Probing Aspects of Nonlinear Conduction in Electrorheological Suspensions

Particle and electrode surfaces were altered to examine the effects on the electrorheological response of barium titanate/silicone oil suspensions. Unmodified suspensions exhibited nonlinear conduction. The dynamic yield stresses scaled as E, where n < 2 at all electric field frequencies, and the current had substantial harmonic content, a hallmark of nonlinear conduction. Modifying the particle surfaces did not affect these nonlinear responses. Casting polymers on the electrode surfaces changed the responses. With polymer coatings, the dynamic yield stresses scaled as E, where n ≥ 2 at some frequencies and increased with coating thickness. With coated electrodes, the current harmonic contents were significantly decreased. These results suggest that nonlinear conduction in ER suspensions is associated with charge injection at the electrode/liquid interface.