Composition and structure of Ni-Co coating depending on the ratio of Ni and Co in a citrate electrolyte (original) (raw)
Related papers
2015
Ni-Co alloys with varying cobalt content are electrodeposited in stationary potentiostatic mode employing citrate electrolyte, either with or without addition of saccharin (SHR) at different Ni/Co ratios and variable content of sodium citrate (Na3citrate) in the electrolyte. The changes in the microstructure, chemical composition and cathodic current efficiency of deposition (CCE) of Ni-Co alloys are studied. Scanning electron microscope, energy dispersive X-Ray and atomic absorbtion analysis are used to characterize the alloy coating.The alloy deposition is proved to be of an anomalous type. It is found that with the increase of the value of ratio Ni/Со in the solution from 1 to 5, the percentage of Ni in the Ni-Co alloy grows to 48 mass %, and the CCE decreases to about 70 %, whereas more fine-crystalline Ni-Co coatings (size of crystallites less than 100 nm) are deposited. The addition of SHR results in a strong decrease of CCE (up to 50 %), but also in formation of smooth and sh...
2015
In the paper the results from the study of the kinetic of joint electrodeposition of Ni and Co in Ni-Co alloy system are reported. It is found that the co-deposition of Ni and Co in Ni-Co alloy system in slightly acidic citrate electrolyte occurs under combined diffusion-kinetic control with a typical mechanism of nucleation similar to those in the case of Co. The application of the method of chronoammetry proved that the mechanism of nucleation for Ni-Co alloy is spontaneous with three-dimensional nucleation and nuclei growth. The difference in the independent deposition mechanisms of the two metals is a possible explanation for their anomalous co-deposition in the electrolyte examined. The anomalous codeposition is more clearly noticeable in electrolytes with higher content of cobalt than nickel. The SEM-analysis proves that the alloys enriched in cobalt have crystallites with more even and rounded shape, which is expected in the case of spontaneous nucleation.
Composition, morphology, structural aspects and electrochemical properties of Ni–Co alloy coatings
Surface and Coatings Technology, 2011
Nickel-cobalt alloys having settled composition can be produced by electrolysis after optimising process operative conditions. In this work nickel-cobalt coatings on 1050 Al net, obtained by electrodeposition under galvanostatic conditions, were investigated. Ni-Co coatings were electrowon, from an acidic sulphate bath containing 40 g/L Ni and Co in the range 0.1-16 g/L, at 60°C temperature and 300 A/m 2 average current density. The experimental results highlight a linear correlation between bath and deposit Co/Ni ratio, with slope change for Co concentration in the electrolyte higher than 3 g/L. Morphology, structure and electrochemical properties are strictly correlated among themselves and with the composition of the coating.
2015
The elecrodeposition of Ni and Co was studied by electrochemical techniques in varying compositions of slightly acidic citrate electrolyte. Cyclic voltammetry and current transient measurements were used to characterize the initial stages of nucleation, growth mechanism and electrodeposition of Ni and Co. The voltammetry analysis showed that the electrodeposition of both Ni and Co occurs under diffusion-kinetic control associated with a typical nucleation process. The deposition of Ni is in one act of charge transfer with exchange of two electrons, the deposition of Co is a two-stage process of reduction of free cobalt ions to cobalt, and reduction of complex ions type CoCit - to cobalt. The application of the method of chronoammetry proved that for cobalt the mechanism of nucleation is spontaneous, with three-dimensional nucleation and nuclei growth, while for nickel the slower progressive mechanism of nucleation is typical. The differences in the deposition mechanisms of the two m...
Electrodeposition of Ni-Co alloy on chemically oxidized Al
2015
The kinetics of deposition of Co, Ni, and Ni-Co from low-acid citrate electrolyte on Cu and on chemically oxidized Al is compared. It is found that the formation of Ni-Co alloy on the Al cathode is hampered to a greater extent in comparison with the Cu electrode. In both cases (Cu and Al electrodes) "anomalous" co-deposition of Co and Ni is registered especially in an electrolyte with higher content of Ni. In case of deposition on Al cathode in stationary potentiostatic mode (cpm), the content of Co in the Ni-Co alloy is by 10 wt% higher than that in case of deposition of Ni-Co on Cu cathode. The Ni-Co alloy deposited on Al may be characterized as island-style coating, with spheroidal shape of the crystals (10-17 µm). The application of pulse potential mode (ppm) of deposition on the Al cathode leads to increased structural homogeneity and higher extent of filling the surface with crystals of Ni-Co alloy. The effect of the application of pulse potential mode, however, is s...
Electrodeposition of Co-Ni alloy from citrate-acetate bath on steel substrate
Zenodo (CERN European Organization for Nuclear Research), 2007
Cobalt-nickel electrodeposition on steel substrate was carried out from solutions containing nickel sulfate, cobalt sulfate, sodium sulfate and sodium citrate and sodium acetate with 1 : 2 and 2 : I ratio respectively. The study dealt with the influence of bath composition, current density, pH, time of deposition, temperature and additives such as saccharin and thiourea on cathodic current efficiency. Throwing power and throwing index was calculated for the best bath for deposition. Also cyclic voltammograms was detected for the optimum bath composition. The efficiency for deposition from citrate-acetate mixed bath is higher than that reported for the separated citrate and acetate baths. The surface morphology of Ni-Co alloy was investigated by using scanning electron microscopy (SEM) while the structure was studied by using X-ray diffraction analysis.
Influence of pH on the electrolytic deposition of Ni–Co films
Thin Solid Films, 2008
Ni-Co alloys obtained by electrolytic deposition on a paraffin impregnated graphite electrode have been characterised by cyclic voltammetry, scanning electron microscopy with energy dispersive X-ray microanalysis, and time of flight secondary ion mass spectrometry (ToF-SIMS), with the objective of qualitatively assessing and comparing their composition and the distribution of chemical species. The effect of pH on the composition and morphology of the deposit and on the proportion of the hydrogenated forms of Ni and Co has been investigated. It has been determined that the predominant species, which give rise to the ToF-SIMS positive ion spectra of the deposits, are the pure metals, their hydrides, hydroxides and oxides as a hydrogen. In negative secondary ion spectra, the most favourable species were found to be: O, OH, as well as hydrides, hydroxides and hydrated ions of the two metals. The proportion of individual species changed depending on the electrolyte pH. The content of Co in the deposit corresponds to the content of Co in the electrolyte and increased moderately with increasing pH value, corresponding to the regular deposition behaviour of Ni-Co film rather than an anomalous deposition.
European Scholar Journal (ESJ), 10
A nickel sulfate solution with a Co suspension was used to electroplate Ni-Co alloy coatings onto a brass substrate. The impacts of the plating bath's pH, temperature, length of time, nanoparticle concentration, and current density on the coating's composition were examined. The best conditions were (C.D. 2A/dm 2 , 55 o C, 60 min, and pH 8) deposit surfaces were examined by X-ray diffraction thin film and Vickers microhardness. The surface hardness peaked at 2 A/dm 2 (278 HV), which is the greatest value possible. It is evident that more cobalt is deposited as the current intensity increases, raising the bath's cobalt concentration by more than 15 g/l. According to the results, the rate of Ni-Co deposition is affected by pH, rising from 7 to 9.5 while falling Co% at pH values over 7.5. At 33 °C, the layer deposition rate was 30 mg/dm 2 .min, rising to 40 mg/dm 2 .min at 63 °C, then dropping to 35 mg/dm2.min as the bath temperature increased to 73 °C. Low deposition rate and temperature were observed in cathodic deposits.
Morphology and composition of Ni–Co alloy powders electrodeposited from ammoniacal electrolyte
Journal of Solid State Electrochemistry, 2006
In this paper, the morphology and phase structure of Ni-Co powders electrodeposited from ammoniacal electrolyte are investigated as a function of alloy powder composition. Composition of the electrolyte, i.e. the ratio of Ni 2+ /Co 2+ concentration is found to influence both, the phase structure and the morphology of Ni-Co alloy powders. It is shown that the current density practically does not influence the morphology of Ni-Co alloy powders as well as alloy powder composition. At the highest ratio of the Ni 2+ /Co 2+ ions typical spongy particles were obtained. With the decrease of the Ni 2+ /Co 2+ ions ratio agglomerates of the size of about 100 lm, composed of a large number of fern-like dendrites on their surface were obtained. At the lowest Ni 2+ /Co 2+ concentration ratio, among more dendritic particles, agglomerates typical for pure Co powder deposition were detected. It is also shown that depending on the Ni 2+ /Co 2+ ratio different types of Ni and Co codeposition could be detected: anomalous and irregular. At the Ni 2+ /Co 2+ ions ratio higher than 1 only b-Ni phase was detected, while at concentration ratios Ni 2+ /Co 2+ <1 h.c.p. a-Co phase together with b-Ni phase was detected in the alloy powder deposit.