Glass, refining

Ce203 is used for decolorizing glasses [6]. At a high temperature, it dissociates with release of oxygen this increases the partial pressure of the gas in the vitrifiable mass and converts the metal to its tetravalent form, which is particularly stable. The conversion facilitates the oxidation of ferrous to ferric ion (colorless) and hence glass refining. 

As described in Chapter 10, ultrasound can be used to improve the quality of cast aluminium. The effect of ultrasound seen in Figure 3.11, in this case for glass refining, is to enhance bubble removal from glass melts, allowing it to take place in minutes rather than hours - see also Chapter 10 for further data and a fuller explanation. In Figure 3.11 the ultrasound probe is visible top centre, penetrating into... 

Glass and ceramics Glass refining Electric fields - ultrasound... 

It is used in certain nickel-based alloys, such as the "Hastelloys(R)" which are heat-resistant and corrosion-resistant to chemical solutions. Molybdenum oxidizes at elevated temperatures. The metal has found recent application as electrodes for electrically heated glass furnaces and foreheaths. The metal is also used in nuclear energy applications and for missile and aircraft parts. Molybdenum is valuable as a catalyst in the refining of petroleum. It has found applications as a filament material in electronic and electrical applications. Molybdenum is an... 

Total consumption of lead in the United States in 1993 reached 1,318,800 t. Of this, 766,000 t (58%) is allocated to battery use suppHed as either a mixed oxide or as metal. Approximately 95% of batteries are recycled and the lead recovered. In 1993, 908,000 t of lead came from secondary smelters and refiners compared to 350,000 t originating in primary mines and smelters (39). Approximately 51,000 t of lead was consumed in U.S. production of all oxides and chemicals appHcable to all industries other than batteries. Estimates include 8000 t for plastics, 6000 t for gasoline additives, 2000 t for mbber, and 30,000 t for ceramics, glass, and electronics. Lead is not used to any extent in dispersive appHcations such as coatings. 

Secondary Platinum-Group Metals. For many PGM appHcations, the actual loss during use of the metal is small, and hence the abihty to recover the PGM efficientiy contributes greatiy to the economics of PGM use. Typical sources of PGM for secondary refining iaclude jewelry and electronics scrap, catalysts, and used equipment, eg, from the glass industry. 

Selenium purification by zone refining is not feasible. At practical zone-refining speeds, crystallization does not occur and impurities do not segregate. However, a controlled differential thermal treatment of selenium in a long vertical glass tube has been described (45). The treatment time is several weeks to several months. 

Corrosion inhibitors Cosmetics, drugs Electrical insulation Electrolytic refining Fertilizers Fire retardants Glass and glass wool Herbicides Insecticides Leather tanning Photography Textile dyes Wax emulsifier Wool preservatives... 

Disodium Tetraborate Pentahydrate, Refined pentahydrate consumed in the Urhted States is used in insulation fiber glass, glass, fertilizers, and herbicides. Smaller amounts are used in antifreeze (see Antifreezes and deicing fluids), ceramic glazes, and cleaning agents. About 40% of the pentahydrate produced in the Urhted States is exported (101). A large-scale apphcation of this chemical is in the preparation of perborate bleaches. 

Hydrogen fluoride Catalyst in some petroleum refining, etching glass, silicate extraction by-product in electrolytic production of aluminum Petroleum, primary metals, aluminum Strong irritant and corrosive action on all body tissue damage to citrus plants, effect on teeth and bones of cattle from eating plants... 

There are less exotic ways of increasing the strength of cement and concrete. One is to impregnate it with a polymer, which fills the pores and increases the fracture toughness a little. Another is by fibre reinforcement (Chapter 25). Steel-reinforced concrete is a sort of fibre-reinforced composite the reinforcement carries tensile loads and, if prestressed, keeps the concrete in compression. Cement can be reinforced with fine steel wire, or with glass fibres. But these refinements, though simple, greatly increase the cost and mean that they are only viable in special applications. Plain Portland cement is probably the world s cheapest and most successful material. 

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