Abstract
Characterization of three differently processed α-FeOOH powders and α-Fe2O3 powders obtained therefrom has been made by means of differential scanning calorimetry, thermogravimetry, electron microscopy and porosimetry.
It was shown that the particle properties of α-FeOOH depended on the aspect ratio. Generally, powders with high aspect ratios had low densities and high pore volumes. The decomposition proceeded in 2 or 4 steps depending on the starting α-FeOOH powders.
The particle properties of α-Fe2O3 powders were influenced by the heating temperature and impurities; a high heating temperature resulted in high density, small open pore volume and small specific surface area due to the sintering of particles. The sulfate ion was found to promote the spheroidization of particles. Incorporation of SiO2, on the other hand, suppressed the surface migration, retarding the sintering and also the deformation of particles.
