Aluminum secondary

Several less important mechanisms, with varying timescales, also contribute to acid neutralization. (i) In soils rich in iron and aluminum secondary phases, excess SO4 from the atmosphere may be reversibly adsorbed or desorbed, thereby retarding acidification and recovery from acidification, respectively (David et al., 1991a,b). Such soils are common in unglaciated areas, (ii) As pH declines, dissociated inorganic carbon species protonate toward H2CO3 and aqueous CO2. (iii) Protonation, condensation, and precipitation of organic acids increases, (iv) Hydroxy- 2+ lated aluminum species shift toward Ar. The... 

The process of making alumina by alkoxide involves three steps hydrolysis of aluminium butoxide, formation of gel and finally pyrolysis of alumina, when aluminum secondary butoxide is hydrolysed at a temperature of about 80°C, it forms pseudoboehmite. The role of solvent and pH in this type of reactions is vital since they partially control hydrolysis and condensation. Therefore, the solvent mixture must dissolve intimately with the reactant species in order to obtain a greater interaction. 

Aluminum salts (e.g. nitrate) have proved to be a popular source for the synthesis of alumina particles through macroemulsions, as clearly shown from the above examples. However, there are other examples where aluminum alkoxides are used for the same purpose. In one example provided by Hardy etai [177], the procedure of emulsification involved ultrasonication of the alkoxide in immiscible, non-reacti ve, polar organic liquids prior to contact with water for direct conversion of the alkoxide droplets to solid particles. Thus, aluminum secondary butoxide dispersed in acetonitrile or propylene carbonate was hydrolyzed by addition of water [ 177] to obtain generally near-spherical particles of alumina varying in size from several microns to several nanometers. These particles, amorphous without calcination, changed to y-alumina of high surface area on calcination at 6(X) C and 0-alumina at IGOO C. 

Hardy et al. [204] reported emulsion synthesis of yttrium aluminum garnet (commonly known as YAG) in which yttrium acetate and aluminum secondary butoxide (heated to 85 -90 C) were used as cation sources in a butanol-water mixture. The oil phase was heptane, mineral oil or Isopar, and the surfactant was a mixture of Span 20 (75%) and Span 80 (25%). The sol droplets were gelled by addition of NH4OH or bubbling NH3. The particle morphology and size were influenced significantly by the nature of the oil phase. 

Aluminum chelate n. Chemically modified aluminum secondary butoxide, used as a curing agent for epoxy, phenolic, and alkyd resins. 

Metallurgical processes By-product coke ovens Foundries gray iron Foundries steel Secondary aluminum Secondary copper Secondary zinc Uranium refining... 

Powders from Colloidal Sol-Based Compotdtions. A common example of the synthesis of a single oxide from a colloidal precursor, following a well-known method (Yoldas, 1975), involves hydrolysis of aluminum secondary butoxide by addition of excess water, formation of boehmite, AlOOH and peptization of boehmite by an add to obtain a colloidal sol. Oh et al. (1996), to dte an application, prepared such colloidal sols and also seeded a part ofsuch a sol with 15 wt% ofa-alumina(<0.12/im). Up to 350°C, both the solid products were amorphous. However, seeding caused early (950°C) crystallization of the a-phase, while the unseeded conqiosition led to a late crystallization (1150°C) of the same phase. 

The protection system design for the ISS is multi-layered. The level of protection employed on the space station Varies by location and criticality. The critical compartments and components have a 0.80 in aluminum bumper and a 0.188 in aluminum secondary protection wall. The spacing between the two is approximately 4.5 in. Between the two are 23 layers of multi-layer insulation, 6 layers of Nextel, and 6 Layers of Kevlar, Reference 10-14, This is designed to withstand an impact of a 1 cm particle traveling at 10 km/sec. 

While with-in the mobile x-ray system, the waste in the sampler, is contained within a replaceable (and disposable) polyvinyl chloride (PVC) sleeve with a wall thickness of approximately 0.2-inches and a sealed bottom. It was anticipated that the PVC tube or sleeve would, with use, become highly contaminated with waste residues which drip of fall-off the sampler. The sleeve is coated with a conductive coating to prevent static electricity buildup . There are no sources of ignition in this sealed spare. The sampler (and waste) is coupling which includes a positive pressure gasket. This barrier is further isolated by a second barrier consisting of an epoxy coated aluminum sleeve also sealed-off from the main x-ray cabinet and PVC sleeve. There are also no potential sources of ignition in this isolated secondary space as well. 

The widely used Moifatt-Pfltzner oxidation works with in situ formed adducts of dimethyl sulfoxide with dehydrating agents, e.g. DCC, AcjO, SO], P4O10, CCXTl] (K.E, Pfitzner, 1965 A.H. Fenselau, 1966 K.T. Joseph, 1967 J.G. Moffatt, 1971 D. Martin, 1971) or oxalyl dichloride (Swem oxidation M. Nakatsuka, 1990). A classical procedure is the Oppenauer oxidation with ketones and aluminum alkoxide catalysts (C. Djerassi, 1951 H. Lehmann, 1975). All of these reagents also oxidize secondary alcohols to ketones but do not attack C = C double bonds or activated C —H bonds. 

Alkyl halides by themselves are insufficiently electrophilic to react with benzene Aluminum chloride serves as a Lewis acid catalyst to enhance the electrophihcity of the alkylating agent With tertiary and secondary alkyl halides the addition of aluminum chlonde leads to the formation of carbocations which then attack the aromatic ring... 

Secondary alkyl halides react by a similar mechanism involving attack on benzene by a secondary carbocation Methyl and ethyl halides do not form carbocations when treated with aluminum chloride but do alkylate benzene under Friedel-Crafts conditions The aluminum chloride complexes of methyl and ethyl halides contain highly polarized carbon-halogen bonds and these complexes are the electrophilic species that react with benzene... 

Reduction to alcohols (Section 15 2) Aide hydes are reduced to primary alcohols and ketones are reduced to secondary alcohols by a variety of reducing agents Catalytic hydrogenation over a metal catalyst and reduction with sodium borohydride or lithium aluminum hydride are general methods... 

Reduction of an azide a nitrile or a nitro compound furnishes a primary amine A method that provides access to primary secondary or tertiary amines is reduction of the carbonyl group of an amide by lithium aluminum hydride... 

Alkyl azides prepared by nucleophilic substitution by azide ion in primary or secondary alkyl halides are reduced to primary alkylamines by lithium aluminum hydride or by catalytic hydrogenation... 

Reduction of amides (Section 22 9) Lithi um aluminum hydride reduces the car bonyl group of an amide to a methylene group Primary secondary or tertiary amines may be prepared by proper choice of the starting amide R and R may be ei ther alkyl or aryl... 

Other Compounds. Primary and secondary amines add 1,4- to isoprene (75). For example, dimetbylamine in ben2ene reacts with isoprene in the presence of sodium or potassium to form dimetby1(3-metby1-2-buteny1)amine. Similar results are obtained with diethylamine, pyrroHdine, and piperidine. Under the same conditions, aniline and /V-metbylaniline do not react. Isoprene reacts with phenol in the presence of aluminum phenoxide (76) or concentrated phosphoric acid (77) to give complex products. 

A conservative estimate of the total value of the products from the mineral industry is ca 3.9 trillion ia terms of 1992 dollars (4). This estimate does not include the value of products derived from secondary sources such as recycling (qv) or reclamation. Secondary recovery is significant for certain commodities. For example, in 1992 ca 30% of the world steel (qv) production, 46% of the world refined lead output, 15% of the world refined copper (qv) production, and ca 30% of the aluminum (see Aluminumand ALUMINUM alloys) output from the Western world were clearly identified as being derived from scrap. The value of the world mineral commodity export trade in 1992 was ca 616,698 million ia 1992 dollars. This accounted for ca 18% of all commodities exported (4). 

In general, if the desired carbon—phosphoms skeleton is available in an oxidi2ed form, reduction with lithium aluminum hydride is a powerful technique for the production of primary and secondary phosphines. The method is appHcable to halophosphines, phosphonic and phosphinic acids as well as thein esters, and acid chlorides. Tertiary and secondary phosphine oxides can be reduced to the phosphines. 

Cross-linked polyester composites have a relatively low coefficient of thermal conductivity that can provide beneficial property retention in thick laminates at high temperatures as well as remove the need for secondary insulation. The coefficient of thermal expansion of glass-reinforced composites is similar to aluminum but higher than most common metals. 

Alkaline earth metal alkoxides decompose to carbonates, olefins, hydrogen, and methane calcium alkoxides give ketones (65). For aluminum alkoxides, thermal stability decreases as follows primary > secondary > tertiary the respective decomposition temperatures are ca 320°C, 250°C, and 140°C. Decomposition products are ethers, alcohols, and olefins. 

Scrap that is unsuitable for recycling into products by the primary aluminum producers is used in the secondary aluminum industry for castings that have modest property requirements. Oxide formation and dross buildup are encountered in the secondary aluminum industry, and fluxes are employed to assist in the collection of dross and removal of inclusions and gas. Such fluxes are usually mixtures of sodium and potassium chlorides. Fumes and residues from these fluxes and treatment of dross are problems of environmental and economic importance, and efforts are made to reclaim both flux and metal values in the dross. 

---