Electrorheological behavior of urea-doped mesoporous TiO2 suspensions

A type of anhydrous electrorheological (ER) material of urea-doped mesoporous TiO2 is synthesized by in micelle-assisted incorporation urea molecules during mesoporous TiO2 synthesis. TEM, XRD demonstrate that the material had mesoporous structure, while the FT-IR spectra and the nitrogen adsorption–desorption isotherms show urea molecules have been fixed in the channel of the mesoporous TiO2. The ER behavior of the suspensions of urea-doped mesoporous TiO2 in silicone oil with the different volume fractions was investigated under an applied electric field. It is found that the suspensions show visible electrorheological behavior which are compared with that of pure TiO2. The dopants of urea molecules change the conductivity of the particles, and produce a proper conductivity of ∼10−7 S m−1 with the molar ratio of urea/Ti = 0.2. Dielectric spectra of the ER fluid was measured to examine the peak of ɛ″ should appear in the frequency range of 102–105 Hz and have a large Δɛ′ in this frequency range. The interfacial particle polarization model can exactly explain the ER behavior of this material.