ELECTRORHEOLOGICAL PROPERTIES AND THE ENHANCED POLARIZATION MECHANISM FOR THE METAL CATIONS MODIFIED AMORPHOUS TIO_2 BASED ELECTRORHEOLOGICAL MATERIALS

摘要

In the present work, we developed a new kind of electrorheological (ER) materials, metal cations modified amorphous TiO_2 gel. The bulk density of gel particles is 2.36 g/cm~3 determined with a pycnometer. The morphology of the gel particle is irregular, and the diameter of gel particles is distributed mainly in the range from 50 nm to 150 nm. The XRD pattern shows the TiO_2 gel has an amorphous structure and the amorphous structure of the TiO_2 gel particle is an important feature of our ER materials. An infrared spectrum of the amorphous TiO_2 gel shows the number of hydroxyl groups will increase when it was modified by metal cations. The ER behaviors of suspensions of pure and metal cations modified amorphous TiO_2 particles in silicone oil have been investigated under a dc electric field. The static yield stress of Sn~(4+) modified amorphous TiO_2 gels with a volume fraction Φ = 38% reaches 26.2 kPa at E = 3.5 kV/mm and the leaking current density is about 42.2 μA/cm~2 at 3.5 kV/mm. The induced shear stress did not change for a long period of time. The ER fluid has a long-term stability against sedimentation. We then proposed a novel ER effect mechanism, metal cations enhanced polarization mechanism, to clarify the experimental results. We believe that it is the metal cations enhanced the polarization of the hydroxyl groups (-OH) which were contained in the amorphous TiO_2 gel that result to the corresponding enhancement of the interfacial polarization.