Preparation and electrorheological activity of mesoporous rare-earth-doped TiO₂

A new kind of mesoporous rare-earth-doped TiO₂ particle with a well-defined crystalline framework was synthesized under a general temperature state for use as electrorheological (ER) active material. The neutral surfactant dodecylamine (DDA) was used as a template to direct the mesoporous structure. The low-angle X-ray diffraction peak showed that the mesoporous rare-earth-doped TiO₂ had an interlayer distance of about 3.4 nm and the high-angle peaks showed that the material possessed an anatase crystalline framework. ER properties of the suspension based on this material and silicone oil were measured in a dc electric field. It had been shown that the extraordinary high yield stress over 8.1 kPa could be induced when a 3 kV/mm electric field was applied. It was 20 times higher than that of pure TiO₂ ER suspension and twice as high as that of single-doped TiO₂ ER suspension as reported in our previous works. Interestingly, the shear stress of this suspension was found to continuously increase with temperature elevation in the range 10-100 °C. These improvements were attributed to the pursuit of slow polarization and suitable conduction properties of this mesoporous-doped TiO₂ suspension in terms of the measured results of dielectric and conduction properties. The present experimental result suggests that both the active internal structure and interface or surface structure of ER particles, which merit the pursuit of suitable dielectric and conduction properties, are the key to high ER activity.