Despite its attractive properties, titanium is limited in use by its high price, due to the cost of smelting and processing the ore. The solid oxide membrane (SOM) process aims to consolidate most of the processing steps required for conventional titanium production into a single step, making it an energy efficient and cost effective method for producing CP billet and ingot and possibly also powders used to make titanium alloys. In the SOM process experiment, a steel crucible contains MgF 2 -CaF 2 -TiO 2 flux; an inert metal/carbon rod serves as the cathode; an oxygen ion conducting yttrium stabilised zirconia (YSZ) membrane in the form of a one end closed tube contains either a liquid metal that acts as the anode or a liquid MgF 2 -CaF 2 ionic flux that connects the YSZ membrane to an anode. During electrolysis, titanium ions are reduced at the cathode while the oxygen ions pass through the YSZ membrane and are oxidised at the anode by a reducing agent, hydrogen gas or carbon, forming steam or CO(g) respectively. To date, a suitable MgF 2 -CaF 2 -TiO 2 flux has been selected and an optimum operating temperature has been determined. Several electrolysis experiments have been performed. As expected, lower valence deposits of titanium oxides have been witnessed at the cathode before depositing pure titanium. Continuing work will aim to extend the electrolysis time to pass enough charge to produce a significant amount (100 g) of titanium at the cathode.
The Solid Oxide Membrane (SOM) process for magnesium production involves the direct electrolysis of magnesium oxide for energy efficient and low-carbon magnesium production. In the SOM process, magnesium oxide is dissolved in a molten oxy-fluoride flux. An oxygen-ion-conducting SOM tube, made from yttria stabilized zirconia (YSZ), is submerged in the flux. The operating life of the electrolytic cell can be improved by understanding degradation processes in the YSZ, and one way the YSZ degrades is by yttria diffusion out of the YSZ. By adding small amounts of YF3 to the flux, yttria diffusion can be controlled. The diffusion of yttria into the flux was quantified by determining the yttria concentration profile as a function of immersion time in the flux and distance from the flux-YSZ interface. Yttria concentrations were determined using x-ray spectroscopy. The diffusion process was modeled using a numerical approach with an analytic solution to Fick’s second law. These modeling and experimental methods allowed for the determination of the optimum YF3 concentration in the flux to minimize yttria diffusion and improve membrane stability. Furthermore, the effects of common impurities in magnesium ores, such as calcium oxide, silica, and sodium oxide/sodium peroxide, on YSZ stability are being investigated
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