AVS 59th Annual International Symposium and Exhibition
    Surface Science Tuesday Sessions
       Session SS-TuM

Paper SS-TuM4
Reactions of Water with Vacuum Fracture Surfaces of Sodium-Aluminosilicate Glass: Effects of Composition on Reactivity

Tuesday, October 30, 2012, 9:00 am, Room 21

Session: Surface Reactivity of Oxides
Presenter: K. Adib, Corning Incorporated
Authors: K. Adib, Corning Incorporated
J.E. Dickinson, Corning Incorporated
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We have synthesized different ternary SiO2:Al2O3:Na2O glasses containing bridging oxygens and non-bridging oxygens (NBO) and fractured them in ultrahigh vacuum to produce pristine surfaces. X-ray photoelectron spectroscopy of oxygen core levels and valence band were used to determine the fraction of non-bridging oxygens (SiONa) to bridging oxygens (SiOSi and SiOAl) on the vacuum fractured surfaces. For those glasses where the NBO fractions of the total oxygen were held constant, a 0.2 eV variance was observed in the binding energies of the NBO O1s core levels consistent with substantial changes, as a function of composition, in the ionicity of the bond between the NBO and sodium. The fracture surfaces were then exposed to partial pressures of H2O at ambient temperature. It was observed that water reacts primarily with the NBO’s to produce SiOH in place of SiONa. Non-bridging oxygens from glass compositions that contained less alumina had lower electron binding energy and were more likely to react with water. Molecular dynamics simulations were used to elucidate the role of H3O+ in the reaction of water with the non-bridging oxygens.