2014 Volume 54 Issue 3 Pages 657-663
The high temperature viscosity of the TiO2-MnO-Al2O3-8.64ZrO2-2.77Na2O welding flux system was measured by the rotating spindle method to identify the relationship between the viscosity and melt structure at various compositions of TiO2, MnO, and Al2O3 contents. At temperatures of 1773 K to 1748 K and fixed TiO2/MnO ratio, the effect of Al2O3 on the viscosity was not significant, but slightly increased with higher Al2O3. At temperatures below 1748 K, the effect of Al2O3 was more pronounced with increments of Al2O3 significantly increasing the viscosity of the molten flux. Increased extended basicity ((TiO2/+1.13MnO)/SiO2) depolymerized the network structure, where TiO2 and MnO works to depolymerize the present melt. Raman analysis of as-quenched oxide melts from 1773 K showed the symmetric [AlO4]-tetrahedral stretching vibrations to increase and the asymmetric [AlO6]-octahedral stretching vibrations to decrease with higher concentration of Al2O3 at various fixed TiO2/MnO ratios suggesting polymerization of the structure with Al2O3 additions. The opposite trend could be observed with increasing extended basicity. XPS (x-ray photoelectron spectroscopy) results showed the bridged oxygen (Oo) to increase and the non-bridged oxygen (O–) to decrease with Al2O3 additions and lower extended basicity also suggesting polymerization of the network structure in the present melt system.