Structure Analysis of CaO-SiO_2-Al_2O_3-TiO_2 Slag by Molecular Dynamics Simulation and FT-IR Spectroscopy

摘要

The structure information in the CaO-SiO_2-14 mass% Al_2O_3-TiO_2 slag was investigated by the molecular dynamics simulation and the FT-IR spectroscopy at 1 773 K. The influence of different additions of TiO_2 and varying CaO/TiO_2 ratios on the structure was studied to clarify the role of TiO_2 in the slag. The results show that there exist three stable units, [SiO_4] tetrahedron and [AlO_4] tetrahedron as well as [TiO_6] octahedron in the CaO-SiO_2-14 mass% Al_2O_3-TiO_2 slag. The average coordination numbers, CN_(Si-Al) and CN_(Al-Al), are all approximately equal to 1 and are barely influenced by additions of TiO_2 and varying CaO/TiO_2 ratios, which indicates that both the [SiO_4] and [AlO_4] tetrahedrons are surrounded by only one [AlO_4] tetrahedron and some other units. Nevertheless, [AlO_4] can be linked by more than one [SiO_4] tetrahedron but [SiO_4] can only be surrounded by one [AlO_4] 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 TiO_2 additions. Replacement of CaO by TiO_2 can only result in a slight change of the degree of polymerization, indicating TiO_2 has the similar role as CaO to be a basic oxide.