The Effect of Surface Charge on the Deposition Rate of Particles with Metals

Abstract

The influence of ζ-potential on the electrodeposition of particles with metals was investigated by the codeposition of three different types of particles (BaSO 4 , CaF 2 and K 1.33 Mn 8 O 16 ) with three different metals (nickel, copper and zinc) from seven different, unsupported (binary) and well-supported plating solutions across the whole pH range. The surface charge of the particles in the plating solutions was modified by adding potential determining ions that are electrochemically silent. The surface charging behavior of the different particles was determined in indifferent electrolytes and in diluted plating baths. In all cases, making the surface potential more positive increased the deposition rate of particles, while if the surface charge is reduced or made negative, the deposition rate of particles decreased. By comparing the magnitudes of the different forces acting on particles and how they are affected by changes in the surface charge of the particles, we conclude that the change in the codeposition are due to either a change in the mass transport of particles by the electrophoretic force or a change in the particle-electrode adhesion due to the double layer force.Electrodeposition of metals and alloys allows easy control over coating thickness and morphology, but the coating properties are restricted to those of the deposited metals. 1 To improve or add specific properties to the coating, particles can be added to the plating bath. As a result, metal matrix composite coatings are formed by incorporation of the particles in the coating during electrodeposition. During the past decades, the electrolytic deposition of such dispersion coatings has become an important industrial technology with applications such as wear resistance 2-6 and corrosion resistance. 7,8 Other, more recent applications include thermal regulation and thermal actuation by codeposition of phase change materials, 9,10 selflubricating coatings containing oil microcapsules 11 and permanent hydrophobicity. 12 The extent to which particles modify the coating properties is determined, to first order, by the amount of particles that are incorporated into the metal. Contrary to what one might expect, the amount of codeposited particles is often disappointingly low (below 1 vol%) despite the fact that particle concentrations of 100 g/L or more are used. Hence, ways have been sought to increase the rate of particle deposition and to understand why in some cases, the codeposition rate is so low.In the past, it was shown that the hydrophobicity and the surface conductivity of particles strongly influences their incorporation during electrodeposition. 13-16 Also the sign and magnitude of the particle surface charge has been mentioned as an important factor and various authors believe that a positive surface charge aids codeposition. [17][18][19][20] During electroplating, the cathode is polarized negatively. Thus it is not surprising that people believed that positively charged particles would be electrophoretically or electrostatically attra...

Codeposition of Particles: Role of Adsorption of the Electroactive Species

“…6). Hence, it can be concluded that the electrophoretic movement contributes to the codeposition of particles, as previously reported, 70 though it is not a fundamental factor for their entrapment. In fact, Fransaer et al 37 established that the electrophoretic force can be neglected when deposition takes place on a rotating disk electrode.…”

“…71 Moreover, Soccol et al found that the ζ-potential strongly influences the codeposition of brownian particles. 70 It is then clear that the relevance of this kind of interaction is different for each case.…”

Mechanisms for the Growth of Thin Films of WO3 and Bronzes from Suspensions of WO3 Nanoparticles

“…When attached, they change the surface energy and diffusional properties of the electrode [30], and may lead to the growth of a film. Soccol et al [31] explain the deposition rate of particles as the product of their transport rate to the electrode times the sticking probability. Transport is governed by the stagnation point, electrophoretic force, gravity, buoyancy, and diffusiophoretic forces, whereas the incorporation probability depends on London-van der Waals forces, double layer, electrophoretic force, diffusiophoretic force, image force, and solvation.…”