Enhanced Electrorheological Activity of Mesoporous Cr-Doped TiO₂ from Activated Pore Wall and High Surface Area

Abstract

To enhance electrorheological (ER) activity by improving interfacial polarization, we prepared a new mesoporous Cr-doped TiO2 ER material by a copolymer-templated sol-gel method. The material was characterized by differential scanning calorimeter and thermogravimetric (DSC-TG) analysis, Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption, and X-ray photoelectron spectroscopy (XPS) techniques. The ER activity was studied by the rheological curve and yield stress under an electric field. The results showed that the mesoporous Cr-doped TiO2 ER material possessed a high surface area over 200 m2/g and a crystalline anatase pore wall doped by different valent Cr ions. The ER activity of mesoporous Cr-doped TiO2 was higher than that of nonporous Cr-doped TiO2. The yield stress and ER efficiency of the mesoporous Cr-doped TiO2 ER suspension was 3 times as high as that of the nonporous Cr-doped TiO2 ER suspension, 7 times as high as that of the mesoporous undoped TiO2 ER suspension, and 20 times as high as that of the nonporous pure TiO2 ER suspension. Furthermore, the ER activity of mesoporous Cr-doped TiO2 showed a dependence on surface area, and the high porosity or surface area samples showed higher ER activity. The dielectric spectra analysis showed that the mesoporous Cr-doped TiO2 ER suspension possessed a significantly larger interfacial polarizability compared with the nonporous Cr-doped TiO2 ER suspension, and the regular change of polarizability with surface area or porosity was in accordance with the change of ER activity with surface area or porosity. The improvement of dielectric properties or polarization could well explain the enhancement of the ER activity of mesoporous Cr-doped TiO2.

One-pot synthesis of bifunctionalized TiO2 mesoporous photocatalyst with visible light response

“…There is only one peak at 102.1 eV to be detected, which implies the existence of only one kind of Si species on the sample. Specifically, the binding energy of Si2p in TSF-0.05 sample is slightly smaller than that of parent SiO 2 (103.4 eV [23] ), which further confirms the formation of Si-O-Ti bond in TSF-0.05. Interestingly, the O1s spectrum of TSF-0.05 contains three peaks: The main peak at 530.1 eV can be assigned to [24,25].…”

Electrorheological performances of poly(o-toluidine) and p-toluenesulfonic acid doped poly(o-toluidine) suspensions

“…With the increase of shear rate, the shear stress increases firstly, and then shows somewhat a decrease; after the shear rate exceeds a certain value, it increases linearly with the shear rate at last. The increase followed by the decrease of shear stress with the increase of shear rate in the low shear rate region and the existence of critical shear rate have been found in several ER fluids [16,24,[26][27][28]. When the shear rates are below the critical shear rates, the suspension was flowed by the shear in a non-Newtonian fluid model, but flowed as Newton fluid model when the shear rates are above these critical shear rates.…”

“…When the polarization of the particles under electric field is slow and weak, the deformation of the chain or column structures is superior to the formation, and then the shear stress decreases with the increase of shear rate. However, when the ER fluids are subjected to high shear rate, the deformation is regarded to be dominant; this high shear rate value is often referred as critical shear rate (γ crit ) [26][27][28]. In the POT suspension, under lower shear rate region, the POT particles show fast polarization, and this makes the formation of the chain or column structures faster than the deformation induced by shear; thus, the shear stress increases with the shear rate in the lower shear rate region.…”

Fabrication of Photocatalyst Composite Coatings of Cr-TiO2 by Mechanical Coating Technique and Oxidation Process

“…The structurally-defective morphology of Cr-TiO2 coatings is affected with adding Cr, as reported by references [35,36]. The structurally-defective morphology is an important role to affect the photocatalytic activity of Cr-TiO2 coatings [37]. On the other hand, the mixed-phase of anatase and rutile has a synergistic effect on enhancing the photocatalytic activity of TiO2 [11,13].…”