Vapor metals

The noble metal thermocouples, Types B, R, and S, are all platinum or platinum-rhodium thermocouples and hence share many of the same characteristics. Metallic vapor diffusion at high temperatures can readily change the platinum wire calibration, hence platinum wires should only be used inside a nonmetallic sheath such as high-purity alumina. 

Lithium Niobate. Lithium niobate [12031 -64-9], LiNbO, is normally formed by reaction of lithium hydroxide and niobium oxide. The salt has important uses in switches for optical fiber communication systems and is the material of choice in many electrooptic appHcations including waveguide modulators and sound acoustic wave devices. Crystals of lithium niobate ate usually grown by the Czochralski method foUowed by infiltration of wafers by metal vapor to adjust the index of refraction. 

Eig. 8. Cost of electricity (COE) comparison where represents capital charges, Hoperation and maintenance charges, and D fuel charges for the reference cycles. A, steam, light water reactor (LWR), uranium B, steam, conventional furnace, scmbber coal C, gas turbine combined cycle, semiclean hquid D, gas turbine, semiclean Hquid, and advanced cycles E, steam atmospheric fluidized bed, coal E, gas turbine (water-cooled) combined low heating value (LHV) gas G, open cycle MHD coal H, steam, pressurized fluidized bed, coal I, closed cycle helium gas turbine, atmospheric fluidized bed (AEB), coal J, metal vapor topping cycle, pressurized fluidized bed (PEB), coal K, gas turbine (water-cooled) combined, semiclean Hquid L, gas turbine... 

After the water and nitrogen oxide are driven off, continued heating drives off vapors of nitric acid, additional water, NO2, and some mercury—metal vapor ... 

Condensation of metal vapors followed by deposition on cooler surfaces yields metal powders as does decomposition of metal hydrides. Vacuum treatment of metal hydrides gives powders of fine particle size. Reaction of a metal haHde and molten magnesium, known as the KroU process, is used for titanium and zirconium. This results in a sponge-like product. 

Reactive Evaporation. In reactive evaporation (RE), metal or alloy vapors are produced in the presence of a partial pressure of reactive gas to form a compound either in the gas phase or on the substrate as a result of a reaction between the metal vapor and the gas atoms ... 

Metals do not generally react with vitreous siUca below 1000°C or their melting point, whichever is lower. Exceptions are alurninum, magnesium, and alkah metals. Aluminum readily reduces siUca at 700—800°C. Alkali metal vapors attack at temperatures as low as 200°C. Sodium vapor attack involves a diffusion of sodium into the glass, followed by a reduction of the siUca. 

Indirect (French) Process. Ziac metal vapor for burning is produced ia several ways, one of which iavolves horizontal retorts. Siace all the vapor is burned ia a combustion chamber, the purity of the oxide depends on that of the ziac feed. Oxide of the highest purity requires special high grade ziac and less-pure products are made by blending ia Prime Western and even scrap ziac. 

Vacuum Deposition-also vapor deposition or gas plating the deposition of metal coatings by means of precipitation (sometimes in vacuum) of metal vapor onto a treated surface. The vapor may be produced by thermal decomposition, cathode sputtering or evaporation of the molten metal in air or an inert gas. 

Very high metal vapor pressures are required to... 

Tetrakis(tnfluoromethyljnn can be prepared via metal vapor [9] or fluonnation techniques [fO] and via reaction with tnfluoromethyl radicals generated by radio-frequency discharge of CF3CF3 [JJ] (equation 7)... 

Perfluoroalkyl or -aryl halides undergo oxidative addition with metal vapors to form nonsolvated fluonnated organometallic halides and this topic has been die subject of a review [289] Pentafluorophenyl halides react with Rieke nickel, cobalt, and iron to give bispentafluorophenylmetal compounds, which can be isolated in good yields as liquid complexes [290] Rieke nickel can also be used to promote the reaction of pentafluorophenyl halides with acid halides [297] (equation 193)... 

The metal-vapor technique was applied to cobalt atoms and r-BuC = P (01JOM(635)212). The mixture of products that resulted includes the mixed-ligand sandwiches 170 and 171. Further interaction of complex 170 with [W(C0)5(THF)] leads to the coordination of the W(CO)5-group via the phosphorus heteroatom of the four-membered ring to yield 172. 

The metal-vapor synthesis, involving co-condensation of nickel vapors, r-BuC = P, and 1,2,4-triphospholyl system leads to the mixed-ligand species 178 (94AGE2330). 

The production of metal vapor upon arc interruption necessary to control current chopping and permit voltage recovery and... 

In these processes, a special base coat is applied to the surface of the plastic product to be metallized. The product is then placed in a vacuum chamber in which a metallic vapor is created and deposited on the product. A protective clear top coat is then applied over the thin metal layer for abrasion and environmental resistance. The simplest vacuum metallizing processes use resistance heating to melt and vaporize the metal. 

Isotope photoseparation techniques for actinides probably will include only gaseous systems, hexafluorides and metal vapors. Hence, aqueous actinide photochemistry is not likely to influence isotope separations. However, the intense interest in laser separation techniques for the gaseous systems promotes interest in the aqueous systems. 

---