Viscosity modelling of ternary CaO–Al2O3–SiO2 melts assisted by in situ high temperature Raman spectroscopy

In this study, the evolution of microstructure and its correlation with the viscosity of CaO–SiO2-based melts, incorporating various Al2O3 additives, have been investigated by employing in situ high temperature Raman spectroscopy and viscosity model. Raman spectra of the melts were procured at 1823 K by using in situ high temperature Raman spectroscopy. After considering the intricate influences of temperature and Raman scattering cross section (RSCS), the original Raman spectra of aluminosilicate melts underwent calibration. Subsequently, the distribution of microstructure species Qi (i = 0–4) was quantitatively performed through meticulous deconvolution of calibrated Raman spectra. The evolution of Qi species with the increasing Al2O3 content reveals a decrease in Q1 and Q2 species, while the fully polymerized Q4 experiences a continuous and significant growth. Concurrently, Q3 initially exhibits an upward trend followed by a subsequent decline. The Qi evolution culminates in an overall enhancement of the degree of polymerization. Viscosity was determined by utilizing a rigorously selected viscosity model, elucidating a consistent upward trajectory as Al2O3 content is incrementally added. Furthermore, a quantitative analysis of the relationship between viscosity and structure was conducted based on the average number of non-bridging oxygen per network-forming tetrahedron (NBO/T). The findings demonstrate a robust linear relationship between the logarithm of viscosity and NBO/T, thereby offering valuable insights for examining and predicting viscosity behavior of aluminosilicate systems.