Search Results (7)

Cobalt–nickel–copper alloys were electrodeposited over a range of current density and with three different aqueous electrolytes having variable metal ion ratios, in order to examine changes in the deposit composition and to use them as cathodes for nitrate electrolysis. The alloys were electrodeposited galvanostatically from a citrate electrolyte onto rotating cylindrical steel substrates. The electrodeposition process exhibited anomalous codeposition behavior, favoring Co reduction over Ni and Cu. These electrodeposits were then used to examine their ability to reduce nitrate in simulated wastewater with 50 mg-N/L of NO₃⁻, sodium chloride, and sodium sulfate. Nitrate conversion and selectivity were characterized after electrolysis in a single-compartment cell with the alloys serving as the working electrode. Despite co-evolving hydrogen, the electrodeposited alloys were effective at generating both N₂ at high electrolysis current densities and ammonia species at lower values, with the deposit composition also affecting the conversion and products. It is the first demonstration of using Co-Ni-Cu ternary alloys for nitrate reduction. Full article

This study investigates the electroplating characteristics of Co-Zn alloy coatings with varying Zn contents (0.55 wt.%~8.8 wt.%) and their influence on intermetallic compound (IMC) formation during reactions with Sn solder. Co-Zn alloy coatings were successfully fabricated by electroplating using cobalt plating solutions with different concentrations of zinc sulfate. The results reveal anomalous co-deposition behavior, where the less noble Zn preferentially deposits over Co. Surface morphologies and microstructures evolve significantly with increasing Zn content, transitioning from columnar to dendritic structures. Zn incorporation into the Co lattice disrupts its crystallinity, leading to decreased crystallinity and partial amorphization. Liquid-state and solid-state interfacial reactions with Sn solder demonstrate that Zn content considerably influences IMC formation. In liquid-state reactions at 250 °C, lower Zn contents (0.55–4.8 wt.%) slightly enhance CoSn₃ growth. It exhibits a dense layered-structure without IMC spallation. In contrast, a higher Zn content (8.8 wt.%) significantly reduces IMC formation by approximately 50% and produces a duplex structure with two distinct layers. In solid-state reactions at 160 °C, the suppression effect becomes even more pronounced. The Co-0.55Zn deposit exhibits significant inhibition of CoSn₃ growth, while the Co-8.8Zn sample forms only a thin IMC layer, achieving a suppression rate exceeding 85%. These findings demonstrate that Zn doping effectively limits CoSn₃ formation during solid-state reactions and improves interfacial stability. Full article

The aim of this study was to systematically analyze the influence of potential and the Co(II)–Ru(III) molar ratio on the electrochemical behavior of the Co–Ru system during codeposition from acidic chloride electrolytes. The equilibrium speciation of the baths was investigated spectrophotometrically and compared with theoretical calculations based on the stability constants of Co(II) and Ru(III) complexes. The codeposition of the metals was characterized using electroanalytical methods, including cyclic voltammetry, chronoamperometry, and anodic stripping linear voltammetry. The alloys obtained at different potentials were analyzed for their elemental composition (EDS, mapping), phase composition (XRD), and surface morphology (SEM). The morphology and composition of the alloys were mainly dependent on the deposition potential, which controlled the cobalt incorporation. Ruthenium–rich alloys were produced at potentials of −0.6 V and −0.7 V (vs. SCE). In these conditions, cobalt anomalously codeposited due to the formation of the CoOH⁺ intermediate, triggered by the intense hydrogen evolution on the ruthenium sublayer. Bulk cobalt electrodeposition began at a potential of around −0.8 V, resulting in the formation of cobalt-rich alloys. The early stages of the electrodeposition were investigated using different nucleation models. A transition from 2D progressive nucleation to 3D instantaneous nucleation at around −0.8 V was identified as being caused by cobalt incorporation. This was well correlated with electroanalytical data, partial polarization curves of alloy deposition, elemental mapping analysis, and the structure of the deposits. Full article

Gradient-structured ternary Fe-Co-Ni alloy coatings electrodeposited on steel substrates at various current densities from chloride baths were numerically and experimentally investigated. The electrodeposition process, considering hydrogen evolution and hydrolysis reaction, was modelled using the finite element method (FEM) and was based on the tertiary current distribution. The experimentally tested coating thickness and elemental contents were used to verify the simulation model. Although there was a deviation between the simulation and experiments, the numerical model was still able to predict the variation trend of the coating thickness and elemental contents. The influence of the current density on the coating characterization was experimentally studied. Due to hydrogen evolution, the coating surface exhibited microcracks. The crack density on the coating surface appeared smaller with increasing applied current density. The XRD patterns showed that the deposited coatings consisted of solid-solution phases α-Fe and γ (Fe, Ni) and the metallic compound Co₃Fe₇; the current density in the present studied range had a small influence on the phase composition. The grain sizes on the coating surface varied from 15 nm to 20 nm. The microhardness of the deposited coatings ranged from 625 HV to 655 HV. Meanwhile, the average microhardness increased slightly as the current density increased from 5 A/dm² to 10 A/dm² and then decreased as the current density further increased. Finally, the degree of anomaly along with the metal ion and hydrogen atom concentrations in the vicinity of the cathodic surface were calculated to investigate the anomalous codeposition behaviour. Full article

In this study, to explore the effect of Co contents on the electroplated Fe–Co–Ni samples, three different Fe–Co₃₃–Ni₆₂, Fe–Co₄₃–Ni₅₃, and Fe–Co₆₁–Ni₃₆ samples were electrochemically grown from Plating Solutions (PSs) containing different amounts of Co ions on indium tin oxide substrates. Compositional analysis showed that an increase in the Co ion concentration in the PS gives rise to an increment in the weight fraction of Co in the sample. In all samples, the co–deposition characteristic was described as anomalous. The samples exhibited a predominant reflection from the (111) plane of the face–centered cubic structure. However, the Fe–Co₆₁–Ni₃₆ sample also had a weak reflection from the (100) plane of the hexagonal close–packed structure of Co. An enhancement in the Co contents caused a strong decrement in the crystallinity, resulting in a decrease in the size of the crystallites. The Fe–Co₃₃–Ni₆₂ sample exhibited a more compact surface structure comprising only cauliflower–like agglomerates, while the Fe–Co₄₃–Ni₅₃ and Fe–Co_61–Ni₃₆ samples had a surface structure consisting of both pyramidal particles and cauliflower–like agglomerates. The results also revealed that different Co contents play an important role in the surface roughness parameters. From the magnetic analysis of the samples, it was understood that the Fe–Co₆₁–Ni₃₆ sample has a higher coercive field and magnetic squareness ratio than the Fe–Co₄₃–Ni₅₃ and Fe–Co₃₃–Ni₆₂ samples. The differences observed in the magnetic characteristics of the samples were attributed to the changes revealed in their phase structure and surface roughness parameters. The obtained results are the basis for the fabrication of future magnetic devices. Full article

The influence of bath hydrodynamics on the resultant micromechanical properties of electrodeposited nickel-cobalt alloy system is investigated. The bath hydrodynamics realized by magnetic stirring is simulated using COMSOL Multiphysics and a region of minimum variation in velocity within the electrolytic cell is determined and validated experimentally. Nickel-cobalt alloy and nickel coating samples are deposited galvanostatically (50 mA/cm²) with varying bath velocity (0 to 42 cm/s). The surface morphology of samples gradually changed from granular (fractal dimension 2.97) to more planar (fractal dimension 2.15) growth type, and the according average roughness decreased from 207.5 nm to 11 nm on increasing the electrolyte velocity from 0 to 42 cm/s for nickel-cobalt alloys; a similar trend was also found in the case of nickel coatings. The calculated grain size from the X-ray diffractograms decreased from 31 nm to 12 nm and from 69 nm to 26 nm as function of increasing velocity (up to 42 cm/s) for nickel-cobalt and nickel coatings, respectively. Consecutively, the measured Vickers microhardness values increased by 76% (i.e., from 393 HV0.01 to 692 HV0.01) and by 49% (i.e., from 255 HV0.01 to 381 HV0.01) for nickel-cobalt and nickel coatings, respectively, which fits well with the Hall–Petch relation. Full article

A comparison was performed between Co-Ni thin films and template-assisted nanowires arrays obtained by electrochemical co-deposition. To reduce the effects of anomalous deposition and increase the Ni content in the deposit, an electrolyte with three times more Ni than Co in atomic ratio was chosen. Electrochemical deposition was performed at constant potentials chosen in the range from E = −0.8 to −1.2 V vs. Ag/AgCl. Cyclic voltammetry, chronoamperometry, and charge stripping techniques were used to characterize and compare the electrochemical behavior of Co-Ni films and nanowires. Morphological and compositional characterization was performed by scanning electron microscopy (SEM/EDAX) to assess the influence of the deposition potential on the growth of film and nanowires. A comprehensive analysis of the deposit growth rates for thin films and nanowires is presented taking into consideration the hydrogen evolution and anomalous deposition. The comparative study of the composition of film and nanowires obtained at different deposition potentials has shown that deposition of nanowires with a film-like composition takes place at more positive potential than thin film. Full article