Formation Mechanism of Crystalline Phase during Corrosion of Aluminum Phosphate Glasses

The formation mechanism of crystalline phases within the corrosion layer of glasses has attracted considerable attention, but research on the microscopic chemical process of their formation has rarely been studied. This study focuses on investigating potassium aluminum phosphate glass with a nominal molar composition of 41.6K(2)O-16.7Al(2)O(3)-41.7P(2)O(5). Liquid- and solid-state nuclear magnetic resonance (NMR) techniques are employed to investigate the evolution of the aluminum species and phosphorus units of the corroded glasses, leachates, and sediments derived from immersing the glass for various durations. Our findings provide compelling evidence that the formation of the crystalline phases during the phosphate glass immersion process is a result of leached glass elements saturating in the solution and subsequently precipitation onto the glass surface. Furthermore, we have identified two distinct dissolution modes in this process, which include the overall dissolution of large molecular units presented in the initial stage and the continuous dissolution of small molecular units that persists throughout the entire corrosion process. The coexistence of these two dissolution modes leads to the formation of crystalline phases on the glass surface even before both the glass and the solution have fully reached dissolution saturation. This study sheds light on the glass corrosion mechanism at the molecular level, providing new insight into comprehending the corrosion process of glass.