Enhanced electrorheological performance and antisedimentation property of mesoporous anatase TiO₂ shell prepared by hydrothermal process

Mesoporous anatase TiO₂ hollow microspheres (MTHMs) with a high surface area (231.1 m² g^-1) were synthesized by sol-gel template-assisted approach and hydrothermal process. The materials possessed a uniform diameter of about 620 nm and a mesoporous shell with thickness of about 180 nm. The microspheres were used as dispersing materials for electrorheological (ER) fluids, which exhibited better ER performance and antisedimentation property than common anatase TiO₂ hollow microspheres and ordinary anatase TiO₂ particles. The yield stress of the MTHM-based ER fluid (30.0 vol%) was approximately 7.8 kPa under an electric field of 3 kV mm^-1, and the sedimentation ratio was maintained above 78% after 250 h. The good ER activity of the MTHM-based ER fluid was mainly attributed to the high surface effect provided by mesoporous and hollow structure of the MTHMs, leading to a high interfacial polarization under the action of an external electric field. The mesoporous and hollow structure also improved the antisedimentation property of the suspensions by lowering the density of microspheres.