Silver fabrication

Fig. 2. A B SEMs of test patterns of silver fabricated using pCP, followed by selective etching C cross-sectional SEM of microchannels etched in Si(100) and D optical micrograph of a microtransformer fabricated using pCP, selective etching and electroplating...

Hydrogen sulfide has traditionally been a problem in the tarnishing of silver and the discoloration of bronze patinas. This gas can be dealt with in the filters of the climate-control system as well as through the use of proper absorbing agents. For example, a paper treated with activated charcoal is fabricated especially for absorbing H2S within a microclimate. 

Skiving is a variant in which the base metal surface oxides are mechanically removed foUowed immediately by pressure rolling of a precious metal or alloy strip. This is commonly used for inlays for electrical contacts and for jewelry fabrication. The common inlay materials include gold, silver, copper, brass, and solder. No heat is needed, and the coating is appHed only to designated areas so there is Htde waste (3,50). 

The demand for silver is an indicator of technically advanced products production. In 1950, when the population in the free-market countries was 1.7 biUion, consumption of silver was 2.9 t/10 people. By 1992, the population had increased to 4.2 biUion and silver consumption reached 4.2 t/10 people. Fabrication demand by country is given in Table 4 and by category in Table 5. 

Typical equipment made from tantalum includes heat exchangers, reaction vessels liners, thermowells, and heating elements or heat shields for high temperature vacuum sintering furnaces. Tantalum fabricated parts are found in the manufacturing of pharmaceuticals, explosives, insecticides, dyes, acidic baskets for silver cyanide barrel platers, and in hydrochloric and hydrobromic acid condensers. 

Other alkaline primary cells couple zinc with oxides of mercury or silver and some even use atmospheric oxygen (zinc—air cell). Frequendy, zinc powder is used in the fabrication of batteries because of its high surface area. Secondary (rechargeable) cells with zinc anodes under development are the alkaline zinc—nickel oxide and zinc—chlorine (see Batteries). 

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. 

Electrical and Electronic Applications. Silver neodecanoate [62804-19-7] has been used in the preparation of a capacitor-end termination composition (110), lead and stannous neodecanoate have been used in circuit-board fabrication (111), and stannous neodecanoate has been used to form patterned semiconductive tin oxide films (112). The silver salt has also been used in the preparation of ceramic superconductors (113). Neodecanoate salts of barium, copper, yttrium, and europium have been used to prepare superconducting films and patterned thin-fHm superconductors. To prepare these materials, the metal salts are deposited on a substrate, then decomposed by heat to give the thin film (114—116) or by a focused beam (electron, ion, or laser) to give the patterned thin film (117,118). The resulting films exhibit superconductivity above Hquid nitrogen temperatures. 

Fite refining adjusts the sulfur and oxygen levels in the bhster copper and removes impurities as slag or volatile products. The fire-refined copper is sold for fabrication into end products, provided that the chemistry permits product specifications to be met. Some impurities, such as selenium and nickel, are not sufficiently removed by fire refining. If these impurities are detrimental to fabrication or end use, the copper must be electrorefined. Other impurities, such as gold, silver, selenium, and tellurium, are only recovered via electrorefining. Virtually all copper is electrorefined. 

Alloys based on Ag—Pd have been used for a number of years and are available from most gold alloy manufacturers (148). The palladium content is 22—50 wt % silver content is from 35 to 66 wt %. Minor amounts of Zn, In, or Sn are often present to increase fluidity. Both In and Sn form intermetaUic compounds with both Pd and Ag and, therefore, some of the commercial alloys are susceptible to age hardening (149). These alloys are somewhat difficult to fabricate and require meticulous processing. They may also produce a greenish discoloration when they are fused with porcelain veneers. Nevertheless, clinical experience generally has been satisfactory, and cost is the primary criterion for use. 

Polymer thick films also perform conductor, resistor, and dielectric functions, but here the polymeric resias remain an iategral part after cuting. Owiag to the relatively low (120—165°C) processiag temperatures, both plastic and ceramic substrates can be used, lea ding to overall low costs ia materials and fabrication. A common conductive composition for flexible membrane switches ia touch keyboards uses fine silver particles ia a thermoplastic or thermoset polymeric biader. 

Materials The damage that air pollutants can do to some materials is well known ozone in photochemical smog cracks rubber, weakens fabrics, and fades dyes hydrogen sulfide tarnishes silver smoke dirties laundry acid aerosols ruin nylon hose. Among the most important effects are discoloration, corrosion, the soiling of goods, and impairment of visibility. 

Glam-silber, n. polished silver (Min.) silver glance, argentite. -stahl, m. polished steel, -stkrke, /. gloss starch, -stoff, m. trade name of a cuprammonium rayon glazed or glossy fabric. 

Silver in the fully annealed state is a soft, ductile metal which is easily fabricated into the very wide range of forms employed in industry by the... 

Bonded silver linings are fabricated for mild steel or copper vessels. They are soldered in situ to the walls of the vessel by means of a special tin-silver solder. The melting point of this solder is approximately 280°C, and 200°C is recommended as the maximum continuous operating temperature for linings bonded with it. Since the whole of the silver is firmly adherent to the vessel, bonded linings are suitable for operation under vacuum conditions, and provide excellent heat-transfer characteristics. 

Bursting discs may be fabricated of gold, silver, platinum or palladium. The recommended maximum temperatures for continuous use are 80 C for gold, 150 C for silver, 300 C for palladium and 450 C for platinum. Figure 6.6 gives bursting pressure/disc thickness data for these metals and for aluminium and nickel. 

Figure 10-12. Lcfi hand side Slruclure of a PPV microcavily. A thin film of ihe conjugated polymer is deposited on top of a highly reflective distributed Bragg refieclor (DBR). The second mirror is then fabricated by evaporation of a silver layer. Right hand side Emission spectra of the microcavily at excitation cnetgics or 0.0S pJ (dashed line) and l. l pJ (solid line), respectively. Laser pulses ol duration 200-300 ps and a wavelength of 355 nm were used for optical excitation (according to Ref. [39]).

Once the micro-channels were fabricated, the manifold were bonded to the substrate by epoxy glue, and the resistor was wired by a silver-based epoxy electric conductor and painted with a 1 pm thin paint to increase the surface emissivity. The triangular micro-channels and the unpainted resistor are shown in Fig. 9.12. 

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