Viscosity and electrical conductivity of melts system B2O3-CaO-FeO.

Vusikhis A.S., Selivanov E.N., Ryabov V.V., Chentsov V.P. 

ABSTRACT

          Boron oxide systems have been used for refining metals in pyrometallurgical aggregates, as well as for the modeling of various metallurgical processes. Aim of this work is to determine viscosity and electrical conductivity of B₂O₃−CaO−FeO system melts depending on compositions and temperature. The work presents viscosity and electrical conductivity of B₂O₃−CaO systems measuring results at B₂O₃/CaO ratios: 3.0, 1.86 and 1.22, respectively. The melts contained FeO additives (up to 20%). The measurements have been carried out in wide temperature range of the glass formation region. Vibration viscometry technique has been used to measure viscosity. Electric conductivity has been measured by contact method using AC bridge. Temperature dependences of viscosity and electrical conductivity in the 1100−1750 K range have been established. Temperature increase leads to viscosity (η) decrease of B₂O₃−CaO−FeO system melts and electric conductivity (æ) increase. In the temperature ranges (Т_max−Т₁) and (Т₁−Т₂) corresponding to the high and low temperature zones of homogeneous melt, the viscosity and electric conductivity in the coordinates lnη − 1/Т and lnæ − 1/T have linear dependence. The activation energies of viscous flow (E_η) and electric conductivity (E_ϰ) are determined. In the high-temperature region, the activation energies of melts viscous flow vary from 13 to 103 kJ/mol. Temperature decrease leads to it changes from 59.7 to 185 kJ/mol. Comparison of the values of Е_η and Е_ϰ showed that its ratio is not constant. This indicates difference of the groupings responsible for viscous flow and electrical conductivity. In the temperature range (T₂−T_min), the presence of nonlinear dependence section is shown, where glass transition occurs in the entire range of changes (B₂O₃/CaO is 3.0). Glass transition takes place up to temperatures close to 1150 K (B₂O₃/CaO is 1.86) with subsequent formation of crystallites. Partial crystallization of melt in the measurement temperature range (B₂O₃/CaO is equal to 1.22) also take place. The results obtained have been used to describe borate melts structure. In addition, the obtained information is useful for recommendation of melts compositions for refining metals in pyrometallurgical aggregates.

KEY WORDS:

oxide melt, borate glasses, viscosity, electrical conductivity, structure.

DOI: 10.31857/S0235010621020109