Relationship between structure and viscosity of CaO–SiO₂–MgO–30.00 wt-%Al₂O₃ slag by molecular dynamics simulation with FT-IR and Raman spectroscopy

ABSTRACT

Structure of CaO–SiO₂–MgO–30.00 wt-%Al₂O₃ slag was investigated using molecular dynamics simulation at 1873 K, and viscosities with different basicities were measured for quantitatively studying the relationship between structure and viscosity. With the increase of basicity, the three-dimensional networks formed by Si and Al are depolymerised, which is consistent with the analysis using FT-IR and Raman spectroscopy. Additionally, FT-IR analysis shows a dampening of [Al–O–Si] trough, indicating a decrease in the linkage between [SiO₄] and [AlO₄]. Increasing the basicity results in that the BO decreases rapidly, while NBO increases from 32.75% up to 50.23%, which leads to the decrease of viscosity. Variations of CN_Al–O and Al–O–Al indicate that Al₂O₃ prefers to form complicated unit, and Al₂O₃ within this slag should act as a network former. Calculated activation energies of samples A11–A14 are 212, 186, 168 and 161 kJ mol⁻¹, respectively. Variation of viscosity linearly depends on Q⁴, and a strong linear relationship could also be found between viscosity and NBO/T. However, the variation of activation energy mainly depends on Q⁴(Si) comparing with Q⁴(Al), Q⁴(Si + Al) or NBO/T.

KEYWORDS:

• Slag structure
• Molecular dynamics
• FT-IR
• Raman
• High Al₂O₃