Glass borosilicate, composition

Bright, J.D., Danchaivijit, S. and Shetty, D.K. (1991). Interfacial sliding friction in silicon carbidc-borosilicate glass composites a comparison of pullout and pushout tests. J. Am. Ceram. Soc. 74, 115-122. 

Cross-section of 65 vol% SiC monofilament-reinforced 7740 borosilicate glass composite (reproduced by permission of Matrix Composite Mat. Sci.)66. 

Boccaccini, A.R., Janczak-Rusch, J., Pearce, D.H., Kern, H. (1999), Assessment of damage induced by thermal shock in SiC-fiber-reinforced borosilicate glass composites , Comp. Sci. Tech., 59, 105-112. 

Several borosilicate glass compositions exhibit immiscibil-ity they separate into two interconnecting phases, one rich in... 

J.-J. Shyu and C.-T. Wang, Sintering and Properties of Li20-Al203-4Si02-Borosilicate Glass Composites,... 

Figure 2-1 Curves for linear shrinkage rate (a) and curves for activation energy (b) in alumina/lead borosilicate glass composites at different programming rates [Ref. 10, 11].

The second approach, sequential additions of different alkoxides to partially hydrolyzed precursors, was invented by Thomas [166] and popularized by Yoldas [167,168]. In this process alkoxides are added in the reverse order of their respective reactivities (least reactive precursors first) and a partial hydrolysis step is performed after each addition. The idea is that the newly added, unhydrolyzed alkoxides will condense with partially hydrolyzed sites on the polymeric species formed by the preceding hydrolysis steps (heterocondensation) rather than with themselves (homocondensation). Unlike the previous method where molecular-level homogeneity is predicted, the homogeneity of the product will depend on the size of the polymeric species to which the last component is added. Two sequential hydrolysis schemes to prepare a multicomponent borosilicate glass composition are shown in Fig. 66 where alkali and alkaline earth metals are introduced as salts or alkoxides. 

For the soda-Hme-silica glasses this is about 2-5 gm/cm for the borosilicate glasses it is very nearly 2-25 gm/cm and hardly changes with slight variations in composition. Wembley L.l. lead glass has a density of 3-08. A very dense lead glass has a density of 5-2. 

One disadvantage of borosilicate glass is the low solubility of sulphates, molybdates, chromates, and halogenides, which may cause separation of metastable phases (Fig. 1) at relatively low contents of these components (1-3 wt%, dependent on glass composition Camara et al. 1980 Kawamoto et al. 1981 Stefanovsky 1989 Stefanovsky Lifanov 1989). At higher concentrations, yellow phase formation may occur (Morris Chidley 1976 Stefanovsky Lifanov 1988 Lutze 1988). The yellow phase, consisting of alkali and alkaline earth molybdates, sulphates, chromates, and halogenides, concentrates Cs and Sr radionuclides, and its presence increases leach rates of these radionuclides. 

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