Calcium Thermal Reduction Tio < Sub > 2 < / Sub > Of Titanium Powder Prepared By Experimental Research

Titanium has been widely used in many fields, such as metallurgy, chemical industry, military and daily life because of its outstanding properties:small density, high strength, high-temperature, non-magnetic, corrosion resistance and so on. With the application fields expanding, its demand is increasing. At present, the main method for industrial production of titanium is Kroll method, but this production process have many drawbacks, such as the process is complex, the cost is high and the energy consumption is large, which greatly limits the titanium applications. New titanium extraction processes technology with the low cost and process simple are studied by researchers in recent years. These methods can be divided into the molten salt electrolysis process metallothermic reduction process, the most typical representative of electrolysis is FFC process, and of metallothermy is the PRP process. Because these processes also exists some problems, so the two methods are currently in the stage of laboratory research not industrialized.In this paper, the PRP is improved. The possibility of reactions in the closed reactor are thermodynamically calculated and analyzed, respectively. The results indicate that:the additives CaCl2is hydrolyzed when the temperature more than973K, which generated CaCl2·H2O and resolved CaO. The reduction reaction temperature is higher than1000K, the moreâ–³G is negative when the when the reduction reaction temperature is higher than1000K, which meets the thermodynamic conditions. During the heating, oxygen and nitrogen reacted with calcium and forms the approximated vacuum in the closed reactor, which be conducive to Ca volatile and form the steam. In the Reduction process, the sequence of TiO2to Ti is: Ti4O7â†'Ti3O5â†'Ti2O3â†'TiO(CaTiO3)â†'Ti.On the basis of thermodynamics, the raw materials have A.R CaCl2, pigment grade TiO2and metallic calcium, the reactor have the stainless steel crucible and graphite crucible which are heated in the vacuum furnace. In the process of calciothermic reduction preparation titanium powders, the influence law of CaCl2, temperature and reduction time to the reaction is systematically studied. The mass of CaCl2and calcium are changed when the temperature more than973K, then temperature exceed1073K the metal calcium react with the reactor air, and CaCl2is hydrolyzed; the mixture of CaCl2and TiO2is analysed and found that the amount of CaTiO3generation is significantly increased when the mass ratio of1:4change into1:1.5. In the sintered product, CaTiO3is generated by CaCl2hydrolyzed and sintered with TiO2. When the temperature is1273K and the sintering time is6h, the crystal form of anatase TiO2change into rutile TiO2, and the remanent CaCl2hydrolyze and form CaO.The content of CaO in the product is measured by the EDTA method, and the results shows that the content of CaO increase with reaction time extending, and the increasing trend is very obvious, the reduction reaction is happening; this trend can be weaken when the time more than6h and the reduction reaction is completed. Different proportions of a mixture of CaCl2and TiO2are reduced at1273K for6h. The reduction products are analysed and found that CaCl2and CaO form molten when the larger proportion of CaCl2are added(mcac12:mTio2≥1:2); the powders high-temperature sintered obviously which prevent gas-solid reduction reaction after the mass ratio is reduced (mcac12:nTio2≤1:9). After pickling and drying the products, it found that titanium oxides (Ca3Ti2O7, CaTi4O9, CaTiO3) is not completely reduced to metallic titanium by calcium vapor at1073K and1173K. However, the temperature is controlled between1373Kand1473K, titanium react with graphite and generate TiC.When the mixture of CaCl2and TiO2(mcac12:mTiO2=1:4) is reduced by calcium vapor at1273K for6h, the titanium powders with single phase and with99.55mass%purity by EDS analysis and irregular shape (8-15μm particle size) were obtained.