Abstract
The structuralization of magnetic particles in magnetic fluids due to the thermodiffusion induced by laser light illumination was experimentally observed in two types of magnetic fluids: one based on a mineral oil with magnetite particles covered by a monolayer of oleic acid as a surfactant and the other a kerosene-based magnetic fluid sterically stabilized by a double layer consisting of oleic acid and dodecylbenzenesulphonic acid (DBS). Forced Rayleigh scattering (FRS) showed different behaviors of magnetic particle structuralization in the observed magnetic fluids. While for the case of mineral oil-based magnetic fluids, there was observed a positive thermodiffusion (S > 0), an indication of negative thermodiffusion (S < 0) was observed in magnetic fluids based on kerosene. This was also confirmed by the time-dependent decay of a grating of magnetic particles. Numerical simulation of aggregation for the case of negative thermodiffusion was confirmed by the observed aggregation after laser illumination in kerosene-based magnetic fluids and enabled an estimated value of the negative Soret constant in the magnetic fluid studied (S ≈ −10−2 K−1).
Published Version
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