Nonoxide Glasses

Figure 3 Optical transmission spectra of silica and nonoxide glasses. ZBLAN glass composition is given in Figure 12...

From 2690474 to 2691059, and 2701852, 2702086, 2702107, 2704654 various colours and pigments, mainly spinels. 2704235 Bone Ash 2706599 Portland cement flue dust 2706667 Feldspar group minerals 2957317 Nonoxide glasses. 

The main part of nonoxide glasses studied at present are fluoride glasses. Three international symposia on nonoxide glasses have been held in Cambridge, 1982, in Troy, NY, 1983, and in Reimes, 1985 (cf. Reisfeld et al., 1985b). 

Nonoxide fibers, such as carbides, nitrides, and carbons, are produced by high temperature chemical processes that often result in fiber lengths shorter than those of oxide fibers. Mechanical properties such as high elastic modulus and tensile strength of these materials make them excellent as reinforcements for plastics, glass, metals, and ceramics. Because these products oxidize at high temperatures, they are primarily suited for use in vacuum or inert atmospheres, but may also be used for relatively short exposures in oxidizing atmospheres above 1000°C. 

Pigment Systems. Most of the crystals used for ceramic pigments are complex oxides, owing to the great stability of oxides in molten silicate glasses. Table 3 fists these materials. The one significant exception to the use of oxides is the family of cadmium sulfoselenide red pigments. This family is used because the colors obtained caimot be obtained in oxide systems thus it is necessary to sustain the difficulties of a nonoxide system. 

PPO has excellent resistance to nonoxidizing acids, alkalis, salts, and polar solvents but is attacked by nonpolar solvents, such as benzene. As shown in Table 15.9, glass-filled PPO has a heat deflection temperature of 145 °C and excellent mechanical properties. 

Many inorganic materials can be dissolved in strong acids with heating. Glass vessels are often useful, but Teflon, platinum, or silver are required for HF, which dissolves silicates. If a nonoxidizing... 

The last quarter of the twentieth century saw tremendous advances in the processing of continuous, fine diameter ceramic fibers. Figure 6.4 provides a summary of some of the important synthetic ceramic fibers that are available commercially. We have included in Fig. 6.4 two elemental fibers, carbon and boron, while we have excluded the amorphous, silica-based glasses. Two main categories of synthetic ceramic fibers are oxide and nonoxides. A prime example of oxide fibers is alumina while that of nonoxide fibers is silicon carbide. An important subclass of oxide fibers are silica-based glass fibers and we devote a separate chapter to them because of their commercial importance (see chapter 7). There are also some borderline ceramic fibers such as the elemental boron and carbon fibers. Boron fiber is described in this chapter while carbon fiber is described separately, because of its commercial importance, in Chapter 8. 

Carbon fiber reinforced ceramic composites also find some important applications. Carbon is an excellent high temperature material when used in an inert or nonoxidizing atmosphere. In carbon fiber reinforced ceramics, the matrix may be carbon or some other glass or ceramic. Unlike other nonoxide ceramics, carbon powder is nonsinterable. Thus, the carbon matrix is generally obtained from pitch or phenolic resins. Heat treatment decomposes the pitch or phenolic to carbon. Many pores are formed during this conversion from a hydrocarbon to carbon. Thus, a dense and strong pore-free carbon/carbon composite is not easy to fabricate. 

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