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Showing papers on "Nickel published in 1993"


Journal ArticleDOI
TL;DR: In this paper, the characterization of oxidic nickel phases in NiO/γ-Al 2 O 3 catalysts in a wide temperature range was carried out by means of temperature-programmed reduction (TPR), oxidation (TPO), and X-ray diffraction (XRD) methods.
Abstract: Investigations on the characterization of oxidic nickel phases in NiO/γ-Al 2 O 3 catalysts in a wide temperature range were carried out by means of temperature-programmed reduction (TPR), oxidation (TPO)and X-ray diffraction (XRD) methods. The results suggest a bimodal nature of oxidic nickel species that are “fixed” to the support. The differences in reducibility of catalysts calcined and reoxidized at the same temperatures were shown.

307 citations


Journal ArticleDOI

230 citations


Journal ArticleDOI
TL;DR: In this paper, two-step reaction mechanisms involving adsorbed monovalent intermediate ions for the electrodeposition of iron and nickel as single metals can be combined to form a predictive model for the codeposition of the iron-nickel alloys.
Abstract: Two-step reaction mechanisms involving adsorbed monovalent intermediate ions for the electrodeposition of iron and nickel as single metals can be combined to form a predictive model for the codeposition of iron-nickel alloys. Inhibition of the more noble nickel in the presence of iron is caused by preferential surface coverage of the adsorbed iron intermediate resulting from a difference between the two elements in Tafel constant for the electrosorption step. The role of hydrolyzed cations and surface pH is investigated and methods for evaluating the influence of pH are explored. The analysis shows that changes in surface pH with potential are not necessary for iron-rich (anomalous) deposits, but that variations in pH from one electrolyte to another may influence deposit composition. The tendency toward iron-rich deposits with increasing overpotential exists in all systems, however, and can be prevented only by decreasing the iron concentration of the bath. An extension of the analysis to account for transport limitations in baths with low iron concentration is developed and calculations with the model are presented to illustrate the effects of current density and electrolyte convection under conditions similar to those investigated experimentally in the literature.

219 citations



Journal ArticleDOI
TL;DR: In this paper, a temperature programmed reduction (TPR) profiles of impregnated nickel exhibit three peaks of hydrogen consumption at 300, 380, and about 500[degrees]C, attributed to the decomposition of nickel nitrate or basic nitrate into NiO, reduction of NiO and reduction of 1:1 nickel phyllosilicates, respectively.
Abstract: Nickel nitrate impregnated onto silica, identified as such after drying at 25[degrees]C, is gradually transformed into basic nickel nitrate, Ni(NO[sub 3])[sub 2][center dot]2Ni(OH)[sub 2], and then into nickel phyllosilicate (1:1 nickel phyllosilicate) upon drying at 90[degrees]C. At this temperature, the amount of phyllosilicates which depends on the drying time, can reach 20% of the overall Ni. The temperature programmed reduction (TPR) profiles of impregnated nickel exhibit three peaks of hydrogen consumption at 300, 380, and about 500[degrees]C, attributed to the decomposition of nickel nitrate or basic nitrate into NiO, the reduction of NiO, and the reduction of 1:1 nickel phyllosilicates, respectively. The last peak corresponds to the reduction of 20% of the overall Ni content regardless of the Ni loading and the conditions of drying at 25 or 90[degrees]C. This fixed percentage proves that phyllosilicate may be still formed at the beginning of the TPR. After TPR up to 700[degrees]C, the nickel is totally reduced and the metal nickel particles have a constant average size of about 65 A while the concentration of particles per surface unit increases with the Ni loading. Before complete reduction, the nickel phyllosilicates are probably located at the interface between silica and the remaining nickel,more » for which they act as anchoring sites. During TPR, after nitrate decomposition, the NiO particles located on the phyllosilicates are reduced into Ni[sup O] at 400[degrees]C without any migration. Between 400 and 700[degrees]C, the increase in metal particle size is due not only to the reduction of the phyllosilicates but also to Ni[sup 0] migration induced by thermal effect and probably also by the weakening of the anchoring strength because of the reduction of phyllosilicates. 47 refs., 8 figs., 12 tabs.« less

146 citations


Journal ArticleDOI
TL;DR: In this paper, the electrocatalytic oxidation of aliphatic alcohols in alkaline solutions at a nickel-based chemically modified glassy carbon electrode (Ni-CME) was investigated.
Abstract: The electrocatalytic oxidation of aliphatic alcohols in alkaline solutions at a nickel-based chemically modified glassy carbon electrode (Ni-CME) was investigated. The electrode was characterized by voltammetry and flow injection and applied for amperometric detection of mono- and polyhydric alcohols separated by liquid chromatography. A mechanistic electrooxidation model is proposed that involves a Langmuir-type adsorption process on different sites: NiO and NiOOH for polyhydric and monohydridic compounds, respectively. The process is followed by a hydrogen abstraction from the carbon α to the OH group through a radical pathway in the rate-determining step

145 citations


Journal ArticleDOI
TL;DR: In this article, the authors used X-ray Absorption Near Edge Structure (XANES) spectroscopy, Extended Xray Absorbption Fine Structure (EXAFS), and Optical Spectral Spectral Analysis (OSA) to investigate the presence of nickel in silicate and aluminosilicate glasses.

144 citations


Journal ArticleDOI
TL;DR: In this paper, an encapsulation experiment of nickel metal within hollow graphitic cages was carried out by using a carbon arc reactor, and the diameter of the tubes was about 30 nm and the length on the order of a few μm.

142 citations


Journal ArticleDOI
TL;DR: In this article, the chemical composition and thermal behavior of the films were established by additional physicochemical techniques, and they were characterized by physicochemical properties of the nano-graphs.
Abstract: Crystalline binary nitride films of tin, copper, and nickel were prepared by reactive sputtering in a nitrogen plasma generated in a dc glow discharge. The chemical composition and thermal behavior of the films were established. The films were characterized by additional physicochemical techniques. Tin nitride, Sn3N4 has an electrical resistivity of 0.02 Ω cm and decomposes into the elements at a maximum rate at 615 °C. The thermal decomposition of Cu3N takes place at 465 °C, while Ni3N decomposes at 405 °C in a stepwise fashion through an intermediate stage at 305 °C. Tin, copper, and nickel nitride decompose into the elements. Nickel nitride crystallized in a new cubic phase with a lattice parameter of 0.446 nm.

135 citations


Journal ArticleDOI
TL;DR: In this article, negative ion photoelectron spectra of Ni−2, Pd−2 and Pt−2 are presented for electron binding energies up to 3.35 eV at an instrumental resolution of 8-10 meV.
Abstract: Negative ion photoelectron spectra of Ni−2, Pd−2, and Pt−2 are presented for electron binding energies up to 3.35 eV at an instrumental resolution of 8–10 meV. The metal cluster anions are prepared in a flowing afterglow ion source. Each dimer exhibits multiple low‐lying electronic states and a vibrationally resolved ground state transition. Franck–Condon analyses yield the anion and neutral vibrational frequencies and the bond length changes between anion and neutral. The electron affinities are determined to be EA(Ni2)=0.926±0.010 eV, EA(Pd2)=1.685±0.008 eV, and EA(Pt2)=1.898±0.008 eV. The electronic configurations of the ground states are tentatively assigned. Comparison of the nickel group dimers to the coinage metal dimers sheds light on the d orbital contribution to the metal bonding in the nickel group dimers.

128 citations


Journal ArticleDOI
TL;DR: In this article, it was established that the interaction of highly dispersed nickel with amorphous carbon substrates is strong enough to break away carbon atoms from the bulk at relatively low temperatures (∼ 700 K).

Journal ArticleDOI
TL;DR: In this article, the hydrogen evolution reaction (h.e.r) was studied in alkaline solutions on two types of electrodes: (1) obtained by alloying Raney nickel without or with nickel and (ii) by pressing Raney Nickel and nickel powders at room temperature.
Abstract: The hydrogen evolution reaction (h.e.r) was studied in alkaline solutions on two types of electrodes: (1) obtained by alloying Raney nickel without or with nickel and (ii) by pressing Raney nickel and nickel powders at room temperature. The obtained electrodes are usually very active for the h.e.r. The most active electrode was obtained by pressing Raney nickel with nickel powder (50 wt %). It was characterized by a large roughness factor, R ∼ 10 000 and a very low overpotential at the current density of 250 mA cm−2, η250 = 56 mV. The mechanism of the h.e.r. was studied using a.c. impedance measurements. The high electrode activity is connected with the increase in the intrinsic activity of the porous electrode surface.

Journal ArticleDOI
TL;DR: In this paper, a structural model describing the turbostratic layered double hydroxides is proposed on the basis of the experimental results, where the brucite-type layers are non-stoichiometric and present hydroxide vacancies: their chemical composition can be written as [Ni1−x2+ Alx3+Alx3+(OH−)2−(y+2z−x)] and the interlamellar layers as [(NO3−)y(CO32−)z·nH2O] with x�
Abstract: Replacement of nickel by aluminium in the brucite-type Ni(OH)2 layers leads to layered double hydroxides (LDH), which can be used as active materials for nickel hydroxide electrodes. Ni/Al LDH compounds [0 < Al/(Ni + Al)⩽ 0.25] were synthesized by precipitation with ammonia from mixed Ni/Al nitrate solutions and characterized by X-ray powder diffraction, infrared spectroscopy, chemical analysis and transmission electron microscopy. X-Ray powder diffractograms of fresh precipitates are characteristic of turbostratic layered double hydroxides. A structural model describing the turbostratic layered double hydroxides is proposed on the basis of the experimental results. The brucite-type layers are non-stoichiometric and present hydroxide vacancies: their chemical composition can be written as [Ni1–x2+ Alx3+(OH–)2–(y+2z–x)] and the interlamellar layers as [(NO3–)y(CO32–)z·nH2O] with x⩽ 0.25. The interlamellar anions (NO3– or CO32–) play two roles: those in D3h symmetry, compensate for the positive-charge excess of Al3+ ions, while those in C2v, symmetry, compensate for that of hydroxide vacancies. When aged, mixed turbostratic Ni/Al hydroxides with the higher aluminium content (x 0, 18) change into synthetic takovites (crystallized Ni–Al–CO3 double hydroxides) through a dissolution–recrystallization process.

Journal ArticleDOI
TL;DR: In this paper, the steady-state rates of carbon formation on a silica-supported Ni-Cu catalyst exposed to CH4 + H2 gas mixtures have been measured for a range of gas compositions (partial pressure of methane, 20-80 kPa, and of hydrogen, 5-15 kPa) and temperatures in the range 723-863 K.

Book
01 Jan 1993
TL;DR: What do you do to start reading biochemistry of nickel?
Abstract: Introduction. Chemistry of Nickel. Urease. Hydrogenase. Carbon Monoxide Dehydrogenase. Methyl Coenzyme M Reductase. Microbial Nickel Metabolism. Plant Nickel Metabolism. Animal Nickel Metabolism. Index.

Journal ArticleDOI
TL;DR: In this article, the authors compare the ability of 2-acetylpyridine azacyclothiosemicarbazones to inhibit the growth of two fungi, compared to their structural differences.

Journal ArticleDOI
TL;DR: It is reported that hydrogen can induce surface reconstructions by adsorption even on close-packed substrates and new low-energy electron-diffraction analyses for H/Ni(111) and H/Fe(110) show that consideration of reconstruction is essential for a convincing experiment-theory fit as well as for reliable determination of the Adsorption site.
Abstract: We report that hydrogen can induce surface reconstructions by adsorption even on close-packed substrates. New low-energy electron-diffraction analyses for H/Ni(111) and H/Fe(110) show that consideration of reconstruction is essential for a convincing experiment-theory fit as well as for reliable determination of the adsorption site. There are two different types of reconstruction: Hydrogen pulls nickel atoms out of the surface but pushes iron atoms towards the bulk. These findings are mirrored by a different sign of work-function change for both systems and demonstrate the correlation between geometric and electronic structure.

Journal ArticleDOI
TL;DR: In this paper, a tentative mechanism involving an oxidative addition-reductive elimination sequence via a nickel hydride intermediate was proposed for the deuteration of deuterated products from organosulfur compounds.
Abstract: A variety of organosulfur compounds containing alkylthio and arylthio groups underwent reductive desulfurization under notably mild conditions when treated with nickel boride, generated in situ from nickel chloride hexahydrate and sodium borohydride in methanol-THF (3:1). Phenyl, chloro, and ester groups are not reduced under these conditions, while iodo, bromo, nitrile, aldehyde, ketone, cyclopropane, and olefinic functions are reduced either completely or partially. Deuterium-labeling studies indicate that the hydrogen that is incorporated into the product originates from both the sodium borohydride and the protic solvent, suggesting the intermediacy of dihydrogen. The epimers 3[alpha]- and 3[beta]-(phenylthio)cholestane afforded 3[alpha]- and 3[beta]-deuteriocholestane, respectively, demonstrating that the reaction proceeds with retention of configuration. The method may thus be employed for the stereospecific preparation of deuterated products from organosulfur compounds. Arguments are presented in support of a tentative mechanism involving an oxidative addition-reductive elimination sequence via a nickel hydride intermediate. 44 refs., 2 tabs.

Journal ArticleDOI
TL;DR: In this article, the electrical and magnetic properties of composite materials prepared by incorporating various nickel-based fillers of different shapes into polyethylene were investigated, and composite samples were characterized in terms of their volume resistivity, dielectric constant, and magnetic permeability values.
Abstract: Electrical and magnetic properties of composite materials prepared by incorporating various nickel-based fillers of different shapes into polyethylene were investigated. The fillers used were nickel powders, nickel filamentary powders, nickel flakes, and nickel-coated graphite fibers. The particle-size distributions of the fillers were determined both before and after the processing of the composite samples. A wide range of filler volume fractions were used. In some cases, the volume fraction approached the maximum packing fraction of the solid phase to significantly exceed the percolation threshold. The composite samples were characterized in terms of their volume resistivity, dielectric constant, and magnetic permeability values. Filler particles of asymmetric shapes were very effective in terms of altering the electrical properties of the composite samples. At the highest loading levels of the nickel fillers, the volume resistivity values of the composites decreased by more than 17 orders of magnitude. AT such high filler concentrations, the dielectric constant values of the composite samples increased considerably, to values that were greater than 1,000. The permeability values of the samples increased linearly with the volume fraction of the nickel filler and were insensitive to the shape of the fillers. The highest relative permeability value measured was 5.8 for compositesmore » with 67% by volume of nickel powder.« less

Journal ArticleDOI
TL;DR: In this article, an atmospheric-pressure chemical vapor deposition method was used to obtain amorphous nickel oxide thin films at a substrate temperature of 250°C, where reduction and oxidation of the films in 1 M KOH resulted in bleaching and coloration, respectively.

Journal ArticleDOI
TL;DR: This article corrects the article on p. 1278 in vol.
Abstract: A study was undertaken to determine the ability of the filamentous bacterium Thiothrix strain A1 to sorb heavy metals from solution. Cells of Thiothrix strain A1 were harvested, washed, and suspended in solutions of metals. After an equilibration period, biomass was separated from solution and the metal content in acid-digested cells and/or filtrates was determined by atomic absorption spectrophotometry. Sorption of nickel and zinc was very rapid; most of the sorbed metal was bound in less than 10 min. The sorption data for copper fit the Freundlich isotherm, and nickel and zinc data fit biphasic Freundlich isotherms. Sorption of both nickel and zinc was dependent on cell age. Cells harvested 24 h after inoculation sorbed approximately one-half of the amount of metal per gram cell protein than did cells harvested after 48, 72, or 96 h. Calcium and magnesium effectively competed with zinc for binding sites, whereas potassium had only a slight effect on the capacity of cells to sorb zinc. The primary mechanism of metal sorption apparently was ion exchange, because 66 to 75% of nickel or zinc could be desorbed by placing metal-laden cells in a solution of 5 mM CaCl(2). A competition experiment with nickel and zinc indicated that both metals occupied the same sorption sites. The strong chelating agents EDTA and NTA effectively prevented metal uptake, but lactate enhanced the uptake of nickel. Thiothrix strain A1 grown in nickel-containing medium had a relatively low uptake of nickel compared with uptake by resting cells suspended in a simple buffer solution.

Journal ArticleDOI
TL;DR: In this article, cyclic voltammetry has been used to examine Ni II/I and Ni II II/III redox potential data for a structurally characterized homologous series of six NiN 2 S 2 complexes, in which the sulfur sites are systematically varied in donor ability: thiolate (RS-), thioether (RSR), sulfinate (RSO 2 - ), and mixtures of these.
Abstract: Cyclic voltammetry has been used to examine Ni II/I and Ni II/III redox potential data for a structurally characterized homologous series of six NiN 2 S 2 complexes, in which the sulfur sites are systematically varied in donor ability: thiolate (RS-), thioether (RSR), sulfinate (RSO 2 - ), and mixtures of these.

Journal ArticleDOI
TL;DR: In this article, the effectiveness of peat in adsorbing copper, nickel and zinc from wastewater was studied and it was found that a contact time of two hours was necessary for the adsorption to reach equilibrium.
Abstract: The effectiveness of peat in adsorbing copper, nickel and zinc from wastewater was studied. Batch kinetic and isotherm studies were carried out to determine the effects of contact time, pH, initial concentration of the adsorbate, and temperature on adsorption. It was found that a contact time of two hours was necessary for the adsorption to reach equilibrium. The optimum pH was found to be between 4.5 and 5.0. The data for the adsorption of copper, nickel and zinc were described well by both the Langmuir and the Freundlich models. The adsorption process was found to be exothermic.

Journal ArticleDOI
12 Mar 1993-Science
TL;DR: In the present study, diamond was synthesized from graphite in the presence of elemental phosphorus at high pressure and temperature (7.7 gigapascals and 1800C) and single-crystal diamond was grown on a diamond seed crystal.
Abstract: As diamond-producing catalysts, 12 transition metals such as iron, cobalt, and nickel were first reported by General Electric researchers more than 30 years ago. Since then, no additional elemental catalyst has been reported. An investigation of the catalytic action of group V elements is of great interest from the viewpoint of producing an n-type semiconducting diamond crystal. In the present study, diamond was synthesized from graphite in the presence of elemental phosphorus at high pressure and temperature (7.7 gigapascals and 1800 degrees C). Furthermore, single-crystal diamond was grown on a diamond seed crystal.

Patent
28 Apr 1993
TL;DR: An airfoil for a gas turbine engine is constructed from a core body formed of conventional nickel-based superalloy and leading and trailing edge components and squealer tip formed of a nickel aluminide alloy as discussed by the authors.
Abstract: An airfoil for a gas turbine engine is constructed from a core body formed of a conventional nickel-based superalloy and leading and trailing edge components and squealer tip formed of a nickel aluminide alloy. The nickel aluminide components exhibit a high degree of thermal conductivity and efficiently transfer heat into the core body by direct conduction.

Journal ArticleDOI
TL;DR: In this article, the surface films on pure Ti and crystalline and amorphous Ti-Ni alloys containing from 30 to 60 at% Ti in a sulfuric acid solution were studied by XPS and photoelectrochemical methods.

Journal ArticleDOI
TL;DR: In this paper, results obtained by treating nickel and molybdenum oxides at a temperature of 523 K, at 10 -4 Pa (in vacuo) and at 10 5 PA (in hydrogen), are reported.

Journal ArticleDOI
TL;DR: In this article, a reversible deactivation phenomenon is observed when copper-nickel particles are reacted in ethylene at temperatures in excess of 700[degrees]C. This deactivation process involves not only the reactions occurring at the gas/catalyst interface but also modifications in the particle chemistry arising from dissolved carbon and hydrogen species, and also the influence of the deposited graphite in the form of a filament at the rear of the particle.

Journal ArticleDOI
TL;DR: In this paper, the authors observed that diamond nucleation occurred only after the substrate and its surface had been carbon saturated, and the length of the interval until saturation was reached depended on the substrate thickness.

Journal ArticleDOI
TL;DR: In this paper, the authors show evidence for the presence of SO42− ions in Td symmetry (originating from the precipitation medium) that are mainly adsorbed on the grain surface.