Processing methods electrodeposition

The processability of certain CEPs has been utilized in the construction of microsystems, particularly miniature sensor systems. For example, simply dip-coating connecting platinum wires with a polyaniline formulation produces a useful humidity sensor.133 CEPs can also be screen-printed or ink-jet-printed to produce the complex shapes needed for various devices. Electrodeposition of CEPs is also a popular processing method, and this technique is compatible with conventional MEMS fabrication, where lithography and etching can be used to prepattern metal electrodes. Subsequent deposition of CEP by electrochemical polymerization produces the CEP microdevice.129... 

Savadogo presents the fundamental thermodynamic and kinetic considerations for fabricating inorganic thin-film materials with special emphasis on chemical deposition from mixed solutions, electrodeposition, and sol-gel methods. The exceptional range of materials that have been prepared by these methods is noteworthy, as is the low cost of the processing methods. Treated in detail are the syntheses of the component chemicals, as well as the mechanistic and synergistic role of the components including the important role played by additives. 

Aluminium may be applied as coatings by metal spraying, cladding, hot-dipping and electrodeposition, though the last-named process is difficult to apply and by far the largest proportion of aluminium-coated metals are produced by the first two methods. 

Electrodeposition This method of paint application is basically a dipping process. The paint is water-based and is either an emulsion or a stabilised dispersion. The solids of the paint are usually very low and the viscosity lower than that used in conventional dipping. The workpiece is made one electrode, usually the cathode, in a d.c. circuit and the anode can be either the tank itself or suitably sized electrodes sited to give optimum coating conditions. The current is applied for a few minutes and after withdrawal and draining the article is rinsed with de-ionised water to remove the thin layer of dipped paint. The deposited film is firmly adherent and contains a minimum of water and can be stoved without any flash-off period. This process is used for metal fabrications, notably car bodies. Complete coverage of inaccessible areas can be achieved and the corrosion resistance of the coating is excellent (Fig. 14.1). 

The induced co-deposition concept has been successfully exemplified in the formation of metal selenides and tellurides (sulfur has a different behavior) by a chalcogen ion diffusion-limited process, carried out typically in acidic aqueous solutions of oxochalcogenide species containing quadrivalent selenium or tellurium and metal salts with the metal normally in its highest valence state. This is rather the earliest and most studied method for electrodeposition of compound semiconductors [1]. For MX deposition, a simple (4H-2)e reduction process may be considered to describe the overall reaction at the cathode, as for example in... 

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