Aluminate density

Multilayer Insulation Miiltilayer insulation consists of alternating layers of highly reflec ting material, such as aluminum foil or aluminized Mylar, and a low-conduc tivity spacer material or insulator, such as fiberglass mat or paper, glass fabric, or nylon net, all under high vacuum. When properly applied at the optimum density, this type of insulation can have an apparent thermal conduc tivity as low as 10 to 50 jlW/m-K between 20 and 300 K. 

In the binary haloaluminate ionic liquids, an increase in the mole percent of the imidazolium salt decreases the density of the liquid (see Table 3.2-2). The bromo-aluminate ionic liquids are substantially denser than their chloroaluminate counterparts, being between 0.57 g cm and 0.83 g cm denser than the analogous chloroaluminate ionic liquids (see Table 3.2-2). Variation of the substituents on the imidazolium cation in the chloroaluminate ionic liquids has been shown to affect the density on the basis of the cation size [17]. 

Materials formed by acid-base reactions between calcium aluminate compounds and phosphate-containing solutions yield high-strength, low-permeability, C02-resistant cements when cured in hydrothermal environments. The addition of hollow aluminosilicate microspheres to the uncured matrix constituents yields slurries with densities as low as approximately 1200 kg/m, which cure to produce materials with properties meeting the criteria for well cementing. These formulations also exhibit low rates of carbona-tion. The cementing formulations are pumpable at temperatures up to 150° C. 

In such complex system as aluminosilicate precursor gels, various lifetime components can appear reflecting material structure. The gel structure is a result of direct interaction of cations with silicate, aluminate and aluminosilicate anions, redistribution of charges and electron density over the system of aluminosiloxane bonds with effect on the formation of different structural units [24],... 

The reaction of complex hydrides with carbonyl compounds can be exemplified by the reduction of an aldehyde with lithium aluminum hydride. The reduction is assumed to involve a hydride transfer from a nucleophile -tetrahydroaluminate ion onto the carbonyl carbon as a place of the lowest electron density. The alkoxide ion thus generated complexes the remaining aluminum hydride and forms an alkoxytrihydroaluminate ion. This intermediate reacts with a second molecule of the aldehyde and forms a dialkoxy-dihydroaluminate ion which reacts with the third molecule of the aldehyde and forms a trialkoxyhydroaluminate ion. Finally the fourth molecule of the aldehyde converts the aluminate to the ultimate stage of tetraalkoxyaluminate ion that on contact with water liberates four molecules of an alcohol, aluminum hydroxide and lithium hydroxide. Four molecules of water are needed to hydrolyze the tetraalkoxyaluminate. The individual intermediates really exist and can also be prepared by a reaction of lithium aluminum hydride... 

Table 3.3 Some aluminized explosive formulations and their density and velocity of detonation .

Aluminized expls exhibit a decrease in performance as their packing density approaches theoretical maximum density (TMD). This effect is more pronounced in compns of high A1 content. Table 9 (from Ref 17) shows equivalent weight ratios (WQd) and relative bubble energies (RBE) of two aluminized expls as a function of %TMD... 

Andersen et al (Ref 6) obtained about the same pressure coefficient of D for NM as Brochet et al. However, theoretical considerations pre diet that this coefficient should decrease at higher ambient pressure. This predicted decrease was not observed. Indeed for NM and a solid aluminized expl, HBX, D increased with ambient pressure in essentially the same manner as it would increase with increasing initial density of the expl due to compression by the ambient pressure. Since the compressibility of liq expls and solid expls at near crystal density is relatively low at moderate ambient pressures, the rather small effect of ambient pressure on D is understandable... 

Focusing collectors are usually cast acrylic Fresnel lenses, or mirrors of aluminized polyester film in frames of aluminum. These reflectors are either enclosed in a bubble of poly(vinyl fluoride) film, or under polycarbonate glazing, which may be covered with a fluorocarbon film to reduce the reflectivity. The absorbers for active systems are copper or aluminum since the temperatures are too high (325—370°C) for plastics. The frames, however, can be molded ABS, high density polyethylene or polyurethane, either solid or structural foam. Polybutylene or chlorinated PVC can be used for piping hot water, and tanks can be made of either reinforced polyester or blow- or rotational-molded, high density polyethylene (12—15). 

A sodium aluminate solution (2.00 moles Al203/liter, 3.40 moles Na20/ liter, density 1.36 grams/ml) produced from hydrargillite was used as the alumina source in each series of tests. Silica was used as sodium silicate solution (5.98 moles Si02/liter, 1.77 moles Na20/liter, density 1.36 grams/ ml) and as solid amorphous silica with different surface areas (Table I). 

It is also of interest to use MAS NMR for the study of the thermal treatment of zeolites which are not in the ammonium-exchanged form. In an X-ray study, Pluth and Smith (179) found electron density at the center of the sodalite cages in dehydrated zeolites Ca-A and Sr-A and attributed this to a partial occupancy of these sites by a four-coordinated aluminous species. No such effect was found in zeolite A exchanged with monovalent cations. Corbin et al. (180) used 27A1 MAS NMR to examine commercial samples of K-A, Na-A and (Ca,Na)-A, as received (see Fig. 41). For K-A and Na-A, only framework tetrahedral Al species were observed, with chemical shifts of 57 and 52 ppm respectively. However, in (Ca,Na)-A an additional intense resonance at 78 ppm, typical of AlfOH) but definitely not due to framework aluminum, was also found (see Fig. 41). A much weaker signal, also at 78 ppm, was detected in zeolite Sr-A its intensity increased greatly on heating the sample to 550°C. Freude et al. (183) came to very similar conclusions in their NMR study of heat-treated zeolite Ca-A. They found that maximum framework dealumination occurs at 500°C and corresponds to ac. 17% of total Al. 

DBX (Depth Bomb Explosive). An Amer aluminized expl developed during WWII to replace the Brit,more sensitive Torpex. It consists of TNT 40, RDX 21, AN 21 A1 18%. Its props are as follows gray solid which can be cast at temps 90-95° Density (for cast material)... 

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