29Si MAS–NMR studies of Qn structural units in metasilicate glasses and their nucleating ability

摘要: The purpose of this work is to verify the possible existence a relationship between similarity local structure network-forming cation Si4+ (Qn units and chemical shifts) in glasses isochemical crystals nucleating ability these glasses. Four metasilicate with widely different volume nucleation rates: Na2Ca2Si3O9 Na4CaSi3O9 (very large), CaSiO3 (intermediate) CaMgSi2O6 (undetectably small) were chosen. We present magic angle spinning nuclear magnetic resonance spectroscopy (MAS–NMR) data for their respective crystalline phases first time. Additionally, we repeat NMR measurements previously studied by other authors (CaSiO3 CaMgSi2O6) test consistency our experimental techniques method analysis. Different central shifts Q2 resonances parent measured, indicating structural differences. relative amount Qn groups each glass was obtained from deconvolution 29Si MAS–NMR spectra. shape distribution system considered as measure connectivities SiO4 tetrahedra respect its crystal (which has only groups). A correlation found tendency glasses, that similarities role determining internal studied.