Analytical Electron Microscopy of Leached Layers on Synthetic Basalt Glass

Abstract

AbstractAnalytical electron microscopy was used to characterize leached layers formed on a synthetic basalt glass after 300 days in deionized water, sodium chloride solutions, or sodium chloride solutions containing magnesium chloride. Ultramicrotomed cross-sections show that the leached layers consist of a mixture of amorphous and crystalline phases whose composition and microstructure are sensitive to solution chemistry. In general, Na, Ca and Mg are selectively leached in all solutions, leaving behind surface alteration products which are rich in Fe, Ti, and Al. In deionized water and the NaCl solution, gibbsite (AI(OH)3) is a major phase; in the Mg-containing solution, Si and Al are retained as smectite clays. Results are compared to the alteration of natural basalt glasses in marine environments, particularly as they relate to the use of basalt glass alteration as a means of verifying the long-term leaching behavior of nuclear waste form borosilicate glasses.