Composition and Properties of Glasses

A very common method for describing the composition of a glass is to quote the content of each component (oxide) by weight fraction (w in wt%) or mole fraction (m,- in mol%). If Mi is the molar mass of the component i, the relationship between the two quantities is given by 

If components other than oxides are used, it is advantageous to define fictitious components, for example the component F2—O (= fluorine-oxygen, with M = 2x 19—16 = 22) this can be used to replace a fluoride with an oxide and this hypothetical oxide component, for exart5)le Cap2 = CaO -H F2—O. This reduces the amount of data required 

Glass type Code Main components (wt%) Si02 1 B2O3 1 AI2O3 1 Na20 1 IVGnor components 10% 

Low dielectric loss glass S 8248 70 27 AI2O3, Li20, Na20, K2O, BaO 

The component-specific factors pt were first systematically determined by Winckelmann and Schott [4.13], and are listed in detail in the standard literature, e.g. [4.14]. 

With given weight or mole fractions, a property P can he calculated (or approximated) via a linear relation of the type 

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Thus far, we have considered the varying chemical compositions and properties of glasses. In this last section, we will examine an important architecture - glass fibers, of paramount importance in our society. The synthesis of glass fibers dates back to... 

Chemical stoneware is similar to the domestic variety, but of higher quality stronger and with a better glaze. It is available in a variety of shapes for pipe runs and columns. As for glass, it is resistant to most chemicals, except alkalies and fluorine. The composition and properties of chemical stoneware are discussed by Holdridge (1961). Stoneware and porcelain shapes are used for packing absorption and distillation columns (see Chapter 11). 

The composition and properties of some common reinforcing fibers were given earlier in Table 1.31, the most common of which is glass fiber. The compositions of some commercial glass fibers were given earlier in Table 1.32, and the most common polymer matrices were given in Table 1.28. For this section, we will concentrate on discontinuous-glass-flber-reinforced polymer-matrix composites. 

Understanding the physical state of food materials requires that food composition and properties of individual food components and their interactions with each other are well known. The physical characterization of a food system needs to consider all components within the system, the molecular environment of the components and all micro- and nanostructural aspects of factors contributing to the properties of the material. The first studies referring to glass formation by food components were those on dairy powders (Supplee 1926) and glucose (Parks and Thomas 1934). These... 

Table 1. Compositions (wt%) and Properties of Glasses for Strengthened Applications...

Table 1. Composition and Properties of Li20-Al203-Si02 and Mg0-Al203-Si02 Glass Ceramics...

Table 13.1 Composition and properties of representative chalcogenide glasses (After Yamane and Asahara, 2000).

There are about 800 different types of glass in common use today. Figure 11.31 shows two-dimensional schematic representations of crystalline quartz and amorphous quartz glass. Table 11.5 shows the composition and properties of quartz, Pyrex, and soda-lime glass. 

TABLE 11.5 Composition and Properties of Three Types of Glass... 

Countless variations in glass composition and properties are possible. If part of the silica is replaced by boron oxide, the glass has less tendency to crack with changes in temperature. Pyrex, the trademarked glass common in kitchens and laboratories, is a borosilicate glass. Many beautiful colors can be produced by adding the substances listed in Table 18.5. The composition and properties of some other types of glasses are listed in Table 18.6. 

In addition to its composition, the properties of glass cement are also influenced by the way in which the original melt was cooled. In general, the reactivity of the cement increases with increasing cooling rate (Hormnertgen and Odler, 1991). 

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