Quantitative studies on the structure of xCaO⋅(1-x)SiO2 glasses and melts by in-situ Raman spectroscopy, 29Si MAS NMR and quantum chemistry ab initio calculation.

• In-situ high temperature raman spectra of binary calcium silicate melts at the temperature of 1873 K have been measured. The corresponding quenched glasses have also been determined for comparison. • A set of clusters existing in binary calcium silicate glasses and melts were optimized and calculated by quantum chemistry ab initio calculations to obtain the raman scattering cross sections of characteristic vibrations of clusters. • A method for quantitatively analyze the microstructure of binary calcium silicate glasses and melts by raman spectroscopy was proposed and verified by 29Si MAS NMR. The quantitative distribution of different Q i species in binary calcium silicate glasses and their melts has been investigated by in-situ high temperature Raman spectroscopy, 29Si MAS NMR and quantum chemistry (QC) ab initio calculations. The structural units and several cluster structure models have been designed, optimized and calculated by ab initio calculations. The attribution of their vibrational modes, vibrational wavenumbers of non-bridging silicon-oxygen (Si-O nb) and Raman scattering cross sections (SCS) have then been worked out and analyzed. The functional relationship between the SCS and stress index of silicon-oxygen tetrahedron (SIT) was established for the model clusters of delicate Q i. Quantitative distributions of Q i in calcium silicate glasses and melts are finally obtained which are in good agreement with the experimental results of 29Si MAS NMR. Although the primary structure present in calcium silicate glasses and melts is the same, the relative distribution of Q i is different. On the basis of the present work, it will be helpful to predict the physicochemical properties of silicate slag. [ABSTRACT FROM AUTHOR]