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Direct iron production at molten metal state from iron oxides by the sole application of electrical energy represents a possible route to decarbonize steel industry. Although chemically simple, this reaction is difficult to implement due to the problem of the multiple valence states of iron and to an operating temperature above 1811 K. Thermal, chemical, and electrical conditions have been identified based on thermodynamic considerations to carry out this reaction in a laboratory device. Experiments were undertaken to determine the contribution of the thermal level to the decomposition of iron oxide and to estimate the electronic current resulting from iron multiple valence states. The production of liquid iron was obtained resulting in recoverable samples produced at liquid state and from a faradaic process checked in real time by its accompanying anodic oxygen evolution. Graphical AbstractKeywords Molten oxide electrolysis · Metal extraction · Oxide melts · Electrochemical engineering · High-temperature processing

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Ag–Cu–O films were deposited on glass substrates by pulsed dc sputtering of a silver–copper target (Ag50Cu50) in reactive Ar–O2 mixtures. The film chemical composition was estimated by x-ray energy dispersive spectrometry and the structure was studied by x-ray diffraction (XRD). Optical properties (reflectance and transmittance) and room temperature electrical resistivity were evaluated using spectrophotometry and the four point probe method, respectively. Since silver atoms are less reactive versus oxygen than copper ones, the increase in the oxygen flow rate introduced into the deposition chamber induced the preferential oxidation of sputtered copper atoms. XRD analysis showed that the structure of the deposited films can be divided into three domains. At low oxygen flow rate, the films were biphased (metallic silver-based solid solution and crystalline copper-based oxide). At intermediate oxygen flow rate, the films were x-ray amorphous (grain size lower than 2 nm). At high oxygen flow rate, the films contained a crystalline silver–copper oxide phase and a crystalline unknown phase. Thanks to the absorption band of silver in the UV range, reflectance measurements were used to show the occurrence of metallic silver phase in the films. It was shown that the chemical environment of silver atoms in the x-ray amorphous region evolved from metallic to oxide when the oxygen flow rate increased. Transmittance evolution versus the oxygen flow rate were well correlated with that of the electrical resistivity. The evolution of Ag–Cu–O film properties was discussed in connection with the structure and chemical composition.