Ana Maria Martinez

New Method for Low-Cost Titanium Production

The present work deals with the investigation of an electrolytic method for titanium production that uses TiO2 enriched titania slag as raw material. The process involves two steps: i) carbothermal reduction of the slag to form titanium oxycarbide powder; and ii) electrolysis in a molten chloride-based electrolyte using a titanium oxycarbide consumable anode. Electrochemical studies show the stability of the different Ti species in the equimolar NaCl-KCl melt at 850oC. These results, together with previous work about the anodic oxidation mechanism of a consumable titanium oxycarbide anode in molten chlorides, allow us to optimize the anode and cathode voltages in the electrolysis experiments. The results show that best quality titanium deposits are obtained when the reduction occurs in a single electrochemical step, i.e. directly from di-valent titanium species to Ti metal. Then, the complete conversion of the Ti(III) ions released from the consumable oxycarbide anode to Ti(II) species by adding Ti sponge to the electrolyte, must be fulfilled.

Electrochemical Production of Titanium from Oxycarbide Anodes

The aim of this work was to improve the quality of the produced titanium at the cathode in electrolysis experiments using a titanium oxycarbide anode, which is made of a solid solution of TiC and TiO. Two different approaches were tested: solid titanium deposition from a NaCl-Na3AlF6 electrolyte, and a standard NaCl-KCl electrolyte with a liquid metal cathode producing a titanium alloy.

Titanium Production from Oxycarbide Anodes

The aim of this work is to investigate the new possibilities for electrochemical titanium production as a way of reducing the production costs of the primary metal. The oxycarbide process is a process which involves electrodeposition of Ti at a cathode substrate, and using anodes of a TiC-TiO solid solution made from TiO2 and C. It looks promising, with cheap raw materials, and with a simpler production route than todays process.

Anode Processes on Carbon in Chloride-Oxide Melts

Alkali and alkaline earth metals such as lithium, sodium, magnesium and calcium are produced by electrowinning in chloride melts. Direct cathodic reduction of metal oxides in chloride melts has been proposed for the FFC process. Fundamental data for the anodic process on carbon in mixed chloride/oxide melts are lacking. Anodes of graphite and vitreous carbon (VC) were studied in NaCl-NaO, and in binary melts of the type NaCl-MCl2-MO with 0-7 mol% oxide, (M = Ca, Sr and Ba), using linear polarization, CV and EIS. The gaseous products were Cl2, CO and CO2 and the exit concentration of carbon oxides were analysed by gas chromatography. In this paper the emphasis is on the NaCl-CaCl2-CaO system.

Electrochemical Behavior of Dissolved Titanium Species in Molten Salts

INTRODUCTION Titanium has many attractive properties and the use of titanium and its alloys can be greatly increased if a new and less expensive process for the production of pure titanium were developed. Electrolysis in a molten salt electrolyte is a possible way to produce titanium, and many attempts to develop an electrolysis process have been reported. Large cells and pilot plants have been run, but no commercial electrolysis production has been achieved. Of importance is the work by Ginatta [1] which resulted in the successful development of a pilot cell for the electrowinning of titanium from TiCl4 dissolved in a molten NaCl based electrolyte. A more recent approach is due to Fray et al. [2] who suggested a new electrolysis method, later known as the FFC Cambridge method. Similar methods have been proposed by Suzuki et. al [3] and Okabe and Waseda [4].

PFC evolution characteristics during aluminium and rare earth electrolysis

In addition to aluminium electrolysis, the electrolysis of rare earth (RE) metals from fluoride melts is a significant source of perfluorocarbon (PFC) emissions to the atmosphere. These processes have many similarities, they are both based on molten fluoride salt electrolysis at temperatures around 1000 °C, and are utilizing carbon materials as the anode. Although PFC emissions from aluminium industry and rare earth electrolysis have similar overall reactions, they are often reported to have different characteristics. In order to get a better understanding of these differences and similarities, different laboratory experiments focusing on anode reactions and gas compositions in Al2O3 saturated cryolite and REF3-LiF melts during aluminium and rare earth metal electrolysis were studied. The results obtained, combined with thermodynamic data analysis allowed to better understand onset, evolution and termination behaviour of PFC evolution in molten fluoride systems of different chemistries.

Electrochemical Processing of Rare Earth Alloys

The light rare earth metals Nd, Pr, La, Ce as well as some alloys with Fe, are today produced in China by electrolysis in molten fluorides using oxide raw materials. A major challenge is to obtain a good cell operation without de-composing the electrolyte leading to emissions of perfluorinated carbon (PFC) green-house gases to the atmosphere. This work is focused on understanding the fundamental requirements to run the electrolysis cells for DyFe alloy production in an efficient and environmental friendly way. Electrolysis experiments was carried out in DyF3-LiF melts at 1050 °C. A Fe rod was used as consumable cathode and the (consumable) anode was made of graphite. To establish at which anode potential PFC occurred and thus enabling optimisation of the oxide batch feed rate, analysis of the anode gases was performed with Fourier Transform Infrared Spectrometer (FTIR). The produced DyFe alloy was characterised by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS).

Direct Method for Producing Scandium Metal and Scandium-Aluminium Intermetallic Compounds from the Oxides

The electrochemical de-oxidation process, also called FFC-Cambridge process, has been proposed previously to produce reactive metals and their alloys through reduction of their metal oxides. The process works by introducing metal oxides into a molten salt bath where it is electrolysed to form metal powders offering both economic and environmental benefits over the traditional metal production methods. Within the frame of the EU-financed project SCALE (GA 730105), SINTEF is investigating the optimal parameters of the direct electrolytic reduction of Sc2O3 and Sc2O3–Al2O3 precursors (dross from Al-Sc alloy production), giving Sc and Al-Sc metallic powders, respectively, in a molten CaCl2-based electrolyte at a working temperature of ca. 900 °C. The influence of the applied cathodic potential in the reduction mechanism and in the metal product has been studied.

Perfluorocarbon Formation During Rare Earth Electrolysis

A challenge during rare earth (RE) electrolysis is to avoid emissions of perfluorocarbon (PFC) green-house gases. The objective of this work was to study how to operate the RE electrolysis process with neither PFC formation nor anode effect. Linear Sweep Voltammetry was carried out at 1050 and 1100 °C, and electrolysis was performed in REF3-LiF melts at ca. 1050 °C during on-line off-gas analysis. To avoid anode effect, the current density values must be strictly less than 0.43 and 0.68 A cm−2 at working temperatures of 1050 and 1100 °C, respectively. The optimal REO batch feed rate for avoiding PFC formation could be established by correlating the onset of PFC with the values and the changes that occurred in the anode potential.

High Temperature Electrolysis for Liquid Iron Production

Introduction The production of iron and steel is by far the largest metal production industry in the world. One major concern is the massive emissions of CO2 which contributes to almost 10 % of the global emissions. A possible alternative to reduce or eliminate the CO2 emissions is to develop an electrolysis process with inert oxygen evolving anodes. Attempts to develop a high temperature electrowinning process to produce liquid iron at temperatures above 1535 C have been reported [1-3]. The main feature of this technique is to dissolve iron oxide in a mixture of other molten oxides and use this as an electrolyte during electrolysis at high temperatures. At such a temperature and in such an environment, the choice of materials is important and very difficult. In particular the selection of an oxygen evolving anode is challenging.