Structure Analysis of CaO-SiO2-Al2O3-TiO2 Slag by Molecular Dynamics Simulation and FT-IR Spectroscopy

The structure information in the CaO-SiO2-14 mass% Al2O3-TiO2 slag was investigated by the molecular dynamics simulation and the FT-IR spectroscopy at '1773 K. The influence of different additions of TiO2 and varying CaO/TiO2 ratios on the structure was studied to clarify the role of TiO2 in the slag. The results show that there exist three stable units, [SiO4] tetrahedron and [AlO4] tetrahedron as well as [TiO6] octahedron in the CaO-SiO2-14 mass% Al2O3-TiO2 slag. The average coordination numbers, CNSi-Al and CNAl-Al are all approximately equal to 1 and are barely influenced by additions of TiO2 and varying CaO/TiO2 ratios, which indicates that both the [SiO4] and [AlO4] tetrahedrons are surrounded by only one [AlO4] tetrahedron and some other units. Nevertheless, [AlO4] can be linked by more than one [SiO4] tetrahedron but [SiO4] can only be surrounded by one [AlO4] tetrahedron. The bridging oxygen, classified into Si-O-Si, Al-O-Al and Si-O-Al, is preferentially localized in Si-O-Al. However, it is found a little violation of the so-called Al avoidance principle which states that the Al-O-Al linkage is absent have been obtained with about (less than) 5% Al-O-Al, and the bond of Al-O-Al is hardly affected by TiO2 additions. Replacement of CaO by TiO2 can only result in a slight change of the degree of polymerization, indicating TiO2 has the similar role as CaO to be a basic oxide.