A solid-state nuclear magnetic resonance study of the intermediate-range order of alkali disilicate glasses and its relationship to crystallization behaviour.

摘要

There are two general mechanisms of crystal nucleation in glass: heterogeneous nucleation from surfaces and impurities, and homogeneous nucleation from the volume. It is thought that structural similarities between glass and crystal at the intermediate-range level influence the mechanism used, however there are few experimental studies to support this. In this thesis solid-state nuclear magnetic resonance is used to probe intermediate-range order in sodium and lithium disilicate glasses through second moments of dipolar couplings. These two glasses undergo heterogeneous and homogeneous nucleation, respectively. It is seen that the second moments measured for the lithium glass agree with the layered structures of the isochemical crystalline phases while those measurements for the sodium glass do not. This observation supports the hypothesis that glasses capable of homogeneous nucleation are structurally more similar to the resulting crystalline phases in comparison to those glasses that are only capable of heterogeneous nucleation.