Stoichiometric measurements in nickel–hypophosphite baths for electroless deposition (original) (raw)
Related papers
Influence of phosphorus content on the structure of nickel electroless deposits
Journal of Materials Chemistry, 2001
Ni±P electroless ®lms prepared from a sulfate-based solution using hypophosphite ion as a reducing agent were optically characterised by ellipsometry. The refractive indices were recorded as a function of the deposition time and the concentration of reductant in the plating bath. To complement the ellipsometric data, X-ray diffraction analysis was performed. It is shown that ellipsometric measurements can be used to elucidate the change from crystalline to amorphous-like phases induced by the phosphorus content and therefore to correlate the composition with the properties required for Ni±P technological applications.
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.
Solid State Phenomena, 2014
The deposition kinetics, structure and magnetic properties of electroless deposited films Ni-P were investigated depending on the amount of sodium hypophosphite in the electroless bath. It was found that the film deposition rate is linear and unambiguously varies with the hypophosphite content from 2 to 13 g/l and from 23 to 25 g/l. The deposition rate varies widely in the hypophosphite concentration range from 13 to 23 g/l. The films are composed of amorphous Ni-P phase and fcc Ni-P solid solution with phosphorus content from 1 to 4 at.% P according to X-ray diffraction. The partial amount of amorphous phase is increased with concentration of sodium hypophosphite. The ferromagnetic resonance field is independent on the concentration of sodium hypophosphite, which assumes to be result from the laminated allocation of the amorphous and fcc phases in the film.
Surface and Coatings Technology, 2008
Effects of added rare earth elements (RE) in the acidic hypophosphite plating bath on the plating rate, bath stability and microstructure of the electroless nickel-phosphorus (EN) deposits were studied. The surface appearance and microstructure were examined under a reflection optical microscope and a scanning electron microscope equipped with an in-situ energy dispersive X-ray spectroscopy, which can evaluate the elemental analysis of deposits. It was demonstrated that the rare earth elements can decrease grain size and refine microstructure. The deposition rate of the NiP deposits was estimated by gravimetric, polarization and quartz crystal microbalance (QCM) methods. Results revealed that up to an optimum concentration of rare earth elements, the deposition rate increases. The stability test method was used to determine the stabilization effect of RE on the stability of the bath. It was found that the addition of RE significantly improved the Pd stability of the EN bath.
The optimized plating bath composition (mol%) of 0.47NiCl 2 :0.23NaH 2 PO 2 :0.13C 4 H 4 Na 2 O 4 :3.47NaCl:95.70H 2 O produced Ni-P films with~10 wt.% P at 85°C over copper and steel substrates. The presence of chloride ions (Cl − ) in the plating solution was found to facilitate initial deposition without any need of surface activation. Film growth rates as high as 7-8 μm/h were achieved with minimal or no deposition on surfaces other than the substrates. Scanning electron microscope (SEM) and atomic force microscope (AFM) studies revealed cauliflower-like morphology with submicron size grains. Increasing the amount of reducing agent increased film smoothness and refined grain size with corresponding increase in P content. X-ray diffraction studies of the deposit revealed semi-crystalline nature of the film which underwent transition to fully crystalline form upon heat treatment with an associated increase in average HK value from~390 to 807 HK. High temperature provided driving force for surface and volume diffusion that subsequently led to reduced porosity and more homogeneous composition through rearrangement of atoms to form certain Ni x P y phases. Acid etching of the deposits transformed shiny films into matte black surfaces due to preferential removal of nickel leading to formation of porous structure with stalagmite-like morphology.
Materials Chemistry and Physics, 2006
The effect of thiourea, succinic acid and lead acetate on the formation and characteristics of electroless Ni–P deposits obtained from an acidic hypophosphite reduced electroless nickel bath is addressed in this paper. The rate of deposition of electroless Ni–P coating is found to be a function of concentration of these additives. Thiourea accelerates the rate of deposition up to 0.8 ppm and started to inhibit at a concentration of 1 ppm. Similarly, succinic acid increases the plating rate up to 12 g l−1 and exhibit an inhibiting effect at higher concentrations of the order of 15 g l−1. Addition of lead acetate inhibits the rate of deposition even at a concentration of 0.5 ppm and the extent of inhibition is increased when the concentration is higher than 1 ppm. Addition of these additives also caused a change in phosphorus content of the deposits; lead acetate (1 ppm) tends to increase the phosphorus content whereas thiourea (0.8 ppm) and succinic acid (12 g l−1) tends to decrease the phosphorus content. The X-ray diffraction patterns of electroless Ni–P coatings obtained in the absence of additives and in presence of 1 ppm of lead acetate exhibit a single broad peak centered at 44.5° 2θ, indicating the amorphous nature of these coatings. The peak broadening suggests a greater tendency to form amorphous structure when lead acetate is used as the additive. In contrast, for electroless Ni–P coatings obtained from thiourea and succinic acid containing baths, besides the reflection from Ni (1 1 1) plane, a weak reflection from Ni (2 0 0) plane is also observed. The X-ray diffraction patterns of electroless Ni–P coatings after annealing at 400 °C for 1 h exhibit the formation of fcc nickel and bct nickel phosphide (Ni3P) phases in all the cases with Ni3P (2 3 1) as the most intense reflection. Electroless Ni–P coatings obtained in presence of thiourea and succinic acid exhibit a nodular feature with a typical cauliflower like structure. The size of the nodules is relatively less in the latter case. In contrast, the electroless Ni–P coating obtained in the absence of additives and in presence of 1 ppm of lead acetate is relatively smooth. However, the deposit obtained in the absence of additives reveals the presence of fine particulates, attributed to the precipitation of Ni3P phases in the absence of stabilizers. The DSC traces of electroless Ni–P coatings exhibit a single well-defined exothermic peak in the temperature range studied in all the cases, which could be attributed to the precipitation of metallic nickel phase and formation of nickel phosphide (Ni3P) phase. The variation in the peak temperature and the energy evolved during the phase transition is due to the slight variation in the phosphorus content caused by the addition of thiourea, succinic acid and lead acetate. The study recommends that the choice of accelerators and stabilizers should be made only after a careful study.
2018
The effect of NaH2PO2 concentration in the electrolyte (pH = 2) on the kinetics of NiP, CoP and NiCoP alloys electrodeposition at room temperature was studied. It was established that at concentration of NaH2PO2 about 0,2 M the deposition rate of NiP alloys decreases; the deposition rate of СоР alloys increases but at the same time the quality of the coating becomes bad. In both cases it was observed a depolarizing effect on the deposition. With increasing of the content of NaH2PO2, the phosphorus content in NiCoP alloys increases to approximately 7 % and the current efficiency of electrodeposition (CEE) goes over 100 %. The comparison of the kinetic data with those of CEE of NiCoP coatings showed that the mechanism of deposition is mixed chemical-electrochemical.
Electrochemical Characterization of Nickel-Phosphorus Based Coatings Containing Cobalt
Solid State Phenomena, 2015
The Ni-P, Ni-Co-P and Ni-P+Co coatings were obtained in galvanostatic conditions at the current density of jdep= -200 mA cm-2. A stereoscopic microscope was used for surface morphology characterization of the coatings. The X-ray diffraction (XRD) method was used to determine phase composition of the coatings and the atomic absorption spectrometry (AAS) was applied to specify their chemical composition. The behavior of the obtained coatings was investigated in the process of hydrogen evolution reaction (HER) from 5 M KOH using steady-state polarization and electrochemical impedance spectroscopy (EIS) methods. It was found that introduction into Ni-P amorphous matrix powder of cobalt produced porous electrode materials which could be used for the HER.
Determination of correct composition in nickel–phosphorus films by XPS angle resolved technique
Applied Surface Science, 2003
Surface sputtering is a commonly used technique for surface analysis. The standard method of Ar þ sputtering was found to produce surface changes or damages. In this work, nickel-phosphorus films are characterized by X-ray photoelectron spectroscopy (XPS) angle resolved technique before and after sputtering. A method is presented to determine the correct atomic ratio between Ni and P in the surface layers, taking into account that nickel atoms are mainly displaced toward inner layers, as a consequence of 4-5 at.% argon ion implantation within top 1.5-3.7 nm from the surface. The experimental argon implantation and nickel displacement ranges match with Lindhard-Scharff model. Metallic nickel formation in the first layer is detected after sputtering by X-ray diffractometry at low glancing angle. No detectable difference was found between the binding energy of nickel in the metallic state and in the Ni-P coating, showing a similar chemical state for nickel in both conditions. #
Journal of the Serbian Chemical Society, 2019
The deposition of Fe-Ni alloys from acidic and alkaline solutions, using hypophosphite as a reducing agent, is studied in this work. The experimental results confirm the autocatalytic nature of this process. The composition of alloys is practically independent of the temperature deposition. Fe-Ni alloys produced from acidic solutions contained less than 1% Fe. The amount of Fe in Fe-Ni alloys produced from alkaline solutions was estimated to be about 15 %. The deposition of Fe-Ni alloys was significantly faster in the alkaline than in the acidic solutions, due to more pronounced hydrolysis of Fe(II) and Ni(II) ions under the alkaline conditions. The Fe-Ni alloys produced from both acidic and alkaline solutions contain phosphorus and as such have amorphous structure .