Chemical durability improvement of glass shells

Abstract

High temperature chemical surface treatments have been used to improve the chemical durability and weatherability of spherical glass shells. The surface treatment consists of exposing heated glass shells to a mixture of sulfur dioxide, air and water vapor. A thin layer of the glass shell is dealkalized as a result of this treatment. The weatherability of treated alkali-silicate and alkali-calcia-silicate shells was improved, as determined qualitatively with the aid of a SEM. The chemical durability of silicate shells containing over 10 wt.% alkali but no calcia was improved by as much as a factor of thirty by the treatment. The chemical durability of glass shells was determined by analyzing the aqueous solutions used for extracting the constituents of the shells. Treated glass shells containing calcia showed greater resistance to dissolution in water than untreated glass shells of the same composition, even though the untreated shells were relatively durable.