Fractal Structures on Fe3O4Ferrofluid: A Small-Angle Neutron Scattering Study

A small-angle neutron scattering (SANS) which is a powerful technique to reveal
the large scale structures was applied to investigate the fractal structures of water-based Fe3O4
ferrofluid, magnetic fluid. The natural magnetite Fe3O4 from iron sand of several rivers in East
Java Province of Indonesia was extracted and purified using magnetic separator. Four different
ferrofluid concentrations, i.e. 0.5, 1.0, 2.0 and 3.0 Molar (M) were synthesized through a coprecipitation
method and then dispersed in tetramethyl ammonium hydroxide (TMAH) as
surfactant. The fractal aggregates in ferrofluid samples were observed from their SANS
scattering distributions confirming the correlations to their concentrations. The mass fractal
dimension changed from about 3 to 2 as ferrofluid concentration increased showing a deviation
slope at intermediate scattering vector q range. The size of primary magnetic particle as a
building block was determined by fitting the scattering profiles with a log-normal sphere
model calculation. The mean average size of those magnetic particles is about 60 − 100 Å in
diameter with a particle size distribution σ = 0.5.