Showing papers on "Nickel published in 1997"

An Electrochemical Route for Making Porous Nickel Oxide Electrochemical Capacitors

Abstract: Porous nickel oxide films were prepared by electrochemically precipitating nickel hydroxide and heating the hydroxide in air at 300 C. The resulting nickel oxide films behave as an electrochemical capacitor with a specific capacitance of 59 F/g electrode material. These nickel oxide films maintain high utilization at high rates of discharge (i.e., high power density) and have excellent cycle life. Porous cobalt oxide films were also synthesized. Although the specific capacitances of these films are approximately one-fifth that of the nickel oxide films, the results demonstrate the versatility of fabricating a wide range of porous metal oxide films using this electrochemical route for use in capacitor applications. Electrochemical capacitors have generated wide interest in recent years for use in high power applications (e.g., in a hybrid electric vehicle, where they are expected to work in conjunction with a conventional battery).

Modeling solid solution strengthening in nickel alloys

Abstract: The yield stress of multicomponent nickel solid solution alloys has not been modeled in the past with respect to the effects of composition and temperature. There have been investigations of the effect on the yield stress of solutes in binary systems at a fixed temperature, but the effects on the yield stress of multiple solute elements and temperature changes have not been investigated. In this article, two different forms of the trough model are considered for nickel-base alloys to determine the most applicable model for solid solution strengthening in the system. The yield stresses of three binary nickel-chromium and three ternary nickel alloys were determined at a range of temperatures. The yield stress of the alloys was then modeled using the Feltham equation. The constants determined in fitting the Feltham equation to the experimental data were then applied to other experimental solid solution alloys and also to published information on commercial solid solution nickel alloys. It was found that the yield stress of the nickel solid solution alloys could be modeled successfully using the Feltham equation.

Nickel filament polymer-matrix composites with low surface impedance and high electromagnetic interference shielding effectiveness

Abstract: The processing of nickel filaments of 0.4 Μm diameter gives polyethersulfone-matrix composites with high electromagnetic interference shielding effectiveness, high reflection coefficient and low surface impedance at 1-2 GHz. With 7 vol.% nickel filaments, the composite exhibited shielding effectiveness 87 dB (compared to 90 dB for solid copper), surface impedance 1.2 Ω (same as for solid copper), tensile strength 52 MPa, modulus 5 GPa, ductility 1.0%, and density 1.87 g/cm3.

Characterization of the Ni(II) Phase Formed on Silica Upon Deposition−Precipitation

Abstract: The nature of the Ni(II) phase formed on silica during the preparation by deposition−precipitation (DP) of Ni/SiO2 samples is shown to depend on the silica surface area and the time of deposition−precipitation. Ni/SiO2 samples have been characterized by XRD, IR, EXAFS, TPR, TEM, STEM-EDX, and BET. With silica of low surface area and for short DP time (≤4 h), the Ni(II) phase is mainly a turbostratic nickel hydroxide with a small amount of 1:1 nickel phyllosilicate. With silica of high surface area and for short DP time (≤100 min), the Ni(II) phase is mainly a 1:1 nickel phyllosilicate. For longer DP time (>4 h) and with both types of silica, the Ni(II) phase is an ill-crystallized 1:1 nickel phyllosilicate. However, the latter is better crystallized with silica of low surface area. Almost the same Ni(II) phases were obtained whether silica was porous or not. However, the Ni(II) phase is better crystallized and the interface with the support is larger with nonporous silica than with porous one.

Induced Codeposition III. Molybdenum Alloys with Nickel, Cobalt, and Iron

Abstract: A comparison was made between the codeposition behavior of NiMo, CoMo, and FeMo alloys on rotating cylinder electrodes when the molybdate concentration in the electrolyte was much lower than that of the iron-group species. More molybdate was codeposited with Co than with either Fe or Ni from an ammonia-citrate electrolyte at pH 7.4. During the NiMo codeposition, the molybdate species is mass transport controlled. Substitution of the nickel by cobalt in the plating bath does not influence the molybdenum deposition rate. However, a higher concentration of molybdate is found in the deposits because the rate of cobalt deposition is lower than that of nickel. On the other hand, substitution of the nickel by iron results in a dramatic lowering of the molybdenum deposition rate. These observations were described by a mathematical model which assumes that iron-group species can adsorb on the electrode surface, competing with the molybdenum intermediate for free surface sites. Thus the diminished partial current density of the molybdenum in iron containing electrolytes can be explained by a blocking mechanism due to the adsorbed iron intermediate.

Application of Transition Metal Catalysts in Organic Synthesis

Abstract: Catalysts, Ligands and Reagents Procedures for the Preparation of Halogen Compounds Cross Coupling between 1-Alkynes and 1-Bromoalkynes Copper Catalyzed Aminoalkylation of Acetylenes Copper(I)halide Catalyzed Oxidative Coupling of Acetylenes Copper(I)halide Catalyzed Substitution of sp2-Halogen by Alkoxide Copper Catalyzed Carbon-Carbon Bond Formation by 1,1- and 1,3-Substitution Reactions Nickel Catalyzed Iodo-Dechlorination and Iodo-Debromination of sp2-Halides Nickel and Palladium Catalyzed Cyanation of sp2-Halides and sp2-Triflates Couplings of Acetylenes with sp2-Halides Nickel and Palladium Catalyzed Cross Coupling Reactions with Organometallic Intermediates.

Immobilization of Heavy Metals by Polynuclear Aluminium and Montmorillonite Compounds

Abstract: Modified montmorillonite compounds and polynuclear Al13 were investigated as potential binding agents to reduce heavy metal solubility in soil solutions. The experiments were carried out in batch reactors with solutions/suspensions containing montmorillonite, polynuclear Al13, Al-montmoril lonite, or Al13-montmorillonite. Nickel, copper, and zinc were adsorbed specifically on Al-montmorillonite and Al13-montmorillonite. These three metals were also incorporated in the interlayers of Al-montmorillonite and Al13-montmorillonite during the aging processes. Al-montmorillonite was most effective in the pH ranges 6−8 for nickel and zinc, 4−6 for copper, and 7−9 for cadmium. The immobilization of the heavy metal cations by Al13-montmorillonite was restricted to a smaller pH range. The polynuclear Al13 decreased the dissolved concentrations of nickel, copper, and zinc by specific binding from pH 6.1 to pH 7.5. In the pH range 5.8−6.1 nickel, copper, zinc, cadmium, and lead formed soluble complexes with Al13, whic...

Microstructural evolution in pulse plated nickel electrodeposits

Abstract: Square-wave cathodic current modulation was used to electrodeposit ultra-fine-grained nickel from an additive-free Watts bath. The influence of pulse parameters, namely, pulse on-time, off-time and peak current density on the grain size, surface morphology and crystal orientation was determined. The study showed that an increase in peak current density resulted in considerable refinement in crystal size of the deposit. The crystal orientation progressively changed from an almost random distribution at the lowest peak current density of 400 mA cm −2 to a strong (200) texture at a peak current density of 1600 mA cm −2 . At constant peak current density and off-time, the crystal size of the deposit was found initially to decrease with pulse on-time before it started to increase with further increase in on-time. The crystal orientation progressively changed from an almost random distribution at the shortest on-time of 1 ms to a strong (200) fibre texture at an on-time of 8 ms. An increase in the pulse off-time at constant on-time and peak current density resulted in a progressive increase in crystal size. However, the crystal orientation remained unaffected with increasing off-time.

Method for electroless nickel plating of metal substrates

Abstract: The present invention relates to a method for plating nickel onto metal substrates. The method broadly comprises the steps of passing the metal substrate to be plated through a dilute organic acid bath solution to remove contaminants and other deleterious materials, agitating the bath solution as the metal substrate passes therethrough, and thereafter electrolessly plating nickel on the surfaces of the metal substrate. The method of the present invention may be used to nickel plate substrates formed from steel, copper and aluminum.

Nickel filament polymer-matrix composites with low surface impedance and high electromagnetic interference shielding effectiveness

Abstract: Nickel filaments of 0.4 μm diameter gave polyethersulfone-matrix composites with high electromagnetic interference shielding effectiveness and low surface impedance at 1–2 GHz. With 7 vol.% nickel filaments, the composite exhibited shielding effectiveness 87 dB (compared to 90 dB for solid copper), surface impedance 1.2 Ω (same as for solid copper), tensile strength 52 MPa, modulus 5 GPa, ductility 1.0% and density 1.87 g/cm3. The low surface impedance is valuable for microwave waveguides.

Self-Assembled Monolayers of n-Dodecanethiol on Electrochemically Modified Polycrystalline Nickel Surfaces

Abstract: Monolayers of n-dodecanethiol molecules on surfaces of polycrystalline nickel electrochemically pretreated are obtained by immersion either in pure n-dodecanethiol or in a solution of the mercaptan in absolute ethanol. The influence of the electrochemical pretreatment on the quality of the organic layer has been studied by contact angle measurements, electrochemistry, and X-ray photoelectron spectroscopy. It is found that n-dodecanethiol monolayers directly adsorbed on nickel surfaces without electrochemical pretreatment are of poor quality and exhibit a significant proportion of the thiols oxidized into sulfonates and sulfinates. On the contrary, the electrochemical pretreatment leads to monolayers with significantly improved physicochemical properties such as better chemical stability, resistance to electrochemical oxidation, and molecular order.

Partial oxidation of methane to syngas over nickel-based catalysts modified by alkali metal oxide and rare earth metal oxide

Abstract: The NiO/Al2O3 catalyst was modified by alkali metal oxide (Li, Na, K) and rare-earth metal oxide (La, Ce, Y, Sm) in order to improve the thermal stability and the carbon-deposition resistance during the partial oxidation of methane to syngas (POM) reaction at high temperature. The reaction performance, thermal stability, structure, dispersity of nickel and carbon-deposition of the modified NiO/Al2O3 catalyst and unmodified NiO/Al2O3 catalyst were investigated by a series of characterization techniques including flow-reaction, BET, XRD, CO chemisorption and TG analysis. The results indicated that the modification with alkali metal oxide and rare-earth metal oxide improves the dispersion of active component nickel and the activity for the POM reaction over the nickel-based catalysts, and enhances their thermal stability during high temperature reaction and the ability to suppress the carbon-deposition over the nickel-based catalysts during the POM reaction. The nickel-based catalysts modified by alkali metal oxide and rare-earth metal oxide have excellent POM reaction performance (CH4 conversion of 94.8%, CO selectivity of 98.1%, 2.7×104l/kg·h), excellent stability and carbon-deposition resistance.

Removal of Lead and Nickel Ions Using Zeolite Tuff

Abstract: The capacity of Jordanian zeolite tuff for the removal of lead and nickel ions from aqueous solutions has been investigated under different conditions, namely zeolite particle size, initial solution pH, initial metal ion concentration, slurry concentration and solution temperature. Equilibrium data obtained have been found to fit both the Langmuir and Freundlich adsorption isotherms. It has been found that this zeolite (phillipsite) tuff is an efficient ion exchanger for removing both lead and nickel ions. Its removal capability is considerably higher for lead ions than for nickel ions under all conditions tested; however, the actual exchange capacities are far below the theoretical values. The finer the zeolite particles used, the higher the metal exchange capacity. An initial solution pH of 4·0 is favourable for obtaining high metal removal. © 1997 SCI.

Micro-PIXE as a technique for studying nickel localization in leaves of the hyperaccumulator plant Alyssum lesbiacum

Abstract: Certain terrestrial plants are able to accumulate metals such as zinc, manganese, nickel, cobalt, or copper in their above-ground biomass. The largest group of these so-called “metal hyperaccumulators” is to be found among certain species in the family Brassicaceae endemic to ultramafic soils. For example, nickel concentrations in members of the genus Alyssum can reach 3% of the leaf dry biomass. However, nickel levels in the root tissue of these plants are low, suggesting that hyperaccumulation is associated with effective metal translocation from root to shoot and sequestration of the metal in non-toxic form within the leaves. To investigate the sites of nickel localization within A. lesbiacum, leaf cross-sections were examined by nuclear microscopy using PIXE and RBS on the Oxford Scanning Proton Microprobe (SPM) with a spatial resolution of 1 μm. This paper describes the sample preparation and analysis methods and presents some preliminary results indicating that nickel is sequestered to a considerable degree within the epidermal trichomes on the leaf surface.

Adsorption of Heavy Metals from Aqueous Solutions onto Activated Carbon in Single Cu and Ni Systems and in Binary Cu–Ni, Cu–Cd and Cu–Zn Systems

Abstract: Single copper and nickel adsorption from aqueous solutions onto a granular activated carbon is reported. Metal removals increase on raising pH and temperature, and decrease on raising the initial metal concentration at constant carbon dose. The adsorption processes are modelled using the surface complex formation (SCF) Triple Layer Model (TLM) with an overall surface bidentate species. A dependence of the SCF constant on pH, initial molar metal/carbon ratio and temperature is observed, and a correlation for log Kads is determined. The SCF model successfully predicts copper and nickel removals in single metal solutions. Adsorption in the binary metal systems copper–nickel, copper–cadmium and copper–zinc is also reported, showing competitive adsorption effects. © 1997 SCI.

Kinetic study of the catalytic oxidation of alkanes over nickel, palladium, and platinum foils

Abstract: The kinetics of the total oxidation of alkanes (methane, ethane, propane, n-butane and isobutane) over Ni, Pd, and Pt foils was studied under fuel-lean conditions by using a recirculating batch reactor with mass spectrometry detection. Approximate first- and zeroth-order kinetics with respect to the hydrocarbon and oxygen concentrations, respectively, was observed in all cases. Significantly slower rates were seen for methane conversion, but other subtle changes were also identified among the other hydrocarbons as well. The reactivity trends could be clearly correlated with C-H bond strengths, since higher rates were seen for the longer and more branched hydrocarbon chains. Also, platinum was found to be the most active catalyst for the oxidation of all the compounds studied here except methane, which is oxidized faster on the nickel substrate. The variations in activity among the three catalysts were shown to be associated mostly with changes in the pre-exponential factor, not the activation energy, suggesting that they have to do with the surface density of active sites on the surface. The nature of the active catalyst during reaction was determined by simple inspection to be the metallic phase in the cases of Pt and Ni but an oxide layer in the case of Pd.