Synthesis of ferrofluids using a chemically induced transition method and their characterization.

Using an altering chemically induced transition route, magnetic nanoparticles as well as nanoparticles modified with oleic acid have been prepared. The modified nanoparticles have been used to synthesize a high-quality kerosene-based ferrofluid, in which the mass fraction percentage of particles consisting of a γ-Fe2O3 core and an oleic acid coating, ϕm, amounted to 55%. Ferrofluids having lower concentrations of particles were obtained by diluting the mother ferrofluid. Magnetization measurements showed the as-synthesized ferrofluids to have excellent dispersity of the particles and field-induced inter-particle interactions. Optical transparency measurements confirmed that the ferrofluids showed a sensitive field-induced effect of chain-like aggregation, with redispersion of the particles after removing the magnetic field. According to results concerning both particle structure and ferrofluid density, the volume fraction percentage of particles, including both the γ-Fe2O3 core and the oleic acid coating, ϕ′v, as well as that of the γ-Fe2O3 alone, ϕv, can be deduced. [ABSTRACT FROM AUTHOR]