Factors that may influence the micro-emulsion synthesis of nanosize magnetite particles

The influence of experimental conditions on the formation of nanosize magnetite by micro-emulsion method was investigated using Mössbauer and FT-IR spectroscopies, FE SEM/EDS and TEM. It was found that the concentration of starting chemicals (FeCl₃/FeSO₄), aeration/de-aeration, high alkalinity and γ-irradiation influenced this precipitation process. Rod-like goethite particles ～200–300 nm long and up to 10 nm wide were obtained by destabilization of the micro-emulsions aged 5 to 45 days at RT. Si-containing ferrihydrite was also formed and it retarded the formation of goethite by the dissolution/re-precipitation mechanism. A small amount of Si from a glass flask was dissolved. A very strong influence of γ-irradiation on the formation of nanosize magnetite by micro-emulsion method was observed. γ-irradiation created strong reductive conditions in the micro-emulsions. At an ～460 kGy dose, nanosize magnetite particles sized ～5 to 20 nm and very small amounts of goethite particles were obtained. The EDS measurements on the particles suggested the formation of sub-stoichiometric magnetite (Fe_3?x O₄) and not of maghemite. This finding is in line with the strong reductive conditions induced with γ-irradiation.