Effective mechanism of BaO on the structure and fluid behavior of CaO-SiO₂-B₂O₃-based melts

Abstract

The influence of BaO contents on structure and fluid behavior of fluorine-free CaO-SiO2-B2O3 based melts were examined using molecular dynamic (MD) simulation, rotary viscometer, X-ray diffraction and Fourier transform infrared spectroscopy. The FTIR results matched well with the MD simulation results that with the addition of BaO contents in CaO-SiO2-B2O3 based melts, more cations were provided to balance the negative charge of [BO4]5– tetrahedrons, leading to the structures of Si-O and B-O were more aggregated and the adjacent structural units were more closely connected, which made the structure complex, so the viscosity of mold fluxes at high temperature in the basicity range 1.15–1.25 was intensify. Meanwhile, when BaO replaced CaO under distinctive basic conditions, the viscous activity of fluorine-free mold flux was decreasing generally, showing that as the temperature was decreased, the tendency of slag to converge into complex network structural units was also decreasing, which states the improvement of lubrication capacity of the slag during cooling process.

Viscosity and desulphurisation behaviour of CaO–SiO 2 –MgO–Al 2 O 3 –BaO–MnO slag

“…Figure 1 shows the variations of viscosity of the slag under varying BaO content and temperature. The viscosity showed a slight increasing trend at 1500°C with an increase in BaO content, which was in accordance with the work from Xing et al [15], Sadaf et al [16] and Wang et al [17], contrary to the work from Piao et al [18] It is widely known that BaO was a strong basic oxide and could provide free O 2- and Ba 2+ . Furthermore, Liu et al [19] revealed that the average length of Ba–O and Ca–O bonds was about 2.65 and 2.32 Å through molecular dynamic simulation, which also suggested that BaO was extremely unstable and tended to generate free O 2− .…”