Sedimentation behaviour of hierarchical porous TiO ₂ microspheres electrorheological fluids

Increasing the specific surface area of particles improves the suspension stability of electrorheological fluids. In this study, we introduced three TiO ₂ electrorheological materials, namely, mesoporous TiO ₂ : Ce ⁴⁺ , hollow TiO ₂ : Ce ⁴⁺ and mesoporous hollow TiO ₂ , all of which possess better sedimentation stability than pure solid TiO ₂ electrorheological materials. We aim to highlight the advantages of nanostructured materials with large surface area in improving the sedimentation stability of electrorheological fluids. The results indicated that the suspension composed of Ce-doped mesoporous TiO ₂ particles in silicone oil exhibited a strong electrorheological effect. The yield stress of a typical Ce-doped TiO ₂ electrorheological fluid was approximately 5.0 kPa at 1.5 kV/mm and 6.0 kPa at 2 kV/mm, which were 10 times higher than that of pure TiO ₂ electrorheological fluid. Hollow TiO ₂ : Ce ⁴⁺ spheres using the polymer polystyrene as the hollow template not only showed good electrorheological effect but also greatly increased settleability. The specific surface area of the mesoporous TiO ₂ hollow spheres was twice that of the mesoporous TiO ₂ and thus showed better suspension stability.