Aluminum oxide bulk materials

Aluminum Oxide Bulk Materials for Straight Phase PLC... 

Chapter 3 through Chapter 8 deal with the basic aspects of the practical uses of PLC. Chapter 3 describes sorbent materials and precoated layers for normal or straight phase (adsorption) chromatography (silica gel and aluminum oxide 60) and partition chromatography (silica gel, aluminum oxide 150, and cellulose), and precoated layers for reversed-phase chromatography (RP-18 or C-18). Properties of the bulk sorbents and precoated layers, a survey of commercial products, and examples of substance classes that can be separated are given. 

Aluminum oxides, similar to silica gels, are available as bulk materials and as precoated plates, to be used not only for straight phase adsorption chromatography, but also for partition PLC (see Table 3.3 and Table 3.4). In particular, the aluminum oxide type 150 (i.e., mean pore diameter 150 A [15 tun]) is suitable for partition chromatographic purposes. 

Figure 6.4. Comparison of the surface area/volume ratio of macroscopic particles (marbles) and nanoscopic aluminum oxide particles. Since nanoparticules contain a proportionately large number of surface atoms, there are a significantly greater number of adsorption/reaction sites that are available to interact with the surrounding environment. Further, whereas bending of a bulk metal occurs via movement of grains in the >100nm size regime, metallic nanostructures will have extreme hardness, with significantly different malleability/ductility relative to the bulk material.

Scully et al. have reviewed the available data on H solubility and permeability in A1 and some of its alloys. Their review shows tremendous variability in the available data. However, H is very insoluble in A1 at 25°C and 1 atm pressure, with values ranging from 10 to 10 " atom fraction. They also concluded from data for A1 alloys that Li and Mg alloying additions increased the solubility of H in A1 because of their chemical affinity for H. A summary of the H diffusivity in A1 also revealed a wide range in values, but if it is assumed that the presence of aluminum oxide (AI2O3) on the surface is likely under all these tests, the fastest diffusivity is expected to be that closest to bulk diffusivity in Al, because this likely results from material with a defective or thinnest oxide film. There are several studies that resulted in diffusion coefficients at 25°C of about 10 cm /sec for Al. 

The three metals commonly used in pharmaceutical packaging are tin, aluminum, and steel. Because of its susceptibility to oxidation and corrosion, steel must be galvanized or coated by an epoxy before use, so its application is primarily reserved for drums of bulk material where very high strength is required. Metals can also be formed into pressure cylinders for the containment of gaseous product. ... 

Monoliths made of metal foils can also be used as substrates in combustion catalysts [19, 20]. The metal is generally an iron- or nickel-based steel containing small amounts of aluminum. The aluminum diffuses to the surface on heating and oxidizes to form an adherent alumina layer. This alumina layer gives the alloy high oxidation resistance and is essentially self-healing as it arises from diffusion from the bulk material. It also provides good adhesion for the alumina washcoat. 

A study by Comyn et al. [8] indicated that low (or no) cure took place in the interphase between an amine cured epoxy and aluminum because the amine was preferentially adsorbed onto the aluminum oxide on the aluminum. Garton et al. [9] showed that the acidic surface of a carbon fiber selectively adsorbed amine and catalyzed the reaction between the amine and an epoxy resin. Nigro and Ishida [10] found that homopolymerization of epoxy resin was catalyzed by a steel surface. Zukas et al. [11] discovered, in a model system of an amine cured epoxy resin and an activated aluminum oxide, a change in the relative rates of the reactions leading to crosslinking of the epoxy, so that the material in the interphase was structurally different from that in the bulk. 

Several other nanoparticles have been studied because physical properties of the nanostructures differ from the bulk materials [5,6]. Metal nanoparticles such as ZnO and titanium dioxide (Ti02), for example, provide nanocomposites the attractive nonlinear properties that make them ideal candidates for nonlinear optical (NLO) based devices [5]. Porous system-based nanocomposites, including porous materials such as silicon, gallium phosphide, aluminum oxide, and structures based on them, were considered by Golovan et al. [6]. The main focus is on the effect of birefringence, which is caused by the anisotropy of pores in the materials. 

This material has gradually replaced potassium chlorate (KCIO 3) as the principal oxidizer in civilian pyrotechnics. Its safety record is far superior to that of potassium chlorate, although caution - including static protection - must stiU be used. Perchlorate mixtures, especially with a metal fuel such as aluminum, can have explosive properties, especially when present in bulk quantities and when confined. 

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