Controlling of Surface Parameters of Particles Used for Electrocodeposition

Abstract

It is well known that colloid-chemical aspects, such as agglomeration processes, wetting and adsorption phenomena, have a decisive influence on the separation behaviour and coating quality of a composite plating. The following processing steps for electrocodeposition have to be considered: preparation of a stable dispersion of the particles in the electrolytic bath, transportation of the particles to the metal surface, adhesion of the particles onto the surface, incorporation of the particles in the metal matrix. Celis [1,2] and Hyashi [3] could show that ion adsorption onto the particle surface is very important for electrophoretic mobility and layer quality. On the other site, Fransaer and others [2,4] showed that surface free energy plays an important role for incorporation of particles in a metal matrix. They could demonstrate that hydrophilic particles do not make contact with the electrode, probably due to repulsive hydration forces. Hydrophobic particles make contact with the electrode, due to an attractive hydrophobic force. Hence it is important to have a method for estimating the hydrophilic/ hydrophobic surface properties of such particles to select a suitable surface modification strategy. A direct way to measure the surface free energy of solid particles is not available so far. Therefore, it is generally accepted to use the phenomenon of capillary penetration of liquids into porous media to determine the wetting properties of particles by measuring the penetration velocity of well-defined liquids in a powder packing. The kinetics of penetration correlates mainly to the geometric structure of the powder packing and the wettability of the particles. By using the equation-of-state approach for solid-liquid interfacial tensions the solid surface free energy of the particles can be determined [5]. In this paper, we show the usefulness of capillary penetration experiments and discuss some parameters that should be considered for the interpretation of the data. Ion adsorption processes, on the other hand, can be described by electrokinetic measurements [6,7].

Surface Properties of Carbon Nanotubes and Their Role in Interactions with Silica

“…The surface tension of the CNTs was indirectly determined by means of the capillary penetration method described in the previous studies [1,2]. Particularly, a CNT powder packed homogeneously in a glass tube was brought into contact with ethanol-water mixtures with different surface tensions γ lv .…”