Composition control of ternary FeCoNi deposits using cyclic voltammetry

Ternary FeCoNi alloys were electroplated through mean of cyclic voltammetry in simple chloride baths with pH of 2.0. The anodic process in the voltammetric curves was found to completely depress the anomalous deposition of binary alloys while this anomaly was still obvious for the deposition of ternary FeCoNi alloys. From the energy-dispersive X-ray results, the Fe/Co ratio in the ternary FeCoNi deposits was equal to the Fe²⁺/Co²⁺ ratio in the deposition solutions when the Ni²⁺ content was continuously changed. The composition of ternary FeCoNi deposits could be precisely predicted and easily controlled by adjusting the Ni²⁺/(Fe²⁺+Ni²⁺+Co²⁺) ratio in the plating solutions although a synergistic effect in depressing the codeposition of Ni onto the FeCoNi matrix due to the coexistence of Co²⁺ and Fe²⁺ was clearly demonstrated in this work.     

Magnetic properties of nanocrystalline iron group thin film alloys electrodeposited from sulfate and chloride baths

Systematic studies of iron group binary (NiCo and CoFe) and ternary (CoNiFe) thin film alloys relating their magnetic properties with film composition, grain size and the corresponding crystal structure were investigated. Anions influence current efficiencies, magnetic properties, surface morphology and phases of electrodeposited films. Higher current efficiencies in chloride baths compared to sulfate baths were observed for CoFe, NiCo and CoNiFe alloys. The higher deposition current efficiencies in chloride baths were attributed to a catalytic effect. Anion types in CoFe and CoNiFe thin film alloys influenced the microstructures and the resulting magnetic properties (coercivity and squareness). The microstructures of NiCo alloys depend on the deposit Co contents rather than anion types. The surface morphologies of CoFe, NiCo and CoNiFe thin films were independent of anion types. CoFe deposits exhibited relatively smooth surface morphology and turned into fine crystallites with increasing solution Fe⁺² concentration. NiCo deposits showed very smooth surface morphology. CoNiFe deposits had the surface morphology of polyhedral crystallites. The deposit Fe content in CoFe electrodeposits linearly increased with increasing solution Fe⁺² concentration for both chloride and sulfate baths. Similar linear behavior of deposit Co contents was observed in NiCo electrodeposits.     

Effect of pH and current density on the electrodeposition of Zn–Ni–Fe alloys from a sulfate bath

An investigation was done on the influences of current density and pH on the electrodeposition behavior of Zn?CNi?CFe alloys using a sulfate bath. The bath consisted of 0.1?M ZnSO₄, 0.1?M NiSO₄, 0.1?M FeSO₄, 0.2?M Na₂SO₄, 0.2?M H₃BO_3, and 0.01?M H₂SO₄. The results of Zn?CNi?CFe alloys?? codeposition revealed that the significant inhibition of Ni and Fe deposition takes place because of the presence of Zn²⁺ in the plating bath. A transition current density was noticed above wherein a transition from normal to anomalous deposition took place. Bright and uniform surface appearance deposits of Zn?CNi?CFe were the results obtained at pH range 2?C5, and the deposits showed high corrosion resistance. During the investigation, the usage of cyclic voltammetry and galvanostatic techniques for electrodeposition were utilized, while linear polarization resistance and anodic linear sweeping voltammetry techniques were used for the corrosion study. Characterization of morphology and the chemical composition of the deposits were performed by means of scanning electron microscopy and atomic absorption spectroscopy.     

Electrodeposition of Zn and In onto vitreous carbon

The deposition of indium and zinc on vitreous carbon was studied by voltammetric, galvanostatic and single potentiostatic pulse techniques. The morphology and composition of deposits were analysed by SEM/EDX. The codeposition process occurs without the formation of alloys or intermetallic compounds. On the one hand under stagnant conditions or at low electrode rotation speeds, localized alkalization produced by the hydrogen evolution reaction (HER) favours deposition through an indium hydroxide layer, and deposits with the same atomic percentage of In and Zn are attained. On the other hand, under electrode rotation, preferred deposition of Zn takes place. In this case, the reduction of H⁺ by the In⁺ species, intermediate in the In³⁺ reduction process, diminishes the electrochemical HER on the substrate thus favouring Zn deposition. The higher nucleation rate on metallic deposits previously formed on the vitreous carbon surface is also likely.     

Kinetic investigation of the chlorine reduction reaction on electrochemically oxidised ruthenium

The rate and mechanism of the electroreduction of chlorine on electrooxidised ruthenium has been investigated with focus on the effect of solution pH. Current/potential curves for the reduction process in solutions with constant chloride concentration of 1.0 mol dm⁻³ and varying H⁺ concentration have been obtained with the use of the rotating disk electrode technique (RDE). It was found that the chlorine reduction rate is highly inhibited in solutions with high H⁺ concentrations and that it can be satisfactorily described by the Erenburg mechanism, previously suggested for the chlorine evolution on RuO₂ and RTO. The expression of the kinetic current as a function of chlorine and H⁺ concentration was obtained by solving the elementary rate equations of the kinetic mechanism. The kinetic constants obtained from the correlation of the kinetic current expression to the experimental data were used to simulate the dependence of the surface coverages and elementary reaction rates on overpotential.     

Performance and cycling of the iron-ion/hydrogen redox flow cell with various catholyte salts

A redox flow cell utilizing the Fe²⁺/Fe³⁺ and H₂/H⁺ couples is investigated as an energy storage device. A conventional polymer electrolyte fuel cell anode and membrane design is employed, with a cathode chamber containing a carbon felt flooded with aqueous acidic solution of iron salt. The maximum power densities achieved for iron sulfate, iron chloride, and iron nitrate are 148, 207, and 234 mW cm^?2, respectively. It is found that the capacity of the iron nitrate solution decreases rapidly during cycling. Stable cycling is observed for more than 100 h with iron chloride and iron sulfate solutions. Both iron sulfate and iron chloride solutions display moderate discharge polarization and poor charge polarization; therefore, voltage efficiency decreases dramatically with increasing current density. A small self-discharge current occurs when catholyte is circulating through the cathode chamber. As a result, a current density above 100 mA cm^?2 is required to achieve high Coulombic efficiency (>0.9).     

Study on the preparation of Mg-Li-Zn alloys by electrochemical codeposition from LiCl-KCl-MgCl2-ZnCl2 melts

Electrochemical codeposition of Mg, Li, and Zn on a molybdenum electrode in LiCl-KCl-MgCl₂-ZnCl₂ melts at 943 K to form Mg-Li-Zn alloys was investigated. Cyclic voltammograms (CVs) showed that the potential of Li metal deposition, after the addition of MgCl₂ and ZnCl₂, is more positive than the one of Li metal deposition before the addition. Chronopotentiometry measurements indicated that the codeposition of Mg, Li, and Zn occurs at current densities lower than −0.78 A cm⁻² in LiCl-KCl-MgCl₂ (8 wt.%) melts containing 1 wt.% ZnCl₂. Chronoamperograms demonstrated that the onset potential for the codeposition of Mg, Li, and Zn is −2.000 V, and the codeposition of Mg, Li, and Zn is formed when the applied potentials are more negative than −2.000 V. X-ray diffraction (XRD) indicated that Mg-Li-Zn alloys with different phases were prepared via galvanostatic electrolysis. The microstructure of typical α + β phase of Mg-Li-Zn alloy was characterized by optical microscope (OM) and scanning electron microscopy (SEM). The analysis of energy dispersive spectrometry (EDS) showed that the elements of Mg and Zn distribute homogeneously in the Mg-Li-Zn alloy. The results of inductively coupled plasma analysis showed that the chemical compositions of Mg-Li-Zn alloys are consistent with the phase structures of the XRD patterns, and that the lithium and zincum contents of Mg-Li-Zn alloys depend on the concentrations of MgCl₂ and ZnCl₂.     

氨基磺酸体系Co-Ni合金电化学共沉积行为及动力学机理

通过稳态阴极极化和电化学交流阻抗(EIS)等方法,研究了在不同钴镍金属离子比例的氨基磺酸电解液中,Co-Ni合金的电化学共沉积行为。结果表明在氨基磺酸体系中,导致Co-Ni合金异常共沉积行为的原因和在硫酸盐,或氯化物体系中的不同。不是由于Co^2 抑制了Ni的沉积,而是由于NH2SO3^-作为双齿配体形成的异核络合物在电极表面吸附,阻滞了镍离子的还原过程。并且以晶体场理论为基础解释了Co^2 和NH2SO3^-形成的高自旋络合物,比Ni^2 所形成的络合物具有较高的晶体场稳定化能(CFSE),容易分解。因此吸附在电极表面的氨基磺酸根离子对Co2^2 沉积的阻滞作用小于对Ni2^ 的。这样就导致了在氨基磺酸电解液体系中Co^2 的优先沉积。阳极线性扫描曲线表明．钴镍合金中镍含量越高,沉积层在热力学上越稳定,耐蚀性也越好。同时通过EIS的测试,利用等效电路的分析方法和交流阻抗谱解析理论,提出了氨基磺酸电解液中Co-Ni合金共沉积的动力学机理,较好地解释了实验结果。     

Electrodeposition of zinc–iron alloy from an alkaline bath in the presence of sorbitol

The chronopotentiometric technique was used to analyze the electrodeposition of Fe–Zn film on a Pt electrode. Three different Fe³⁺/Zn²⁺ molar ratios, Fe26.8 wt.%–Zn73.2 wt.%, Fe46 wt.%–Zn54 wt.% and Fe66.6 wt.%–Zn33.4 wt.%, were used in a solution containing sorbitol as the Fe³⁺-complexing agent, with a total concentration of the two cations of 0.20 M. Coloration of Fe–Zn films were light gray, dull dark gray and bright graphite, depending on the Fe³⁺/Zn²⁺ ratios in the deposition bath. The highest stripping to deposition charge density ratio was 47.5%, at 15 mA cm⁻² in the Fe26.8 wt.%–Zn73.2 wt.% bath. Energy dispersive spectroscopy indicated that the codeposition type of Fe and Zn in the Fe26.8 wt.%–Zn73.2 wt.% and Fe46 wt.%–Zn54 wt.% baths was normal at all j_d tested, while in the Fe66.6 wt.%–Zn33.4 wt.% bath there was a transitional current density from normal to equilibrium codeposition at 50 mA cm⁻². Scanning electron microscopy showed that Fe–Zn films of high quality were obtained from the Fe66.6 wt.%–Zn33.4 wt.% and Fe26.8 wt.%–Zn73.2 wt.% baths, since the films were smooth. X-ray analysis of the Zn–Fe films obtained at 15, 25 and 50 mA cm⁻², in the Fe26.8 wt.%–Zn73.2 wt.%, Fe46 wt.%–Zn54 wt.% and Fe66.6 wt.%–Zn33.4 wt.% plating baths, suggested the occurrence, in general, of a mixture of Fe₁₁Zn₄₀, Fe₄Zn₉, βFe, αFe, Fe₂O₃, Zn and PtZn alloys in the deposit.     

Studies of latex paint films exposed to aqueous SO2: pH effects

Latex paint films containing the acid-soluble extender calcium carbonate have been exposed to aqueous SO₂ and other acidic solutions to evaluate the effects of acidic deposition at different pH values on the coatings. CaCO₃ is completely removed from these films upon immersion in acidic solutions. The leaching process was monitored with weight loss and infrared measurements. The removal rate was found to be strongly dependent on pH, decreasing with increasing pH. Removal of CaCO₃ occurs even for distilled water which has been allowed to equilibrate with atmospheric CO₂ (pH 5.6). The removal rate seems to depend only on [H⁺]; the identity of the acidic anion is apparently insignificant. An empirical relation between the rate of removal and pH was formulated from the weight loss data. The analyses of the results from both weight loss and infrared methods suggested that the mechanism of removal at pH 2.0 is diffusion controlled, whereas a chemical reaction involving H⁺ becomes more important at higher pH values.     

Electrodeposition of Co–Cu alloy coatings from glycinate baths

The cathodic polarization, cathodic current efficiency of codeposition, composition and structure of Co–Cu alloy as a function of bath composition, current density and temperature were studied. Electrodeposition was carried out from solutions containing CuSO₄ · 5H₂O, CoSO₄ · 7H₂O, Na₂SO₄ and NH₂CH₂COOH. The cathodic current efficiency of codeposition (CCE) was high and it increased with increasing temperature and Cu²⁺ content in the bath, but it decreased with current density. The codeposition of Co–Cu alloys from these baths can be classified as regular. The Co content of the deposit increased with Co²⁺ content and current density and decreased with glycine concentration and temperature. The structure of the deposited alloys was characterized by anodic stripping and X-ray diffraction techniques. The data showed that the deposited alloys consisted of a single solid solution phase with a face-centred cubic (f.c.c.) structure.     

The influence of chloride ions and benzotriazole on the corrosion behavior of Cu37Zn brass in alkaline medium

This paper describes an investigation of the corrosion behavior of Cu37Zn brass in a solution of sodium tetraborate, at pH 10.0, with the addition of chloride ions and benzotriazole (BTA) inhibitor. The application of cyclic voltammetry has led to the conclusion that the anodic current densities increase with increase in immersion time in sodium tetraborate solution as well as in solutions of sodium tetraborate containing chloride ions of various concentrations. The values of anodic current density are considerably smaller in sodium tetraborate solutions with the addition of BTA compared with those in the inhibitor-free solution.The study also analyses the electrochemical behavior of Cu37Zn brass after various times of alloy exposure to BTA solution, as well as its behavior in BTA solutions of various concentrations. Also, the study describes the electrochemical behavior of Cu37Zn brass after the effect of Cl⁻ ions, but subsequent to the formation of a polymeric protective film on the electrode surface.     

Evaluation of citric acid added cleaning solution for removal of metallic contaminants on Si wafer surface

We have investigated cleaning solutions based on citric acid (CA) to remove metallic contaminants from the silicon wafer surface. Silicon wafers were intentionally contaminated with Fe, Ca, Zn, Na, Al and Cu standard solution by spin coating method and cleaned in various CA-added cleaning solutions. The concentration of metallic contaminants on the silicon wafer surface before and after cleaning was analyzed by vapor phase decomposition/inductively coupled plasma-mass spectrometry (VPD/ICP-MS). And the surface micro-roughness was also measured by atomic force microscopy (AFM) to evaluate the effect of cleaning solutions. It was found that acidic CA/H₂O solution has the ability to remove metallic contaminants from silicon surfaces. Fe, Ca, Zn and Na on silicon surface were decreased from the order of 10¹² atoms/cm² to the order of 10⁹ atoms/cm² even at low CA concentration, low temperature of CA solution and with short immersion time. CA was also effective in alkali cleaning solution. Fe, Ca, Zn, Na and Cu were reduced down to the order of 10⁹ atoms/cm² in CA added with NH₄OH/H₂O₂/H₂O solution without degradation of surface micro-roughness.     

Electrodeposition of CoNiMo thin films using glycine as additive: anomalous and induced codeposition

The present study focuses on the behavior of the CoNiMo mixed anomalous/induced codeposition process, using glycine as a probe to influence the coverage of adsorbed intermediates. In order to facilitate the investigation of a wide variation of parameters the electrodeposition of the alloy films was performed using a rotating cylinder Hull cell. Alloy composition, current efficiency and partial currents of each metal were analyzed. The partial current densities and hence alloy composition was affected by the amount of glycine in the electrolyte: increasing glycine enhanced both cobalt and molybdenum deposition rates and hindered nickel deposition. It is suggested that the glycine facilitates the adsorption of M(I) adsorbed intermediates that control the anomalous and induced codeposition behavior. The current efficiency ranged from 30 up to 75% and was only slightly affected by glycine at high applied current densities. Films with a tridimensional porous structure were obtained applying current densities higher than 200 mA cm⁻², formed as a consequence of the large hydrogen evolution side reaction, presenting conditions for a novel Mo-alloy electrode structure.     

Electrodeposition and characterization of thin layers of Zn–Co alloys obtained from glycinate baths

An alkaline bath containing CoSO₄ · 7H₂O, ZnSO₄ · 7H₂O, Na₂SO₄ and NH₂CH₂COOH is proposed for the deposition of thin layers of Zn–Co alloys onto steel substrates. Electrodeposition was carried out at 0.216–1.080 A dm^–2, pH 10 and 10–55 °C. The influence of bath composition, current density and temperature on galvanostatic cathodic polarization, cathodic current efficiency and alloy composition was studied. Different proportions of the two metals were obtained by using different deposition parameters, but at all Zn(II)/Co(II) ratios studied, preferential deposition of zinc occurred and anomalous codeposition took place. Increasing the bath temperature enhanced the cobalt content in the deposit. X-ray diffraction measurements indicated that the phase structure of the deposits was controlled by the applied current density. The Co₅Zn₂₁ phase was formed at low current density, while the CoZn₁₃ phase was formed at high current density. The potentiodynamic dissolution of the coatings showed that they contained Zn–Co alloy of different content and structure.     

Investigation of electroless plating of Ni–W–P alloy films

The electroless deposition of Ni–W–P alloy coatings onto metal substrates using H₂PO₂ ^– as reducing agent from solutions containing nickel sulfate, sodium tungstate, sodium citrate, ammonium sulfate and other additives was studied. At most temperatures (60–80 °C) and pHs (7–11) investigated, bright and coherent coatings uniform in appearance were produced. Phosphorous and tungsten contents ranging from 3.5 to 8 wt % and 0.5 to 6 wt %, respectively, were obtained depending upon solution temperature and pH. Trends such as the effects of pH and temperature on average metal deposition rate and the P content in the alloy are similar to that reported previously for the Ni–P system. Correlation of open-circuit potentials with events occurring at the electrode surface in different solutions and polarization curves provide strong evidence that Ni²⁺ ions participate in W and P deposition, H₂ evolution and H₂PO₂ ^– oxidation and that H₂PO₂ ^– ions participate in cathodic reduction. This indicates that the partial reactions for the Ni–W–P system do not occur independently of one another.     

Reverse Osmosis Separation of Metal Ions in Acid Mine-Water

Abstract

Cellulose acetate membranes obtained from Osmonics Inc. were characterized in terms of pure water permeability constant, solute transport parameter, and mass transfer coefficient with the reference system of aqueous sodium chloride solution. Reverse osmosis separation behavior of Ca, Mg, Zn, Mn, Cu, Al, and Fe as nitrate, chloride, and sulfate salts was studied. The effect of the addition of sodium sulfate to Mg(ClO₄)₂ and Mn(NO₃)₂ solutions on solute separation was also investigated. Acid mine-water obtained from New Brunswick was subjected to reverse osmosis, and separation of metal ions in the range of 95 to 99 % was obtained along with the recovery of product water of suitable quality for use in recycle operations.     

Removal of Copper(II) and Zinc(II) from Aqueous Solutions Using a Lignocellulosic-Based Polymeric Adsorbent Containing Amidoxime Chelating Functional Groups

In this study, the adsorption of Cu(II) and Zn(II) ions from aqueous solutions onto amidoximated polymerized banana stem (APBS) has been investigated. Infrared spectroscopy was used to confirm graft copolymer formation and amidoxime functionalization. The different variables affecting the sorption capacity such as pH of the solution, adsorption time, initial metal ion concentration, and temperature have been investigated. The optimum pH for maximum adsorption was 10.5 (99.99%) for Zn²⁺ and 6.0 (99.0%) for Cu²⁺ at an initial concentration of 10 mg L^?1. Equilibrium was achieved approximately within 3 h. The experimental kinetic data were analyzed using pseudo-first-order and pseudo-second-order kinetic models and are well fitted with pseudo- second-order kinetics. The thermodynamic activation parameters such as ΔG^o, ΔH^o, and ΔS^o were determined to predict the nature of adsorption. The temperature dependence indicates an exothermic process. The experimental isotherm data were well fitted to the Langmuir model with maximum adsorption capacities of 42.32 and 85.89 mg g^?1 for Cu(II) and Zn(II), respectively, at 20°C. The adsorption efficiency was tested using industrial effluents. Repeated adsorption/regeneration cycles show the feasibility of the APBS for the removal of Cu(II) and Zn(II) ions from water and industrial effluents.     

Role of ethylamines on the electrochemical behaviour of Fe–Ni alloy films

Cyclic voltammetric experiments were carried out on platinum in acidic solution (pH 3) containing ferrous sulfate, nickel sulfate and ethylamines (EtNH₂, Et₂NH, Et₃N). Spectral ultraviolet absorption studies indicate the complexation of both Fe²⁺ and Ni²⁺ ions with ethylamines. The results under transient polarisation conditions indicate the reduction of Fe²⁺ ions through the intermediate species FeOH⁺, with second electron transfer as a slow step. The higher charge transfer rate of FeOH⁺ over NiOH⁺ reduction causes the anomalous codeposition of Fe–Ni alloy film. Among the ethylamines, Et₃N considerably assists the alloy deposition process. A gradual variation in free energy of alloy formation with Fe²⁺:Ni²⁺ (mol:mol) in the bath suggests the formation of an alloy intermediate phase rich in iron. Stripping voltammetric curves indicate the preferential dissolution of iron from iron rich alloy intermediate phase. X-ray diffraction studies further confirm the phase to be b.c.c. Fe–Ni alloy. The extent of corrosion of the Fe–Ni alloy film in the presence of ethylamines is in the following order: Et₃N > Et₂NH > EtNH₂.     

Electrochemical behavior of palladium-gold alloys

The behavior of Pd-Au alloys, prepared by electrochemical codeposition, has been studied in acidic solutions (1 M H₂SO₄) using mainly the cyclic voltammetry technique. Morphology of the alloy surface and bulk compositions were examined by SEM/EDAX method. Various types of voltametric behavior during potential cycling in the oxygen region are presented. The influence of hydrogen absorption on electrochemical properties of surface oxides is demonstrated. The problem of the nature of oxygen electrochemisorbed on Pd-Au alloys is discussed.