Preparation Of Carbides Of Titanium, Vanadium And Chromium By Electro- Chemical Reduction Of The Self-sintered Cathode In Molten Salt

FFC is a novel method of compact metallurgical process which is developed rapidly in last decade. Compared with the traditional molten salt electrolysis for preparing metal or metal alloy, the metallic oxide cathode avoids being dissolved in molten salt is the biggest advantage of FFC. This method averts the unsatisfactory result of solubility and dissolution rate of metal oxides in molten salt. Besides that, the metal oxide can be reduced in home position by electrochemical reaction in order to precisely control the alloy composition and electrolysate production. But one deficiency of FFC method is that the cathode piece must be sintered for meeting the strength requirement, it obviously goes against consumption reduction of this method.At the present stage, carbon thermal reduction method is still the main preparation technology of carbides of titanium, vanadium and chromium. In this paper, carbides of titanium, vanadium and chromium were prepared by electro-chemical reduction of the self-sintered cathode in molten salt in order to decrease the energy consumption of the carbide which was prepared by FFC.Electrochemical reduction of self-sintered cathode was used to prepare TiC power in molten CaCl2 and CaCl2 base chloride. A graphite rod was employed as the anode and TiO2-C was served as cathode respectively. The electrochemical reduction mechanism of TiO2-C was obtained by cyclic voltammetry, chronoamperometry and the reduction process were known by the constant potential electrolysis at different times. The results supported that the prepared process of TiC was three-step electrochemical reduction mechanism:Ti4++(C)â†'Ti3++(C)â†'Ti2++(C)â†'Ti (C), and the reduction reaction was completed with irreversible process. The effects of molten salt temperature, time and voltage on the electrolysis were studied. The optimized electrolysis conditions of TiO2-C in CaCl2 melt were found to be 3.2V, 800 ℃ and 12h, respectively. Under these conditions, the electrolytic efficiency reached 40.67%around and the power consumption reached 0.77kWh·kg-1 around. The TiC powder could be prepared from the cathode 100 times the mass of original cathode by electrochemical reduction of self-sintered cathode in molten salt. The optimized electrolysis conditions of it in CaCl2 melt were found to be 3.2V,800℃, 32h, respectively. The current efficiency reached to 47.27% around. The electrolysate prepared from TiO2-C was more satisfying in CaCl2 molten salt than in CaCl2-NaCl molten salt. Besides, TiC power was prepared by electrochemical reduction from complex CaTiO3-C, which was prepared from TiO2-CaO-C mixed powder by sintering. This implied that electrolytic CaO can improved the electrolysis efficiency during preparation of TiC by constant potential electrolysis. But compared with preparation process without CaO, the additional sintering process made total energy consumption reduced little.Electrochemical reduction of self-sintered cathode was used to prepare VCx power in molten CaCl2. A graphite rod was employed as the anode and V2O5-C was served as cathode respectively. The electrochemical reduction mechanism of V2O5-C was obtained by cyclic voltammetry, chronoamperometry and the reduction process were known by the constant potential electrolysis at different times. The results supported that the prepared process of VCx was three-step electrochemical reduction mechanism:V5++(C)â†'V3++(C)â†'V2++(C)â†'V(C), and the reduction reaction was completed with irreversible process. The effects of molten salt temperature, time and voltage on the electrolysis were studied. The optimized electrolysis conditions of V2O5-C in CaCl2 melt were found to be 3.2V,800℃ and 10h, respectively. Under these conditions, the electrolytic efficiency reached 36～42% around and the power consumption reached 1.57kWh·kg-1 around.Electrochemical reduction of self-sintered cathode was used to prepare Cr3C2 power in molten CaCl2. A graphite rod was employed as the anode and Cr2O3-C was served as cathode respectively. The electrochemical reduction mechanism of Cr2O3-C was obtained by cyclic voltammetry, chronoamperometry and the reduction process were known by the constant potential electrolysis at different times. The results supported that the prepared process of Cr3C2 was one-step electrochemical reduction mechanism:Cr3++(C) â†'Cr3C2, and the reduction reaction was completed with irreversible process. The effects of molten salt temperature, time and voltage on the electrolysis were studied. The optimized electrolysis conditions of Cr2O3-C in CaCl2 melt were found to be 3.2V,800℃ and 18h, respectively. Under these conditions, the electrolytic efficiency reached 37.3% around and the power consumption reached 0.96 kWh·kg-1 around.