Abstract:

Multinuclear solid-state NMR, including (29)Si、(23)Na、(11)B MAS and （29）Si CP/MAS NMR was employed to study the structure change of Na2O-B2O3-SiO2 glasses after 24 hour heat-treatment of phase separation at different temperatures. Then the glasses were etched with acid. The results show that there is a turning point temperature. Being confined by dynamical factors, phase separation did not reach equilibrium below this temperature. The degree of phase separation was reduced when the temperature was decreased. When the temperature was above this turning temperature, the phase separation could reach equilibrium. Being controlled by thermodynamics, the degree of mtiscibility was enhanced when the temperature was increased. The phase separation was the best when the heat-treatment of phase separation was proceeded at this turning temperature. The NMR results obtained from different resonant nuclei were consistent with one another.

Key words: Sodium borosilicate, Phase separation, Etching, NMR