Alkali borosilicate glasses

A large number of commercial glasses are based on alkali borosilicate systems, with a majority of these glasses primarily containing soda instead of any of the other alkali oxides. Most of the commercial glasses, while transparent, are actually phase separated with a very fine scale morphology. 

Even though the microstructure of sodium borosilicate glasses is so fine that regions of a given phase may be only 5 to 20 nm in diameter. 

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Roderick, J. M., Holland, D. Scales, C. R. 2000. Characterization and radiation resistance of a mixed-alkali borosilicate glass for high level waste vitrification. Materials Research Society Symposium Proceedings, 608, 721-726. 

Enameling meets decorative as well as protective requirements. Ceramic enamels are mainly based on alkali borosilicate glasses. The part to be enameled is dipped into or sprayed with a slip, ie, a water suspension of glass fragments called frit. The slip coating is dried and fused in an enameling furnace under careful heat control (see Enamels, porcelain or vitreous). 

Porcelain enamels are basically alkali borosilicate glasses. These enamels are complex, however, because of the large number and types nf oxides which are needed to develop proper adherence and functional properties. Network-forming ingredients and modifiers arc used as in normal glass... 

PVG disks with thickness 0.4 mm. Corning Co., Code-7930, have been used. PVG has been prepared by phase separation of an alkali borosilicate glass and subsequent acid leaching. The NA measurement has been performed at 77K on a Sorptomatic 1900 (Carlo Erba Instruments). The sample has been degassed at 393 K for 8h. Adsorption and desorption isotherms were measured over a range of relative pressures P/Pq from 0 to 1.0. 

Phase separated alkali borosilicate glasses tend to consist of a silica-rich phase and an alkali borate-rich phase. Several studies have shown that impurities, including transition metals and hydroxyl, are concentrated in the alkali borate-rich phase. Since the alkali borate-rich phase is much more readily dissolved in HCl than is the silica-rich... 

Very small quantities of Pu are carried over into the HLW stream and these are incorporated in the vitrified product. However, the mixed alkali borosilicate glass used in WVP can only accommodate -3-5 wt% PUO2, before glass quality and durability are impaired. The glass currently used is therefore unsuitable for immobilizing large quantities of Pu. 

Molten lead/unleaded borosilicate or alkali borosilicate glasses Low-temperature glaze stains, underglaze colors, colored pellets and granules Tableware, wall and floor tiles... 

In alkali borosilicate glasses, the alkali is believed to prefer its association with boron thus, no NBOs are present in the structure for mol Na20/B20j < 0.5. Thereafter, the alkalis are distributed between borons and silicons, depending on the composition and temperature. 

This is consistent with hydrolysis mechanisms proposed by Bunker to explain the aqueous corrosion of alkali borosilicate glasses [181]. 

Ti02-opacified porcelain enamels are alkali borosilicate glasses containing Ti02 which have been fused onto metal substrates for decorative purposes and for corrosion resistance. 

Searching product specifications on the internet (from glass manufacturers and suppliers websites), a number of values for thermal conductivity for alkali borosilicate glasses have been quoted. It seems that below the glass transition temperature, values for thermal conductivity are quoted around 1.0 0.25 W m K at around room temperature, increasing to a value of about 2.5 0.25 W m K at about 1400 K. These values seem reasonably insensitive to composition and so may be used as markers for our glass thermal conductivity. 

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