Borosilicate glasses chemical durability

The slow rate of dissolution of, or leaching from, durable glasses has led to proposals for the vitrification of nuclear waste. Glasses based on the sodium borosilicate system appear to be favoured because of their ability to dissolve the waste, combined with good chemical durability. Intensive development has taken place over recent ycars and a regular journal is devoted to this topic . 

Fig. 1. Secondary electron micrograph of Na-borosilicate glass loaded with 30 wt% waste oxides and containing 0.9 wt% S03 (etching with 0.1 M HC1). Droplets with chemical durability lower than matrix are a sulphate-enriched phase (Stefanovsky 1989).

Chemical Properties. The chemical durability is a function of the durability of the crystals and the residual glass. Generally, highly siliceous glass-ceramics with low alkali residual glasses, such as glass-ceramics based on quartz and (3-spodumene, have excellent chemical durability and corrosion resistance similar to that obtained in borosilicate glasses. 

Borosilicate (usually 5-13% B203) Very good thermal shock resistance and chemical durability easy to melt and shape Not suitable for longterm high temperature use Labware kitchenware special light bulbs glass pipe sealed beam headlights... 

Borosilicate glass is soda-lime glass to which boric oxide has been added. It is known under the brand names of Pyrex and Kimax . The addition of boron to the glass produces a product with superior durability, chemical, and heat resistance. 

The above considerations of the chemical durability and corrosion of glass were concerned with current types of silicate and borosilicate glasses. Special types of glass may exhibit quite different behaviour and also require special test methods. 

Non-alkaline-earth borosilicate glass with Si02 > 80% and B2O3 at 12-13%, these glasses show high chemical durability and low thermal expansion (about 3.3x10- K ). 

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