalline Ni2Si formed at the nickel/amorphous‐nickel‐silicide interface. Further heating caused the simultaneous growth of both the amorphous nickel silicide and crystalline Ni2Si. Comparison of thermodynamic data to kinetic models for silicide formation and the analysis of calorimetry data suggests that nucleation barriers are responsible for the initial formation of the amorphous nickel silicide a...

Preparation, structure, and properties of pseudotetrahedral, D2d complexes of copper(II), nickel(II), cobalt(II), copper(I), and zinc(II) with the geometrically constraining bidentate ligand 2,2'-bis(2-imidazolyl)biphenyl. Examination of electron self-exchange for the Cu(I)/Cu(II) pair

Abstract: The bidentate ligand 2,2'-bis(2-imidazolyl)biphenyl (3=L) has been synthesized and used to prepare perchlorate complexes. X-ray structure analysis reveals pseudotetrahedral, MN(imH) 4 chromophores, each with approximate D 2d point symmetry. The ligand 3 experts an unprecedented degree of geometric control of the coordination spheres for complexes of this type

Time-Resolved X-Ray Diffraction Study of Solid Combustion Reactions

Abstract: Real-time synchrotron diffraction has been used to monitor the phase transformations of highly exothermic, fast self-propagating solid combustion reactions on a subsecond time scale down to 100 milliseconds and in some instances to 10 milliseconds. Three systems were investigated: Ti + C --> TiC; Ti + C + xNi --> TiC + Ni-Ti alloy; and Al + Ni --> AlNi. In all three reactions, the first step was the melting of the metal reactants. Formation of TiC in the first two reactions was completed within 400 milliseconds of the melting of the Ti metal, indicating that the formation of TiC took place during the passage of the combustion wave front. In the Al + Ni reaction, however, passage of the wave front was followed by the appearance and disappearance of at least one intermediate in the afterburn region. The final AlNi was formed some 5 seconds later and exhibited a delayed appearance of the (210) reflection, which tends to support a phase transformation from a disordered AlNi phase at high temperature to an ordered CsCl structure some 20 seconds later. This new experimental approach can be used to study the chemical dynamics of high-temperature solid-state phenomena and to provide the needed database to test various models for solid combustion.

Electronic structure of NiAl.

Abstract: The valence-band structure of nickel aluminum was measured by use of angle-resolved photoemission with synchrotron radiation and calculated using the local-density approximation. The overall agreement between theory and experiment is remarkably good---much better than for pure nickel. This means that the self-energy'' corrections are significantly less in NiAl than in pure nickel. The core-level binding energies in NiAl are compared experimentally and theoretically with the equivalent levels in Ni and Al. Surprisingly, the Ni core shifts to higher binding energy and the Al to lower as if charge were transferred from Ni to Al---opposite to the direction predicted from electronegativity. These observations are discussed in terms of bonding in NiAl.

Pre-concentration of copper, cobalt and nickel with 3-methyl-1-phenyl-4-stearoyl-5-pyrazolone loaded on silica gel

Abstract: 3-Methyl-1-phenyl-4-stearoyl-5-pyrazolone loaded on to silica gel was used as a pre-concentration reagent for copper, cobalt and nickel prior to atomic absorption spectrometric determination. Both batch and column methods were used for the concentration of the above metals. These metals are quantitatively retained on the proposed adsorbent above pH 4. The adsorption-elution cycle can be repeated ten times with no observable decline in the efficiency of the adsorbent. As there are no observable effects due to changes in the volume of sample solution up to a volume of 1 l, a concentration factor of 40 can be achieved. The method has been applied to samples of sodium chloride solution and tap water.

Role of Sulfur in Catalytic Hydrogenation Reactions

Abstract: Publisher Summary This chapter discusses the role of sulfur in catalytic hydrogenation reactions. One of the most severe causes of metallic catalyst poisoning is the adsorption of species containing sulfur. Sulfur-containing compounds are present in natural sources of hydrocarbons, and are found in industrial feedstocks. The poisoning of metallic catalysts by sulfur has been extensively studied, essentially on nickel, palladium, and platinum, for numerous reactions and consequently under very different experimental conditions, particularly for temperatures ranging from 300 to 1300 K. Such desorptions, depending on the metal-sulfur binding energy and the thermodynamic properties of the surface-adlayer interface, play an important role in controlling the sulfur coverage. The distribution of adsorbed sulfur on the metallic surface and the resulting effect on activity and selectivity of the metal depends on this coverage. At low coverage, for which interactions between adjacent adatoms are negligible, sulfur atoms adsorbed on a heterogeneous surface are located on sites that have the highest binding energies. At higher coverages, sulfur atoms could be gathered into islands. Catalytic reactions performed at low temperatures (below 400 K) show that adsorption of sulfur-containing compounds is then irreversible, the equilibrium being wholly displaced toward the left.

Nickel plating by pulse electrolysis : textural and microstructural modifications due to adsorption/desorption phenomena

Abstract: Nickel growth from an organic-free Watts bath working under d.c. plating conditions is governed by several interfacial inhibitors such as H2, Hads or Ni(OH)2. These inhibitors determine most of the structural or macroscopic properties of the nickel plates. Pulse electrolysis (p.e.) is thus a powerful means of perturbing the adsorption-desorption phenomena occurring at the nickel/electrolyte interface and hence offers an opportunity of preparing deposits exhibiting better properties. Through an analysis of the textural and microstructural changes produced by p.e., we show that molecular inhibitors desorb during the relaxation time, while conversely other inhibitors like Hads or anions are more strongly adsorbed and inhibit the nickel cathodic process.

Carcinogenic Sulfide Salts of Nickel and Cadmium Induce H2O2 Formation by Human Polymorphonuclear Leukocytes

Abstract: Some derivatives of nickel, cadmium, and cobalt are carcinogenic in humans and/or animals but their mechanisms of action are not known. We show that they are capable of stimulating human polymorphonuclear leukocytes (PMNs), as measured by H2O2 formation, a known tumor promoter. Most effective were the carcinogens nickel subsulfide, which caused a 550% net increase in H2O2 over that formed by resting PMNs, followed by cadmium sulfide, 400%, and nickel disulfide, 200%. Nickel sulfide and cobalt sulfide caused statistically nonsignificant increases of 45 and 20%, respectively. Noncarcinogenic barium and manganese sulfides, and sulfates of nickel, cadmium, and cobalt were inactive. The enhancement of H2O2 formation by CdS and Ni3S2 (1 mumol/2.5 x 10(5) PMNs) was comparable to that mediated by the potent tumor promoter 12-O-tetradecanoylphorbol-13-acetate, used at 0.5 and 1 nM, respectively. Concurrent treatment of 12-O-tetradecanoylphorbol-13-acetate-stimulated PMNs with Ni3S2 or NiS caused a decrease in H2O2 accumulation from that expected if the effects were additive. Including catalase in the reaction mixture proved that the oxidant formed by stimulated PMNs was H2O2, whereas adding superoxide dismutase showed that superoxide was also present in PMN samples treated with NiS but not with Ni3S2. Since nickel- and cadmium-containing particulates are deposited in the lungs and cause infiltration of PMNs, the ability to activate those cells and induce H2O2 formation may contribute to their carcinogenicity.

Process for eliminating mercury and possibly arsenic in hydrocarbons

Abstract: Process for elimination of mercury in hydrocarbon charges wherein said charge is contacted, under hydrogen, with a catalyst containing at least one metal from the group consisting of nickel, cobalt, iron and palladium followed by--or mixed with--a capture mass containing sulfur or a metal sulfide.

Characterization of oxide structures formed on nickel-chromium alloy during low pressure oxidation at 500–600°C

Abstract: Low pressure oxidation studies of Ni-18%Cr alloy were carried out at temperatures of 500–600°C for very brief periods. Detailed XPS, AES, SEM, and TEM studies identified four stages in the initial oxidation. These are: (1) formation of a mixed nickel-chromium oxide overlayer; (2) growth of submicron-sized oxide nodules; (3) development of dark “hole-like” patches on the surface; and (4) growth of “second generation” oxide nodules. Both types of nodules consist primarily of a nickel structure depleted in oxygen. Their formation appears to result from a very rapid outward movement of nickel from localized defects in the metal. The dark patches result from the presence of a chromium oxide-rich underlayer, which appears to form by a lateral migration of chromium from adjacent oxide/metal interface regions and from grain boundaries.

In Situ Raman Spectroscopy Study of the Nickel Oxyhydroxide Electrode (NOE) System

Abstract: An in situ analysis using laser Raman microprobe spectroscopy was undertaken for an operating nickel oxyhydroxide electrode (NOE), which showed that the NOE was fully oxidized to γ-NiOOH, at positive polarizations, under the experimental conditions employed. A limited spectral library was constructed by preparing model compounds of the different phases of the hydroxides and oxyhydroxides of nickel and characterizing them with the use of laser Raman microprobe spectroscopy. A factor group analysis for the fundamental building block of all the polymorphs, β-Ni(OH)2, was also performed, and mode assignments were made for the infrared and Raman spectra.

EPR and electrochemical study of nickel(III) complexes of bis(3,5-dichlorosalicylaldehyde) o-phenylenediimine. Evidence for adduct formation with pyridines

Abstract: Electrochemical oxidation of [bis(3,5-dichlorosalicylaldehyde) ο-phenylenediiminato]nickel(II), [Ni(3,5-Cl 2 saloph)] (1), was performed in DMF and (CH 3 ) 2 SO. In these strong donating solvents (S) the Ni(II) complex is oxidized to a Ni(III) complex (low-spin d 7 electron configuration), which can be formulated as [Ni(3,5-Cl 2 saloph)•S 2 ] + . Upon addition by pyridines to freshly electrolyzed solutions of compound 1, novel electron paramagnetic resonance (EPR) spectra indicate the formation of new paramagnetic species, the species formed depending on the basic strength of the pyridines added