Electrochemical Behaviour Of Nickel Research Articles

Electrochemical Behavior of Nickel and Electroplating with Nickel–Molybdenum (Tungsten) Alloys in Oxide Melts

The electrochemical behavior of nickel in tungstate melts and the effect of electrolysis conditions on the composition and structure of nickel–molybdenum (tungsten) alloys in tungstate–molybdate melts are studied. It is shown that with an increase in the molybdenum (tungsten) concentrations and a decrease in the nickel concentration in the melt, the phase composition of cathodic deposits changes from nickel through nickel–molybdenum (tungsten) alloys of different composition to pure molybdenum (tungsten).

Anodic Dissolution of Ni50Zn Alloy in the Presence of Mixtures of Organic Additives with Sodium Chloride

Electrochemical behavior of nickel and nickel-zinc alloy in an acidic perchlorate media was studied as influenced by some organic additives, sodium chloride, and their binary mixtures.

99/03186 Electrochemical behavior of nickel deposited on reticulated vitreous carbon

99/03186 Electrochemical behavior of nickel deposited on reticulated vitreous carbon

Morphological and electrochemical characterization of Ni–polyvinylchloride composites

Morphological characteristics and electrochemical behaviour of nickel– Polyvinylchloride (Ni–PVC) composite were studied in alkaline solutions. It was found that prolonged cathodic polarization and continue potential cycling on samples seriously alters the surface morphology, surface composition and adsorption properties of the composite samples. This was confirmed by SEM, EDS, IR spectroscopy and osmometry. Oxygen evolution reaction (oer) was also studied on fresh and pre-activated samples by stationary polarization curves.

The effect of non-equilibrium grain boundary segregation on the tensile properties and the electrochemical behaviour of nickel

The effect of non-equilibrium grain boundary segregation on the tensile properties and the electrochemical behaviour of nickel

Synthesis, spectral and electrochemical properties of divalent metal complexes containing thiohydrazone and thiosemicarbazone ligands

The L 1H 4 and L 2H 6 complexes of metal halides MX 2 (M = Cu, Ni, Co, Zn, Cd or Hg, X = Cl, Br or I) have been prepared. The complexes were characterized on the bases of 1H NMR, IR, electronic and mass spectra, magnetic studies, conductance and analytical data. The stoichiometry and the spectroscopic data indicate that the complexes 1–8, 11, 12 and 15 the metal ions are coordinated by ligand anions and the complexes 9, 10, 13, 14 and 16 contain the neutral ligand. Electrochemical behaviour of nickel and cobalt complexes was determined by cyclic voltammetry. The reduction of complexes are related to metal-centred reductions. In addition, complexes 3, 11 and 12 show irreversible waves associated to Ni(II)/Ni(III) process. The reduction/oxidation potentials depend on the unsaturation grade present in the complexes.

Electrolytic production of nitrogen trifluoride from a molten CsFHFNH 4F system

In order to decrease the vapor pressure of hydrogen fluoride ( HF) and corrosion of the nickel anode in an electrolytic cell for the production of nitrogen trifiuoride, the electrochemical behavior of nickel was investigated in the temperature range of 50–100 °C using a molten CsFHFNH 4F system. Anodic reaction on nickel seemed to vary with increasing potential, permitting division into four regions as follows: anodic dissolution of nickel in Region I (0–1 V vs. H 2), deposition of a Ni(II) compound on nickel in Region II (1–3 V), oxidation of Ni(II) film to Ni(III) and/or Ni(IV) compounds in Region III (3–5 V), and electrochemical fluorination of NH 3 in Region IV (more positive than 5 V). The addition of CsF to the molten electrolyte reduces the corrosion of the nickel anode and reduces the vapor pressure of HF in the melt. A maximum current efficiency for NF 3 formation was recorded at 100 °C.

Influence of surface segregation of sulphur on the corrosion resistance of 270 nickel in acidic and alkaline media

270 Nickel has a sulphur content lower than 1 p.p.m. However, surface concentrations close to saturation values can be obtained after several hours of cold-hammering followed by annealing procedures. The effects of this segregation on the electrochemical behaviour of nickel are analysed using current-potential curves and by examining the corrosion features via scanning electron microscopy (SEM). An overall increase in dissolution for the nickel with surface segregation of sulphur with respect to the homogeneous metal is observed in acidic (1m H2SO4) as well as in alkaline medium [(K2SO4+LiOH) at pH 9.5]. The reaction model proposed here, which depicts the dissolution kinetics, allows specification of the depassivating role of sulphur.

A new electrolytic production of nitrogen trifluoride in a molten CsFHFNH 4F system

In order to decrease the vapor pressure of hydrogen fluoride and the anodic dissolution of the nickel anode for the electrolytic production of nitrogen trifluoride, the electrochemical behavior of nickel and some nickel-based alloys were investigated at 50 °C or 100 °C in a molten CsFHFNH 4F system. A platinum wire was used as the reference electrode, and a part of potential was reduced to a standard of the hydrogen electrode. Anode gas was analyzed by both infrared spectroscopy and gas chromatography. In the potentiostatic electrolysis at 6 V vs. Pt and 50 °C, the ratio of the anodic dissolution of nickel to total amount of passing electricity ( Q a Q t ) was only 1.32 % in calculation from the electron number in the discharge of 2. In the case of nickel-based alloys, only monel consisted of nickel and copper was available for the anode material and its ratio of Q a Q t was almost similar to that of nickel. The anodic polarization curve on monel was also similar to that on nickel, but the current density was smaller than that of nickel. In the galvanostatic electrolysis at the current density of 25 mA·cm −2 and 100 °C, the anode gas was composed of N 2, O 2, N 2O, NF 3, N 2F 2 and so on. The current efficiency of NF 3 increased with decreasing the concentration of NH 4F and reached the value of about 60 % in the molten 0.3NH 4F·CsF·2.6HF. In contrast, the ratio of Q a Q t of nickel decreased with decreasing the concentration of NH 4F and its value in the same electrolyte was 2.78 %.

Cyanide Oxidation at Nickel Anodes: II . Voltammetry and Coulometry of Systems

Coulometric experiments with a Ni plate electrode in 1 kmol containing showed that cyanide could be oxidized at high current efficiency with negligible nickel dissolution. However, current densities were low for potentials below those at which was oxidized to , when oxygen evolution occurred, causing a sharp decrease in current efficiency. The electrochemical behavior of nickel in alkaline cyanide solutions was studied by cyclic voltammetry using a rotating (Pt) ring‐disk (Ni) electrode system. No cyanide oxidation products were detected at the platinum ring electrode. However, by plating the Pt with Pb from alkaline solution, and using potentials < −1.4V vs. with cyanide concentrations >10 mol m−3, species other than oxygen (reduction) and hydrogen (oxidation) generated by the nickel disk electrode could be detected transiently, prior to passivation. From thermodynamic calculations for systems in the preceding paper, the most likely species involved were predicted to be ions, formed by reduction of and the simultaneous oxidative dissolution of the underlying metal. The reaction(s) was observed only on the negative‐going potential sweep of the nickel disk; no nickel dissolution was found to have occurred when the electrode was anodically polarized at constant potentials due to the presence of adsorbed on the electrode, as predicted from the thermodynamic calculations.

Electrochemical Behavior of Nickel in the 2HF-KF Mixture at 80°C

Electrochemical Behavior of Nickel in the 2HF-KF Mixture at 80°C

A new synthesis and the electrochemical behaviour of nickel(II) dithiophosphate and dithiophosphinate complexes

The [Ni(S2PR2)2] complexes (R=i-PrO, PhO, or Et) can be conveniently prepared by reaction of [Ni{P(OPh)3}4] with [R2P(S)S]2 (R=i-PrO, PhO, or Et) in refluxing CHCl3. The electrochemical behaviour of the complexes in CH2Cl2 and MeCN has been studied by cyclic voltammetry and coulometry. The oxidation of complexes at a glassy carbon reveals an e.c. mechanism. The [Ni(S2PR2)2] complexes undergo a one-electron irreversible reduction.

ChemInform Abstract: The Influence of Heat Treatment on the Electrochemical Behavior of Nickel

Abstractis studied in the temp. range 500‐900 °C using TGA and cyclic voltammetric measurements.

Influence of heat treatment on the electrochemical behaviour of nickel

Heat pretreatment of nickel in the temperature range 500–700 ° C gives a non-stoichiometric nickel oxide which shows metallic conductivity and low activity for oxygen evolution; at higher temperatures (> 700° C) a non-conducting NiO (p-type semiconductor) is formed.

Potentiodynamic behaviour of the nickel electrode in acid media

The electrochemical behaviour of nickel has been investigated in H 2SO 4 and HCl solutions of various concentrations by means of the potentiodynamic method. In very dilute solutions, the low anodic current is controlled by the presence of pre-existing film. At higher concentrations the film is removed and dissolution occurs. In H 2SO 4 solutions, pseudopassivity, primary passivity, transpassivity and secondary passivity are observed prior to oxygen evolution. In all these regions, the rate of dissolution increases with acid concentration. In HCl solutions, the anodic polarization curves exhibit a current peak followed by a passivation region; the latter may not involve complete passivity. In the active region, the uniform dissolution is controlled by diffusion processes. In the passive region, local attack in the form of pitting occurs. In both acid solutions, the cathodic and anodic polarization curves satisfy Tafel's relation.

Behavior of nickel in methanol water sulfuric acid solution

The electrochemical behavior of nickel in water-methanol-acid solutions has been investigated; the concentration of the three constituents of the solution have been extensively varied. The mechanisms of Ni dissolution and passivation seem to be the same as in water solution; the previously proposed model is well satisfied by the experimental results. Methanol seems to act as an inhibitor of the free corrosion of nickel, while water is the main passivating agent. Both active corrosion and passivation are diffusion controlled reactions: their rates in the presence of small amounts of water, are lowered.

Electrochemical behaviour of nickel in nitric acid

The electrochemical investigations of nickel in a wide range of concentrations (1–14.6 M) of nitric acid were studied by potentiostatic, potentiodynamic and coulostatic method and by weight-loss measurements. The potentiostatic current-potential curves of nickel in nitric acid solutions can be classified into three categories, according to the proportion of the concentration of the acid. An increase of nitric acid concentration increases the influence of the cathodic reactions in the systems. The importance of cathodic reactions has been investigated by eliminating HNO 2 by additions of p-nitro aniline in the electrolyte. The coulostatic polarization has given distinct repassivation curves, indicating an intermediate state of nickel electrode between active and passive state. In the first part of repassivating process the potential value is more positive than the stationary potential of spontaneous passivation of nickel electrode in concentrated nitric acid. The return of the stationary potential of the passivity is a slow, time-dependent process. According to the experimental results and data given in the literature, it may be possible that in the beginning of the passivation process on nickel Ni(NO 3) 2 × 4 H 2O forms which changes to NiO 2 and than transforms slowly to NiO.

The potentiodynamic response of polycrystalline nickel electrodes in 0.5mK2CO3

The electrochemical behaviour of nickel in 0.5 M K2CO3 is investigated by applying simple and combined potentiodynamic techniques in the potential regions of the Ni(OH)2/Ni and Ni(III)/Ni(II) redox couples. The diffusion controlled hydrated NiCO3 precipitation interferes with the electroformation of the Ni(OH)2 prepassive layer. Both anodic and cathodic peak multiplicities are observed in the potential range of the Ni(III)/Ni(II) electrode. The presence of CO32− ions is tentatively associated with a change in the hydration of the composite Ni(OH)2/NiOOH layer and eventually with HCOc ions coming out from the CO32−/HCO3− equilibrium, which depends on the local change in pH produced during the corresponding anodic and cathodic reactions.

A potentiodynamic study of anodic film formation on nickel in borate solutions

The potentiodynamic behaviour of Ni in buffered borate electrolytes (7.6 ⩽ pH ⩽ 9.3) is investigated. The reactions taking place in the potential region of the Ni/Ni(OH)2 and Ni(II)/Ni(III) redox couples can be formally interpreted with the same reaction patterns postulated for the electrochemical behaviour of nickel in strongly alkaline media including the multiplicity of phases related to the corresponding reactants and products. The main differences between the electrochemical characteristics of nickel over the whole pH range are in the growth rate of the anodic film and the change of its structure in relation to its degree of hydration, overall oxidation state and inner ionic composition.

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NaNO&lt;SUB&gt;3&lt;/SUB&gt;-KNO&lt;SUB&gt;3&lt;/SUB&gt;共晶塩におけるニッケルおよびニッケル基合金の電気化学的挙動