Response Surface Methodology Study on Magnetite Nanoparticle Formation under Hydrothermal Conditions

In a hydrothermal preparation of crystalline magnetite (Fe 3 O 4 ) nanoparticles, the influence of the experimental parameters (initial molar ratio of ferrous/ferric ions, initial concentration of ferrous ions, and heating time), and their interactions, on the particle formation was studied using response surface methodology (RSM), based on a statistical design of experiments (DOE). As indices indicating particle formation and crystallization, the variation in the particle diameter and crystallite size with the synthesis conditions was examined. The crystallite size was greatly affected by both the initial ferrous/ferric ion molar ratio and the heating time, whereas the particle diameter strongly depended on the heating time, and on the interaction between the initial ferrous/ferric ion molar ratio and the initial concentration of ferrous ions. The results from a statistical analysis suggest that the polycrystalline Fe 3 O 4 nanoparticles form via crystal growth and/or thermal aggregation, after nucleation during hydrothermal treatment.