Abstract
The ion-exchange and associated interfacial reaction mechanisms of silicate glasses are critical in elucidating their aqueous corrosion behaviors, surface modification and property changes, hence have potential impact on both science and technology. This work reports findings of the atomic and nanoscale details of the glass–water interfacial reactions revealed by applying reactive force field (ReaxFF) based molecular dynamics (MD) simulations, from which the key mechanisms of the ion exchange, as well as the kinetics of associated interfacial reactions, are elucidated. It was found that the Na+ and H+ ion exchange can happen between two oxygen ions on a single silicon oxygen tetrahedron or adjacent tetrahedra. In addition, the clustered reaction of two non-bridging oxygens mediated by an adjacent water molecule was also identified. The latter reaction might be the main mechanism of water transport after initial surface reactions that consume the non-bridging oxygen species on the surface. Water molecules thus can play two roles: as an intermediate during the proton transfer processes and as a terminator of the clustered reactions. Statistical analyses were performed to obtain reaction kinetics and the results show that silanol formation is a more favored process than the silanol re-formation within the first 3 ns of interfacial reactions. The results obtained thus shed lights on the complex ion-exchange mechanisms during glass hydration and enable more detailed understanding of the corrosion and glass–water interactions of silicate glasses.
Highlights
Glass as an ancient yet modern material has transformed our lives in many ways, with applications ranging from window panes, cookwares, and containers in our daily lives to high technology applications such as display, optical communication, biomedical devices, and nuclear waste disposal[1,2]
Understanding glass–water interactions is challenging due to the complex interfacial reactions that happen in the nanometer scales and varying time scales ranging from nano-seconds to years, which makes direct observations very challenging[1,6]
Based on the dynamic simulation data, both the mechanisms and kinetics of we investigated the initial stage of water–sodium silicate glass interactions using the ReaxFF based molecular dynamics (MD) simulations[16]
Summary
Glass as an ancient yet modern material has transformed our lives in many ways, with applications ranging from window panes, cookwares, and containers in our daily lives to high technology applications such as display, optical communication, biomedical devices, and nuclear waste disposal[1,2]. In many of these applications, glass will be in contact with water, either the liquid or vapor phase, in their lifetime and the property changes due to these interactions are of critical scientific and technological importance. Recent developments of first principles and classical atomistic simulations[12,13], especially those with reactive potentials[14,15], have enabled detailed investigations of the surface and interfacial reactions with atomic level resolution[16,17,18]
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