Insight into the TiO2 on transport behavior and heat transfer of the CaO–SiO2–FeO–MgO system at different basicities: Molecular dynamics simulation and thermodynamics

Abstract

In order to promote the resource utilization of Ti-containing converter slag and reduce the loss of metallic Ti, it is necessary to clarify the relationship between the oxygen network structure and thermophysical properties of the slag. The present work uses classical molecular dynamics (CMD) simulation to study the effects of basicity (1.0–3.0) and TiO2 content (0%–10 %) on the local structural properties, viscosity, and thermal conductivity of the CaO–SiO2–FeO–MgO–TiO2 (CSFMT) system at 1873 K. The M − O (M = Ca, Si, Fe, Mg, and Ti) bond length calculated based on CMD is consistent with the experimental results, and the [SiO4] tetrahedron and [TiO6] octahedron are the basic structural units of the CSFMT system. The increase in basicity promotes the break of bridging oxygen (BO) Si–O–Si and the formation of non-bridging oxygen Si–O-M. The increase in TiO2 content promotes the formation of Ti–O–Si in the system. The basicity and TiO2 content affect the thermophysical properties of the CSFMT system by promoting and inhibiting the depolymerization of the oxygen network structure, respectively. The diffusion abilities of different atoms in the CSFMT system are in descending order of Fe > Mg > Ca > O > Si > Ti. The viscosity of the CSFMT system decreases with increasing basicity and increases with increasing TiO2 content. Increasing the proportion of BOs can weaken the anharmonicity in the polyhedral structural units and reduce phonon scattering. With increasing basicity and TiO2 content, the effective phonon mean free path decreases and increases, respectively, resulting in a decrease and an increase in the thermal conductivity of the CSFMT system. The changes in the microstructure properties of the CSFMT system can be reasonably explained by the changes in its thermodynamic properties such as enthalpy. It is worth noting that the basicity has a greater effect on the viscosity, while the TiO2 content has a more significant impact on the thermal conductivity of the CSFMT system.