Process Investigation On The Preparation Of Rare Metal Vanadium By Low Cost Method

Rare metal vanadium has a series desirable properties such as high melting point, high hardness, low density, good anti-corrosion, steady nuclear physics properties and high hydrogen storage capacity etc, and has been widely used in aviation, marine, nuclear industry, hydrogen storage materials, superconductivity, metallurgy, energy and construction. It is a strategic significance metal in the word and its world consumption increases every year.Vanadium is prepared mainly by metal thermreduction from its oxide and hydrogen reduction from its chloride. But high product cost and complicated process greatly restrict its use. Therefore it is of critical importance to develop a low process of low cost and high efficiency. FFC Cambridge process is a new method which can be used to produce metal and alloy by electrolysis in molten salt. It has many advantages of low cost, short production process and non-pollution.In this work, V2O3 pellet was prepared as solid porous electrode and was reduced by electrolysis in the temperature lower than that of the melting point of vanadium. The applied voltage is lower than the decomposition of CaCl2 and NaCl. The affects of press pressure and additive on the properties of cathode and electrode reaction were studied. The best conditions are determined as follows:1.7% (mass ratio) polyvinyl alcohol in the powder of V2O3,10-20 MPa molding pressure,1000-1100℃sintering temperature and 2-4 h sintering time and 10: 1 mol ration of CaCl2 over NaCl. The voltage and temperature are 2.9-3.0 V and 900-1000℃. In order to study the reaction mechanism, the electrochemical reduction was interrupted after different reaction time accord with the current-time curve. X-ray diffraction(XRD), transmission electro microscope(TEM) and X-ray spectroscopy(EDS) are applied to analyze the partially reduced sample.The result show that V2O3 is reduced step by step from outside to inside and from high valence to low valence oxide until to metal. In the process, Ca2+ from electrolyte infiltrates the inside of cathode and improves the re-distribution of oxygen.