The structural role of water in silicate glasses: proton and silicon-29 NMR evidence.
Proton and silicon-29 NMR were used to examine the structural role of H2O in 2/hydrous Na2Si4O9 glasses with different H2O-contents as an Al-free model system. The Al-free Na2Si4O9 system is particularly well-suited for high-resoln. solid-state NMR investigations as the various Q-species can easily be resolved in the resp. 29Si MAS and CP/MAS spectra. Various high-resoln. solid-state NMR techniques were used: 29Si single pulse MAS, 1H -> 29Si-CP/MAS, and 1H-CRAMPS. Only the combined use of all these methods provides an insight into the interactions between the Si-network and the proton system. Addnl. modifications of these std. techniques were then used to confirm and to refine the picture of the Na2Si4O9/H2O system.
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