Mechanical Strengthening by Phosphates

Beer bottles can be strengthened by spraying with phosphate solutions and heat treating. This allows ion exchange to take place, whereby PO4 groups are substituted for other components near the surface of the bottle glass. The process allows local stresses to be evened out [52]. 

Glass ceramics are microcrystaUine solids produced by the controlled devitrification of glasses. Many of these solid materials are opalescent. 

Interest in phosphate glasses and partly devitrified glass-ceramic products has greatly intensified over the past 15 years. Small amounts of P (as P2O5) play an important role in the formation of glass ceramics by controlling devitrification of the parent glass. 

Glasses can generally be rendered opalescent or opaque by the introduction of discontinuities into their structure. Such discontinuities provide internal surfaces which refract and diffuse the incident light. 

In practice, opalescence may be achieved by (a) immiscibility of two or more phases, (b) devitrification, (c) addition of small crystals and (d) introduction of microcavities. 

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