CaCl2 Bath Research Articles

Preparation of titanium metal by electrochemical reduction of titanium dioxide

Preparation of titanium metal by direct electrolytic reduction of TiO2 in molten CaCl2 bath was studied using sintered TiO2 pellets as cathode. The process was carried out at 950°C under normal atmosphere without using any inert gas. Titanium was obtained in the form of powder/compact product depending on the method of preparation of the pellets and the reaction conditions. The product was characterized by XRD, SEM and EPMA. The purity of the product was >99% as evidenced from EPMA analysis.

Electrochemical Deoxidation of Titanium Foam in Molten Calcium Chloride

Titanium foam, prepared by using a patented powder-metallurgy–based process involving a powder blend that was molded, foamed, and sintered using a three-step thermal treatment, was deoxidized in a molten CaCl2 bath. The polarization experiments were carried out by cathodically polarizing the foam (working electrode) against a counter (graphite) electrode. Under constant potential (polarization) mode, the dominant mechanism of deoxidation was the ionization of oxygen, present in the foam, and its subsequent discharge, as CO2/CO, at the anode surface. More than ∼85 pct oxygen could be effectively removed by carrying out the electro-deoxidation experiments in fresh and pre-electrolyzed melt(s) at an electrolyte temperature of 950 °C. Scanning electron microscopy–energy dispersive X-ray (SEM-EDX) detection of the deoxidized foams did not show a presence of any inclusion(s) or secondary phase(s).

Calciothermic reduction of titanium oxide and in-situ electrolysis in molten CaCl2

A concept for calciothermic direct reduction of titanium dioxide in molten CaCl2 is proposed and experimentally tested. This production process consists of a single cell, where both the thermochemical reaction of the calciothermic reduction and the electrochemical reaction for recovery of the reducing agent, Ca, coexist in the same molten CaCl2 bath. A few molar percentages of Ca dissolve in the melt, which gives the media a strong reducing power. Using a carbon anode and a Ti basket-type cathode in which anatase-type TiO2 powder was filled, a metallic titanium sponge containing 2000 ppm oxygen was produced after 10.8 ks at 1173 K in the CaCl2 bath. The optimum concentration of CaO in the molten CaCl2 was 0.5 to 1 mol pct, to shorten the operating time and to achieve a lower oxygen content in Ti.

Semi-continuous Production of Niobium Powder by Magnesiothermic Reduction of Nb<SUB>2</SUB>O<SUB>5</SUB>

An electronically mediated reaction (EMR) has been explored to produce a niobium powder semi-continuously by the magnesiothermic reduction of niobium oxide. Nb2O5 feedstock and reductant magnesium alloy were isolated electronically in a molten CaCl2 bath at 1173 K . The feed was freshly recharged twice, but the bath was reused without replenishment during three repeated tests, providing an external path for electron flow. The current flow through the external path between the feed (cathode) and the reductant (anode) was monitored. A small current between 0.05 and 0.1 A was measured in the external circuit. A niobium powder was readily obtained, but its purity decreased from 93 to 82% Nb as the reduction number increased. This, however, demonstrated the possibility of semi-continuous production of niobium powders by the EMR without the direct physical contact between the reactants. The mechanism of the magnesiothermic reduction of Nb2O5 in the molten salt was discussed, using an isothermal chemical potential diagram.