Comparison of the critical conditions for initiation of dendritic growth and powder formation in potentiostatic and galvanostatic copper electrodeposition

Critical current densities for the initiation of dendrite growth and powder formation in potentiostatic and galvanostatic deposition are determined. Induction times for dendritic growth formation in potentiostatic and galvanostatic deposition are discussed.Nomenclature C ₀ bulk concentration - D diffusion coefficient - F Faraday constant - h height of a protrusion - h _i height of ith protrusion - h ₀ initial height of a protrusion - i current density - i _c current density at which dendrites appear instantaneously - i _i minimal current density at which dendritic growth becomes possible - i _L limiting current density - i ⁰ initial current density - i ₀ exchange current density - k proportionality factor - n number of electrons - N number of protrusions - R _t tip radius - S electrode surface area - S ₀ initial electrode surface area - t time - t _i induction time - V molar volume - thickness of the diffusion layer - overpotential - _c critical overpotential of instantaneous dendritic growth - _c,t critical overpotential of dendritic growth following non-dendritic roughness amplification - _i critical overpotential for the initiation of dendritic growth - ₀ initial overpotential - 2.3 ₀ slope of the Tafel line - quantity defined by Equation 3 - surface tension - time constant     

析氢对电沉积镍枝晶生长的影响

采用点电极电沉积的方法,在环形电解池中用自行设计的试验装置研究了不同电压和NiSO4质量浓度时,析氢对电沉积金属镍枝晶二维生长行为的影响。研究发现,析氢对沉积产物的形貌影响显著,氢气的大量析出有利于枝晶产生分枝,使沉积物的形貌趋于致密。     

Synthesis and characterization of nickel tungsten alloys by electrodeposition

The objective of the current work was to study in detail the effect of bath chemistry, additives and operating conditions on the chemical composition, microstructure and properties of Ni-W alloys deposited from citrate-containing baths, in the absence of ammonia or ammonium salts, on stationary working electrodes. The morphology of the deposits was studied by scanning electron microscopy (SEM) as well as atomic force microscopy (AFM), and the approximate composition by energy dispersive spectroscopy (EDS). Metallographic cross-sections were also analyzed, and micro-hardness tests conducted. The results are discussed in detail with emphasis on routes to increase the tungsten content and deposit thickness, while reducing the extent of cracking.     

Nucleation and crystal growth in gold electrodeposition from acid solution Part II: Hard gold

The mechanism of nucleation and crystal growth of hard gold (Au-Ni) on a gold rotating disc electrode from a proprietary bath (Renovel N) was investigated using linear sweep voltammetry and chronoamperometry. It was shown that two distinct mechanisms in two potential ranges are involved in this process. Experimental current-time transients at more positive potentials were described in terms of three-dimensional progressive nucleation and growth of right-circular cones. Time-independent inhibition of the vertical crystal growth was observed with an increase in negative potential, similar to the soft gold deposition. A modified inhibition model, in which vertical growth rate was assumed to decrease exponentially with time to a constant value, was derived to interpret experimental current-time transients recorded at more negative potentials. The chronoamperometric transients were well described by this model. Potential dependence of initial minima, maxima and final steady-state current was discussed.     

Nucleation and crystal growth in gold electrodeposition from acid solution Part I: Soft gold

The initial stages of gold electrodeposition on a gold electrode were studied in a proprietary bath (Renovel N) using linear sweep voltammetry and chronoamperometry. Tafel plots with two different slopes were obtained, indicating that the mechanism for gold deposition depends on potential. An inhibition phenomenon was observed during gold electrocrystallization. Experimental current-time transients were analysed using nonlinear least-squares approximations by various models of nucleation and crystal growth. The electrodeposition mechanism changes from three-dimensional progressive at lower overpotentials to three-dimensional instantaneous at higher overpotentials. Moreover, additional two-dimensional progressive or a secondary three-dimensional progressive processes take place in certain potential ranges. It was shown that the outward growth rate of the substrate's base plane displays a linear Tafel relationship whereas the vertical growth rate of gold crystals decreases at more negative potentials due to an inhibition process.     

Simulation of electrochemical nucleation in the presence of additives under galvanostatic and pulsed plating conditions

Galvanostatic nucleation of copper onto pretreated ruthenium is investigated using experimental methods and numerical simulations in the presence of two different suppressor molecules; polyethylene glycol (PEG) and ethylene glycol-propylene glycol-ethylene glycol block copolymer (EPE). The model parameters have been largely determined from electrochemical characterization. Results suggest that a fast adsorption rate of the suppressor results in higher nucleus densities. Simulation results provide insight why EPE is more effective than PEG at increasing nucleus density. In addition, the simulations are used to predict the impact of pulse plating paramaters, showing that both the properties of the additive and the waveform need to be considered to optimize nucleus density enhancement.     

Effect of surface pretreatment on the galvanostatic oxidation of nickel

The open-circuit, cathodic reduction and anodic charging characteristics of oxide films on both electropolished and electropolished + HNO₃ etched nickel electrodes have been studied in aqueous Na₂SO₄ solutions. While the oxide film thicknesses are approximately the same, the film on etched nickel dissolves much more rapidly than that on electropolished nickel. To galvanostatically passivate etched nickel at charging rates in the range 20–200 μA cm^?2 in pH 2.8 Na₂SO₄, the rate of oxide chemical dissolution has to be substantially decreased and this is achieved by lowering the electrolyte temperature from 25°C to 5°C. The transient anodic passivation charge thus observed for etched nickel is ～ 2x larger than that for electropolished nickel. With either pretreatment, the current efficiency for oxide formation is low (～ 20%), the majority of the transient charge (～ 80%) accounted for by Ni²⁺ in solution. Chemical dissolution of the oxide alone cannot explain the observed charging differences between etched and electropolished nickel since the individual charges and oxide formation current efficiencies are not influenced by anodic charging rate or solution aggressiveness. The results are best explained in terms of a continual breakdown and repair of the oxide film at defect areas during anodic charging, with most of the charge consumed by inefficient film repair. The influence of the oxide defects and the reason for the differences in behaviour between electropolished and etched nickel are discussed.     

Model of nickel electrodeposition from acidic medium

A step-wise computer model is presented for simultaneous deposition of nickel and nickel hydroxide in aqueous solutions. In acidic solutions ({pH} 1), the potentiostatic current-time transient response on glassy carbon or titanium was analysed with respect to nucleation and radial growth mechanism. pH changes influence the current-time response greatly. A marked maximum in the current transient appears for slightly acidic solutions ({pH} 4.5) and a consecutive decrease in the deposition current density at long times is obtained. This behaviour is attributed to early precipitation of nickel hydroxide due to a local pH increase at the cathode surface.     

Fabrication of egg-shell-roofed macroporous nickel films by a template-mediated electrodeposition process

Through an electrostatics-induced adsorption effect, nickel ions were found to be preferentially adsorbed onto the surface of colloidal particles at template top during the template-mediated electrodeposition process for preparing macroporous structures. This phenomenon results in the preferential reduction and growth of nickel on colloid surface on the template top, instead of filling into the channels among the colloids. After removing the template, an egg-shell-roofed macroporous nickel, consisting of macroporous film covered with monolayer of hollow spheres, can be created.     

Anodic formation of thin CdS films. I. Kinetics and mechanisms under galvanostatic and potentiodynamic conditions

The formation of thin anodic films of CdS is studied in 1 mol dm^–3 NaHCO₃ + 0.1 mol dm^–3 Na₂S solutions under galvanostatic and potentiodynamic conditions. Under both experimental conditions, films up to about 50 Å are formed according to the high field model of growth. In this thickness range an insufficient space charge is developed to noticeably affect the kinetics. From galvanostatic experiments at different temperatures, the activation energy was determined to be 10.6 kcal mole^–1. The surface density,N of the species participating in the rate determining step is unusually low, about 5×10⁶ cm^–2. So low a value forN precludes a process at the Cd/CdS interface as the rate determining step. The significance of various parameters in the observed rate equation are compared with and discussed in relation to the respective parameters in the rate equations developed for the high field model of growth.     

Effect of nickel impurities on zinc electrodeposition

The kinetics of nickel-zinc co-deposition and the effect of nickel on zinc morphology have been studied by means of chemical analysis, X-ray diffraction and SEM observations of cathodic deposits obtained in various experimental conditions, including acid and alkaline baths. It has been shown that nickel ions, even if present in the electrolyte at very low concentrations (1 ppm), do not deposit under mass transport controlled conditions but are dragged by zinc ions whose concentration influences the nickel current. With regard to zinc morphology, it has been observed that nickel reduces the grain size of the zinc crystals formed during the electrodeposition.     

Investigations on electrodeposition of nickel from dimethylsulfoxide

Process of cathodic deposition of nickel mainly from Ni(BF₄)₂ solution in DMSO has been investigated using various experimental techniques. It has been found that this process is complicated. The collected experimental data indicate that passivation of fresh cathodic layer of Ni by chemisorption of DMSO molecules takes place. By basing on the rde methods the values of αn_m = 0.4 (± 0.05) and k_fh = f(E_c) have been estimated.     

Exploratory study of copper particles electrodeposition on nickel by induction heating

Copper and the oxides which are spontaneously formed on its surface have numerous interesting properties that can be exploited in fields such as catalysis, gas sensing, antimicrobial activity, etc. Furthermore, metallic nanoparticles (NPs) have many size-dependent properties such as a large surface area to volume ratio that can enhance these copper/copper oxides properties. This work aims to highlight the beneficial effect of induction heating versus conventional heating on the electrodeposition of copper particles on nickel substrates. We showed that in temperature-equivalent conditions, conventional heating leads to a low coverage of the Ni electrode with weakly adherent copper microparticles (these particles having a very large size distribution and uncontrolled morphology) while induction heating leads to a high coverage of the surface with copper nanoparticles (these particles having a sharp unimodal size repartition and a truncated octahedron/octahedron shape exposing mainly (1 1 1) facets). Furthermore, while no crystalline copper oxide could be highlighted for copper nanoparticles electrodeposited at room temperature, induction heating leads to the formation of a crystalline Cu₂O shell that could have interesting catalytic properties, among others.     

Development of an electrodeposition nickel polymer composite by a zwitterionic surfactant

A nickel-fluoropolymer composite was produced by electrodeposition. This composite offers many attractive properties that make it ideal for a wide range of industrial applications; it offers very low friction and wear properties on sliding contact surfaces. Several studies were carried out with aqueous zwitterionic surfactant solutions. Critical micelle concentrations, area occupied per molecule, surface excess concentration, free energy of micellization, adsorption, and efficiency were investigated at the solution-air interface. The relationship between the adsorption isotherm at the solution-air interface and at the solid-solution interface was studied. Moreover, the mechanism of incorporation of polytetrafluoroethylene was suggested, and the relationship between thermodynamic parameters of the surfactant and the development of a composite coating was investigated. The results are discussed according to the critical micelle concentrations of the zwitterionic surfactants.     

Magneto-sensitive nickel nanowires fabricated by electrodeposition into multi- and single-ion track templates

Polycarbonate templates of (30±1) μm thickness containing cylindrical etched-track nanochannels of (500±50) nm diameter were used for electrodeposition of Ni nanowires. Using 10⁴ channels per cm², the most favourable deposition potential of  − 1.0 V was determined in a potentiostatic mode by varying the deposition potential with respect to an Ag/AgCl reference electrode over a range between  − 0.1 V and  − 1.5 V. The deposition efficiency at  − 1.0 V was estimated around 10%. The resulting single wires had a resistance around 200 Ω and showed an anisotropic magnetoresistance (AMR) effect of 1%, applicable to directionally sensitive magnetic field sensors.     

Effect of temperature on nickel electrodeposition from a nickel sulfamate electrolyte

The effect of temperature on nickel electrodeposition from a nickel sulfamate electrolyte has been investigated. All the experimental points in a plot of nickel film thickness vs. current density collapse onto a single straight line irrespective of deposition temperature. A relation derived from the Butler–Volmer equation is successful in predicting cathode potential shifts caused by change of deposition temperature. Moreover, an interface width, which characterizes the roughness of the surface and is defined by the root mean square of fluctuation in the height, is shown to have a saturated value that is related to the deposition temperature. Thus, two kinds of activation energies for the charge transfer reaction and for grain growth are estimated from the temperature dependence of the cathode potential shift and the grain size.     

Oxide film growth on Al-In alloys in a borate buffer solution in conditions of galvanostatic anodising

Anodic oxide films have been formed galvanostatically on Al-In alloys (containing up to 0.074% In) in a borate buffer solution (pH 7.8) at different current densities (20-100 μA cm⁻²). The mechanism, kinetics of growth and properties of formed oxide films have been investigated. The study of charge curves suggests that the growth of oxide films on Al-In alloys occurs by an activation-controlled ionic conduction under the influence of the high electric field through the oxide film according to an exponential law, like on valve metals. The following parameters have been calculated: the constants of the exponential law, ionic conductivity through the film, the effective activation distance for ion movement and the corresponding field strength. The values for the field strength, of the order of magnitude of 10⁶ V cm⁻¹, justify the application of the high field migration mechanism. Properties of anodic oxide films have been determined by means of electrochemical impedance spectroscopy; the resistance and thickness of the oxide film have been found to increase with the increase in the indium content in the alloy and with increased anodic current density. It has been established that the current efficiency in oxide films formation on Al-In alloys is lower than 100%: the increase of the indium content in the alloy, as well as the increase in anodic current density, increases the value of current efficiency.     

Effect of nickel on the electrodeposition of copper

The mechanism of copper electrocrystallization from various solutions has been investigated to determine the influence of foreign cations and, particularly, of nickel. The study was performed by cyclic voltammetry and scanning electron microscopy. In sulphate solutions the Na⁺ and NH⁴⁺ cations affect the copper deposition by changing the nucleation overpotential and the presence of nickel cations makes the copper deposition easier by decreasing the nucleation overpotentials of both copper and nickel. In chloride solutions, the strong adsorption of the chloride species prevents all other influences by blocking the active sites of nucleation and growth and, therefore, Na⁺ or NH⁴⁺ addition does not modify the copper deposition. Consequently, the nickel does not modify the nucleation overpotential of copper. Whatever the solution, sulphate or chloride, the anodic behaviour of the copper-nickel codeposits are similar to the anodic behaviour of bulk Cu-Ni alloys.     

Kinetics of electrodeposition of nickel from watts baths

Tafel slopes and reaction orders for the electrodeposition of nickel from Watts type baths onto a vitreous carbon electrode have been determined by both steady state and transient methods. After correcting the currents for concurrent hydrogen evolution, and taking the composition of the deposit into account, the following kinetic parameters have been obtained: Tafel slope 120 mV decade^?1, reaction orders with respect to nickel and chloride both +1. The agreement between the two methods was excellent. No dependence of cathodic rate constants on pH could be found. The cathodic results do not therefore support the widely held opinion that an adsorbed complex involving a hydroxide ion is an intermediate in active dissolution.Results for the nucleation constant are given in the Appendix. The nucleation constant for nickel on vitreous carbon is found to depend on potential and concentration of nickel ions, and to be independent of pH and concentration of chloride ions.     

Improving electrochemical performance of NiO films by electrodeposition on foam nickel substrates

NiO films for lithium-ion batteries were deposited on copper plates and foam nickel substrates by electrodeposition and subsequent heat treatment at 300 °C. At a discharge/charge rate of 0.1 C, foam NiO films delivered reversible capacity larger than 650 mAh g⁻¹ and capacity retention over 93% after 50 cycles. NiO films deposited on foam nickel exhibited higher reversible capacity, better cyclability, as well as higher rate capability than those on copper plates. The unique three-dimensionally porous morphologies of foam NiO films were responsible for the better electrochemical performance, which provided not only high electrode/electrolyte contact area but also a good electronic conduction matrix. The present finding offers a new pathway for the large scale fabrication of high-energy-density electrodes for lithium-ion batteries.