Structure and electrorheological properties of nanoporous BaTiO₃ crystalline powders prepared by sol–gel method

In this paper, a novel nanoporous barium titanate (BaTiO₃) crystalline powder was synthesized by using triblock poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) based systems (P-123) as the soft template via a sol–gel method and their structure-dependent electro rheological property was studied. The pore diameter and specific surface area of BaTiO₃ were precisely controlled by varing the calcined temperature. The chemical composition, structure and surface morphology of BaTiO₃ were characterized by X-ray diffraction (XRD), thermo gravimetric analysis (TGA), and nitrogen adsorption–desorption method, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The result revealed that the pore volume and specific surface area of BaTiO₃ decreased with the increment of calcined temperature. The electro rheological fluids (ERFs) were obtained by dispersing BaTiO₃ crystallites in silicon oil and three kinds ERFs were fabricated by using three kinds of BaTiO₃ which were prepared under different calcined temperature (550, 600 and 900 °C) as the precursors. The behaviors of the ERFs were evaluated via a rotational rheometer fixed with electric field generator. The results showed that electro rheological effect was related to the pore volume and specific surface area of BaTiO₃. Due to the distinct advantage of sol–gel method for preparing nanoporous BaTiO₃ without contamination of the materials, the markedly low current destiny of the ERFs was obtained. The yield stress of ERFs with large specific surface area of BaTiO₃ reached the maximum of 3 kPa, which is higher than that of ERFs using traditional pure BaTiO₃ crystallites (lower than 1 kPa).