Codeposition Of Particles Research Articles

Electrolytic Codeposition of Silica Particles with Aluminum from AlCl3-Dimethylsulfone Electrolytes

The electrolytic codeposition of silica particles with aluminum was investigated from an -dimethylsulfone electrolyte containing monodisperse silica particles with a diam of 0.2 μm. The electrodeposition was done at and at current densities between 6 and Dense aluminum coatings with a thickness of 20 μm were obtained at a plating rate of 77 μm/h. The coatings contained a homogeneous dispersion of individual silica particles. The amount of codeposited silica particles was found to depend on the concentration of silica particles suspended in the electrolyte and the current density. © 2001 The Electrochemical Society. All rights reserved.

Autocatalytic nickel coatings on aluminium with improved abrasive wear resistance

The heat treatment temperature required to maximize the wear resistance of autocatalytic nickel deposits exceeds the age-hardening temperature of aluminium alloys. As a consequence, a careful selection of the heat treatment temperature is required in order to preserve the mechanical characteristics of the aluminium substrate while improving coating performance. The abrasive wear resistance of the nickel–phosphorus/Al 6063-T6 system was evaluated taking into account several criteria, such as: phosphorus (P) content, SiC particle codeposition, and heat treatment. The results of wear resistance were related to the structural changes (i.e. phase transition, grain size) observed by X-ray diffraction for different phosphorus coatings and after the applied heat treatments. With increasing the phosphorus content, the abrasive wear resistance of as-deposited particle-free coatings decreased and their structure changed from a nanocrystalline supersaturated solid solution of phosphorus in nickel ( P≤6 wt.%) to an amorphous nickel–phosphorus phase ( P≥10 wt.%). The composite coatings with 30–35 vol.% SiC were more wear resistant relative to particle-free coatings. Finally, a heat treatment temperature of 220°C with 1 h holding time proved to further enhance the abrasive wear resistance of low- and medium-phosphorus coatings (particle-free and composites), whereas no improvement was observed for the amorphous coatings. The selected thermal treatment did not affect the hardness of the aluminium substrate.

Electrochemical investigation of the codeposition of SiC and SiO2 particles with nickel

The use of electrochemical impedance spectroscopy (EIS) for the in situ control of the electrolytic codeposition of Ni/SiO2 and Ni/SiC was investigated. An attempt was made to clarify why silica particles hardly codeposit in comparison to silicon carbide particles. It was found that the presence of SiO2 and SiC particles influences the metal deposition process in diAerent ways. SiC particles that are being embedded in the growing metal layer cause an apparent decrease in the electrode surface area, probably due to blocking oA a part of the surface by partly engulfed particles. In the case of SiO2 particles, which embed in the metal matrix to a very limited extent, no blocking was observed. It was found that the presence of particles in the solution causes an apparent increase in the electrode surface area, probably due to increased surface roughness.

Codeposition of Hydrophilic and Hydrophobic Silica with Copper from Acid Copper Sulfate Baths

The influence of the hydrophobicity of silica particles on the electrodeposition of composite coatings from acid copper sulfate solutions on rotating disk electrodes was studied. Spherical, nearly monodisperse hydrophilic and hydrophobic silica particles were used. The hydrophilic silica particles were prepared by the Stöber process. These particles were made hydrophobic by a treatment with oligodimethyl siloxane‐α,ω‐diol. The effect of cetyl trimethyl ammonium hydrogen sulfate (CTAHS) and sodium 1-dodecane sulfonate on the codeposition behavior was investigated. Hydrophilic silica did not codeposit from surfactant‐free nor from surfactant‐containing acid copper sulfate solutions, but up to 4 wt % (≅ 14 vol %) of hydrophobic silica codeposited from solutions containing 15 g/L of silica particles and . The codeposition rate of hydrophobic silica slowly decreased with time. The amount of codeposited particles was highest for a current density of and a rotation speed of 400 rpm. © 2000 The Electrochemical Society. All rights reserved.

The relation between anionic/non‐ionic surfactant and electrodeposition of nickel‐polytetrafluoro ethylene polymer composite

A nickel‐fluoropolymer composite was produced by electrodeposition using Watt’s nickel bath containing polytetrafluoro ethylene (PTFE) in suspension. Various experimental conditions including the PTFE concentration, the pH values, current density and the temperature on the volume per cent of PTFE were evaluated. Also several studies were carried out with aqueous surfactant mixture solutions including surface tension (γ), critical micelle concentration (CMC), micellar composition (Xm), activity coefficient (υ), micellar interaction parameter (βm). Effectiveness (ΠCMC) and efficiency PC20 were investigated at different mole fraction of anionic surfactant. The relation between efficiency of anionic/non‐ionic surfactant mixture and codeposition of PTFE particles was discussed according to micellar composition and the above mentioned physical parameters.

Hydrogen evolution, incorporation and removal in electroless nickel composite coatings on aluminium

The mechanism of electroless nickel deposition involves generation of hydrogen which can be entrapped in the NiP layer. In this study hydrogen evolution in several electroless composite coatings, that is, NiP–X (X=SiC, Al2O3 and boron particles), deposited on an aluminium (6063-T6) substrate, was investigated by the solid extraction method. It was found that particle codeposition can promote hydrogen occlusion in the layers, a fact correlated with the adsorption capacity and affinity of particles towards water or hydrogen itself. Hydrogen removal efficiency from coatings, after heat treatment, increased with the applied temperature (130, 160 and 190 °C for 1.5h each). For the same heat treatment (190 °C for 1.5h), most composite coatings showed lower removal efficiencies (35–54%) compared to NiP layer (80%) and, as the amount of hydrogen in the composite coating increased, its removal efficiency decreased.

An adsorption strength model for the electrochemical codeposition of α-Al2O3 particles and a Fe–P alloy

An adsorption strength model is developed to describe the mechanism of codeposition of α-alumina and Fe–P alloy. Based on hypotheses concerning the effective adsorption and the distribution of the adsorption strength of particles on the cathode, a general expression relating the content of embedded particles to the suspension concentration and the current density is deduced. This relationship is in good agreement with the experimental results. The variation of the content of particles in deposits with current density is an overall balance of two opposing effects which leads to a maximum in the particle content against current density curve.

Electrochemical deposition of zinc–polystyrene composites in the presence of surfactants

The electrochemical codeposition of polystyrene particles and zinc on a rotating cylinder electrode was investigated. Rheological measurements indicate strong aggregation of the PS particles in the zinc deposition electrolyte. Addition of cetylpyridinium chloride, a cationic surfactant, prevents aggregation and enhances polystyrene codeposition. Other surfactants also increase suspension stability, but diminish polystyrene codeposition, irrespective of their charge. Hence, the surfactant charge does not affect polystyrene codeposition. The variation of polystyrene incorporation with the amount of suspended polystyrene, current density and electrode rotation speed signifies that polystyrene codeposition with zinc is determined by the competition between particle removal forces and particle adhesion forces at the cathode surface. The effect of the surfactants can be related to changes in surface roughness of zinc due to surfactant adsorbed on the electrode. Cetylpyridinium chloride behaves differently from the other surfactants, because it is reduced at the cathode.

A parallel plate flow cell for the investigation of the role of surfactants in the codeposition of polymer particles in nickel electroplating

A parallel plate flow cell was designed for the study of particle codeposition in metal electrodeposition. Particle deposition was visualized and recorded with a microscope/video assembly. The effects of two surfactants (anionic sodium dodecyl sulphate and cationic cetyl trimethyl ammonium bromide) on the adhesion of anionic polystyrene particles to a nickel substrate were examined. The deposition rate in laminar flow was measured as a function of the main parameters, that is, electrode potential, Ni(ii) concentration, surfactant concentration and pH. The hydrodynamic drag force applies uniformly and tangentially to the collector under laminar flow in contrast with rotating disc or impinging jet cells. No deposition is observed unless specific attractive forces carry the particles through the boundary layer. Particle attachment takes place over a limited range of surfactant/Ni(II) composition and correlates with the formation of a surface film visible under the microscope. Results discussed are based on the adsorption of SDS and CTAB on to both the electrode and the particles, an adsorption which significantly alters the interaction potential at a short distance. The cell gives interesting evidence for the occurrence of specific interactions in electrolytic codeposition. It also proves useful for observing other phenomena, such as hydrogen bubbling.

Oxygen Incorporation during the Electrodeposition of Ni, Fe, and Ni‐Fe Alloys

This study sought to quantify the oxygen content of electrodeposited Ni, Fe, and Ni‐Fe alloys and to identify mechanisms by which the oxygen is incorporated in the deposits. In the absence of boric acid in the bath, the oxygen content of electrodeposited Ni increases with increasing applied current density. This behavior corresponds to a significant increase in the pH of the solution adjacent to the cathode, which results in the precipitation of on the cathode and occlusion of this material in the growing deposit. The incorporation of oxygen during Ni‐Fe electrodeposition is similar, except that an increase in the concentration in the bath reduces the oxygen content. This behavior results from buffering provided by that accompanies the in this system. When boric acid is present in the bath, oxygen incorporation is low in all three electrodeposition systems. This observation is consistent with buffering of the cathode pH resulting from boric acid’s ability to complex with , which generates as a by‐product. The oxygen that is incorporated may be attributed to hydroxide ion that fails to leave the surface following its participation in the electroreduction process. In Ni‐Fe electrodeposition, oxygen incorporation by particle codeposition is shown to play an insignificant role.

Particles Co-Deposition by Electroless Nickel

Laboratory of Materials Science, Delft University of Technology,Rotterdamseweg 137, 2628 AL Delft, The Netherlands(Received November 4, 1997)(Accepted in revised form January 23, 1998)IntroductionElectroless, as well as electrochemical co-deposition of inert particles, represents a method to obtainmetal matrix composite materials as thin foils (coatings) at low temperature (’90°C). Compared toelectrodeposition, electroless can be applied on different substrates (conductive and nonconductive) andthe obtained layer has a very homogeneous distribution regardless the substrate geometry [1].An electroless nickel composite coating consists of small inert particles, such as: oxides, carbides,nitrides polymers etc., uniformly dispersed into a nickel-based matrix. During the redox reactionbetween Ni

Electroless Ni–P Composite Coatings: The Effect of Heat Treatment on the Microhardness of Substrate and Coating

A possibility to increase materials performance for different applications is to protect them by coatings. Electroless nickel deposition represents an alternative method to obtain coatings on various substrates (metallic and nonmetallic). The process is based on a redox reaction in which the reducing agent is oxidized and Ni ions are reduced on the substrate surface. Once the first layer of nickel is deposited it is acting as a catalyst for the process. As a result, a linear relationship between coating thickness and time, usually occurs [1]. If the reducing agent is sodium hypophosphite, the obtained deposit will be a nickel–phosphorus alloy. The as-deposited Ni–P alloys were reported to have a non-equilibrium phase structure [2]. It is generally accepted that a microcrystalline, amorphous or a co-existence of these two phases can be obtained depending on phosphorus content [2–6]. A recent advance in electroless Ni–P deposition is the co-deposition of solid particles within coatings. These solid particles can be hard materials (SiC, B4C, Al2O3, diamond [7–10]) and dry lubricants (PTFE, MoS2 and graphite [11–13]). By this method, composite layers with very good characteristics for specific applications can be produced. Electroless Ni–P–SiC coatings are recognized for their hardness and wear resistance and can replace “hard chromium” in aerospace industry [1, 10, 14]. Also, the electroless Ni–P–PTFE films present excellent self-lubricating properties [12]. One of the more increasingly used substrate materials in electroless nickel deposition is aluminium and its alloys [15]. However, aluminium is a very reactive metal which easily form a hard to remove oxide film during rinsing or exposure to air. This oxide film represents a disadvantage for electroless nickel deposition where a metal-metal bond is required. To overcome this problem, a suitable pretreatment sequence including a deoxidizing step followed by a double immersion in a modified alloy zincate (MAZ) solution can be applied [15, 16]. To increase the hardness and the abrasion resistance of electroless Ni–P deposits, heat treatments are performed. Studies carried out in this direction [7] showed that a maximum hardness can be achieved after a heat treatment at 400°C for 1 h, when the hardness of the deposit increased from 500–600 up to 1000–1100 HV100. In this study, the electroless Ni–P and Ni–P–X (X 5 SiC, Al2O3 and B) coatings deposited on a heat treatable Al alloy (6063-T6) were investigated. Coating structure investigated by XRD and DSC, and Pergamon Scripta Materialia, Vol. 38, No. 9, pp. 1347–1353, 1998 Elsevier Science Ltd Copyright © 1998 Acta Metallurgica Inc. Printed in the USA. All rights reserved. 1359-6462/98 $19.00 1 .00 PII S1359-6462(98)00054-2

A Study of the Hydrogen Evolution Reaction on a Ni/NiFeS Electrodeposited Coating

Composite cathode materials based on nickel, such as NiFe, NiMo, NiMoCd, NiS, and , are of considerable practical interest as possible electrocatalysts for hydrogen production in alkaline water electrolyzers. This work describes the development of a new composite material of Ni and FeS (referred to as Ni/NiFeS) that shows a high electrocatalytic activity toward the hydrogen evolution reaction. Ni/NiFeS coatings were obtained by codeposition of Ni and FeS particles on Ni previously electrodeposited on a mild steel substrate. The evaluation of this material as ‐evolving cathodes was done in alkaline solution through steady‐state techniques. The polarization behavior of the material shows two distinct regions exhibiting different Tafel slopes over the temperature range 273 to 353 K. A detailed mechanistic study of the hydrogen evolution reaction on Ni/NiFeS was carried out by ac impedance techniques. The rate constants for the elementary steps were obtained and suggest a mechanism that involves an electron transfer followed by an electrochemical desorption step. The consistency of the analysis was confirmed by establishing that the apparent activation energy calculated from the dependence of the rate constant of the rate‐determining step with has the same value as that found for the overall reaction.

Nickel/microcapsules composite electrocoatings; the synthesis of water-containing microcapsules and preparation of the coatings

Composite coatings, the product of electrolytic codeposition of solid particles in a metallic matrix have been developed and utilized in industry as wear resistant coatings. The work described in this paper concerns the development of water-containing metallic coatings prepared by the electrolytic codeposition of water-containing microcapsules from nickel Watts plating baths under pulse reversed current conditions. The water-containing polystyrene microcapsules employed in the codeposition experiments were produced by the complex emulsion/solvent evaporation technique. The influence of the use of two types of stabilizers on the size and the surface chemistry of the microcapsules is discussed. The microcapsules prepared in both cases are rigid spheres with compact walls and a smooth surface. The different stabilizers showed a significant influence on the dispersability of the capsules in the plating solution and their codeposition behaviour. The codeposition experiments carried out with the use of a rotating disc electrode revealed the influence of the plating parameters on the incorporation procedure and on the quality of the composite electrodeposits.

Electrocodeposition of Nickel−Diamond and Cobalt−Chromium Carbide in Low Gravity

Codeposition of particles and metals was studied under low-gravity conditions. Ni−diamond and Co−chromium carbide coatings were investigated. Experiments were run aboard two sounding rockets, each providing 7 min of 10-4g, and one shuttle mission providing 4 h of deposition. Reduced gravity proved to eliminate sedimentation and edge effects and promote easier particle dispersion in the electrolyte, yielding uniformly distributed particles in the metal matrix. Large nonconducting diamond particles were codeposited in higher volume percents as opposed to bench experiments. The trend was opposite for particles of ≤1 μm size with fine chromium carbide particles depositing in higher volume percent in 1g than low g.

Electrochemical codeposition of inert particles in a metallic matrix

A survey on electrochemical codeposition of inert particles in a metallic matrix is given. Particles held in suspension in an electroplating bath are codeposited with the metal during electrodeposition. The particles used are inert to the bath and can be of different types, that is, pure metals, ceramics or organic materials. Combining this variety of types of particles with the different electrodeposited metals, electrochemical codeposition enables the production of a large range of composite materials with unique properties. Many experimental factors were found to influence the codeposition process, which led to some understanding of the mechanism. Models to predict the codeposition rate were developed, but were only partly successful.

Adsorption of Ni(II) Ions of the Surface of SiC Powder in the Formation of Dispersion Coatings

The adsorption of Ni(II) ions on SiC powder in NiSO4 solution has been measured as part of the codeposition of solid particles with a metal. The influences of SiC concentration in suspension, of the initial nickel ion concentration and pH of the bath, and of the sort, particle size and preliminary preparation of the SiC have been determined.Some facts indicating that both Ni(II) and H+ ions adsorption processes coexist on SiC and compete with each other have been established. Application of the Freundlich and Langmuir isotherms to the system studied has been tested and the effect of temperature on a change of adsorption determined.

Ｎｉ‐ＴｉＯ２分散めっき皮膜の光電気化学的挙動

Photoelectrochemical technique was applied to characterize the dispersion state of TiO2 particles in Ni-TiO2 composite films. Ni-TiO2 composite films were prepared by dispersion plating under various conditions, and when they were used as the photoelectrode in sulfuric acid solution, the differences in the dispersion of the TiO2 particles in the films modified the photocurrent-potential curve. The photocurrent obtained showed one peak (A) in the region of less noble potential and an ordinal increase (B) in the noble potential region. The increased exposure of TiO2 particles on the surface as a result of chemical etching caused an increase in photocurrent (B), and the thicker the film grew, the smaller its photocurrent (B) became. This is due to the fact that the TiO2 particles in the film acted as an electrical resistance. When composite films were formed under high plating current density, codeposition of TiO2 particles was suppressed and the corresponding photocurrent (A) was relatively small. The condensation of TiO2 particles in the film reduced the photocurrent park (A), but increased photocurrent (B). This behavior suggests that the first photocurrent peak (A) located in the less noble potential region corresponds to the photoelectrochemical dissolution of the nickel matrix, and that the second increase (B) located in the noble potential region corresponds to the photoelectrochemical oxidation (probably O2 evolution) on the TiO2 particles.

Analysis of the Electrolytic Codeposition of Non‐Brownian Particles with Metals

A model for the electrolytic codeposition of spherical particles with metals on a rotating disk electrode is presented, based on a trajectory analysis of the particle deposition, including convective mass transport, geometrical interception, and migration under specific forces, coupled to a surface immobilization reaction. A number of relevant forces were included and their effects determined. Theoretical predictions of this model are compared with experimental results for the codeposition of spherical polystyrene particles with copper during electrolysis from an acid copper sulfate solution. The influence of fluid flow velocities, particle concentration, and current density on the rate of particle deposition is illustrated. Experiments done on a rotating disk electrode allow the adhesion forces to be determined from the distribution of particles on the surface. It is shown that codeposition is governed by colloidal interactions that can, in first order, be approximated by the Derjaguin‐Landau‐Verwey‐Overbeek interactions plus an additional short range repulsion that was associated with the hydration force.

Co-deposition of fine particles on glass surfaces

The deposition of latex particles on glass surfaces in the presence of a CaF 2 precipitant has been studied in the impinging jet cell. The initial flux of latex particles in 5 × 10 −4 M CaCl 2 solution was increased by a factor of thirty when the glass collector surface was modified by contact with CaF 2 precipitant. However, after a period of time necessary to dissolve the positively charged CaF 2, the flux had declined and eventually the previously deposited particles were washed out. Small amounts of the CaF 2 precipitant added to the latex solution also promoted deposition, although in this case the flux increase was not as large as it was previously. Significant influence of the CaF 2 precipitant on the latex particles flux to the glass collector was noted even for quantities of CaF 2 which should have dissolved after being added to the latex suspension. For very small amounts of CaF 2 precipitant, the initially constant flux declined sharply after some period of time. However, one could not see the escape of the deposited particles. The experimental data presented herein indicate a great number of possible interactions during the deposition process from binary mixtures of chemically dissimilar colloid particles. This paper also briefly presents a theory of the phenomenon.