Redox-structure dependence of molten iron oxides

• Published in: Communications materials Vol. 1; no. 1
• Main Authors: Shi, Caijuan, Alderman, Oliver L. G., Tamalonis, Anthony, Weber, Richard, You, Jinglin, Benmore, Chris J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 05.11.2020; Nature Publishing Group
• Subjects: 639/301/119/1002; 639/766/94; 704/445/598; Atomic structure; Chemistry and Materials Science; Coordination numbers; Distribution functions; Fugacity; Iron and steel making; Iron oxides; Laser beam heating; Levitation melting; Magma; Materials Science; Oxygen; Thermodynamic properties; Thermophysical properties
• ISSN: 2662-4443; 2662-4443
• DOI: 10.1038/s43246-020-00080-4

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 Fe 2 O 3 , significantly lower than most existing reports. Ferric iron is dominated by FeO 4 , FeO 5 and FeO 6 units in the oxygen rich melt. For ferrous iron under reducing conditions FeO 4 and FeO 5 units dominate, in stark contrast to crystalline FeO. Knowing the atomic structure of liquid iron oxide is key to understanding steelmaking processes and magma flows. Here, Fe-O atomic coordination numbers are determined during levitation melting at a range of temperatures and oxygen partial pressures, revealing low coordination numbers.