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Water speciation in hydrous silicate and aluminosilicate glasses: Direct evidence from ²⁹Si-¹H and ²⁷Al-¹H double-resonance NMR

Institute for Study of the Earth’s Interior, Okayama University, Misasa, Tottori 682-0193, Japan

Correspondence: ^* E-mail: xianyu{at}misasa.okayama-u.ac.jp

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.

Key Words: Aluminosilicate • silicate • glass • melt • NMR • water speciation • structure

This article has been cited by other articles:

				W. J. Malfait The 4500 cm-1 infrared absorption band in hydrous aluminosilicate glasses is a combination band of the fundamental (Si,Al)-OH and O-H vibrations American Mineralogist, May 1, 2009; 94(5-6): 849 - 852. [Abstract] [Full Text] [PDF]