Thermodynamic characterisation and simulation for the electrolytic extraction of titanium from oxide melts. (2019)
Type of ContentElectronic Thesis or Dissertation
Thesis DisciplineChemical Engineering
Degree NameMaster of Engineering
PublisherUniversity of Canterbury
AuthorsWeaver, Nicholasshow all
This thesis investigates the use of electrolytic methods on high temperature oxide melts to reduce TiO₂ into metallic Ti. Initially, a slag by-product from New Zealand Steel containing Al2O3-CaO-MgO-SiO₂-TiO₂ was considered due to it containing a high TiO2 content (32 wt%). Thermodynamic characterisation was then performed on this slag system to aid in the selection of an appropriate thermodynamic soft- ware for the investigation of extraction from this system. FactSage was then chosen as an appropriate software package and was used to predict the required reduction potentials of components in the system. This model accounts for the impact of the activities of the oxide components within the molten system which has not been ac- counted for in any previous studies. Simulations predicted that the presence of SiO₂ in the slag solution inhibits the production of pure Ti and suggests that SixTiy alloys will instead be the primary product. Simulations were then run at different slag compositions to investigate if it was possible to use this melt for the deposition of pure Ti with little success. A combination of simulation and experimental work was then performed to find a suitable metal oxide to act as an electrolyte and allow the electrolytic deposition of Ti. In this investigation three potential electrolytes Na2O, MgO and CaO were identified using FactSage and Na2O was then experimented upon. Metallic titanium was successfully deposited into a Pt-Rh working electrode from the oxide melt by applying a slight negative potential of 0.1-0.2 V against a Ti reference electrode. This resulted in a Ti-Pt-Rh alloy with 20-25 At% Ti with an overall calculated deposition efficiency of 1.0±0.8%.