Resumo

MORALES-MORALES, Jimmy Alexander. Synthesis of Hematite a-Fe ₂ O ₃ Nano Powders by the controlled precipitation method. Ciencia en Desarrollo [online]. 2017, vol.8, n.1, pp.99-107. ISSN 0121-7488.

Recently increased attention has been paid to the synthesis of hematite nanoparticles, due to its properties and application in various fields of modern technology. The aqueous route has shown to be simpler and more versatile than the non-aqueous routes. In this study, nanopowder particles of OC-Fe2O3 (hematite) were synthesized by controlled precipitation method in three stages: precursors' precipitation, washing and calcination. The precipitation was controlled with ferric chloride as precursor, and sodium hydroxide as precipitant, in constant agitation and pH 6.

There were tested with different reaction times: With 1 and 2 days. With one day reaction, the synthesis of hematite accompanied by maghemite, was verified by XRD. After 2 days of the reaction was proved that it is possible to obtain hematite and maghemite in greater quantities, but with magnetite impurities, and less chloride content, thanks to repeated washings. This is an interesting observation since impurities magnetite has not been reported in the synthesis of hematite by controlled precipitation method.

It was found that the reaction time and repeated washings used in the synthesis process, played an important role in determining the iron oxides and particle size, plus phase formation and transformation, which was confirmed at different reaction times and repeated washings by XRD analysis, FT-IR, Raman and SEM.

Samples with two days reaction, washed and calcinated at 425 °C, with a size less than 100 nm are associated with a hematite, magnetite and maghemite mixture, with almost a plate-shaped sphere morphology and the aggregates are formed by hemispherical primary particles, whose size apparently is in the nanometers' order.

Palavras-chave : Magnetite; Maghemite; Hematite Nanoparticles; -Fe₂O₃ Nanopowder; Raman.

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