Abstract
The α-Fe particles were prepared by reducing the ferrous ion in sodium borohydride aqueous solution in the presence of surfactant, sodium oleate. The particles prepared were dispersed stably in tetramethylammonium (TMA) hydroxide aqueous solution with sodium dodecylbenzenesulfonate (SDBS). The stability of the suspension depended on the SDBS and TMA hydroxide concentration. The effect of iron concentration on the viscosity of suspension was studied and the apparent adsorbed layer thickness was evaluated to be about 10 nm. The suspension when exposed to a magnetic field distribution was separated into two phases. The sunk black phase retained the flowability and did not coagulate under the employed magnetic field distribution, this being considered as a stable magnetic fluid. For example, a magnetic fluid with saturation magnetization of 0.036 T was prepared. Optical microscopic observation of 2 μm thin magnetic fluid film under magnetic field showed the existence of iron particle clusters. The viscosity of the magnetic fluid measured in a cylindrical viscometer showed about two fold increase in viscosity under a magnetic field of 280 kA/m.
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