Lithium alumina

Copper Powder Aluminum Powder Iron Powder Lithium Alumina Silicate Silica... 

Low coefficient of thermal expansion and the consequent resistance to thermal shock arises when the thermal expansion of the crystalline phase is very low. In the lithium-alumina silicate system described in Table 6.16, the crystals are either )8-quartz or /3-spodumene solid solutions that have very low, or even negative, volume thermal expansion. [Expansion is positive along one crystal axis (c) and negative along the other two a and >).] These properties led to applications as varied as cookware, stovetops and stove windows, and giant (8-meter-diameter) earth-based telescope mirror substrates. 

One gram of silver /3-alumina (see above) is placed into a fused quartz test tube about 2 cm in diameter and about 14 cm long. Five grams of lithium chloride is added. It is important that the lithium chloride used have a very low content of other alkali-metal impurities, except Cs, since the ion-exchange equilibria greatly favor the presence of the other alkali metals in the j8-alumina crystals over lithium. Essentially all the impurity ends up in the crystals. The fused-quartz test tube is heated to 650° in a furnace. For crystals 1-cm in diameter the time to reach 99% equilibrium is approximately 16 h. The molten salt is decanted and the crystals are allowed to cool to room temperature. Methyl alcohol containing about 10% propylamine or ethylenediamine is used to wash the product and thereby remove the silver chloride and residual lithium salts. The sample is dried at 400° and stored in a desiccator. The lithium /S-alumina crystals contain less than 0.05% Ag. If the lithium chloride used contains a trace of sodium or potassium, it can be prepurified by treatment with silver /3-alumina at 650°. Each gram of silver jS-alumina will remove about 30 mg of sodium from the melt. The molten lithium chloride, after decantation from the pretreatment silver /3-alumina, can be used to prepare the product, lithium -alumina. 

The preparation of this substance from silver /3-alumina is similar to the preparation of lithium -alumina. The melt consists of 10 g of rubidium chloride. The exchange temperature is 800°. For crystals 2 mm in diameter it takes about 16 h to reach 99% of equilibrium. The rubidium salts used should contain less than 0.02% potassium and less than 0.1% sodium. After decantation of the melt the crystals are washed with water containing 2% propylamine of ethylenediamine to remove residual potassium salts and silver chloride. They are dried at 200°. The rubidium -alumina crystals contain less than 0.05 wt.% silver. 

In the vapor phase, acetone vapor is passed over a catalyst bed of magnesium aluminate (206), 2iac oxide—bismuth oxide (207), calcium oxide (208), lithium or 2iac-doped mixed magnesia—alumina (209), calcium on alumina (210), or basic mixed-metal oxide catalysts (211—214). Temperatures ranging... 

Flint clays and other related rocks are another potential lithium source. These are high alumina clays that are composed largely of we11-crysta11i2ed kaolinite [1318-74-1] and are used for the manufacture of refractories (qv). The lithium content ranges from <100 to 5000 ppm. Deposits occur in many states, including Missouri, Peimsylvania, and Ohio. Lithium (at ca 1.3%) is present in a chlorite mineral that is similar to cookeite [1302-92-7]. High lithium contents may be the reason why some deposits are unsatisfactory for refractory use. 

Fig. 11. Modulus inciease as a function of fibei volume fraction alumina fiber-reinforced aluminum—lithium alloy matrix for (a) E (elastic modulus),...

Alkali moderation of supported precious metal catalysts reduces secondary amine formation and generation of ammonia (18). Ammonia in the reaction medium inhibits Rh, but not Ru precious metal catalyst. More secondary amine results from use of more polar protic solvents, CH OH > C2H5OH > Lithium hydroxide is the most effective alkah promoter (19), reducing secondary amine formation and hydrogenolysis. The general order of catalyst procUvity toward secondary amine formation is Pt > Pd Ru > Rh (20). Rhodium s catalyst support contribution to secondary amine formation decreases ia the order carbon > alumina > barium carbonate > barium sulfate > calcium carbonate. 

Aluminum chlorite, (Al,Fe)4(Si,Al)402Q(0H)g, in which a gibbsitelike interlayer proxies in part for the bmcitelike interlayer, is being discovered in increasing occurrences and abundance (11,141). Chloritelike stmctures have been synthesi2ed by precipitation of Mg and Al between montmorillonite sheets (143). Cookite [1302-92-7], an aluminous chlorite containing lithium, has been found in high alumina refractory clays and bauxite [1318-16-7] (139). 

The ionic bond is the most obvious sort of electrostatic attraction between positive and negative charges. It is typified by cohesion in sodium chloride. Other alkali halides (such as lithium fluoride), oxides (magnesia, alumina) and components of cement (hydrated carbonates and oxides) are wholly or partly held together by ionic bonds. 

Certain chemicals (sorbents) have the ability to absorb moisture from a gas they may be either solid or liquid. Performance of a chemical dehumidifi cation device depends on the sorbent used. The sorbent must t>e able to attract and remove the sorbate, such as water, from the gas stream, Stirbems absorb water on the surface of the material by adsorption or by chemically combining with water (absorption). If the unit is regenerative, the process is reversible, allowing water to be removed. This is achieved by a sorbent such as silica gel, alumina gel, activated alumina, lithium chloride salt, lithium chloride solution, glycol solution, or molecular sieves. In the case of nonregenerative equipment, hygroscopic salts such as calcium chloride, urea, or sodium chloride are used. 

To a solution of 0.5 g of lithium aluminum hydride in 35 ml of ether is added 0.2 g of the A -cyanoaziridine. The mixture is heated at reflux temperature for 3.5 hr, cooled, and treated with excess saturated sodium sulfate in water. Filtration and evaporation of the ethereal filtrate gives 0.18 g of a glass which is chromatographed on 10 g of basic alumina (activity III). The benzene-petroleum ether (1 3) eluate gives 0.12 g of 2a,3a-imino-5a-choles-tane, mp 117.5-118.5°, after crystallization from methanol. 

Cyanoamidines such as (10) are converted into the more useful 2-formyl-A-norsteroids (11) by reduction with lithium in methylamine (buffered with ammonium acetate) followed by hydrolysis on hydrated alumina. This yields a mixture containing approximately 5 parts of the 2j5-aldehyde and 3 parts of the 2a-aldehyde (11). Both aldehydes are smoothly dehydrogenated by 2,3-dichloro-5,6-dicyanobenzoquinone in the presence of acid to the 2-formyl--A-iiorsteroids (12). ... 

Due to the above requirements, typical optically-transparent materials, such as oxides (glass, quartz, alumina, zirconium oxide etc.) and halides (sodium chloride, lithium fluoride, calcium fluoride, potassium bromide, cesium bromide etc.) are usually unsuitable for use with fluoride melts. Therefore, no standard procedure exists at present for the spectral investigation of fluoride melts, and an original apparatus must be created especially for each particular case. 

Quite a large variety of interesting fast lithium-ion solid conductors is now known, as compiled in Fig. 9 and Table 1. In the case of sodium- and potassium-ion conductors only the / / / " -alumina fam-... 

For lithium, counterparts structurally related to the sodium- and potassium-P / /3" -aluminas and NASICON with similar high ionic conductivities were not found, possibly because of the small ionic... 

In contrast, transmetalation of the lithium enolate at —40 C by treatment with one equivalent of copper cyanide generated a species 10b (M = Cu ) that reacted with acetaldehyde to selectively provide a 25 75 mixture of diastereomers 11 and 12 (R = CH3) which are separable by chromatography on alumina. Other diastereomers were not observed. Similar transmetalation of 10a (M = Li0) with excess diethylaluminum chloride, followed by reaction with acetaldehyde, produced a mixture of the same two diastereomers, but with a reversed ratio (80 20). Similar results were obtained upon aldol additions to other aldehydes (see the following table)49. 

The raw materials needed to supply about ten million new automobiles a year do not impose a difficult problem except in the case of the noble metals. Present technology indicates that each car may need up to ten pounds of pellets, two pounds of monoliths, or two pounds of metal alloys. The refractory oxide support materials are usually a mixture of silica, alumina, magnesia, lithium oxide, and zirconium oxide. Fifty thousand tons of such materials a year do not raise serious problems (47). The base metal oxides requirement per car may be 0.1 to 1 lb per car, or up to five thousand tons a year. The current U.S. annual consumption of copper, manganese, and chromium is above a million tons per year, and the consumption of nickel and tungsten above a hundred thousand tons per year. The only important metals used at the low rate of five thousand tons per year are cobalt, vanadium, and the rare earths. 

Purification of 1,2-dibromoethane was accomplished by passing a small quantity rapidly through a 5-cm. column of alumina. Addition of 1,2-dibromoethane to the lithium dispersion is accompanied by visible evolution of ethylene (ethene). 

High-alumina cement is a rapid-hardening cement made from bauxite and limestone. It is comparatively resistant to chemical attack. Milling retards the setting of aluminous cement [1582]. On the other hand, setting accelerators such as lithium carbonate increase their effect by this treatment. 

The Alcoa (Aluminum Company of America) process involves the electrolysis of aluminum chloride which is carried out in a molten bath of the composition 50% sodium chloride, 45% lithium chloride and 5% aluminum chloride, maintained at 700 °C. The Bayer process, which involves the production of pure alumina by the dissolution of bauxite with caustic soda and which has been described in the chapter on hydrometallurgy, must be taken into account while presenting a complete picture of the aluminum extraction flowsheet. It... 

Control shrinkage after moulding. Any filler will decrease shrinkage most commonly used are silica, clay, calcium carbonate, alumina, talc, powdered metals and lithium aluminium silicate. 

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