Abstract
The atomic structural arrangements of liquid iron oxides affect the thermophysical and thermodynamic properties associated with the steelmaking process and magma flows. Here, the structures of stable and supercooled iron oxide melts have been investigated as a function of oxygen fugacity and temperature, using x-ray diffraction and aerodynamic levitation with laser heating. Total x-ray structure factors and their corresponding pair distribution functions were measured for temperatures ranging from 1973 K in the stable melt, to 1573 K in the deeply supercooled liquid region, over a wide range of oxygen partial pressures. Empirical potential structure refinement yields average Fe–O coordination numbers ranging from ~4.5 to ~5 over the region FeO to Fe2O3, significantly lower than most existing reports. Ferric iron is dominated by FeO4, FeO5 and FeO6 units in the oxygen rich melt. For ferrous iron under reducing conditions FeO4 and FeO5 units dominate, in stark contrast to crystalline FeO.
Highlights
The atomic structural arrangements of liquid iron oxides affect the thermophysical and thermodynamic properties associated with the steelmaking process and magma flows
We have considered the X-ray pair distribution functions of FeOx melts, to be composed of six partial pair distribution functions: Fe2+-Fe2+, Fe2+-Fe3+, Fe3+Fe3+, Fe2+-O, Fe3+-O, and O-O correlations
Discussion we obtain Fe-O coordination numbers in reducing atmospheres that are substantially lower than the octahedral coordination found in Wustite, our measurements are in good agreement with first principles molecular dynamics (MD) calculations in related liquid systems
Summary
The atomic structural arrangements of liquid iron oxides affect the thermophysical and thermodynamic properties associated with the steelmaking process and magma flows. Total x-ray structure factors and their corresponding pair distribution functions were measured for temperatures ranging from 1973 K in the stable melt, to 1573 K in the deeply supercooled liquid region, over a wide range of oxygen partial pressures. Iron redox has previously been studied in multicomponent silicate liquids and glasses[3,7,8], where the oxidation states and coordination numbers have a direct effect on melt viscosity, density, phase stability, and heat capacity[7]. The assignment of the local Fe coordination environment and its relationship to the oxidation state is not straightforward This is because iron redox depends on many factors, including oxygen partial pressure, temperature, and composition. Was considered as being distributed between sites coordinated by either 4 or 6 oxygen atoms based on crystal structures[16,17]
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