Viscosity and structure of MgO-SiO2-based slag melt with varying B2O3 content

The effect of B2O3 content on the rheological behavior and molten structure of the MgO-SiO2-based ferronickel slag were studied at a fixed (SiO2 + Al2O3)/(MgO + CaO) mass ratio of 1.4. Results show that the viscosity of the slag melt decreased with the addition of B2O3, and B2O3 had a relatively little effect when its content was over 7 mass%. The break temperature of ferronickel slag reduced from 1711 to 1596 K and its apparent activation energy deceased from 95.34 +/- 2.61 to 23.08 +/- 1.65 kJ/mol with the addition of B2O3 from 3 to 9 mass%. Structural analyses indicate that B2O3 stripped the oxygen from the silicate structure. The formation of B-O-B structures connected by non-ring [BO3]-trihedral and [BO4]-tetrahedral structural units led to boroxol rings. These resulted in higher degree of polymerization (DOP) of both silicate and borate structures. However, the O- in [BO2O-], the dominant 2D [BO3]-trihedral structure and the formation of asymmetric Si-O-B structural units could depolymerize the network structures of ferronickel slag.