Enhancement of structural stability of nanosized amorphous Fe2O3 powders by surface modification

The surface of low-dimensional solids plays a key role in their phase transition. In the present study, to enhance the structural stability of nanosized amorphous Fe₂O₃ powders their surfaces were modified by employing NaOH solution, which leads to an increase in both the crystallization temperature from 364 °C to 411 °C and the crystallization activation energy from 81.5 kJ/mol to 156.8 kJ/mol. The surface-modified amorphous Fe₂O₃ powders show an entirely different crystallization behavior as compared with the as-prepared amorphous powders. The enhanced structural stability is attributed to the increase of the amount of hydroxide groupings at the surfaces of amorphous powders, which lowers their surface energy.