Investigation of Chemical Durability Mechanism in Fluoride Glasses

Abstract : In our previous research, leaching data on two families of fluoride glasses were collected in aqueous media and in solutions buffered at various pH values. The corrosion process was analyzed, leading to the development of a model for dissolution. In this 2nd year of research, we have broken down the dissolution model into component mechanisms and have analyzed each component separately. While many processes take part in the aqueous corrosion of fluoride glasses, we have been able to identify the results of these processes and have developed a quantitative description of each part and of what role it plays in the dissolution of zirconium-fluoride based glasses. A paper, presently under review by the American Ceramic Society, was written to present these results. We are currently applying this analysis method to thorium-fluoride glasses and are preparing a publication on those results. The comparison between the leach rates of different classes of fluoride glasses (ZrLF4, ThF4 and UF4) has been of great value in understanding the effect of composition variations on the leaching processes. Monitoring the pH variations and conducting tests in pH buffered solutions have led us to understand the effects which enhance the corrosion rate of these glasses, and makes them far less durable than silicates.