Titanium metal (Ti) is the ninth most abundant element found in the Earth’s crust, being strong as steel but much less dense. Because of this, it is a very important alloying agent with many other metals including aluminium, iron and molybdenum. These alloys are used in aircraft as they are materials with low density that can resist to high temperatures. Titanium is also used to cover the hulls of ships and other structures exposed to water, as well as in desalinisation plants which convert sea water into fresh water . However, the largest use of this metal is in the form of titanium (IV) oxide, which accounts for over 96% of titanium consumption worldwide. Because of its excellent physical properties, which are the lack of colour, high refractive index and chemical inertness, titanium dioxide is the principal inorganic synthetic pigment on the market with over 3,000,000 tonnes per annum produced accounting for 66% of the global production capacity of pigments as shown in table 1: 
Pigment Tonnes per annum Tonnes per annum (%)
Titanium dioxide (white) 3,170,000 66
Iron oxides (red) 720,000 15
Pigment blacks 530,000 11
Lithopone (white) 190,000 4
Chromate yellow 145,000 3
Others 45,000 1
Total 4,800,000 100
Table 1: Global production capacities for the major inorganic synthetic pigments.
Because TiO2 is related to non-essential products, it was observed that the demand is fluctuating depending on the GDP (gross domestic product), as it can be seen in figure 8 :
Figure 8: Relationship between GDP and TiO2 demand.
At the beginning of the TiO2 industry, Europe and North America showed the most demand and the highest growth rates. However, in the past years, because the markets have fully grown, the growth rate is slower and shows a decrease in market share . At this point, the Asia/Pacific Region is in a transition period where lifestyle becomes westernised and the demand for TiO2 is increasing. The Rest of the World suffered a decline in demand, but this was only temporary due to the political instability  and as Figure 10  shows, in the next years, both Asia/Pacific and Rest of the World regions will experience an increase in demand for TiO2.
Figure 10: Predicted growth in TiO2 demand
TiO2 is a polymorph, showing three distinct crystalline forms: rutile, anastase and brookite, from which only anastase and rutile are technically and commercially important. 
The rutile TiO2 form has TiO6 octahedrons that form columns by sharing two edges. Titanium has six oxygen nearest neighbours, while oxygen has three titanium neighbours and the adjacent columns are linked through sharing corners of each octahedral. The unit cell is shown in Fig. 1 below :
Fig 1.The unit cell of Rutile TiO2 . Titanium atoms are represented by the grey atoms and oxygen atoms are represented by the red atoms.
The anatase form of TiO2 is composed of distorted TiO6 octahedrons...