Electrorheological Behavior of Nanometric Powders Suspensions

The sol–gel method was used to prepare amorphous TiO 2 powders with sub-micrometric grain size. These powders together with commercial nanometric TiO 2 were characterized with FT-IR spectroscopy, X-ray diffraction, scanning electron microscopy, and a light scattering method. Then electrorheological suspensions were composed out of these powders and their flow curves under electric field were recorded. The ER activity of the synthesized powders was relatively high which probably resulted from residual amounts of polar organic matter present in the prepared titania. It was found, however, that the studied suspensions underwent a very well pronounced agglomeration process clearly observed in suspensions of higher concentrations and particularly in those fluids which were exposed to electric field for some time. Therefore, the studied ERFs which were originally prepared out of nanometric powders contain in fact aggregated particles of considerably bigger size. The agglomeration process strongly influences all basic properties of the studied electrorheological suspensions.