Titania is a potential high-performance electrorheological (ER) material due to its relatively high dielectric constant and polarization ability. The size and shape of titania particles are critical factors influencing ER activity. In this paper, we have developed an acetic acid (AA) assisted sol–gel strategy for the synthesis of uniform titania microspheres with good ER effect. The diameter of the titania microspheres (from 420 to 240 nm) can be tuned by changing the amount of AA added. The facile route has the great potential in bulk synthesis of the titania based ER materials. Results from surface area, rheological, conductivity and dielectric properties measurements indicate that the enhanced ER performance is due to the combined effect of the increased polar molecules content and reduced particle size.

A simple co-precipitation route was developed to synthesize uniform core-shell structured calcium and titanium precipitation (CTP) particles with ideal morphology and no aggregation. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), and interface tension/contact angle (CA) measurement were utilized to characterize the components, structure, morphology, and wettability of the SiO(2)-CTP materials. The obtained core-shell structural SiO(2)-CTP particles were well dispersed spherical nanoparticles with a narrow size distribution. The electrorheological (ER) properties were studied by the shear stress under various electric fields. The SiO(2) (2.3 wt%)-CTP ER fluid showed notable ER activity with a shear stress of about 109 kPa (at 5 kV mm(-1)), which outclassed the shear stress (65 kPa) of the CTP ER fluid. The ER properties of samples can be tuned by a few factors in the experimental process, such as the concentration of SiO(2) particles and citric acid, pointing out the great potential for application of this route in bulk synthesis of many other types of ER materials.

Insufficient yield stress and electrorheological (ER) efficiency have already become the limitations for the practical application of ER fluids. Herein, we report a simple and scalable co-precipitation method for synthesizing surfactant-modified calcium titanyl oxalate (SCTO) particles with a rod-like structure. The obtained SCTO materials not only present a yield stress twice as that of granular CTO ER fluids but also demonstrate low zero-field viscosity, which results in a high ER efficiency. In terms of microstructure and dielectric analysis, we infer that the exceptional ER activity is in large part due the anisotropic morphology and improved wettability of the rod-like SCTO. This work provides the basis for the future development of ER fluids and the promotion of their practical application.

A novel micro/nanoparticle hybrid calcium titanyl oxalate electrorheological (ER) material composed of micron-sized spindly particles and nanometer-sized irregular particles was successfully fabricated. The giant ER fluid based on the composite exhibits enhanced not only yield stress but also low field-off viscosity, thereby resulting in an ultrahigh ER efficiency that greatly exceeds that of any existing giant ER (GER) material. The synergistic effect between the spindly microparticles and irregular nanoparticles discovered in this study suggests a promising method for solving the long-standing ER efficiency problems. Moreover, the one-step synthesis approach presented in this work can be readily expanded for mass production of other GER materials in practical applications.