Aluminum oxide translucency

Porcelain dental cements were developed by Steenbock [6] who produced silico-phosphate dental material using 50 wt% concentrated phosphoric acid solution and an aluminosilicate glass. Wilson et al. [7] showed that various brands of commercial cements consist of powdered alumina-lime-silica glass mixed with phosphoric acid, which form a hard and translucent product. The phosphoric acid used in these cements is partially neutralized by aluminum oxide. 

Ionic Compounds Chrysoberyl is a transparent or translucent mineral that is sometimes opalescent. It is composed of beryllium aluminum oxide, BeAl204. Identify the oxidation numbers of each of the ions found in this compound. Explain the formation of this ionic compound. 

Synthetic Marble. Highly filled monomer or monomer-polymer syrup mixtures are used to form synthetic marble materials. A single belt approach can be employed in the formation of synthetic marble with only one smooth side (57,58). Aluminum oxide, calcium carbonate, titanium dioxide, etc, are used at loading levels of 60% the specific materials of choice are determined according to the translucence, chemical-resistance, and water-resistance properties desired (59,60). 

Figure 21.10 The hght transmittance of three aluminum oxide specimens. From left to right single-crystal material (sapphire), which is transparent a polycrystaUine and fully dense (nonporous) material, which is translucent and a polycrystaUine material that contains approximately 5% porosity, which is opaque. (Specimen preparation, P. A. Lessing.)...

Silicates and other minerals such as titanates containing divalent metals have been used in place of oxides. Silicates provide a translucent structure to the product. Aluminum also gives a denser and stronger structure. 

Composites of MEEP/Al were more difficult to prepare than other composites because of the extreme moisture sensitivity of the aluminum alkoxides. Nonetheless, translucent, tough films were prepared from equal weights of aluminum tri-sec-butox-ide and polymer. As with the composites discussed above, differential scanning calorimetry (DSC) revealed the glass transition at -79°C, indicating the backbone motion of a large portion of polymer segments was not perturbed by the metal oxide. 

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