In the displacement reaction, iron iii oxide is displaced by aluminium. Aluminium has a high reactivity in comparison to iron, so it can easily oxidise and eliminate the oxygen present in iron iii oxide.
Iron oxide is an important component in many manufacturing processes and is used in the production of metals such as steel. It is also used as a catalyst in various reactions such as oxidation of nitrogen oxides, photocatalytic splitting of water, Fischer-Tropsch synthesis of hydrocarbons, and catalytic oxidations of organic compounds.
It is a polymorphic compound that can form two or more solid phases based on its crystal structure. Despite its broad range of physicochemical properties, no polymorphic iron(III) oxide phase has been discovered to be stable at room temperature and atmospheric pressure.
The z-Fe2O3 polymorph is the first iron(III) oxide phase with a monoclinic crystal structure to be identified. Its structural features resemble those of the cubic b-Fe2O3 phase, but it shows unusual pressure-induced changes in the lattice.
The z-Fe2O3 phase is characterized by its Rwp-factor of 7.4 (compared to b-Fe2O3’s value of 3.7). It has several structural resemblances to the octahedral b-Fe2O3, but has the b angle between the a- and c-axis increased by 98deg, indicating an increased surface area for the Fe d-site. This increases the enthalpy of transformation to 870 kJ/mol, which makes z-Fe2O3 a highly exothermic phase. It has a much higher reactivity than the octahedral Fe2O3 phase, suggesting that its phase transition may be related to its higher chemical potential and/or to its larger surface-to-volume ratio.