Particle properties composite plating

The deposition variables are the process parameters most suited to regulate the particle composite content within the limits set by the particle properties and plating bath composition. Particle bath concentration is the most obvious process variable to control particle codeposition. Within the limits set by the metal plating process and the practical feasibility also current density, bath agitation and temperature can be used to obtain a particular composite. Consequently the deposition process variables are the most extensively investigated parameters in composite plating. The models and mechanisms discussed in Section IV almost exclusively try to explain and model the relation between these process parameters and the particle codeposition rate. 

Any study of colloidal crystals requires the preparation of monodisperse colloidal particles that are uniform in size, shape, composition, and surface properties. Monodisperse spherical colloids of various sizes, composition, and surface properties have been prepared via numerous synthetic strategies [67]. However, the direct preparation of crystal phases from spherical particles usually leads to a rather limited set of close-packed structures (hexagonal close packed, face-centered cubic, or body-centered cubic structures). Relatively few studies exist on the preparation of monodisperse nonspherical colloids. In general, direct synthetic methods are restricted to particles with simple shapes such as rods, spheroids, or plates [68]. An alternative route for the preparation of uniform particles with a more complex structure might consist of the formation of discrete uniform aggregates of self-organized spherical particles. The use of colloidal clusters with a given number of particles, with controlled shape and dimension, could lead to colloidal crystals with unusual symmetries [69]. 

Plate-like particles of interest in this context include mica, aluminum flake, hammered glass, magnesium hydroxide and talc. Physical properties of composites containing these additives depend strongly on the flow-induced morphology and on the distribution of residual stresses [31]. 

CLAYS. The terms chy or cloys commonly refer to cither rocks that are consolidated or unconsolidated sediments, nr a group of minerals having unique properties. Traditionally, clays (rocks) are distinctive in al least two properties that render them technologically useful plasticity and composition. Clays are predominantly composed of hydrous phyllosilicates. referred to as clay minerals. These are hydrous silicates of Al. Mg. K, anti He. and other less ahundanl elements. Clay minerals arc extremely fine crystals or particles, often colloidal in size and usually plate-like in shape. The nonclay mineral portion of clays (rocks) may consist of other minerals, portions of rocks, and organic compounds. 

However, granulometric composition is also dependent on several technological factors, more specifically, the properties of source material and binder liquid, their ratio and particle size of material on the plate. 

Apart from the surface composition the bulk properties of a particle material will affect composite deposition. Particle mass transfer and the particle-electrode interaction depend on the particle density, because of gravity acting on the particles. Since the particle density can not be varied without changing the particle material, experimental investigations on the effect of particle density have not been performed. However, it has been found that the orientation of the plated surface to the direction of gravity combined with the difference in particle and electrolyte density influences the composite composition. In practice it can be difficult to deposit composites of homogeneous composition on products where differently oriented surfaces have to be plated. 

The metal surface properties also change with the bath constituents and thereby affect the particle-electrode interaction. Metal deposition constitutes a multi-step reaction mechanism that depends on the bath composition. In quite a number of reaction mechanism adsorbed intermediates, e.g. the presence of chromium and catalyst polyoxides on the metal surface during chromium plating, are involved. Not the metal surface, but the adsorbed intermediates will determine the particle-electrode interaction and might even compete for adsorption sites on the electrode surface with the particle. Although the reverse, i.e., the change in metal deposition mechanism due to the presence of particles has been investigated (see Section 3.U), no studies on the effect of the deposition mechanisms on particle codeposition have been reported. 

The ZrB2-SiCp (ZS) composite were fabricated by hot pressing in a graphite die at Materials and Machines, Inc, Tucson, AZ, and contained 20 v/o SiC particles. Cu-clad-Mo plates, obtained from H.C. Starck, Inc, Newton, MA, had Cu-to-Mo-to-Cu layer thickness ratio of 13%-74%-13%. The commercial brazes, Palco, Palni, Cusil-ABA and Ticusil were obtained in foil form (thickness 50 pm) from Moigan Advanced Ceramics. The compositions, liquidus and solidus temperatures, and selected properties of the braze alloys are given in Table 1. 

Additionally, supramolecular carbon nanostructures have been made from nanoballs, -rods, and -tubes. New materials can be formed with the different nanosized structures but preparation of their materials and properties is somewhat different than for traditional materials. For example, nanocrystalline metals are much harder. These materials and unusual properties combine to create composites, for example, from the co-deposition of particles with metals in a plating process or in compositionally modulated multi-layers. Also of interest are core-shell particles, which consist of an inorganic core and a conducting polymer shell, and the traditional composites with larger subunits. Ways leading to the preparation of such nanocomposites is an interesting topic and will be discussed in this chapter. 

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