Preparation and Characterization of a Magnetic Binary System Comprise of γ-Fe2O3 and α-FeO(OH) Nanoparticles
Magnetic nanoparticles were prepared from a low crystalline ferrihydrite (Fe5O7(OH)·4H2O) precursor by a chemically-induced transformation method using mixed FeCl2/NaOH solution. The products obtained were characterized using a vibrating sample magnetometer, X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. Experimental results show that while the concentration of NaOH was 0.17 mol/L, and the FeCl2 concentration was increased from 0.09 mol/L to 0.42 mol/L in the mixed solution, the as-prepared products were binary nanoparticle systems comprised of ferrimagnetic γ-Fe2O3 sphere-type particles and antiferromagnetic α-FeO(OH) rod-type particles. The resulting particles were highly crystalline. The volume ratio of γ-Fe2O3 and α-FeO(OH) particles was estimated from magnetization data, which showed that the volume of γ-Fe2O3 particles decreased and α-FeO(OH) particles increased with increasing FeCl2 concentration. Such nanoparticle systems could be suitable for synthesis of binary ferrofluids, which have different behavior to conventional ferrofluids.