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

Abstract

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 TiO2in 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.