Alkali metal silicate glasses, structure

Two-dimensional schematic structure of an alkali metal silicate glass ... 

Huang, C. and Cormack A. N. (1992) Structure and Energetics in Mixed-Alkali-Metal Silicate Glasses from Molecular Dynamics, J. Mater. Chem., 2, 281-287. 

Lead silicate glasses having different mole ratios of Si02 to PbO and containing different amounts of alkali/alkaline earth metal oxides were prepared by conventional melt-quench method. The different structural units of Si present in these glasses were identified by Si MAS NMR. ... 

This new nanostructured binder was obtained by laminar mixing of the liquid glass containing alkali metal cations as Na, TFS, and a water-soluble silicate, containing an organic alkaline cation (WSS) such as l,8-diazabicycloundecene-7 (DBUS, Structure 7.1) or l,5-diazabicyclononene-5 (DBNS, Structure 7.2). 

Two reactions can convert alkali silicate glass into a solid mass with which contaminated sludges can be bound (1) by adding acid to form silica gel, whereby the evaporation of water does not occur (alternative to vaporization ) and (2) reaction with multi-valent metal ions (e.g., calcium chloride) while forming aqueous metal silica gel, where heavy metals are precipitated and are mechanically bonded into the gel structure. The CHEM-FIX-Process is primarily used in the United States for inorganic contaminants the Belgian SOLIROC-Process contains additives to make it usable for the solidification of organic wastes. 

Introduction of additional species into silica creates silicate glasses with properties quite different from those of the parent pure silica system. Structurally, the addition of alkali metals to silica alters the structure, creates non-bridging oxygen (NBO), lowers the liquidus, and decreases durability in aqueous solution (Weyl and Marboe 1964 Doremus 1979 De Jong and Brown 1980 De Jong et al. 1981 ... 

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