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. Un modified suspensions exhibited nonlinear conduction. The dynamic yield stre sses scaled as En, where n < 2 at all electric field frequencies, and the c urrent 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 pol ymer coatings, the dynamic yield stresses scaled as E-n, where n greater th an or equal to 2 at some frequencies and increased with coating thickness. With coated electrodes, the current harmonic contents were significantly de creased. These results suggest that nonlinear conduction in ER suspensions is associated with charge injection at the electrode/liquid interface.