Explicating Electrical Conductivity and Melt Structure of the SiO₂–MnO–TiO₂ Welding Fluxes with Various MnO/TiO₂ Mass Ratios

The electrical conductivity of the SiO₂–MnO–TiO₂ welding fluxes with various MnO/TiO₂ mass ratios was measured by the four-electrode alternating current (AC) impedance method. Molecular dynamics (MD) simulations were employed to detect the effect of MnO/TiO₂ mass ratio on the structure of SiO₂–MnO–TiO₂ welding fluxes. The experimental results showed that within the temperature range of 1673 K to 1793 K, the electrical conductivity of the welding fluxes increased while their apparent activation energy reduced with the increased MnO/TiO₂ mass ratio from 1.03 to 3.63. Molecular dynamics simulations indicated that the coordination numbers of Si–Si, Si–Ti and Ti–Ti, and the proportion of complex structural units (bridging oxygen, Q³(Si) and Q⁴(Si)) reduced with the increased MnO/TiO₂ mass ratio. Additionally, it could be concluded that the electrical conductivity of the SiO₂–MnO–TiO₂ welding fluxes positively correlated with the decrease in the degree of polymerization of the fluxes caused by the increased MnO/TiO₂ mass ratio.