Aluminum specific properties

Anthracite. Anthracite is preferred to other forms of coal (qv) in the manufacture of carbon products because of its high carbon-to-hydrogen ratio, its low volatile content, and its more ordered stmcture. It is commonly added to carbon mixes used for fabricating metallurgical carbon products to improve specific properties and reduce cost. Anthracite is used in mix compositions for producing carbon electrodes, stmctural brick, blocks for cathodes in aluminum manufacture, and in carbon blocks and brick used for blast furnace linings. 

Plastics can also be combined with other materials such as aluminum, steel, and wood to provide specific properties. Examples include PVC/wood window frames and plastic/ aluminum-foil packaging material. All combinations require that certain aspects of compatibility such as processing temperature and linear coefficient of thermal expansion or contraction exist. 

Cince the catalytic activity of synthetic zeolites was first revealed (1, 2), catalytic properties of zeolites have received increasing attention. The role of zeolites as catalysts, together with their catalytic polyfunctionality, results from specific properties of the individual catalytic reaction and of the individual zeolite. These circumstances as well as the different experimental conditions under which they have been studied make it difficult to generalize on the experimental data from zeolite catalysis. As new data have accumulated, new theories about the nature of the catalytic activity of zeolites have evolved (8-9). The most common theories correlate zeolite catalytic activity with their proton-donating and electron-deficient functions. As proton-donating sites or Bronsted acid sites one considers hydroxyl groups of decationized zeolites these are formed by direct substitution of part of the cations for protons on decomposition of NH4+ cations or as a result of hydrolysis after substitution of alkali cations for rare earth cations. As electron-deficient sites or Lewis acid sites one considers usually three-coordinated aluminum atoms, formed as a result of dehydroxylation of H-zeolites by calcination (8,10-13). 

Taking into consideration a) the specific properties of organoaluminum compounds, especially lower aluminumtrialkyls, and their hydride-, halo-gene- and alkoxy derivatives, which are highly flammable in air and explode at contact with water b) the use of hydrogen, ethylene, isobutene, ethylene, isobutene, ethylchloride, sodium and aluminum (finely dispersed and active, which can self-inflame in air), the production of organoaluminum compounds can be considered one of the most dangerous chemical productions. Therefore, safety measures and fire prevention are especially important. 

Owing to the outstanding performance qualities of aluminum, there has been no lack of attempts to coat metals with aluminum in order to combine the favorable properties of the base matrial with the specific properties of the aluminum covering layer. Today there are various methods available for plating workpieces with aluminum, for example ... 

The various possible applications of aluminum oxide ceramics corresponding to specific properties are listed in Table 5.5-4. 

Polymer matrix composites (PMCs), or fiber-reinforced plastics (FRPs). provide a wide range of properties and behavior. Materials with discontinuous fibers are slightly stiffer than conventional unreinforced plastics, whereas the fully aligned continuous fiber systems can record exceptionally high specific properties (property divided by density), exeeeding those of competing materials such as steel and aluminum. There are a virtually infinite number of materials, and material formats that can be combined to form a composite material, as shown in Table 1. 

Figure 9.7 Specific properties (strength and modulus + specific gravity) of RPs, wood, aluminum, and steel...

Functional Fillers. A variety of fillers can be used to add specific properties. Metals, and beryllium and aluminum oxides, can be added to increase thermal conductivity (Table 3.33). Metals can be added to increase electrical conductivity (Table 3.34). Graphite increases lubricity and electrical conductivity. Mica increases elec-... 

Duplex Coatings (two metal layers). A layer of zinc followed by a layer of another metal (usually aluminum) is occasionally advocated to provide a barrier or more slowly corroding surface initially or to give specific properties such as reflectivity. 

Specified impurity elements must be at or below the maximum limit. Individual nonspecified impurities should be less than the "0.05% each" level with the total less than 0.15%. It should be recognized that, as shown in Table 19.3, some impurity elements will be present, but usually well below the allowed limit. Every sample will not contain all of the impurity elements, but some amount of iron and silicon are usually present except in ultrarefined pure aluminum. Certain alloys are produced in several levels of purity, with the less pure levels being less expensive and the higher pimty levels improving a specific property. For example, when the iron and silicon levels are both less an 0.10%, toughness is improved. 

The aluminum titanate (tialite, Al2TiOs) has specific properties such as high melting point, low thermal expansion coefficient ((-l-3)-(-19)" K" ), and high thermal shock resistance that make it interesting for applications such as exhaust port lines in automobiles, turbocharge liners, and missile cone nose. 

Physical Properties. Physical properties of importance include particle size, density, volume fraction of intraparticle and extraparticle voids when packed into adsorbent beds, strength, attrition resistance, and dustiness. These properties can be varied intentionally to tailor adsorbents to specific apphcations (See Adsorption liquid separation Aluminum compounds, aluminum oxide (alumna) Carbon, activated carbon Ion exchange Molecular sieves and Silicon compounds, synthetic inorganic silicates). 

The surface of activated alumina is a complex mixture of aluminum, oxygen, and hydroxyl ions which combine in specific ways to produce both acid and base sites. These sites are the cause of surface activity and so are important in adsorption, chromatographic, and catalytic appHcations. Models have been developed to help explain the evolution of these sites on activation (19). Other ions present on the surface can alter the surface chemistry and this approach is commonly used to manipulate properties for various appHcations. 

Metal or metal oxides may be added to perform specific functions. Brass chips and copper powder are frequently used in heavy-duty organics where these metaUics act as scavengers to break up undesirable surface films. Zinc chips used in Class A organics contribute significantly to recovery of normal performance following fade. Aluminum is also used. Most of these inorganic materials tend to detract from antinoise properties and mating surface compatibihty. 

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