Encyclopedia of Glass Science, Technology, History, and Culture. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

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Издательство: John Wiley & Sons Limited
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Жанр произведения: Техническая литература
Год издания: 0
isbn: 9781118799499
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F. Stebbins, Geological Sciences, Stanford University, Stanford, CA, USAA. Takada, Research Center, Asahi Glass Co. Ltd., Yokohama, Japan

       Bjorn Mysen

       Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC, USA

      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).

      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.

      The degree of polymerization of the aluminosilicate network affects most glass and melt properties. Melt polymerization can be expressed as the proportion of nonbridging oxygen (NBO) per tetrahedrally coordinated cations (T), NBO/T. The NBO/T can be calculated from the chemical composition of a glass and melt, provided that types and proportions of network‐forming cations are known. Then, NBO/T = (2·O–4·T)/T, where T and O are atomic proportions of tetrahedral cations and oxygen, respectively, and T is given a formal charge of 4 can be readily calculated.

      The principal network‐formers (tetrahedral cations) in complex glasses and melts are Si4+ and Al3+. These will be discussed first.

      2.1 SiO2

Schematic illustration of the compositional environment of complex silicate melts and glasses. Peralkaline denotes compositional range where there is excess metal cations over that necessary for charge-balance of tetrahedrally coordinated Al3+. Meta-aluminous compositions are those where the proportion of alkali metals + alkaline earths is exactly equal to that needed for charge-balance of tetrahedrally coordinated Al3+. Peraluminous compositions are those where there is excess Al3+ over that which can be charge-balanced with alkali metals + alkaline earths.

      Source: Modified from [1]

Window glass Pyrex Glass wool Rockwool Rhyolite Dacite Andesite Basalt Phonolite
SiO2 72.6 81.1 65 46.6 72.18 65.13 57.51 50.29 56.56
TiO2 2.4 0.39 0.64 0.93 2.06 0.87
Al2O3 0.6 0.43 2.5 13.3 13.23 15.67 16.93 14.79 19.31
B2O3

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