Electrodeposition electrical

Ruthenium is a hard, white metal and has four crystal modifications. It does not tarnish at room temperatures, but oxidizes explosively. It is attacked by halogens, hydroxides, etc. Ruthenium can be plated by electrodeposition or by thermal decomposition methods. The metal is one of the most effective hardeners for platinum and palladium, and is alloyed with these metals to make electrical contacts for severe wear resistance. A ruthenium-molybdenum alloy is said to be... 

Copper is universally used as the metal plating for tape because it can be easily laminated with copper and the various plastic tapes. Copper is readily etched and has excellent electrical and thermal conductivity in both electrodeposited and roUed-annealed form. The tape metal plating is normally gold- or tin-plated to ensure good bondabiUty during inner- and outer-lead bonding operations and to provide better shelf life and corrosion resistance. 

Electrodeposition. Electro deposition, the most important of the unit processes in electrorefining, is performed in lead- or plastic-lined concrete cells or, more recently, in polymer—concrete electrolytic cells. A refinery having an aimual production of 175,000 t might have as many as 1250 cells in the tank house. The cells are multiply coimected such that anodes and cathodes are placed alternately and coimected in parallel. Each cell is a separate unit and electrically coimected to adjacent cells by a bus bar. 

One potential difficulty with CF-EF is the electrodeposition of the particles at the electrode away from the filtration medium. This phenomenon, if allowed to persist, will result in performance decay of CF-EF with respect to maintenance of the electric field. Several approaches such as momentaiy reverses in polarity, protection of the electrode with a porous membrane or filter medium, and/or utilization of a high fluid shear rate can minimize electrodeposition. 

Gold coatings on separable electric contacts and slip rings make use of the high hardness possible with electrodeposition to resist wear. Rhodium is another metal which can be exceptionally hard. Thick coatings have a cracked-sealed structure similar to that of chromium. 

The principal use of gold is as a very thin coating about 0-05 /xm thick for electrical and electronic applications. Because of the thinness of gold electrodeposits, porosity must be very carefully controlled since seepage of corrosion products from substrate or undercoat exposed at these pores can have serious adverse effects on both appearance and electrical properties of the composite. The porosity can vary with the thickness of the deposit (Fig. 13.1), and with the type of plating bath and with its method of operation (Fig. 13.2), and the phenomenon has been extensively studied by Clarke and many other workers. 

Singh RP, Singh SL, Chandra S (1986) Electrodeposited semiconducting CulnSe2 films. I. Preparation, structural and electrical characterisation. J Phys D Appl Phys 19 1299-1309... 

Menke EJ, Brown MA, Li Q, Hemminger JC, Penner RM (2006) Bismuth telluride (Bi2Te3) nanowires Synthesis by cyclic electrodeposition/stripping, thinning by electrooxidation, and electrical power generation. Langmuir 22 10564-10574... 

Lyden et al. [92] used in situ electrical impedance measurements to investigate the role of disorder in polysulfide PEC with electrodeposited, polycrystalline CdSe photoanodes. Their results were consistent with disorder-dominated percolation conduction and independent of any CdS formed on the anode surface (as verified by measurements in sulfide-free electrolyte). The source of the observed frequency dispersion was located at the polycrystalline electrode/electrolyte interface. 

The composition of the electrolyte is quite important in controlling the electrolytic deposition of the pertinent metal, the chemical interaction of the deposit with the electrolyte, and the electrical conductivity of the electrolyte. In the case of molten salts, the solvent cations and the solvent anions influence the electrodeposition process through the formation of complexes. The stability of these complexes determines the extent of the reversibility of the overall electroreduction process and, hence, the type of the deposit formed. By selecting a suitable mixture of solvent cations to produce a chemically stable solution with strong solute cation-anion interactions, it is possible to optimize the stability of the complexes so as to obtain the best deposition kinetics. In the case of refractory and reactive metals, the presence of a reasonably stable complex is necessary in order to yield a coherent deposition rather than a dendritic type of deposition. 

The current efficiency also depends on the nature of the electrode and of the electrodeposit. Generally the current efficiency is high with electrodes which do not specifically polarize with respect to the desired reaction. The current efficiency is observed to be low when a powdery or a dendritic type of deposit is formed on the electrode. This is because of the relatively poor adherence of such deposits which results in mechanical loss and also because of the possibility of electrical short-circuiting between the electrodes, resulting in flow of an electrical current which does not contribute to the electrochemical reaction. 

---