The effects of surfactants on the dynamics and characteristics of plain and composite electroless nickel plating (ENP) are highlighted and discussed herein. An outline of the rudiments of surfactants and some underlying selection criteria is presented at the outset, before emphasis is laid on the salient benefits of introducing such external agents during the plating process. Evidence suggests that their influence on key coating characteristics such as the rate of deposition, structure, corrosion resistance, and the degree of second-phase particle incorporation into the nickel matrix is significant, and depending on the nature and concentration of surfactant employed, can be of immense value to the system.
The influence of a surfactant on the composition of nickel-yttria stabilised zirconia (YSZ) cermet coatings, applied by electroless nickel plating technique was examined. The amphiphilic characteristics of anionic surfactant sodium dodecyl sulphate (SDS), was relied upon for enhanced dispersion of YSZ particles co-deposited for use as anodes in solid oxide fuel cell technology and potential heat absorbing layers in thermal barrier coatings. Optical microscopy was employed to study the correlation between the plating thickness, level of ceramic loading and SDS concentration while the effect of the surfactant and fineness of YSZ particles on the as-deposited coating's ceramic to metal ratio, was analysed using energy dispersive X-ray analysis (EDXA) characterisation technique.
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 ) ¼ 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.Electroless co-deposition of nickel and the ceramic yttria stabilized zirconia (YSZ) recently emerged as a method of manufacturing solid oxide fuel cell (SOFC) electrodes (Davidson and Waugh, 2009). Its non-requirement of a high energy sintering stage not only significantly reduces currently high SOFC manufacturing costs, but also offers an opportunity to eliminate certain high-temperature related problems such as material warpage. While nickel provides the essential platform for electronic conductivity and fuel catalysation, YSZ, in addition to preventing the coarsening of nickel at high operating temperatures ($1000 C), relieves the thermal expansion mismatch between the anode and the electrolyte. Electroless nickel solution is the medium wherein the co-deposition process occurs. Addition of second-phase particles such as YSZ to the solution results in the manufacture of a composite coating.
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