Anomalous Codeposition Research Articles

Stripping voltammetry of nanoscale films of Zn–Ni alloy

Nanoscale Zn–Ni alloy films of ~ 20…90 nm thickness were obtained from ammonia-glycinate electrolyte in the potential range from − 1.15 to − 1.475 V. Chemical and phase composition of films were analyzed by stripping voltammetry in alkaline ammonia-glycinate electrolyte. It is shown that the method of stripping-voltammetry in this electrolyte allows estimation of the content of both crystalline and amorphous phases of Zn–Ni alloy, including films with small content of components. All alloy films contain a γ-phase in the mentioned range of potentials. Its maximum content (95%) is observed at a potential of − 1.2 V corresponding to the beginning of the limiting current on the polarization curve of the alloy deposition. Despite the fact that Zn is a more negative metal in the zinc–nickel pair, its content in the alloy decreases with an increase in the polarization of deposition due to anomalous codeposition of Zn with Ni. As the Ni content increases, the contributions of the β-phase and the Ni-phase increase. It is shown that in an electrolyte of the same composition, layers of an alloy of different chemical and phase composition are deposited depending on the potential. Results can be useful both for analyzing the composition of films obtained from other electrolytes, and for choosing the architecture of multilayer coatings deposited by the single-bath method.

Electrodeposition of Zn-Co Alloy from an Acid Sulphate Bath Containing Triethanolamine and Thiaminehydrochloride

Electrodeposition of Zn-Co alloy from an acid sulphate bath has been carried out in this research work. The effects of metal ion ratio in the bath, pH current density, temperature, stirring, thickness and concentrations of triethanolamine and thiaminehydrochloride on the alloy composition and on cathodic current efficiency have been investigated. The deposition potentials of Zn-Co alloy are less noble of zinc and cobalt. The structure of Zn-Co alloy was investigated by X-ray diffraction indicates zinc structure. The surface morphology of alloy deposits is found to depend on the percentage of cobalt in the alloy. Under the optimum operating conditions, Zn-Co alloy deposition follows anomalous co-deposition.

Physico-Chemical Properties of Zn-Fe Alloy Deposits from an Acid Sulphate Bath Containing Triethanolamine

The composition, properties, structure and morphology of electrodeposited Zn-Fe alloy deposits obtained from an acid sulphate bath containing triethanolamine have been investigated. A bath containing less zinc (20%) produced an alloy deposit with higher zinc content (80%), i.e. anomalous co-deposition process. The composition of alloy remained constant with pH of the plating bath and thickness of the alloy deposit. The cathodic current efficiency depends on plating variables. The shift in deposition potentials of Zn-Fe alloy is a chief cause in the co-deposition process to produce alloy of varying composition. Phase structure determination by X-ray diffraction studies showed a wide variety of inter metallic phases. Zn-Fe alloy showed a superior corrosion resistance than zinc coatings. An alloy containing greater than 40% Fe showed a good paintability. Hardness of the alloy deposits increased with increase in iron content in the alloy. Smooth, uniform and fine grained deposits were obtained for the Zn-Fe alloy containing 20% Fe.

Spectrophotometric Monitoring of Chloride Electrolyte for the Electrochemical Deposition of Permalloy

The use of chloride electrolytes for the electrochemical deposition of the Ni81Fe19 permalloy is promising because sulfate electrolytes are unstable in the presence of sulfur. The magnetic properties of the Ni81Fe19 alloy are very sensitive to the deviation of the composition from the molar ratio of 4.26 between components. In this study, the accuracy of preparing the chloride electrolyte for the electrochemical deposition of a permalloy is controlled using spectrophotometry. Analysis of the spectra of light absorption and scattering by the iron hydroxide colloidal species of the electrolyte reveals that the electrolytic dissociation of bivalent iron and the mechanism of anomalous nickel and iron codeposition depend on the temperature and affect the electrochemical deposition of permalloy films. It is noted that the precipitation of ferrous hydroxide in the form of a colloidal species with boric acid as a complexing agent is a specific feature of ferrous chloride during hydrolysis. It is shown that, after filtrating iron chloride solution, nickel is precipitated from the chloride electrolyte better than iron. It is established that the normal congruent deposition of Ni81Fe19 alloy films takes place and abnormal codeposition is excluded.

Electrodeposition of Single γ-phase Zn–Ni Alloy from Deep Eutectic Solvents using Metal Oxides as Precursors

The electrodeposition behavior of Zn–Ni alloy on a Cu electrode has been studied in the choline chloride-urea-ethylene glycol (ChCl-urea-EG) based deep eutectic solvent (DES). The nickel and zinc sources are introduced into the solvent by the dissolution of nickel oxide (NiO) and zinc oxide (ZnO), respectively. Cyclic voltammetry indicates that the electroreduction of Ni(II) or Zn(II) species in the DES is a diffusion-controlled process and the diffusion coefficient of Zn(II) species is an order of magnitude larger than that of Ni(II) species. Under the examined condition, the anomalous codeposition of Zn–Ni alloy is observed, which is different from normal codeposition of Zn–Ni alloy in similar DESs using metal chlorides as precursor. The deposition potential is found to play an important role in controlling the composition and surface morphology of the resultant Ni-Zn alloys. The phase structure of the deposits depends on the Ni content, and changes from a mixture of η-phase and γ-phase to single γ-phase with (411) plane orientation. A mechanism for this electrodeposition process has been proposed on the basis of the formation of complex ions [NiO·urea·Cl]−, [ZnO∙urea·Cl]− and [ChCl·O·urea]2− in ChCl-urea-EG-ZnO-NiO electrolyte during the electrodeposition, emphasizing that the metal oxides were dissolve in DES by forming metal complex ions, the cathodic reduction of metal complex ions generates complex ions [ChCl·O·urea]2− with alloys (NixZny), and [ChCl·O·urea]2− is oxidized to release O2 at anode.

Electrochemical Deposition of NiFe Alloy at a Temperature of 70°C

The heating of chloride electrolyte to a temperature of 70°C excludes anomalous codeposition of NiFe alloy components as a result of a change of the nature of discharging iron ions from the single-charged (Fe2+Cl–)+ ions to the double-charged ions. Chloride electrolyte with a pH value corrected by hydrochloric acid provides the electrochemical deposition of permalloy at a concentration ratio cNi/cFe = 4.26. Conventional (not anomalous) codeposition of nickel and iron is observed also in the dilute solutions at room temperature due to their virtually complete dissociation.

Influence of Ni2+/Co2+ ratio in electrolyte on morphology, structure and magnetic properties of electrolytically produced Ni-Co alloy powders

Nickel-cobalt (Ni-Co) alloy powders were produced galvanostatically by using sulphate electrolytes with various ratios of Ni 2+ /Co 2+ (mole ratios). The morphology, phase structure, chemical composition and magnetic properties were examined by scanning electron microscope (SEM), X-ray diffractometer (XRD), atomic emission spectrometer (AES), and SQUID-based magnetometer, respectively. Morphology of the particles changed from cauliflower-like and dendritic to coral-like and spongy-like ones with increasing Ni 2+ /Co 2+ ratio from 0.25 to 4.0. XRD analysis of the Ni-Co powders revealed that the decrease of Ni 2+ /Co 2+ ratios (the increase of Co content) caused a change of structure from face centered cubic (FCC) obtained for the ratios of 4.0, 1.5 and 0.67 to a mixture of FCC and hexagonal closed-packed (HCP) phases for the ratio of 0.25. The increasing content of nickel led to change of mechanism of electrolysis from irregular (up to ~40 wt.% Ni in the electrolytes) to close to equilibrium (between ~40 and 60 wt.% Ni in the electrolytes) and anomalous co-deposition (over 60 wt.% Ni in the electrolytes) type. All of the obtained Ni-Co alloy samples behaved as soft magnetic materials while their magnetic parameters showed immediate composition dependence since both coercivity and saturation magnetization almost linearly increased with increase of the Co content.

Impact of Deposition Potential on Structural and Magnetic Properties of Nano-Crystalline CoFe Alloy Thin Films

The influence of the electrodeposition potential on the compositional, magnetic, and microstructural properties of CoFe alloy thin films grown on a Cu sputtered silicon substrate was studied. Grazing incidence X-ray diffraction results indicate a diffraction peak at 2θ ≈ 45° related to (110) plane of a body-centered cubic structure of CoFe alloy. Field emission scanning electron microscopy images reveal densely packed uniform nano-granular morphology in all films. Energy-dispersive X-ray spectroscopy results indicate a variation in CoFe alloy film composition while varying the deposition potential, attributed to anomalous co-deposition. The magnetic hysteresis loop measurement shows films are having an easy magnetic direction oriented along in-plane, with high saturation and low coercivity. Surface and microscopic magnetization measurements prove that the deposition potential modifies the film roughness and influences the magnetic domain formation.

Electrodeposition of Ni[sbnd]Co alloy from methansulfonate electrolyte. The role of the electrolyte pH in the anomalous codeposition of nickel and cobalt

The kinetic characteristics of the electrochemical codeposition of nickel and cobalt from a methanesulfonate electrolyte have been investigated. An analysis of the partial voltammograms of the nickel and cobalt deposition into the alloy showed that the potentials of the metal deposition into the alloy are significantly shifted in a positive direction compared to the deposition of the pure metals. This effect is more pronounced in the case of cobalt, and is the cause of the anomalous codeposition of nickel and cobalt. In the presence of the H3BO3 as a buffering agent in the electrolyte, the electroreduction of nickel(II) and cobalt(II) ions is inhibited; this reveals a significant role of the near-electrode pH in the kinetics of these reactions. The thermodynamic and kinetic aspects of the NiCo alloy electrodeposition were considered. It has been found that the kinetic factor is the determining factor responsible for the anomalous codeposition of nickel and cobalt. It has been shown that an adequate explanation of the observed regularities is possible using a concept that assumes equally accessible electroreduction of alloy components at the catalytic centers formed during the adsorption of their hydroxo complexes on the electrode surface. Based on the proposed mechanism, a kinetic model has been developed that correctly describes the features of nickel and cobalt codeposition.It has been found that the microhardness and internal stresses of NiCo electrolytic alloys obtained from methanesulfonate electrolytes are higher than those of coatings deposited from sulfate electrolytes. This is due to the difference in the degree of distortion of their crystal lattices. The low buffering properties of methanesulfonate electrolytes in comparison with sulfate electrolytes cause the formation of a greater number of hydroxide compounds in the near-electrode layer, which are incorporated into the cathode deposit and affect its structure.

Bath temperature-dependent structural properties, coercive force, surface morphology and surface texture of electrochemically grown nanostructured Ni–Co/ITO thin films

This work investigates the role of the temperature of the bath on the structural properties, coercive force, surface morphology and surface texture of the electrochemically produced binary Ni–Co/ITO deposits in detail and presents the first results. It was found that the Ni/Co ratio of the deposit structure was not affected by increasing bath temperature. All resultant Ni–Co thin films comprising 19.5–20 wt% Co and 80–80.5 wt% Ni displayed a slightly anomalous co-deposition behavior. In all deposits, the crystallographic phase structure was the face-centered cubic with the [111] out-of-plane texture. Raising bath temperature gave rise to an improvement in the crystallization and an increment in the crystallite size. The roughness of the surface structure and the size of the surface particles first decreased with increasing bath temperature from 22 to 32 °C and then increased with further increase in the bath temperature. From the surface texture analysis, it was understood that increasing bath temperature did not affect the nature of the surface texture. When the bath temperature was 32 °C, the deposit exhibited the lowest coercive force. The results also indicated that the surface roughness and the particle size were predominant factors on the coercive force.

Electrodeposition of Fe–Ni alloy on Au(111) substrate: Metastable BCC growth via hydrogen evolution and interactions

The electrodeposition of Fe–Ni alloy is usually complicated by the effects of anomalous codeposition and hydrogen evolution. Although the influence of the deposition conditions on the alloy composition has been studied extensively, very few works considered the influence of growth conditions on the phase constitution. In this work, various electrodeposition conditions were investigated to grow Fe–Ni alloy films (<30 nm) with similar compositions in the Invar-to-equiatomic range on Au (111) substrate. Highly (110) oriented BCC phase Fe–Ni with a Ni fraction (ca. 40 at.% Ni) well beyond the equilibrium solubility limit (5 at.% Ni) was obtained with a significant alloy deposition partial current. An increase in the fraction of the BCC phase was found to be associated with a higher alloy deposition partial current, but not necessarily with an increase in the hydrogen evolution partial current. Motivated by the findings from this work, the formation of the metastable BCC phase is speculated to depend on the competing kinetics between the inclusion and desorption of hydrogen adatoms at the electrodeposited growth front.

Controlling the surface morphologies, structural and magnetic properties of electrochemically fabricated Ni–Co thin film samples via seed layer deposition

In this study, the influence of the seed layer deposition on the surface morphologies, structural and magnetic features of the thin film samples of Ni–Co was investigated and results are reported. The samples were produced on indium tin oxide (ITO)-coated glass substrates with and without a seed layer by electrochemical deposition technique under a constant deposition potential. To explore the effect of the seed layer current density (SLCD) on thin films, prior to actual deposition, Ni–Co seed layers were introduced on the ITO substrates at varying current densities. The EDX analysis indicated that the samples exhibited identical deposit compositions and an anomalous co-deposition behavior regardless of the SLCD. The Ni–Co samples fabricated under this study had a face centered cubic (fcc) phase structure with preferred crystallographic orientation being in the [111] direction perpendicular to the sample plane. Furthermore, the crystallite size, crystallinity, particle size and surface roughness of the samples showed a strong dependency on applied SLCD. All Ni–Co samples, irrespective of the SLCD, featured stripe magnetic domain structure and in-plane magnetic hysteresis loop with an out-of-plane magnetization component. It was also observed that while a semi-hard magnetic characteristic was detected in all samples, the coercive field varied with the SLCD.

The Effect of a Substrate Material on Composition Gradients of Fe-Ni Films obtained by Electrodeposition

The electrodeposition of FeNi alloy films was performed galvanostatically in the sulfate solution (Fe2+/Ni2+ mass ratio 1:2) in order investigate their co-deposition mechanism. The FeNi layers were deposited at variable substrates (copper, brass, silver) under the same chemical (electrolyte composition) and electric plating (current density value) conditions. After applying various time, substrates and external magnetic field orientation, the quality of the obtained film was examined. The surface morphology and crystallographic texture variation were investigated by the Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Wavelength Dispersive X-ray Fluorescence (WDXRF) and Laser Confocal Scanning Microscope (LCSM). The anomalous co-deposition of iron group metals is evidently dependent on the substrate.

Нанопроволоки из сплавов FeNi и FeCo: синтез, структура и мёссбауэровские измерения

Nanowires (NWs) of FeNi and FeCo alloys were obtained by matrix synthesis based on galvanic filling of pores in track membranes. The change in the elemental composition of NWs when changing the composition of the electrolyte and when changing the deposition potential was studied. The effect of anomalous co-deposition of Fe is observed in the FeNi NWs: the iron content in the NWs is noticeably higher than that in the electrolyte. This difference increases when the initial concentration increases and when the growth potential decreases. An increase in the concentration of iron at the tops of the wires was also detected. For FeCo NWs, the composition corresponds to the composition of the electrolyte and did not change much when the potential changed. X-ray diffraction analysis allowed to determine the nature of changes in the spectra when the growth conditions change. The dependence of the X - ray spectra of FeNi on the growth potential is found- the intensity of the phase peaks changes. Mössbauer measurements revealed spontaneous magnetization for all samples of NW arrays along their axes. The dependence of the value of the ultrathin magnetic field Bh f on 57Fe nuclei on the composition of NWs (FexCo1−x and FexNi1−x) was obtained for the first time. It was found that the value of Bh f decreases with an increase in the speed of the electrodeposition process (or with an increase in the value of the deposition potential U).

Study of Ni63-Co37 nanocrystalline electrodeposited alloy as anti-wear coating on mild steel substrate

Ni63-Co37 nanocrystalline electrodeposited alloy is studied as wear protective coating on StW24 mild steel. The analyses of coatings composition by XRF demonstrate an anomalous codeposition behavior of Ni-Co alloy. SEM shows that saccharine leads to the nanometric granular grains of Ni-Co coatings. XRD pattern of Ni-Co deposits confirms that the addition of saccharin in the electrolyte leads to crystallites size in the nanometric order and also to the predominance of (111) as preferential crystallographic orientation. Vickers micro-indentation shows that the solid solution hardening and the Hall-Petch strengthening lead to hardness of Ni-Co coating three times higher than that of substrate. The pin-disc wear tests under dry sliding conditions reveal that Ni-Co coated steel has much higher wear resistance than the uncoated substrate thanks to its relatively higher hardness, but the coated substrate shows higher friction coefficient because the formation of uncompleted tribofilm on its worn surface due to its specific wear mechanism, where SEM observations on the wear tracks morphologies of the uncoated and Ni-Co coated substrate show that the mechanism governing the wear of the bare steel is an abrasive oxidative mechanism, whereas that of the Ni-Co coated substrate is a mixed adhesive-abrasive oxidative mechanism.

Electrodeposition of equiatomic FeNi and FeCo nanowires: Structural and magnetic properties

In the present work, equiatomic FeNi and FeCo magnetic nanowires (NWs) have been electrodeposited in Anodic Aluminum Oxide (AAO) membranes with 70 nm pore size. The role of the electroactive species Ni2+ and Co2+ on the anomalous codeposition behavior in thin films and nanowires has been discussed and compared. Field Emission Gun-Scanning Electron Microscope (FEG-SEM), X-ray diffraction (XRD) and Vibrating Sample Magnetometer (VSM) were used to evaluate the morphology, composition, crystalline structure and magnetic properties of the materials. SEM-FEG analysis showed very homogeneous NWs lengths for both FeNi and FeCo NWs, Energy dispersive X-ray spectroscopy (EDS) analysis revealed a stable composition along the FeCo NWs and a change in composition along the FeNi NWs. The XRD patterns indicate the predominance of the bcc structure for both alloys. Except for additional peaks of fcc phase found on FeNi alloy, the same crystalline bcc structure is observed after annealing treatment of 300 °C during 20 h. TEM analysis confirmed the ordered character of the bcc FeCo alloy. The hysteresis loops show an easy magnetization direction parallel to the wires due to the predominance of the shape anisotropy. The coercive field (Hc) of FeNi NWs increases with the length of the wires while that of FeCo NWs decreases. The annealing treatment doesn’t affect the magnetic properties of FeNi NWs, whereas a remarkable increase in the coercivity of the FeCo NWs is observed.

The influence of anomalous codeposition on few coating alloys properties

Due to the presence of tungsten, Fe-W alloys can be applied as anticorrosive coatings. However, the conditions in which they are obtained influence their polarization resistance. This paper investigates how to electrodeposit them in order to increase their anticorrosive properties. The Fe-W alloys were produced by electrodeposition in different experimental conditions. The samples were characterized by X-ray diffraction (XRD) and scanning electronic microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The corrosion resistance was evaluated by Tafel extrapolation. This paper reports that alloys that have higher mass composition of tungsten have higher polarization resistance, up to 9924.05 ohm∙cm². Fe-W alloys had 38.85–69.59% tungsten in mass basis, and the alloys with most tungsten were obtained with temperature of 60°C, continuous direct electric current density of 50 mA/cm², 0.01 mol/L iron sulfate concentration, 0.1 mol/L ammonium citrate and 0.1 sodium tungstate concentration. This study obtained alloys with higher tungsten composition, up to 69.59%, in comparison to papers with similar results of faradaic efficiency (10–15%). Using 0.1 mo/L iron sulfate concentration, the decrease of the temperature and the current density increases the tungsten composition, making the FeW alloys more anticorrosive.

Coupled Electrodeposition of Fe-Co-W Alloys: Thin Films and Nanowires.

The electrodeposition of Fe–Co–W alloys was examined using a rotating cylinder Hull (RCH) cell and conditions were determined to create nanowires. The metal ion reduction mechanism was a combination of induced and anomalous codeposition, with water reduction as a gas evolving side reaction, rending deposition into recesses a challenge. In thin film deposition, under kinetic control, the addition of Fe ions into the electrolyte, greatly reduced the Co partial current density, and thus it's content in the deposit. The change of Co partial current density was attributed to an anomalous codeposition behavior, but it had a minimal effect in changing the W wt% in the deposit, despite the expected inducing characteristic of Fe when codeposited with tungsten. Deposition conditions were determined to electrodeposit Fe–Co–W nanowires having similar concentration as the thin films. Nanowires were electrodeposited into polycarbonate membranes under pulsed current at room temperature.

Extraction Effect of Ni-Zn By Electrodeposition from Aqueous Acid Solutions

The electrodeposition of Zn-Ni is classified by Brenner (1) as anomalous codeposition, because zinc, the less noble metal, is preferentially deposited to nickel the more noble metal. The inhibition of H+ reduction occurs with increasing Zn ions concentration in solution (2). Anomalous codeposition is favored in chloride medium and inhibited in boric acid (3). The reaction kinetic of Zn-Ni codéposition was investigated in acid solutions .The effects of solution composition and pH were analyzed. The inhibition of H+ reduction occurs with increasing Zn ions concentration in solution. Increasing pH values causes Zn deposition during Ni-Zn codeposition. Anomalous codeposition is favored in chloride medium and inhibited in boric acid. When alloy deposition becomes the main process, the interfacial pH is governed by the individual metal deposition that controls the kinetic behavior. The interfacial pH increases during separate Ni deposition, meaning that it occurs with simultaneous consumption of H+. Anomalous codeposition process is not due to a saturation of species at the electrode surface. Results show that it is possible to obtain alloys rich in either nickel or zinc , from an acidic solution,depending on the Ni/Zn concentration ration. For Ni/Zn concentration ratios in the range of 1-5, zinc rich alloys are obtained despite Zn is the less noble metal and even when it is present lower concentrations than nickel. For the highest Ni/Zn concentrations ratio ≥100, the formation of the alloy occurs by a normal deposition, resulting in Ni-rich alloys. Boric acid extends the proton discharge potential to more cathodic values. Thus it can reduce anomalous codeposition since the presence of 0,8M of acid reduces the intensity of the peak corresponding to δ phase that is rich in zinc and enhances the intensity of γ phase containing more nickel than the δ phase.

Electrochemical nucleation and growth of Zn-Ni alloys from chloride citrate-based electrolyte

In this work, the effects of deposition potential, [Ni2+]/[Zn2+] molar ratio, pH and bath temperature on the electrocrystallization mechanism of ZnNi alloy from an aqueous solution containing zinc chloride (ZnCl2), nickel chloride (NiCl2) and tri‑sodium citrate as complexing agent were studied. The Zn–Ni alloys were deposited from solutions with different molar ratios (0.25; 1; 2; 4), pHs (1.5; 3; 4) and bath temperatures (20; 40; 60°C). Scharifker and Hills model, used to analyze the potentiostatic current transients, revealed that in a plating bath containing low [Ni2+]/[Zn2+] molar ratios (R≤1), the nucleation mechanism was instantaneous with a typical three-dimensional (3D) growth process, regardless of the bath pH and temperature. In Ni-rich electrolytes (R≥2), the nucleation becomes more consistent with the theoretical progressive nucleation type. The nuclei number density increased with increasing the applied cathodic potential and bath pH and decreases for both of high [Ni2+]/[Zn2+] molar ratios in solution and elevated plating temperatures. The morphological, compositional and structural characterizations of the deposits were carried out using Field-Emission Scanning Electron Microscopy (FESEM), Wavelength Dispersive X-ray Fluorescence Analysis (WDXRF) and X-ray diffraction (XRD) respectively. The obtained results revealed that nickel content of the coatings was increased by increasing cathodic potential and [Ni2+]/[Zn2+] molar ratio and ranged between 5.82 and 29.3wt% (6.44–31.59at.%). ZnNi alloys coated at room temperature from an equimolar ([Ni2+]/[Zn2+]=1) bath were composed of a mixture of two major phases: the δ-phase (Ni3Zn22) with a monoclinic structure and the γ-phase (NiZn3) with an orthorhombic structure, while for deposits obtained in Ni-rich bath, the γ-NiZn3 phase was particularly prevailing. A mechanism of anomalous co-deposition of zinc with nickel is proposed and discussed.