Preparation of kaolinite/titania coated nanocomposite particles and their electrorheological properties

Kaolinite/TiO₂ coated nanocomposite particles were synthesized by using a sol-gel technique and electrorheological fluids (ERF) prepared by dispersing the particles in silicone oil. Particle characterization was carried out by XRD, FT-IR, SEM etc. Structure analysis showed that TiO₂ was deposited on the surface of the kaolinite with anatase nano-crystallites. A distinct enhancement in the yield stress, under a dc electric field, compared to that of pure kaolinite and pure TiO₂was found by using such particles due to a synergistic effect. The yield stress of the optimum titania-coated kaolinite suspension was about 3.40 kPa at 3 kV mm^-1 and 4.45 kPa at 4 kV mm^-1, which were 5 times of that of a pure kaolinite suspension. The yield stress of kaolinite-TiO₂ nanocomposite ERF showed a marked dependence on the mass percent of TiO ₂in the composite particle; when the content of TiO₂ was about 34 wt%, the yield stress of kaolinite-TiO₂ ER fluid reached its maximum. The improvement of the dielectric properties of the kaolinite-TiO₂ nanocomposite is the intrinsic reason for the enhancement of the rheological properties. Furthermore, the electrorheological fluid also exhibits good temperature effect and sedimentation properties.