Morphological control of Fe3O4 particles via glycothermal process

Acicular magnetite (Fe3O4) powders were synthesized through new glycothermal dehydration by using crystalline α-FeOOH as precursor and glycols as solvent. When ethylene glycol was used as solvent, the phase was in-situ transformed from acicular α-FeOOH to α-Fe2O3 and finally to Fe3O4 at 270 °C for 6 h without morphological change. When water was added as a co-solvent in glycothermal reaction, Fe3O4 powders were synthesized through dissolution–recrystallization process at 230 °C for 3 h. The volume ratio of ethylene glycol to water (E/W) in the reaction has a strong effect on the morphology of the synthesized Fe3O4 particles. The particle shape of Fe3O4 particles changed from needle to sphere when the water content in E/W volume ratio increased from 0.5 to 1 mL in mixed glycothermal condition. When the water were added by more than 10 ml, the particle shape of Fe3O4 changed from sphere to octahedron truncated with the {100} faces and finally distinct octahedron with only {111} faces. Also, it is demonstrated that the size of Fe3O4 particles can be controlled from 1–2 μm to 100–200 nm by varying the reaction conditions such as the volume ratio of water to ethylene glycol and additive in glycothermal reaction.