| The thesis investigated how the particles size of a nanoparticles suspension will affect the rheological parameters (such as the yield stress) when an electric field is applied to it. The second study was done on how the coatings on core-shell nanoparticles affect the rheological behavior of nanoparticle suspensions when an electric field is applied. In the first study, four different sizes- 30nm, 50nm, 100nm, and 165nm are used to study the size effects on ER behavior. In the second study, four different types of coatings have been employed, which are Si, Si-Al, Si-Al-Stearic acid, and silicone oil with a constant particle size of 30nm. These particles were suspended in silicone oil of 500cst viscosity at a uniform concentration of 10% wt. Before making any measurements, care was taken to ensure that all the particles have been properly dispersed for a uniform suspension. Nano-titania suspensions were subjected to steady flow tests and dynamic mechanical testing (oscillatory tests). The smallest particles showed the highest storage modulus of up to 100kpa at an electric field strength of 4 kV/mm. The first study showed that as the particle size increased the ER effect of the suspensions decreased showing that smaller particles form stronger structures. In the second study, the coatings had a strong effect on the rheological behavior. Based upon the results from the second study we infer that the dielectric constant, conductivity and hydrophobic/hydrophilic nature play a role in determining the electrorheological response. |
