Pure titanium is a lustrous silver-white metallic element used principally to make light, strong alloys. The metal has a low density, good strength, and has excellent corrosion resistance. The element is the ninth most abundant in the earth's crust but is never found in the pure state. It occurs as an oxide in the minerals ilmenite (FeTiO3), rutile (TiO2) and sphene (CaO. TiO2. SiO2) but it mainly contains rutile and ilmenite that are more stable than the pure titanium.
The process of extracting titanium from its ore mainly involves 2 different chemical reactions. The magnesium reduction process, or the Kroll process is the most popular production process for titanium. It involves the action of chlorine and carbon on ilmenite or rutile. The resultant titanium tetrachloride, TiCl4 is separated from the iron trichloride, FeCl3, by fractional distillation. Finally TiCl4 is reduced to metallic titanium by reduction with magnesium, Mg. Air is excluded so as to prevent contamination of the product with oxygen or nitrogen.
2FeTiO3 + 7Cl2 + 6C (900
•XC) á• TiCl4 + 2FeCl3 + 6CO.
TiCl4 + 2Mg (1100
•XC) á• 2MgCl2 + Ti.
Excess magnesium and magnesium dichloride is removed from the product by treatment with water and hydrochloric acid to leave a titanium "sponge". The metal is then melted and cat into ingots.
Titanium has features of high strength, high corrosion resistance and lightweight. It is used for alloys with aluminium and other metals. These alloys of titanium are used principally in the airspace and marine industry for airframes, structures, and engines. They have an excellent resistance to seawater and an ability to withstand extremes of temperature, which are important features in military and commercial aviation and navigation. A commercial jet transport uses between 300 ~ 1000 kg of the metal and a supersonic transport uses from 14 to 45 metric tons of titanium.
