Layered Sodium Disilicates As Studied By Solid-State NMR

In this dissertation, the progresses of modern solid-state NMR spectroscopy and its application in solid-state chemistry and material science were first reviewed. Then, advanced multinuclear and multi-dimensional solid-state NMR techniques were used to study the hydration processes of layered sodium disilicates and to investigate the proton-silicon spatial proximity and proton chemical shift anisotropy tensor in a polylayered silicate kanemite, with corresponding results indicated as follows:The stability of a model layered disilicate SKS-5 (which has relatively simple crystal structure) in atmosphere was thoroughly studied by 1H, 29Si and 23Na MAS NMR. The results indicate that hydrolysis of the silicate framework in SKS-5 is the crucial factor of the instability of this material. After carefully analyzing the experimental data, the corresponding hydration mechanisms about SKS-5 were given.Similar hydration reactions and condensation reactions were deduced from the study of the hydration process of layered sodium disilicate SKS-6, although SKS-6 has a more sophisticated crystal structure than that of SKS-5. In this study, multi-dimensional solid-state NMR method such as nuclear Overhauser enhancement spectroscopy and cross-polarization technique with variable recycle delays show their superior abilities in structural elucidation.The variations of coordination of sodium ions during the hydration processes of SKS-5 and SKS-6 were investigated by combining 23Na MQMAS with 1H ? 23Na CP/MAS NMR. Three different types of sodium ions during the hydration processes were identified and their possible coordination structures were proposed.The validity of FSLG decoupled heteronuclear correlation spectroscopy was first verified on a hydrated SKS-6 sample, then this NMR method was applied to a layered silicate kanemite to determine the 1H chemical shift anisotropy parameters of the hydrogen-bonded proton.