Electrolytes fabrication

Most of the literature focuses on the aspects of sinterability and microstructure, but limited data on the electrical properties is available. Tok [152] reported a conductivity of 18.3 x 10-3 Scm-1 at 600°C for Gd0 jCeo.gOj 95, and we measured a high conductivity of 22 x 10-3 scm-1 for Sm0 2Cc08O 9 at the same temperature. Their activation energies are relatively low—less than 0.7 eV. Although conductivity data reported for doped ceria prepared with carbonate precipitation is varied from different authors [153-155], the conductivity is generally high and the activation energy is usually low for ceria electrolytes fabricated with this method. 

These cells contain solid electrolytes fabricated by sintering green ware prepared by electrophoretic deposition. 

From these results, it vras concluded that the electrochemical performance of the as-prepared single cells with an 8YSZ electrolyte fabricated from a sol-gel route was lower than that of the State-of-the-Art FZJ-type cells, which had a mean current density value of around 1800 mA/cm at 700 mV cell voltage and at a test temperature of 1073 K. There might be three reasons for the limited electrochemical performance. First of all, the cathode was partly delaminated during the cell test. Secondly, the pores in the top electrolyte layers resulted in incomplete contacts with the intermediate electrolyte layers (Figure 5b). The last and most important reason was the diffusion of Strontium (Sr) from the LSCF cathode into the electrolyte during the operation of electrochemical... 

A. L. Yerokhin, A. A. Voevodin, V. V. Lyubimov, J. Zabinski, and M. Donley, Plasma electrolytic fabrication of oxide ceramic suriace layers for tribotechnical purposes on aluminium alloys. Surf. Coat. Technol, IIO, 140-46(1998). 

Basu, R.N., Altin, O., Mayo, M.J., Randall, C.A. and Eser, S. (2001), Pyrolytic carbon deposition on porous cathode tubes and its use as an interlayer for solid oxide fuel cell zirconia electrolyte fabrication, J. Electrochem. Soc., 148, A506-A512. 

The result is the formation of a dense and uniform metal oxide layer in which the deposition rate is controlled by the diffusion rate of ionic species and the concentration of electronic charge carriers. This procedure is used to fabricate the thin layer of soHd electrolyte (yttria-stabilized 2irconia) and the interconnection (Mg-doped lanthanum chromite). 

In electrolytic processes, the anode is the positive terminal through which electrons pass from the electrolyte. Anode design and selection of anode materials of constmction have traditionally been the result of an optimisation of anode cost and operating economics, in addition to being dependent on the requirements of the process. Most materials used in metal anode fabrication are characteristically expensive use has, however, been justified by enhanced performance and reduced operating cost. An additional consideration that has had increasing influence on selection of the appropriate anode is concern for the environment (see Electrochemical processing). 

The positive plates are siatered silver on a silver grid and the negative plates are fabricated from a mixture of cadmium oxide powder, silver powder, and a binder pressed onto a silver grid. The main separator is four or five layers of cellophane with one or two layers of woven nylon on the positive plate. The electrolyte is aqeous KOH, 50 wt %. In the aerospace appHcations, the plastic cases were encapsulated in epoxy resins. Most usehil cell sizes have ranged from 3 to 15 A-h, but small (0.1 A-h) and large (300 A-h) sizes have been evaluated. Energy densities of sealed batteries are 26-31 W-h/kg. 

Container. The battery container is made up of a cover, vent caps, lead bushings, and case. Cost and appHcation are the two primary factors used to select the materials of constmction for container components. The container must be fabricated from materials that can withstand the abusive environment the battery is subjected to in its appHcation. It must also be inert to the corrosive environment of the electrolyte and soHd active materials, and weather, vibration, shock, and thermal gradients while maintaining its Hquid seal. 

Purity. Electrolytic copper is one of the purest of the materials of commerce. The average copper content of ETP copper, for instance, is over 99.95%, and even the highest level of impurities other than oxygen are found only to the extent of 15—30 ppm. Up to 0.05% oxygen is present in the form of copper(I) oxide. Even at these low impurity levels, properties of interest to fabricators are affected in varying degree. 

Nawa, M., Nogami, T. and Mikawa, H., Application of activated carbon fiber fabrics to electrodes of rechargeable battery and organic electrolyte capacitor, J. Electrochem. Soc., 1984, 131(6), 1457 1459. 

Conceptually elegant, the SOFC nonetheless contains inherently expensive materials, such as an electrolyte made from zirconium dioxide stabilized with yttrium oxide, a strontium-doped lanthanum man-gaiiite cathode, and a nickel-doped stabilized zirconia anode. Moreover, no low-cost fabrication methods have yet been devised. 

The excellent resistance of zinc to corrosion under natural conditions is largely responsible for the many and varied applications of the metal. In fact nearly half the world consumption of zinc is in the form of coatings for the prevention of corrosion of steel fabrications exposed to the atmosphere and to water. For its varied applications zinc is obtainable in a number of grades. Ordinary commercial (G.O.B.) zinc contains up to about I -5% total of lead, cadmium and iron. Electrolytic zinc has a minimum zinc content of 99-95% and contains small amounts of the same impurities. Special high-purity zinc has a minimum of 99-99% zinc. Even purer zincs are commercially available. 

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