Preparation and characterization of iron-based magnetorheological fluids stabilized by addition of organoclay particles.

Suspensions of micrometer-sized iron particles (10 vol %) dispersed in kerosene and stabilized by addition of organoclay particles were prepared. The magnetization curves of these suspensions were measured, and their sedimentation and redispersion behaviors were analyzed as a function of clay concentration by means of optical and rheological methods. Furthermore, their magnetorheological properties were investigated using a controlled rate magnetorheometer and the effect of clay concentration on these properties was also analyzed. These experiments showed that the addition of clay slows down iron particle settling and eases the redispersion of the iron-based suspensions without masking their magnetorheological properties. Two mechanisms were found to be involved in this behavior: (i) the formation of a clay gel network and (ii) the presence of heterogeneous iron-clay adhesion.