Structural and Magnetic Characterization of a Ferrofluid Obtained Through an Economical Way of Chemical Synthesis

The structural and magnetic characterization of several batches of ferrofluids produced by an economical co-precipitation production method that allows obtaining the material in a relevant quantity for use in technological applications was carried out. These ferrofluids are composed of magnetite nanoparticles stabilized with citrate in aqueous suspension. The reagents are easily accessible and inexpensive, such as steel-wool and ferric chloride. Structural characterization was performed using X-ray diffraction (XRD), transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS). The diffractograms indicate the presence of iron oxides like magnetite (Fe
₃
O
₄
) and maghemite (γ-Fe
₂
O
₃
) types. The average crystallites diameter of the obtained nanoparticles is 8.0
nm
by XRD-Scherrer, 6.0
nm
by TEM and 6.9
nm
by SAXS curves. The agglomerate size is around 65 nm (hydrodynamic radius, DLS), and 37.5 nm by analyzing the Guinier region of the SAXS curves. Magnetization vs temperature measurements yield results consistent with a wide distribution of small-sized interacting particles and superparamagnetic behavior, also corroborated in magnetization versus magnetic field measurements. The repeatability of the method used was verified when performing both types of characterization on different batches of ferrofluids.