The water-based Fe3O4 magnetic fluids were prepared by chemical co-precipitation of Fe2+ and Fe3+ using NaOH to control the pH, different surfactants were added to modify the magnetic particles. The stability, viscosity of the fluids and the magnetic property of magnetic particles were evaluated. The influences of different factors, such as reacting time, temperature, stirring speed, pH value, supersonic dispersing time, molar ratio of Fe2+/Fe3+, and surfactant, on properties of magnetic fluids were discussed. The experimental results showed that the optimal conditions were: molar ratio of Fe2...
