Electroless Nickel Solution Research Articles

Parametric optimisation of microhardness on heat-treated electroless Ni-YSZ cermet coating

The paper discusses the parametric optimisation of the electroless Ni-YSZ cermet coating microhardness upon heat treatment. Heat treatment is a process to increase the mechanical properties of the electroless nickel coating and it can be enhanced by manipulating its parameters. Parametric optimisation is conducted by the design of experiment full factorial 3x3 with 27 runs. Treating temperature, treating time and ceramic particle size parameters at 3-level are evaluated using statistical tool ANOVA in Minitab20. Ni-YSZ cermet coating is deposited onto a high-speed steel substrate using the electroless nickel co-deposition method. The temperature and time were varied in a range of 300-400oC and 0-2 hours respectively. The microhardness measurements were carried out using a Vickers microhardness tester (Shimadzu) according to ISO 6507-4. The surface characterisation was analysed using Cambridge Stereoscan 90 Scanning Electron Microscope (SEM) coupled with Energy Dispersive X-ray Analysis (EDXA). The optimum condition in obtaining high microhardness on Ni-YSZ cermet coating is evaluated by statistical tool ANOVA in Minitab20 software. It is found that the most significant parameter for high microhardness is at the treating temperature of 400oC followed by treating time at 2 hours using nano-sized YSZ particles. The ceramic particle size is found not a significant parameter in obtaining a high microhardness, however it has effect on interaction between treating temperature and treating time. The paper only limits to the optimisation condition of microhardness on Ni-YSZ cermet coating hardness property by varying heat treatment parameters. The optimisation condition obtained might only applicable to the electroless Ni-YSZ cermet coating with similar electroless nickel solution and treatments. The value of this work is the heat treatment parametric optimisation to obtain high microhardness on electroless Ni-YSZ cermet coating by using the design of experiment 3-level full factorial.

Textile-based triboelectric nanogenerators via electroless plating for fabricating electrode material: Study of the relationship between electrostatic-charge density and strain in dielectric material

Textile-based cotton was developed to fabricate the support for triboelectric nanogenerators (TENGs), which would facilitate the improvement of the device wearability and comfort. But, it is difficult to achieve the fabrication of metal textile-based cotton for electrode materials using traditional technology. In this regard, a textile-based TENGs via electroless plating on cotton surface for fabricating electrode material was established, the output performances under different external forces were studied comprehensively to obtain a full understanding of the relationship between the density of electrostatic charge (δ) and strain of polydimethylsiloxane (PDMS) dielectric material. Results showed that active groups on the rough cotton surface would facilitate the adsorption of Pd2+, and then reduce of Ni2+ to Ni atom in electroless nickel solution. As a result, core-sheath micronfiber yarn with weave structure was fabricated. It is flexible, lightweight, flexible with typical performance of TENGs electrode. The device had stable and excellent performances, and a maximum open-circuit voltage of about 8.3 V was observed from stress of 3.8 kPa or strain of 1.7 × 10−6 on PDMS layer. More importantly, a new calculation method for the PDMS strain of formation δ was proposed by equation of state. It was also revealed that the δ and PDMS strain represented a linear regression relation when the device under weigh mass of 0.22–0.52 kg, stress of 0.69–1.63 kPa and strain of 0.3–0.72 × 10−6. Nevertheless, further increasing stress, actual δ value is firstly higher and then lower than the theoretical value due to fabric fiber deformation.

Design of a scheelite production pilot plant for the treatment of spent electroless nickel plating solutions in Field Service Solution S.A.S.: an alternative source for tungsten recycling

In this contribution, the design considerations to assemble a pilot-plant for tungsten recovery and further conversion into synthetic scheeliteas raw material, as an eco-friendly improvement for the current electroless nickel process in Field Service Solution (FES) S. A. S., arepresented. This low-cost methodology scale-up aims to provide an alternative treatment for spent electroless nickel solutions (Ni-P-W) asa secondary tungsten source. The plant is projected to treat up to 750 L of industrial waste per week, achieving a maximum scheeliteproduction of 9.1 kg per week. This prototype serves as a model of eco-sustainability in the nickel-plating industry by controlling thedisposal of heavy metals and by facilitating the production of other tungsten derivatives and their feasible reuse in the process.

Full Optimization of an Electroless Nickel Solution: Boosting the Performance of Low-Phosphorous Coatings.

Univariate and multivariate optimizations of a novel electroless nickel formulation have been carried out by means of the Taguchi method. From the compositional point of view, adjustment of the complexing agent concentration in solution is crucial for fine-tuning free Ni2+ ions concentration and, in turn, the mechanical properties of the resulting coatings. The Ni (II) concentration and the pH are the main parameters which help restrict the incorporation of phosphorous into the Ni layers. On the other hand, the stirring rate, the pH and the reducing agent concentration are the most influential parameters for the corrosion resistance of the coatings. Multivariate optimization of the electrolyte leads to a set of optimized parameters in which the mechanical properties (hardness and worn volume) of the layers are similar to the optimal values achieved in the univariate optimization, but the corrosion rate is decreased by one order of magnitude.

Scheelite production from spent electroless nickel solutions as an alternative tungsten recycling source

Tungsten, considered a specialty metal, plays a remarkable role in the development of new tools for aerospace, defense, and other trending technological applications. However, due to its high supply risk index, extensive research on alternative sources for recycling has been conducted. In this contribution, the recovery of tungsten from spent electroless nickel solutions as a secondary metal source for this element is described for the first time. Laboratory experimental procedures are presented, involving the acid-promoted tungstite precipitation where the oxidizing properties of nitric acid demonstrated to play a key role in the tungsten oxide product formation. Further reaction with calcium hydroxide allows the rapid isolation of high-purity scheelite (>98%) in good yield. This protocol serves as a model for a tungsten recovery pilot plant scale-up, where other reactions for the preparation of additional tungsten derivatives, employing scheelite as starting material, can be implemented.

Influence of inorganic coating over diamond particles on interaction force and dispersability in electroless solution

The inorganic coating of Al2O3 was introduced on nanoparticles to weaken their tendency of agglomeration in electroless plating bath. The influence of the coating on interaction energy and interaction forces between the coated particles was evaluated in this study. The Al2O3-coated diamond particles were prepared by the heterogeneous nucleation process. The attractive interaction and repulsive interaction between the coated particles in electroless nickel (EN) solution were calculated by the classical DLVO theory. Sedimentation tests were conducted to verify the modelling. The calculation predictions are well in agreement with the experimental results. The Al2O3 coating could reduce van der Waals attraction by enlarging the surface separation distance of diamond particles, and could increase electrical double layer repulsion by increasing the surface potentials in EN solution. Consequently, it could weaken the net attractive interaction, whose net attractive force decreased from −3.77×10−2N/m between bare particles to −1.12×10−2N/m between the coated ones, a reduction by 70%, at the separation distance of 1κ−1. The coated diamond particles in EN solution show a slower settling rate than bare ones. The Al2O3 coating contributes to the high dispersability of the coated particles under the agitation condition.

Influence of magnetic field on the mass transfer of Ni–P-diamond electroless composite plating and deposit properties

Nickel–phosphorus (Ni–P)-diamond composite coatings were manufactured by the addition of sub-micrometre sized diamond particles to electroless nickel solution. In the process of this reaction, a magnetic field was introduced. This research studied the effect of the magnetic field on the Ni–P-diamond composite coatings by changing the concentration of sub-micrometre sized diamonds and the magnetic field intensity. The surface morphology, the coating composition and the coating adhesion were tested using scanning electron microscope and energy-dispersive spectrometer, a metalloscope and an automatic scratch tester. The results showed that the magnetic field influenced the mass transfer process of the composite plating by accelerating the oxidation rate of the hypophosphite, so that the deposition rate was increased, the coating morphology was improved and the bonding force between the coating and the matrix was improved.

Interaction Between Fine Diamond Particles in Electroless Nickel Solutions

The classical DLVO theory was applied to calculate the interaction potential energy between diamond particles in electroless nickel (EN) solution and its diluted solutions with deionized (DI) water to predict their dispersion and sedimentation rates. Sedimentation tests and particle size distribution for all particle dispersions were measured to verify the DLVO calculations. Results show that the curve features of interaction potential energy vary with the dilution ratio of dispersions. The energy barrier in the curves requires the minimum 1:100 dilution of the EN solution. A sufficient energy barrier results in an extremely slow sedimentation rate of particles by keeping them separate. Otherwise, they settle down quickly due to the agglomeration resulting from their attractive forces at any separation distance. The prediction results are in good agreement with the measurement of sedimentation tests and particle size distribution. The classical DLVO theory is applicable to the field of electroless plating.

Effects of Complexing Agent Concentration and Bath pH on Electroless Nickel Deposition for Tungsten Carbide Powders

An elemental nickel (Ni) or cobalt (Co) is typically introduced to tungsten carbide (WC) prior to powder injection moulding process (PIM) for hard metal fabrication to enhance toughness and tool life. Mixing of powders is normally practiced, although it requires a long processing time for homogeneous mixing. In this study, as an alternative method, an addition of Ni via the electroless deposition method is investigated. The key process parameters, including the concentration of the complexing agent, namely sodium citrate, and bath pH, are systematically examined in relation to deposition rate and deposits size, microstructure, and chemical compositions. As the bath pH is increased to higher alkalinity of 10 and the Ni ion to complexing agent mole ratio is controlled under 1:1, a stable electroless nickel solution and a relatively high deposition rate with about 15% weight gain for 1 hour deposition duration are achieved. The phosphorus (P) content, obtained in the range of 5-9 wt%, is largely influenced by the bath pH. While a rapid deposition rate is associated with preferentially deposition of Ni on pre-deposited Ni sites, a low to moderately high deposition rate results in more uniform incorporation of Ni-P alloys in WC powder mixture.

EFFECT OF SDS ON THE DISPERSION STABILITY OF YSZ PARTICLES IN AN ELECTROLESS NICKEL SOLUTION

Optimum particle dispersion is an essential feature for composite coatings carried out on the autocatalytic electroless nickel plating platform. In this regard, the potential influence of an anionic surfactant, sodium dodecyl sulphate (SDS), on the dispersion stability of a ceramic, yttria stabilized zirconia (YSZ), in an acidic electroless nickel solution of pH 4.9 has been assessed in this study. Ultra violet-visible spectrophotometry was used in accordance with the Beer-Lambert law (–log (I 1/I 0) = A) to evaluate the rate of YSZ particle sedimentation in electroless nickel solutions with and without surfactant. Measurement of the particles' zeta potential at each surfactant concentration was conducted in parallel with the UV-vis tests with the aim of establishing the interaction among the surfactant, YSZ particles, and electroless nickel solution. A slight increase in the negative magnitude of the particles' zeta potential indicated the adsorption of SDS onto the particles' surface and a possibility of contributing to its stability. However, the surfactant's inability to counteract an electroless nickel solution–induced particle accretion resulted in the observation of poor YSZ particle stabilities at all the investigated surfactant concentrations.

Dispersion of micro diamond particles in electroless nickel solution

The dispersion behavior of micro-diamond particles ranging from 0 to 0.5 micron was compared between in DI water and in electroless nickel solution. The effects of the concentration of electroless solution, temperature, ultrasonic treatment, stirring speed, and baffles on the size distribution of micro diamond particles in electroless nickel solution were studied. Results show that the dispersion of micro diamond particles in DI water is obviously superior to that in electroless nickel solution. Micro diamond particles agglomerate evidently when the concentration of electroless solution V elect:V DI in dispersion media exceeds 5‰. Diamond particles agglomerate more and more seriously with the increase of the ion concentration. Applying ultrasonic, increasing stirring speed and adding baffles are helpful to improving the dispersion of diamond particles in the electroless nickel solution and its uniform distribution in the Ni-P coating.

The use of ultrasound to enable low temperature electroless plating

PurposeElectroless plating is an important process in printed circuit board and electronics manufacturing but typically requires temperatures of 70‐95°C to give a suitable deposition rate. This is becoming problematic in industry due to the rising price of energy and is a major contribution to production costs. Previous studies have noted beneficial effects of ultrasonic irradiation upon electroless plating processes and it has been reported that sonication can increase the plating rate and produce changes to the chemical and physical properties of the deposited coating. The purpose of this paper is to reduce the operating temperature of an electroless nickel bath by introducing ultrasound to the process.Design/methodology/approachThe deposition rate of an electroless nickel solution was determined by two techniques. In the first method, test coupons were plated in an electroless nickel solution at temperatures ranging from 50‐90°C and the plating rate was calculated by weight gain. In the second approach the mixed potential (and hence the current density at the mixed potential) was determined by electrochemical analysis of the anodic and cathodic reactions. In both cases the plating rate was found with and without the application of an ultrasonic field (20 kHz). The electroless nickel deposits obtained in the plating tests were also analysed to determine the phosphorus content, microhardness and brightness.FindingsThe plating rates under ultrasonic agitation were always higher than under “silent” conditions. Most importantly, considering the objectives of this study, the deposition rate under sonication at 70°C was significantly higher than that found with mechanical agitation at 90°C. In addition, the results indicated that the deposits produced in an ultrasonic field had consistently lower phosphorus content, higher microhardness and were brighter than those prepared in an electroless nickel bath that was not sonicated.Originality/valueAlthough previous work has been performed on the effect of ultrasound on electroless plating, all these studies have been carried out at the normal operating temperature of the electroless process. In this paper, ultrasound has been applied at temperatures well below those normally used in electroless nickel deposition to determine whether sonication can enable low temperature electroless plating.

Selectivity Improvements and Response Time Scale of Porous Silicon Conductometric Gas Sensors

Nanopore covered microporous silicon conductometric gas sensors have been fabricated using electrochemical etching in an HF and acetonitrile solution and standard cleanroom microfabrication techniques. Sensing of NH3, NOx, PH3, and SO2 at or below the ppm level has been accomplished. A porous silicon (PS) surface has been modified using selective depositions formed from electroless tin, gold, nickel, and copper solutions to increase the response to several gases including PH3. The diffusion of the PH3 analyte has been investigated in the nanopore and micropore regimes by numerical analysis. By comparing the response time of the hybrid porous sensor surface with numerical diffusion calculations based on a realistic model of the pores, it is demonstrated that Knudsen diffusion time scales dominate the sensor response.

Effects of complexing agents on acidic electroless nickel deposition

Our previous study reported the influences of different complexing agents on electroless nickel (EN) by examining the properties of the deposits. In the present work, the effects of four common-used complexing agents on EN deposition rate and the stability of solution pH values were examined, either with an acetic pH buffer agent or absent of them. It is indicated that the pH buffering effect of them is dominative when the EN solution is lack of the pH buffer. Under this situation, the EN deposition rate increases with the concentration of complexing agents increasing. The EN deposition rate decreases with further adding the complexing agent when the solution already has enough pH buffer capability. Electrochemical impedance spectroscopy obtained during EN deposition illustrates that, in this case, the enhanced reaction resistance is the main reason for a lower deposition rate. However, the influence of polarization caused by mass transfer is not negligible at high complex ratio for sodium citrate and malic acid EN solutions.

Gas Transport and Response in Porous Silicon Sensors

AbstractNanopore covered microporous silicon conductometric gas sensors have been produced via electrochemical etching and standard microfabrication techniques. Reversible and sensitive gas sensors working at room temperature have been fabricated. Sensing of NH3, NOx and PH3 at or below the ppm level have been achieved. The porous silicon (PS) surface has been modified using selective coatings including electroless tin, gold, nickel and copper solutions to increase the response to NOx, NH3, and PH3 respectively. The diffusion of the analyte species has been investigated in the nanopore and micropore regimes by numerical analysis. Comparing the response time of the hybrid porous sensor surface with numerical diffusion calculations on the pores, it has been observed that Knudsen diffusion time scales dominate the sensor response. A transduction model is proposed based on nanopore limited gas diffusion and the experimental response and recovery data.

Studies on black electroless nickel coatings on titanium alloys for spacecraft thermal control applications

A process of blackening of electroless nickel coating is investigated to produce ultra black coating on titanium alloys with higher optical properties. Process optimization was carried out by investigating the influence of various operating conditions, namely, processing time of etching solutions, thickness of electroless nickel deposit, temperature of blackening solutions, and pH of electroless nickel solution on the physico-optical properties of the black coating. It was observed that an optimum thickness of 35 + 5 μm of electroless nickel is required to achieve the ultra high optical properties after blackening. Energy dispersive X-ray spectroscopy studies suggested that films containing ~7% phosphorous are good for further blackening. Scanning electron and optical microscopic studies confirmed that the surface morphology played the major role to get the ultra high optical properties. The environmental tests, namely, humidity, corrosion resistance, thermal cycling, thermo vacuum performance, and thermal stability tests were used to evaluate the space worthiness of the coating. Optical properties of the coating were measured before and after each environmental test to ascertain its stability. The blackened electroless nickel provides higher optical properties in the order of ~0.85; this coating has good adhesion, uniformity, and stability in adverse space conditions. Hence, these coatings were extremely suitable for spacecraft thermal control applications.

Electrolytic Recovery of Nickel from Spent Electroless Nickel Bath Solution

Plating industry is one of the largest polluting small scale industries and nickel plating is among the important surface finishing process in this industry. The waste generated during this operation contains toxic nickel. Nickel removal and recovery is of great interest from spent bath for environmental and economic reasons. Spent electroless nickel solution from a reed relay switch manufacturing industry situated in Chennai was taken for electrolytic recovery of nickel. Electrolytic experiment was carried out with mild steel and gold coated mild steel as cathode and the different parameters such as current density, time, mixing and pH of the solution were varied and recovery and current efficiency was studied. It was noticed that there was an increase in current efficiency up to 5 A/dm2 and after that it declines. There is no significant improvement with mixing but with modified cathode there was some improvement. Removal of nickel from the spent electroless nickel bath was 81.81% at 5 A/dm2 and pH 4.23. Under this condition, the content of nickel was reduced to 0.94 g/L from 5.16 g/L. with 62.97% current efficiency.

Homogeneous Ni-P/Al 2O 3 nanocomposite coatings from stable dispersions in electroless nickel baths

The dispersion stability of aluminum oxide colloidal particles stabilized with comb-polyelectrolytes in an electroless nickel (EN) solution was studied under plating conditions (80–90 °C). The nanodispersions which were stable at room temperature for several weeks flocculate rapidly as the temperature approached ∼65 °C. Hydrotropes such as propylene glycol and urea are found to induce stability under plating conditions. A dependency of the critical flocculation temperature (CFT) on additives, comb-polyelectrolyte polyether side chain, and particle morphology is found. The codeposition of stabilized and nonstabilized nanoparticle dispersions resulted in very different particle density and distribution in the composite coatings. Highly homogeneous Ni-P/alumina nanocomposite coatings plated from stabilized baths with up to 50 vol% particle incorporation have been demonstrated.

Interactions and dispersion stability of aluminum oxide colloidal particles in electroless nickel solutions in the presence of comb polyelectrolytes

The effect of comb polyelectrolytes on the dispersion stability of colloidal alumina particles in DI water and commercial electroless nickel (EN) solutions was investigated. Adsorption of polyelectrolytes and major EN components onto colloidal alumina was assessed by TGA, chemical analysis, and zeta potential measurements. Zeta potential measurements were made during titrations of comb-polyelectrolyte-stabilized dispersions with EN solutions to full ionic strength for the first time. The compilation of titration curves made with varying amounts of comb polyelectrolytes provides high resolution and novel insight into the particle/surfactant/EN systems. Continuous decrease in particle/EN components surface interactions with the increase in comb polyelectrolyte coverage is observed. Laser diffraction measurements reveal steric stabilization of nano- and submicronmeter alumina dispersions in both DI water and EN solutions with >7 wt% and >2 wt% comb polyelectrolyte, respectively.

Stability of nano-/microsized particles in deionized water and electroless nickel solutions

A major problem in the co-deposition of nano- and microsized particles within electroless NiP coatings is particle dispersion in the electroless nickel solution because of the strong tendency of particles toward agglomeration and sedimentation. The stability of colloidal Al 2O 3, CeO 2, and BN particles and Al 2O 3 CeO 2 and Al 2O 3 BN particle mixtures in deionized water and electroless nickel solution was investigated by zeta potential measurements and sedimentation tests. Dispersions of Al 2O 3 and CeO 2 particles showed good stability in deionized water with zeta potential values of 55 and 39 mV, respectively. BN dispersion in deionized water was found to be relatively unstable at pH 4 with zeta potential values of −13 mV, but at higher pH (i.e., pH 5.5), the values decreased up to about −40 mV. When the dispersions were made in electroless nickel solution, a significant decrease of the zeta potential values was observed for both single particles and mixtures of particles, indicating a change in the surface charge from high positive to low negative with detrimental effects on dispersion stability. Further, the findings suggested that the stability of particle mixtures is dominated by one type of particle, i.e., the Al 2O 3 CeO 2 dispersion is governed by the single CeO 2 particles, whereas the Al 2O 3 BN dispersion is governed by the Al 2O 3 particles. All the zeta potential measurements were in line with the results of the sedimentation tests (i.e., low zeta potential values corresponded to short settling times, whereas high zeta potential values corresponded to long settling times).