The effect of Al 2O 3 on viscosity in the calcium silicate melt-based system containing Na 2O and CaF 2 was investigated and correlated with the melt structure using FTIR (Fourier transform infrared) spectroscopy, XPS (X-ray photoelectron spectroscopy), and Raman spectroscopy. Substituting SiO 2 with Al 2O 3 modified the dominant silicate network into a highly structured alumino-silicate structure with the aluminate structure being particularly prevalent at 20 mass% of Al 2O 3 and higher. As the melts become increasingly polymerized with higher Al 2O 3 content, the fraction of symmetric Al-O 0 stretching vibrations significantly increased and the viscosity increased. XPS showed a decrease in the amount of non-bridged oxygen (O -) but an increase in bridged oxygen (O 0) and free oxygen (O 2-) with higher Al 2O 3. Although changes in the structure and viscosity with higher CaO/(SiO 2 + Al 2O 3) were not significant, the symmetric Al-O 0 stretching in the [AlO 4] 5--tetrahedral units decreased. The apparent activation energy for viscous flow varied from 118 to 190 kJ/mol.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry