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Structural and Thermal Expansions in Alkali Silicate Binary Glasses
Author(s) -
TILTON LEROY W.
Publication year - 1960
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1960.tb09146.x
Subject(s) - mineralogy , alkali metal , molar volume , silicate , thermal expansion , silica glass , materials science , silicate glass , oxide , annealing (glass) , coordination number , analytical chemistry (journal) , ion , thermodynamics , chemistry , composite material , metallurgy , chromatography , organic chemistry , physics
Two volume‐changing processes that should be considered in detail are (1) distention of networks by added oxides which may swell glass volumes in proportion to the added oxide volumes and (2) angular change in intertetrahedral bonding which may take place at and above annealing temperatures in proportion to the number of metal ions introduced by the modifications. Accordingly, the partial molar volumes of modifiers, ν R , are assumed as those of their crystal or liquid states and the partial molar volumes of silica are computed from (1/ν S ) = 2.20 + 0.00057 ( r m – 0.12) (1723 – t ). Tentative glass volumes are then computed as V g = S m ν S + r m ν R by use of the mole fractions S m and r m for silica and nonsilica, respectively. The excess of computed glass volumes, V 0 , over V as derived from observed densities is taken as a measure of the penetration of modifiers into the network cavities without corresponding distention of the network. By using the computed density of 1.95 for vitron, the value 2.20 for silica glass, and 2.30 as reported for irradiated silica, one can estimate that silica glass consists of 28% vitron and 72% disordered silica in the intervitron tissues. The values of V g , – V mentioned are found to be in fair accord with expectations computable from the vitron theory.