Effect of sintering temperature on the electrolysis of TiO₂

Abstract

The effects of sintering temperature on the microstructure and the conductivity of TiO₂ cathodes were studied by examining the phase composition, microstructure, and element contents of the sintered cathodes and the cathodic products using X-ray diffraction and scanning electronic microscopy-energy dispersive spectrometry. The oxygen vacancy, conductivity, average pore diameter, and specific surface area of the sintered cathodes were detected by X-ray photoelectron spectroscopy, four-point probe, and ASPA 2010. The results showed that TiO₂ phase transformations occurred, and oxygen vacancies formed with the increase of sintering temperature. The cathodic conductivity improved, but the average pore diameter and the effective response area of the TiO₂ cathode were reduced when the sintering temperature increased. These phenomena could weaken the contact between reaction ions and electrons and also had the same effect on the cathodes and the molten salt. Moreover, they were disadvantageous to ion migration, so a lower sintering temperature was favorable for the microstructure of electrolysis. Consequently, the cathodic conductivity may be improved, but the microstructure became compact with the increase of sintering temperature. The cathodic products at different temperatures indicated that the cathodic conductivity was more important for electrolysis.

Keywords

titanium dioxide / electrolysis / sintering / microstructure

References

[1] Chen G.Z., Fray D.J., Farthing T.W. Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride. Nature, 2000, 407(6802): 361

[2] Cox A., Fray D.J. Mechanistic investigation into the electrolytic formation of iron from iron(III) oxide in molten sodium hydroxide. J. Appl. Electrochem., 2008, 38(10): 1401

[3] Yan X.Y., Fray D.J. Direct electrolytic reduction of solid alumina using molten calcium chloride-alkali chloride electrolytes. J. Appl. Electrochem., 2009, 39(8): 1349

[4] Mohandas K.S., Fray D.J. Electrochemical deoxidation of solid zirconium dioxide in molten calcium chloride. Metall. Mater. Trans. B, 2009, 40(5): 685

[5] Barnett R., Kilby K.T., Fray D.J. Reduction of tantalum pentoxide using graphite and tin-oxide-based anodes via the FFC-Cambridge process. Metall. Mater. Trans. B, 2009, 40(2): 150

[6] Peng C., Chen S., Wu Y.K., Wang L.J. Preparation of boron powder by molten salt electrolysis. Chin. J. Rare Met., 2010, 34(2): 264.

[7] Wang B.X., Lan X.Z., Zhao X.C., Zhang J. Reaction mechanism on electrochemical reduction of TiO2 to titanium. Chin. J. Rare Met., 2010, 34(4): 618.

[8] Li Z.Q., Wang H.H., Bai C.G., Zhang N., Ru L.Y. Research progress in effect factors of porosity and conductivity of the cathode in electro-deoxidation. Mater. Rev., 2011, 25(3): 1.

[9] Wu Y.K., Chen S., Xu Z.G., Wang L.J. Zirconium powder prepared by fused salt electrolysis. Chin. J. Rare Met., 2009, 33(1): 62.

[10] Du J.H., Xi Z.P., Li Q.Y., Li Z.X., Tang Y. Process of reduction of TiO2 using electrodeoxidation. Rare Met. Mater. Eng., 2006, 35(7): 1045.

[11] Deng L.Q., Xu Q., Li B., Zhai Y.C., Huang Z.Q. Preparation of niobium by direct electrochemical reduction of solid Nb₂O₅. Chin. J. Nonferrous Met., 2005, 15(4): 541.

[12] Guo C.F., Dong Y.H., Yu X.J., Li D.G., Zhang L.P. Preparation of zirconium by direct electrodeoxidation. Chin. J. Nonferrous Met., 2007, 17(6): 1019.

[13] Wang B.X., Cui J.T., Lan X.Z., Zhao X.C., Zhang J. Study on cathode sintering technology in the proess of electrochemical reduction of TiO₂. Foundry Technol., 2008, 29(10): 1388.

[14] Wang Z.L., Tang H.Q., Guo Z.C., Ye W., Cai Z.F. Cathode preparation for dysprosium electro-deoxidation. Chin. J. Rare Met., 2010, 34(5): 755.

[15] Li Z.Q., Ru L.Y., Bai C.G., Zhang N., Wang H.H. Progress in main influence factors for electrolysis efficiency of electro-deoxidation. Chin. J. Rare Met., 2011, 35(2): 301

[16] Jiang C.Y. Principle of Material Processing, 2003, Harbin, Harbin Institute of Technology Press, 119.