Electrochemical processes during plating Fe powder particles by Ni and Ni/Cu coating in the fluidized bed (original) (raw)
Related papers
The study of Ni–Co alloy deposition on iron powder particles in a fluidized bed from sulphate bath
Journal of Solid State Electrochemistry, 2006
This paper describes a process of electrolytic deposition of nickel–cobalt (Ni–Co) binary alloy on Fe powder. Electrochemical behavior of this binary alloy was studied by cyclic voltammetry with a paraffin impregnated graphite electrode as a working electrode. Deposition of individual metals (Ni, Co), as well as the simultaneous nickel–cobalt co-deposition, was performed in aqueous solutions (Watts-type electrolyte) both with and without Fe powder. Special attention was paid to the influence of suspension density on the electrode process. This density affects on the quality of iron powder electroplating. Preferential deposition of the less noble metal (Co) leading to its higher content in the deposit was observed in contrast to the more noble one (Ni) in spite of higher content of Ni in the plating solution. This anomalous phenomenon–known already for other metals (Zn, Cd, Sn)–has been confirmed and investigated for iron-group metals (Fe, Co, Ni) in this work. Electrolytic deposition of Ni–Co binary alloys, including anomalous behavior is a complicated process. Understanding the anomalous behavior would lead to better control of the deposition process and to explanation of the mechanism of Ni–Co co-deposition.
Impedance study of Ni–Co electro-deposition on Fe powder particles in fluidised bed systems
Journal of Solid State Electrochemistry, 2006
The electrochemical impedance method was applied during the electrochemical deposition of a binary Ni-Co coating on iron powder in a fluidised bed electrode system. The influence of the suspension density on the charge transfer in the course of the electro-deposition process was studied. At a potential of À900 mV (vs. Ag/AgCl/3 M KCl), when the binary Ni-Co layer was formed, the impedance data were characterised by two semicircles with the semicircle at high frequencies being larger in magnitude. A contribution of the diffusion process to the overall current was observed. The optimal suspension density for the charge transfer in the bed was 10·10 À3 -15·10 À3 (i.e., 4-6 g of iron powder in 50 ml of electrolyte). The most probable mechanism of the charge transfer for the studied concentrations of powder particles is the convective mechanism. The iron particles dispersed in the electrolyte were considered to act as either a depolariser or an additional working electrode depending on the applied electrode potential and on the suspension density.
Chemistry and Materials
This research was conducted to determine the effect of solution variations, electrical current, thickness, weight, metal composition, and the characteristics of the Fe-Ni alloy synthesized using the electrodeposition method. The instruments used in this study were atomic absorption spectroscopy (AAS) to determine the metal composition in the deposit, X-ray diffraction to determine the diffraction patterns, and scanning electron microscopy (SEM) to observe morphology and energy dispersive X-ray spectroscopy for elemental analysis. The SEM micrographs obtained showed that morphology of the Fe-Ni alloy was in the form of refined grains. The percentage of Fe in the deposit decreases with the increase in the used current. The AAS data also showed that a high Ni composition in solution will affect the atomic percent of each metal in the deposit. The formation of the alloy was confirmed by diffraction peaks at 2θ of 44°, 53°, and 76° that associated with reflection planes of the face cente...
Electrodeposition of Ni–Fe Alloys in the Presence of Complexing Agents
Russian Journal of Electrochemistry, 2002
The electrodeposition of binary Ni–Fe alloys is studied in chloride-based solutions with organic additives. Specific codeposition composition of the electrolyte and operating variables are taken for deposition a wide range of Ni–Fe deposits. Results reveal that in solutions containing sodium citrate and glycolic acid, the nickel content always increases with the current density and nickel concentration. Therefore, nickel reduction rate
Electrodeposition of Fe powder from acid electrolytes
Journal of the Serbian Chemical Society, 2008
Polarization characteristics of the electrodeposition processes of Fe powders from sulfate and chloride electrolytes and the morphology of the obtained powders were investigated. The morphology depended on the anion presence in the electrolyte but not on the current density in the investigated range. A characteristic feature of the dendritic powder with cauliflower endings obtained from sulfate electrolyte is the presence of cone-like cavities and the crystallite morphology of the powders surface. On the other hand, Fe powders electrodeposited from chloride electrolyte appear in the form of agglomerates. A soap solution treatment applied as a method of washing and drying provides good protection from oxidation of the powders.
Electrodeposition and Electroless Deposition of Metallic Powders: A Comparison
ECS Transactions, 2011
Electrodeposition and electroless deposition of metallic powders were comparatively investigated. Electrodeposition of copper is accompanied with the simultaneous hydrogen evolution, which significantly influences the morphology of Cu powder. At lower overpotentials, branched dendrites were produced. At higher overpotentials honeycomb-like deposits of copper were obtained. Formation of silver powders was characterized by the comparison of the exchange and limiting current densities. Instantaneous growth of dendrites starts at low overpotential due to large exchange current density in silver nitrate solution. Formation of powders such as Ni, Co, Ag, Pd and Au from homogenous solutions using an appropriate reducing agent or via galvanic displacement reaction was demonstrated. The hydrolysis of metallic ions is crucial in the deposition metallic powders via electroless deposition from homogenous solutions. Oxides, such as Ag2O, Cu2O and CuO, suspended in water can successfully be reduc...
2009
The electrodeposition of the Fe-Ni powders from citrate containing electrolytes for different Ni/Fe ions concentration ratios, using Fe(III) and Fe(II) salts at pH 4.5 and pH 4.0 respectively was investigated by the polarization measurements and cyclic voltammetry. The morphology and composition of the electrodeposited powders were investigated by SEM and EDS analysis. The EDS analysis of the alloy powders confirmed anomalous co-deposition of Fe and Ni from both solutions, with the one obtained using Fe(III) salt being more pronounced. The morphology of electrodeposited powders was found to depend on the Ni/Fe ions concentration ratio, as well as on the valence of Fe ions used. A common characteristic for all powder samples was the presence of cone shaped cavities and nodules, while for the ratio Ni/Fe = 9/1 in both electrolytes pagoda like crystals, corresponding to the FeNi 3 single crystal, have been detected. In the case of Fe(III) containing electrolytes current efficiency for powder electrodeposition was very small (about 1-2%) due to the first step in the electrochemical reaction being reduction of Fe(III) into Fe(II), while in the case of Fe(II) containing electrolytes current efficiency for powder electrodeposition varied between about 15% and 8% depending on the Ni/Fe ratio.