Room temperature Raman spectroscopy and 29Si MAS NMR combined with high temperature Raman spectroscopy and DFT calculation of xMgO-(1-x) CaO-SiO2 glasses and melts

In order to study the effect of MgO on the microstructure and macroscopic thermos-physical properties of calcium silicate melt, quantitative analysis of the various silicon-oxygen Qi species in magnesium-calcium silicate glasses and melts at a constant alkalinity has been performed by in-situ high temperature Raman spectroscopy, 29Si MAS NMR and DFT (Density Functional Theory) calculation. Several cluster models, probably existed in magnesium-calcium silicate glasses and melts, modified by Ca2+ or Mg2+ have been designed, their Raman vibrational modes and scattering activities were thus simulated and calculated. A function correlating the wavenumbers of Si-Onb (non-bridge oxygen) of various SiOTs (silicon-oxygen tetrahedrons) with their RSCS (Raman scattering cross sections) was constructed and used to calibrate the experimental Raman spectra. The abundance of each primary Qi species of various magnesium-calcium silicate glasses can be composed by all the deconvoluted hyperfine peaks within the same Qi species. The quantitative description for glasses was proven to be consistent with the result from 29Si MAS NMR. Thus, Qi species distributions for melts were also quantitatively derived. It demonstrated that the abundances of Q1 and Q3 species increased while Q2 species decreased with the increasing replacing amount of MgO. The relationship between the viscosity and Qi species distributions as well as different cations has been investigated and correlated. Q3 species was predominantly responsible for the contribution of viscosity of melt.