Iranian Journal of Materials Science and Engineering

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The synthesis of advanced materials from low cost minerals concentrates is a new field of study that has great potential applications. In this paper, the effect of milling time on the temperature of initiation and amount of carbothermic reduction of ilmenite has been investigated. The stoichiometric molar ratio (1:4) of ilmenite to graphite was mixed and mechanically activatedfor 30-70 hours at room temperature. Then homogenized mixture heated for one hour at 1000-1400°C in coal reducing atmosphere. The results show that complete conversion of ilmenite to Fe and TiC can not be achieved in the unmilled powder at 1400°C, while with milling of mixture for 30 hours, complete reduction of ilmenite to Fe and TiC at 1400° C was observed. With increasing milling time from 30 to 70 hours the temperature of complete reduction decreases from 1400 to 1200° C. Leaching of final product in HCI 3% solution dissolve Fe but leave pure titanium carbide intact. Determination of TiC unit cell size from X-ray diffraction pattern shows that unit cell size of synthesized TiC is less than stoichiometric one, which suggests that some oxycarbide phases (TiCxO1-x), is present into the final product.

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  Abstract

  The effect of mechanical activation using an attrition mill on the particle size of an ilmenite concentrate and its effect on the ability of the concentrate for Iron separation during hydrochloric acid leaching and the kinetics of the dissolution process have been investigated. It was observed that mechanical activation in an attritor significantly enhances the dissolution of iron in hydrochloric acid while have a slight effect on dissolution of titanium. With the mechanically activated ilmenite using an attrition mill, leaching conversion at 90 ^oC reached to 80%. The kinetic data of leaching of mechanically activated ilmenite was found to follow shrinking core model. Mechanically activating ilmenite using the attrition mill was found to cause the activation energy of leaching to be decrease from 43.69 , found for samples leached without mechanically activated, to 18.23 .

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Al2O3/TiC composites are used as cutting tools for machining gray cast iron and steels. The addition of iron improves the toughness of Al2O3/TiC composites. Ilmenite, aluminum and graphite can be used to produce in-situ Al2O3/TiC–Fe composites. However, the formation mechanism and reaction sequences of this system are not clear enough. Therefore, the present research is designed to determine the reactions mechanism of the first step of reactions that may be occurred between raw materials. In this research, pure ilmenite was synthesized to eliminate the effects of impurities available in the natural ilmenite in the system. The milled and pressed samples, prepared from the synthesized ilmenite, aluminum and graphite mixture with a molar ratio of 1:2:1, were heat treated at 720°C for 48h. In addition, two samples one containing ilmenite and aluminum with a molar ratio of 1:2 and ilmenite and graphite with a molar ratio of 1:1 were heat treated at 720°C for 48h. The final products were analyzed with XRD. It was found that at 720°C, aluminum reacts with FeTiO3, forming Fe, TiO2 and Al2O3. Since the aluminum content used in the mixture was more than the stoichiometry for reaction of ilmenite and aluminum, some unreacted aluminum remains. Therefore, the residual aluminum reacts with the reduced Fe to form Fe2Al5.