Nickel fabrication methods

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. 

There are a variety of materials that can be used as sacrificial cores. Inorganic sacrificial materials include Si02 and metals such as aluminum, " titanium, and nickel. Polymers such as PI, PMMA, PC, and photoresist have also been used as sacrificial materials. After deposition of the cover film, removal of the sacrificial layer can be achieved by dissolution, etching, or thermal degradation. These removal methods each have benefits and drawbacks selection of the optimal approach is specific to particular combinations of substrate, sacrificial layer, and cover film 73, 3 Recently Whitesides and coworkers " implemented a fabrication method using water-soluble sacrificial cores. Poly(acrylic acid) and dextran proved to be effective sacrificial layers that could be dissolved in water or aqueous NaCl, for making metallic microstructures by nickel electrodeposition. 

T. Kodas et al, Nickel Powders, Methods for Producing Powders Devices Fabricated from the Same , US Patent No.6, 316, 100, 2001. 

These features have been found to be highly correlated with the fabrication method/sequence as well as materials selected. For example, anode support cells have stable anodes but there remain several points to be optimized for a cathode-complex-layer structure. On contrary, cathode-support cells have the stable performance for cathodes, but anodes may have some changed in microstructure because of nickel sintering [63]. 

Careful specification of purity, unallowable impvuities, fabrication method, post-fabrication treatments, packaging, etc. of the source materials purchased can be important in obtaining a reproducible process. Using inexpensive material or material of unknown origin often creates problems. Often impurities such as O, N, C, and H are not specified by the supplier and they may be present in significant quantities. Examples of unspecified impurities are oxidized surfaces of reactive metals, hydrogen incorporated in electrorefined chromium, carbon monoxide in nickel purified by the carbonyl process, and helium in natural quartz. Generally it is better to specify vacuum-melted materials from the supplier when possible. 

There are many methods of fabricating the electrodes for these cell systems. The eadiest commercially successhil developments used nickel hydroxide [12054-48-7] Ni(OH)2, positive electrodes. These electrodes are commonly called nickel electrodes, disregarding the actual chemical composition. Alkaline cells using the copper oxide—2inc couple preceeded nickel batteries but the CuO system never functioned well as a secondary battery. It was, however, commercially available for many years as a primary battery (see BatterieS-PRIMARY cells). 

Almost all the methods described for the nickel electrode have been used to fabricate cadmium electrodes. However, because cadmium, cadmium oxide [1306-19-0], CdO, and cadmium hydroxide [21041-95-2], Cd(OH)2, are more electrically conductive than the nickel hydroxides, it is possible to make simple pressed cadmium electrodes using less substrate (see Cadmium and cadmium alloys Cadmium compounds). These are commonly used in button cells. 

Other Cells. Other methods to fabricate nickel—cadmium cell electrodes include those for the button cell, used for calculators and other electronic de dces. Tliis cell, the construction of which is illustrated in Figure is commonly made using a pressed powder nickel electrode mixed with graphite that is similar to a pocket electrode. Tlie cadmium electrode is made in a similar manner. Tlie active material, graphite blends for the nickel electrode, are ahnost the same as that used for pocket electrodes, ie, 18% graphite. 

All AB, alloys are very brittle and are pulverized to fine particles in the hydrid-ing-dehydriding process (see Sec. 7.2.1). Thus electrodes must be designed to accommodate fine powders as the active material. There are several methods of electrode fabrication Sakai et al [35] pulverize the alloy by subjecting it to several hydrogen absorption-desorption cycles, before coating the resulting particles with Ni by chemical plating. The powder is mixed with a Teflon dispersion to obtain a paste which is finally roller-pressed to a sheet and then hot-pressed to an expanded nickel mesh. The fabrication of a simple paste electrode suitable for laboratory studies is reported by Petrov et al. [37],... 

Because of the brevity of this paper, it is possible to outline only the more important developments. Hundreds of petroleum-base lubricants are available, each of which is suitable for one or more applications. Most of these lubricants contain additives to modify or improve their properties. Pure iron is rarely satisfactory for fabrication of structures and machines. Its performance is improved by regulation of the amount of carbon present, and by addition of carefully controlled amounts of other metals such as manganese, chromium, and nickel. Similarly, striking improvements in the performance of lubricants are obtained by addition of modifying chemicals in proportions of less than 0.001 to 25% or more. At present there appears to be little promise of improving the performance of lubricants through development of new methods of refining. It seems probable that the development of additives will be the major effort for some years. 

Nickel-mesoporous silicon structures are of considerable industrial interest for various applications. Anisotropy of magnetic properties of the nickel nanowires inside porous silicon conditioned by their high aspect ratio is applicable for the magnetic store production [1], Moreover, these structures offer much promise for the rectenna (a special type of antenna that is used to directly convert microwave energy into DC electricity) fabrication. So, it is of value to study in detail the process of the nickel electrodeposition into pores of porous silicon and elaborate control methods for pore filling with metal. 

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