Influence of Calcium Ion on Initial Alkali Corrosion Process of Zirconia Containing Glass

Abstract

The influence of calcium ion on the initial alkali corrosion process of zirconia containing glass was investigated. Alkali-resistant glass fiber which contains about 15wt% zirconia was immersed in an alkali solution of pH 12.6 containing calcium ion ranging from 0 to 0.74mg/ml at 65°C. The amounts of Si dissolved, depth profiles of atomic ratios at near surface region by XPS analysis and morphology of glass surface by SEM varied with calcium ion concentration, immersion time and acid treatment. These changes showed that reaction process in the low calcium ion concentration region was different from that in the high concentration region. In the low concentration region, Si was dissolved and Zr-rich surface region was formed as in the case of NaOH immersion; however, surface reaction layer was formed by deposited Ca and decreased the reaction rate without showing any surface morphological change. In the high concentration region, calcium was deposited on surface despite little Zr-rich region formation. Thereafter the precipitates containing calcium began to encrust the surface reaction layer on the glass intermittently and this layer was corroded from the near site of these deposits. The concentration dividing these two regions was about 0.1mg/ml in case that surface area of the glass to soaking liquid volume ratio was about 5.75cm-1. Reaction between zirconia containing glass and cement extract solution was considered to be determined by calcium ion concentration per unit glass surface area. The effect of other ion such as sodium or potassium was not observed under these experimental conditions.