In this work, electrosynthesis of Fe3O4 nanoparticles was carried out potentiostatically in an aqueous solution of C4H12NCl which acts as supporting electrolyte and electrostatic stabilizer. γ-Fe2O3 nanoparticles were synthesized by controlling oxidation of the electrooxidized Fe3O4 nanoparticles at dierent temperature. Finally the phase transition to α-Fe2O3 nanoparticles was performed at high temperatures using sintering treatment. The synthesized particles were characterized using X-ray diraction, Fourier transformation, infrared scanning electron microscopy with energy dispersive X-ray analysis, and vibrating sample magnetometry. Based on the X-ray diraction results, the transition from Fe3O4 to cubic and tetragonal γ-Fe2O3 was performed at 200• C and 650• C, respectively. Furthermore, phase transition from metastable γ-Fe2O3 to stable α-Fe2O3 with rhombohedral crystal structure was approved at 800• C. The existence of the stabilizer molecules at the surface of Fe3O4 nanoparticles was conrmed by Fourier transformation infrared spectroscopy. According to scanning electron microscopy images, the average particles size was observed around 50 nm for electrooxidized Fe3O4 and γ-Fe2O3 nanoparticles prepared at sintering temperature lower than 900• C, however by raising sintering temperature above 900• C the mean particles size increases. Energy dispersive X-ray point analysis revealed that the nanoparticles are almost pure and composed of Fe and O elements. According to the vibrating sample magnetometry results, saturation magnetization, coercivity eld, and remnant magnetization decrease by phase transition from Fe3O4 to Fe2O3.

Electrocrystallized iron oxide nanoparticles were prepared by a chronoamperometric technique in the presence of β-cyclodextrin. The electrocrystallization process was performed with two iron electrodes in an electrolytic bath. The effect of β-cyclodextrin concentration, applied potential and bath temperature on the structural properties and magnetization of the nanoparticles was studied. FT-IR spectroscopy, X-ray diffraction, electron microscopy, magnetometry and Mössbauer spectroscopy were used to characterize the samples. XRD patterns confirmed the formation of the spinel Fe 3 O 4 crystal structure. FT-IR spectra confirmed the presence of organic molecules at the surface of the particles. Electron microscopy images showed that the mean particle size is in the range 20-80 nm. Based on these images, we found that tuning the growth conditions has a strong effect on the particle size and morphology. High-resolution transmission electron microscopy images showed the aggregation of very fine crystallites with different orientations. The lattice striations confirmed the well-crystallized nature of the nanoparticles. The ring-like electron diffraction patterns are attributed to diffraction from the crystal planes of iron oxide nanoparticles.Room-temperature magnetization loops showed that all samples are magnetically soft with very little hysteresis, but the specific magnetization ranging from 14-80 A m 2 kg −1 is highly dependent on the particle size and the experimental conditions. The room-temperature Mössbauer spectra are typical of nonstoichiometric Fe 3−δ O 4 , with a small excess of Fe 3+ (0.07 ≤ δ ≤ 0.18). Our results showed that it is possible to improve the crystal structure of the particles by tuning the growth parameters.

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Magnetite nanoparticles were synthesized by electrocrystallization in the presence of thiourea or sodium butanoate as an organic stabilizer. The synthesis was performed in a thermostatic electrochemical cell containing two iron electrodes with an aqueous solution of sodium sulfate as electrolyte. The effects of organic concentration, applied potential and growth temperature on particle size, morphology, structure and magnetic properties were investigated. The magnetite nanoparticles were characterized by X-ray diffraction, electron microscopy, magnetometry and Mössbauer spectrometry. When the synthesis is performed in the presence of sodium butanoate at 60 °C, a paramagnetic ferric salt is obtained as a second phase; it is possible to avoid formation of this phase, increase the specific magnetization and improve the structure of the oxide particles by tuning the growth conditions. Room-temperature magnetization values range from 45 to 90 Am2kg−1, depending on the particle size, type of surfactant and synthesis conditions. Mössbauer spectra, which were recorded at 290 K for all the samples, are typical of nonstoichiometric Fe3−δO4, with a small excess of Fe3+, 0.05 ≤ δ ≤ 0.15.