Mechanism of water dissolution in sodium-silicate melts and glasses: Structural interpretation of spectroscopic data

Sodium-silicate glasses with varying water contents were studied by ²³Na NMR and ¹H NMR spectroscopy. The ²³Na NMR spectrum is made up of two Gaussian-Lorentzian components corresponding to rigidly bound and free Na ions. The rigidly bound Na is allocated in the disilicate-like domains corresponding to Q₃ species of sodium-silicate glasses. Unbound Na is associated with Q₂ and Q₁ species. It was shown that, during water dissolution, some hydroxyls are incorporated into the disilicate unit of the structure to form NaHSi₂O₅, while others hydrate silica (Q₄species). Our ²³Na NMR data are consistent with available data on Q speciation and the proportions of water species in sodium-silicate glasses in the frameworks of a proposed detailed structural scheme of water dissolution.