Electrochemical Behavior of Nickel ACD-Electroless Deposition (original) (raw)
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Determination of electroless deposition by chemical nickeling
Metalurgija, 2013
Increasing of technical level and reliability of machine products in compliance with the economical and ecological terms belongs to the main trends of the industrial development. During the utilisation of these products there arise their each other contacts and the interaction with the environment. That is the reason for their surface degradation by wear effect, corrosion and other infl uences. The chemical nickel-plating allows autocatalytic deposition of nickel from water solutions in the form of coherent, technically very profitable coating without usage of external source of electric current. The research was aimed at evaluating the surface changes after chemical nickel-plating at various changes of technological parameters.
8 ELECTROLESS DEPOSITION OF NICKEL
Electroless (autocatalytic) plating involves the presence of a chemical reducing agent in solution to reduce metallic ions to the metal state. The name electroless is somewhat misleading, however. There are no external electrodes present, but there is electric current (charge transfer) involved. Instead of an anode, the metal is supplied by the metal salt; replenishment is achieved by adding either salt or an external loop with an anode of the corresponding metal that has higher efficiency than the cathode. There is therefore, instead of a cathode to reduce the metal, a substrate serving as the cathode, while the electrons are provided by a reducing agent. The process takes place only on catalytic surfaces rather than throughout the solution (if the process is not properly controlled, the reduction can take place throughout the solution, possibly on particles of dust or of catalytic metals, with undesirable results).
Structure and electrokinetic study of nickel electrodeposition
Russian Journal of Electrochemistry, 2008
Electrodeposited layers of nickel show different growth characteristics depending on the composition of the electrolyte, namely the type of the anion, the presence or the absence of boric acid and the pH. These process parameters are examined in the present work in order to elucidate their influence upon the growth texture and the related surface morphology of the electrodeposits. The relationship between process and structure is investigated by studying the transient electrochemical behavior during deposition, in order to discriminate between different interface conditions corresponding to different growth modes. The observed preferred orientations can be in this way linked to different reactive species, which are assumed to be present at the surface, and to their stability. The correlation between kinetics and structure in nickel electrodeposition reported in the present work and the similar correlation found in cobalt electrodeposition suggest a rationalization of the growth modes of ECD inert metals, based on the correspondence between the transient Tafel parameter and the growth texture observed in defined conditions.
Influence of Technological Parameters on the Evolution of Nickel Films Deposited by Electrolysis
The influence of technological parameters on the structure of nickel layers electrodeposited on a copper substrate in a Watts bath has been studied. The complex influence of current densities, temperature and pH values on the formation of the deposition layers are compared. The surface morphology of the nickel films was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). X-ray diffraction (XRD) was used to investigate the crystallinity of the prepared samples. The increase in the current density leads to fine crystallized films, while layers obtained at even higher current density have dendritic structures. The temperature increasing results in a structure change from fine to coarse.
Chemical mechanisms in electroless deposition
Journal of Non-Crystalline Solids, 1988
Mechanisms of formation of electroless NiP amorphous alloys have been studied with special emphasis on the role of hydrogen. It is proposed that hydrogen atoms produced during layer nucleation and growth are occluded by the deposit during the process of formation and that they have an important role in stabilizing the amorphous structure. The hydrogen may also play a part in the whole autocatalytic process. The hydrogen evolution is accompanied by incorporation of phosphorus, which to some extent takes over the role of the metalloid necessary to stabilize the amorphous structure. Airation of the electroless bath is found to decrease hydrogen liberation and to make the layers more uniform, but causes their thermal stability to decrease. Possible explanations for these effects are discussed.
Surface Review and Letters, 2008
The processes of nickel electrodeposition on Pt/Si(100) substrate from an aqueous sulfate, Watts, and chloride solution have been studied using electrochemical techniques and atomic force microscopy (AFM). It was found that hydrogen evolution reaction (HER) was shifted more cathodically and the nickel electrodeposition obeys to inhibition process, caused by adsorbed species in surface substrate. At early stage of the deposition chronoamperometric results were compared with Sharifker and Hills theoretical model. The nucleation was in agreement with progressive mode followed by 3D diffusion growth mechanism. The nucleation is generally slow at low over potentials, in all studied baths. AFM images show distribution nickel clusters, with different sizes.
The evaluation of nickel deposit obtained via Watts electrolyte at ambient temperature
Journal of Coatings Technology and Research, 2010
A series of electroplating works were conducted to investigate the best conditions for the electrodeposition of nickel on a mild steel substrate. The electrodeposition was done at ambient electrolyte temperature with mild agitation and under current density ranging from 10 to 50 mA/cm2. X-ray diffraction analysis (2θ for first three peaks = 44.6, 51.9, and 76.8) and Energy Dispersive Spectrometer verified the presence of a pure nickel coating. Under field emission scanning electron microscopy analysis, the coating shows a typical nodular surface morphology, while cross-sectional microstructures show a compact nickel layer. Vickers hardness testing shows that the coating hardness gave the highest value of 293 HV at 30 mA/cm2 current density.
2014
In the present paper, electroless deposition of nickel from alkaline hypophosphite baths on copper substrates, using gluconate, as complexing agent, were studied. The dependence of the deposited NiP alloy on various operating parameters and solution components were examined. The deposited NiP coatings was characterized using different techniques such as energy dispersive X-ray (EDX), X-ray diffraction (XRD), scanning electron microscope (SEM), and the hardness, corrosion resistance for the coated substrates were measured. The coated substrate from these baths shown high deposition rate (unexpected from alkaline hypophosphite), and lower activation energy beside good appearances and enhancement in the hardness and corrosion resistance for the deposited layer were observed.
Initial Deposition of Electroless Nickel from Borohydride-Reduced Bath on Various Ferrous Alloys
2012
Electroless plating is based on the chemical reduction in aqueous solution of metallic ions, in the present case, nickel ions, that are reduced by sodium borohydride. The initial steps of the deposition and growth process were studied in depth during this work on substrates made of various ferrous alloys chosen for their chemistry: mild steel, cryogenic steel with 9% Nickel, austenitic and duplex stainless steel (with both nickel and chromium). The samples were prepared by grinding to 1200 mesh with silicon carbide abrasive paper and activated by acidic etching. They were then immersed in the plating solution for times varying from 5 s to 1 h. The morphological evolution of the deposit during the early stages of plating was observed by scanning electron microscopy (SEM) on the surface of the sample and on prepared cross sections. Growth rates were measured by weight gains as well as by SEM measurements. Energy dispersive X-ray spectrometry (EDX) and glow discharge optical electro sp...