Activation Bath Research Articles

Electroless plating on the surface of kapok fibres: analysis of an effective palladium-free nickel salt activation process

ABSTRACTA two-step, palladium-free, nickel salt activation process was tested on kapok fibres (KF). The results showed that the ratio of the concentration of hydrogen ions to the concentration of hydroxide ions ([H+]/[OH−]) in the activation bath needs to be controlled within a range to achieve an optimal outcome. The final amount of deposited active Ni is not only dictated by [NiSO4·6H2O] but also dependent on the concentration of the reducing agent, [NaBH4], whose proper value is complicated by its self-decomposition reaction that can be catalysed by the active Ni and H+ ions. The concentration of NiSO4 employed needs to be capped to attain reasonable mass density and high electrical conductivity as required by light-weight electromagnetic interference shielding materials. An effective activation bath was formulated and experimentally confirmed to successfully initiate and sustain such an electroless plating process and a compact, uniform and amorphous Ni-P layer was formed on the KF surface.

Optimization Of Nickel Deposition On Boron Carbide Particles Using Design Of Experiments

Abstract Amount of nickel deposition on Boron Carbide particles used as reinforcements in Aluminium metal matrix composites plays a vital role on wettability and bonding properties. In this work an attempt is made to investigate the influence of different bathing conditions of nickel deposition using electroless process onto boron carbide particles with average particle size as 44 µm. Sensitization bath is controlled by SnCl2, Activation bath is controlled by PbCl2, Coating bath is controlled by NiSO4.6H2O and the pH value of the solution. Two levels for the four factors are considered for the study, using half fractional factorial design 24-1 with two replicate 8runs are conducted. Nickel deposition on the boron carbide particles is observed by SEM images of the powder samples and the weight percentage of the Nickel deposited is observed by EDS smart quant results. Experimental results were analysed to study the influencing factors on the process by Analysis of Variance using design expert software. From ANOVA it is observed that most influencing factors on the process are amount of NiSO4.6H2O, PdCl2 and interaction of SnCl2 and NiSO4.6H2O respectively. From the regression model confirmation test has conducted and verified for maximum nickel deposition on Boron Carbide particles.

Manganese Phosphatizing Coatings: The Effects of Preparation Conditions on Surface Properties.

Manganese phosphate coating could be used to protect the surface of steel products. However, it is essential to determine the effects which process parameters, as well as the types of additives used, have on the efficiency of coating deposition. Thus, we present here a process of phosphatization of low-alloy steel (for 15 min at 95 °C) in manganese/nickel baths followed by a passivation process with the use of a silicon and zircon compounds. The microstructure and morphology of the surface were analyzed by SEM EDX and XRD methods. The obtained results showed that the manganese phosphate could be effectively formed at 95 °C in the solution containing nickel and guanidine derivatives. Anodic polarization of manganese coating was investigated in 0.5 M KCl by the analysis of polarization resistance. The effects of the activation process on corrosion properties of the coating have been examined. It was observed that an increased concentration of activating substances in the activation bath results in the enhancement of corrosion resistance.

Effect of Activation Site Density on Copper Encapsulation of MWCNTs by Electroless Deposition

Importance of the activation site density on final encapsulation of multi-walled carbon nanotubes (MWCNTs) with copper was investigated in this study. MWCNTs, sensitized with tin and activated with silver, were used as precursors to prepare copper-decorated nanotubes. The effect of activation bath pH was found to be critical to control the density of silver-activation sites and to produce uniform encapsulation of carbon nanotubes (CNTs) with copper in the subsequent electroless deposition method. The morphology of the copper decorated nanotubes was studied using Field Emission Gun Scanning Electron Microscope (FEG SEM) and Energy Dispersive Spectroscopy (EDS).

Hemispherical flower-like N-doped porous carbon/NiCo2O4 hybrid electrode for supercapacitors

The N-doped porous carbon/NiCo2O4 (NPC/NiCo2O4) substance is designed and synthesized via hydrothermal treatment, polymerization, carbonization, activation, and chemical bath deposition. The as-prepared NPC/NiCo2O4 holds hemispherical flower-like structure that consists of two things: a porous bowl-shaped NPC at the inside, and sheet NiCo2O4 at the whole outside, in which NPC works as a scaffold for NiCo2O4 to restrain NiCo2O4 nanosheets from aggregation in the synthesis process and NiCo2O4 acts as a capacitive coating layer, and causing a synergic effect. The composite electrode has a specific capacitance of 948.30 F g−1 at a current density of 1 A g−1, enhanced rate capability (727.43 F g−1 at 16 A g−1) and good conductivity. Additionally, NPC/NiCo2O4 reaches a desirable cycling stability (87.4% capacitance retention after 2000 cycles even at a high current density of 10 A g−1), suggesting a hopeful electrode material for the electrochemical supercapacitors.

Electrochemically triggered nucleation and growth of zinc phosphate on aluminium-silicon-coated steel

Steels with an aluminium silicon (AS) metallic coating behave passive in standard phosphating solutions. An electrochemical process was used to increase pH near the surface by polarising to potentials in which hydrogen is evolved, subsequently triggering the formation of phosphate coatings. These conversion coatings have similar morphology and composition than those produced on reactive metal surfaces. Size histograms after different active phosphating times obtained from image analysis show instantaneous nucleation of phosphate crystals with subsequent growth. The use of a commercial titanium phosphate based activation bath leads to homogeneous crystal growth, but appears not to affect significantly the crystals observed shortly after nucleation. Phosphating with a sequence of short potential pulses leads to nucleation of new crystals near the interface of previously nucleated crystals and is hence not an alternative to obtain morphologies with small crystals. Comparing layers prepared here with layers on the same AS coating prepared under open circuit conditions using fluoride additives shows that electrochemically grown layers are more homogeneous.

Experimental Investigations on Electroless Deposition of Copper on Basalt Fibers

In this work, an electroless method of coating copper on the basalt short fibers using copper sulphate solution is described. In order to avoid any interfacial reactions in the basalt fiber reinforced metal matrix composites, the basalt fibers were coated with copper. The effects of the time of sensitization, activation, metallization, PdCl2 concentration, pH and temperature bath on the extent of copper coating on basalt fiber are reported. The conditions used for electroless coating were optimized to obtain a uniform and continuous layer of copper. Using this method, it is possible to deposit up to about 25 wt% copper on the basalt fiber. The resultant composite fiber was characterized by scanning electron microscopy (SEM)/energy-dispersive X-ray (EDX) during and after the coating process. The effects of the thickness of copper coating on surface condition and also the tensile strength of the basalt fibers have been investigated. The study of surface condition of the coated basalt fibers by SEM showed that the copper coating at the thickness of about 0.2 μm had the best continuity on the basalt fibers. The results of tensile tests of basalt fibers coated with different thickness of copper showed that increasing the thickness of coating layer decreased the overall strength of fibers.

Activation and Fluoride-Assisted Phosphating of Aluminum-Silicon-Coated Steel

Phosphating is a crucial process in the corrosion protection of metals. Here, activation and fluoride-assisted tricationic phosphating is investigated on aluminum-silicon (AS) coated steel surfaces. Dynamic light scattering results from the activation bath show a bimodal size distribution, with hydrodynamic radii of ~400 nm and ~10 μm. For the smaller particle fraction, static light scattering results are consistent with the interpretation of disklike particles as scattering objects. Particles of the larger fraction sediment with time. In the presence of electrolyte, the scattering intensity from the larger particle fraction increases. Coagulation with time is suggested to be related to the decrease in activity of the activation bath. Scanning Auger microscopy (SAM) shows a higher phosphorus concentration after titanium phosphate activation in the Al-rich areas compared to the Si-rich areas of the AS coatings. There is no correlation between the size of the species in the activation bath, and the size of the phosphate-containing regions on the activated surface. Phosphating was performed in the presence of hexafluorosilicic acid, H2SiF6, ammonium hydrogen difluoride, NH4HF2, and both, at an initial pH of 2.5. The absence of crystals after phosphating with H2SiF6 is an indication that SiF6(2-) is the final product of the oxide dissolution in the presence of fluoride. In the presence of NH4HF2, the Si-rich regions of the surface are phosphated before the Si-poor (Al-rich) regions. Hence, the phosphate distribution after activation and after phosphating are opposite. These results show that a high surface concentration of phosphate after activation is not sufficient for a high coverage with phosphate crystals after phosphating.

Improvement of Al coating adhesive strength on the AZ91D magnesium alloy electrodeposited from ionic liquid

Adhesive strength of Al coatings electrodeposited on AZ91D in aluminum chloride/1-ethyl-3-methylimidazolium chloride was improved by the development of a zincate pretreatment and optimized current pulse electrodeposition method. A dense Zn layer was deposited on both the α- and β-phase surfaces of AZ91D substrate pre-treated in a Cu2+ added activation bath prior to the zincate process. On this zincated substrate an Al coating was electrodeposited by bipolar current pulse polarization and the adhesive strength of the Al coating to the substrate was better than 11MPa. The Al coating obtained under the optimal condition also showed good corrosion resistance in 3.5wt.% NaCl solutions.

Effect of copper pretreatment on the zincate process and subsequent electroplating of a protective copper/nickel deposit on the AZ91D magnesium alloy

To obtain a durable Ni coating with excellent adhesion strength on an AZ91D Mg alloy, a pretreatment was performed with a small amount of Cu 2+ ions added to the activation bath used in the pretreatment prior to the plating process. In the pretreatment activation process, a high density Cu layer was deposited on both the α-phase and β-phase areas of the substrate accompanied with Mg dissolution. The Cu deposit acted as nucleation seeds for the Zn deposition in the following zincate process which provided a uniform and dense Zn layer almost completely covering the substrate. Then a thin Cu layer was electroplated on this zincated substrate as an undercoating for the succeeding electroplating with Ni. Cross-sectional scanning electron microscopy observations showed that the Cu deposited by the pretreatment enabled the deposition of a protective Ni layer with few defects. This structure also contributed to the improvement of adhesion strength and corrosion resistance as compared with the non-Cu added sample.

Effect of Copper Pretreatment on the Zincate Process and Subsequent Copper Electrodeposition of AZ31 Magnesium Alloy

A small amount of Cu2+ ions was added to the activation bath used for pretreatment of the plating process of an AZ31 Mg alloy. In the activation process, a small amount of Cu was deposited at high density on the substrate surface accompanying Mg dissolution (Cu pretreatment). These Cu deposits acted as nucleation seeds for Zn deposition in the following zincate process and provided a uniform and dense Zn layer almost completely covering the substrate. The Cu layer electroplated on this zincated substrate showed considerable improvement in density and uniformity compared with those of the sample without Cu pretreatment. Cross-sectional SEM observation revealed that a less-defective interface between the Cu layer and substrate was obtained for the Cu-prepared sample. This structure also contributed to the improvement of adhesion strength. The mechanism of this improvement was investigated using electrochemical measurement and scanning electron microscopy observation with energy dispersive X-ray spectroscopy analysis.

Properties of fluoride film and its effect on electroless nickel deposition on magnesium alloys

The physical characteristics and microstructure of the fluoride film formed during activation were investigated using SEM, XPS and SAM, and its stability in electroless nickel (EN) bath was analyzed. The effects of the fluoride film on EN deposition were studied additionally. The results show that the fluoride film on magnesium alloys is a kind of porous film composed of MgF 2 with thickness of 1.6-3.2 μm. The composition of the activation bath and pretreatment of EN processing have influence on the composition of the fluoride film. The fluoride is stable and dissolves little in EN bath; as a result, the fluoride film can protect magnesium substrate from the corrosion of EN bath. The composition of fluoride determines the initial deposition of EN and part of the fluoride film finally exists as inclusion in EN coating.

Formation of PdS Compounds in Direct Metallization via Pd/Sn Catalyst Activation

The reaction mechanism between a Pd/Sn catalyst and sulfide ions which were used to promote direct copper plating was studied. The identity of reaction products after activation, acceleration, sulfide promotion, and plating bath dipping were analyzed by infrared absorption spectroscopy and X‐ray diffraction. It was found that the chemically adsorbed sulfides ions do not readily form PdS. The stable PdS appears only after it is dipped in the plating bath. The major agent responsible for this transformation was found to be the sulfate ions. © 1999 The Electrochemical Society. All rights reserved.

Activation bath for electroless nickel plating

Activation bath for electroless nickel plating

Contact Reactions in Pd / n ‐ GaAs Junctions Formed by Palladium Electroless Deposition

We report on the contact reactions in junctions. The palladium deposition occurs by chemical displacement of Ga and As in acidic palladium baths. When a bath containing glacial acetic acid is used in the activation step, 100 Å of palladium is deposited. Another bath, containing only to enhance the exchange mechanism, results in deposition of 2500 Å palladium. In each case, by neutron activation analysis, gallium and arsenic are detected in the bath. These results allow the formulation of a displacement mechanism according to the reactionin which there is no marked preference for arsenic or gallium. It can be assumed that these acidic baths allow in situ etching of native oxides. The 100 Å Pd film synthesized by the activation bath has been investigated using Auger electron spectroscopy and sputter profiling, grazing incidence x‐ray diffraction, and N2+ ion backscattering. Intermixed layers were obtained directly after palladium deposition. The compounds obtained vary with annealing temperature, forming ternary phases , , and, finally, a single binary phase.

Mössbauer Study of Tin(II) Sensitizer Deposits on Kapton

Mössbauer spectroscopy has been used to study tin(II) sensitizer deposits formed on Kapton films (du Pont polyimide) for use in the recently reported photoselective metal deposition (PSMD) process. Combined with previous results, this work shows that the sensitizer is present as a colloid in the sensitizing bath and is adsorbed on the substrate when it is dipped. This activation mechanism would be expected to apply to other insulating substrates as well. The photosensitive substance contains more tetravalent tin than divalent. The divalent tin is oxidized by exposure either to air or to the Pd activation bath. The photosensitive compound is not any well recognized tin oxychloride or hydroxide.