Atomic bonds Glasses

The silane coupling agents undergo chemical reaction with the surface of inorganic substances to form an SiOM bond (M Si atom in glass). 

Table 1 Approximate chemical shift regions ( 5 ppm) for species in aluminophosphate glasses. Here n refers to the number of bridging oxygen atoms and m is the number of A1 atoms bonded to P...

Consider a glass of water. If you could magically travel inside the water and examine its individual parts, you would see particles consisting of two hydrogen atoms bonded to an oxygen atom ... 

Glass is a classic example atomic bonds can stretch (elasticity) or rupture, but typically do not reform. In metals, atomic bonds can slide and reform, a phenomenon described by dislocation theory this gives rise to energy dissipation, which makes it much more difficult to propagate a crack in metals. 

Understanding atomic bonding helps us understand the structures of crystals and glass. When we think of crystals, we think of atoms arranged in a perfect way. We traditionally think in terms of crystal defects, but we will also consider how these ideas apply to defects in glass. 

Figure 21. Snapshot of two silica surfaces in contact with water between them. Atoms in glass not drawn, although bonds between Si and O are drawn. The large spheres that are drawn represent the O in water, Ow, the small dark spheres are the H in water, and the small hght spheres are the H that are at the silanol sites. Arrows denote interface where most water remains, but water diffuses in upper right into sihca. (see text)...

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