摘要
The phase transformation of α-Fe 2 O 3 to Fe 3 O 4 was observed by the hydrothermal treatment of a ferric solution at 160-220 °C with the addition of both KOH and EDA into the reaction system. The reactions began with the formation of α-Fe 2 O 3 hexagonal plates followed by the phase transformation involving the dissolution of the α-Fe 2 O 3 hexagonal platelets, the reduction of Fe 3+ to Fe 2+ , and the nucleation and growth of new Fe 3 O 4 polyhedral particles. The activation energies for the phase transformation of α-Fe 2 O 3 to Fe 3 O 4 under hydrothermal conditions are estimated to be 96.4 ± 11, 113.1 ± 5, and 118.3 ± 11 kJ mol -1 for the addition of 0.5, 1 and 1.5 ml of EDA, respectively, which are about the same for the typical phase transformation of α-Fe 2 O 3 to Fe 3 O 4 in a hydrogen atmosphere. This journal is