Water speciation in hydrous silicate and aluminosilicate glasses: Direct evidence from 29si-1h and 27al-1h double-resonance NMR

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    Abstract

    Through a combination of 1H MAS NMR, 1H → 29Si → 1H double cross-polarization (CP) MAS NMR and 27Al → 1H CP MAS NMR, different OH species [SiOH, AlOH, and (Ca,Mg)OH (free OH)] have been unambiguously identified for hydrous Ca,Mg-(alumino)silicate glasses. This confirms my earlier speciation assignments made partially on the basis of 1H chemical shift arguments. The dissolution mechanisms of water in both Al-free silicate and aluminosilicate glasses (quenched melts) are fundamentally similar. For relatively polymerized compositions, it involves dominantly the formation of TOH species (T: Si, Al) through the rupture of T-O-T linkages, in addition to molecular H2O; for more depolymerized compositions containing network-modifying cations of large field strength (e.g., Ca, Mg), free OH species are also important.

    Original languageEnglish
    Pages (from-to)395-398
    Number of pages4
    JournalAmerican Mineralogist
    Volume94
    Issue number2-3
    DOIs
    Publication statusPublished - 2009

    Keywords

    • Aluminosilicate
    • Glass
    • Melt
    • NMR
    • Silicate
    • Structure
    • Water speciation

    ASJC Scopus subject areas

    • Geophysics
    • Geochemistry and Petrology

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