ABSTRACT
This chapter focuses on why glasses form, their structure and the properties that make them unique, such as their glass transition temperature and viscosity. It addresses the question of how rapidly a melt would have to be cooled to form a glass. The chapter describes glass structure and also focuses on trying to understand the origin of the glass transition temperature and the temperature and composition dependence of viscosity. It deals with another technologically important class of materials, namely glass-ceramics, their processing, advantages and properties. The two main mechanisms by which a liquid crystallizes are homogeneous and heterogeneous nucleation. Since glasses possess only short-range order, the idea of a repeating unit cell is inapplicable. Glasses are supercooled liquids that solidify without crystallizing. They are characterized by having only short-range order. Glass structure is best described by a random network model and is determined by the relative amounts of network formers to network modifiers.
