Читать книгу Encyclopedia of Glass Science, Technology, History, and Culture - Группа авторов - Страница 252

Chemically complex silicate glasses and melts include natural magmatic liquids as well as many commercial glasses. Magmatic rocks sometimes also are used for commercial purposes with slight compositional adjustment made to optimize processes or material properties and reduce costs (e.g. rock wool, Chapter 9.3).

Glass families such as boro‐ and phosphosilicates are specifically dealt with in Chapters 7.6 and 7.9, respectively. The chemically complex glasses and melts considered here are mainly aluminosilicates with Si⁴⁺ and Al³⁺ as the main network‐formers and alkali metals, alkaline earths, and Fe²⁺ the dominant network‐modifiers. Their structure, properties, and structure/property relations can be described with the aid of information obtained with compositionally simpler unary, binary, and ternary compositions and composition joins (Figure 1). The principal composition variables are metal oxide/silica, alumina/silica, and types and proportions of metal cations with different electronic properties (see also [1]).

The structural environment changes when pressure during melting is sufficiently high to cause oxygen coordination changes of Al³⁺ and Si⁴⁺ (≥6 GPa). High‐pressure data are so limited, however, that a survey will not be very informative and high‐pressure industrial processes are virtually nonexistent. Pressure will not, therefore, be discussed here.