Preparation and Rheological Response of Dual-Coated Carbonyl Iron Based Magnetorheological Fluid

Magnetorheological fluid (MRF) is a stimuli-responsive materials whose rheological properties can instantaneously transform into a solid-like state under the stimulation of an external magnetic field (MF). However, MRF still has problems in engineering applications which should be improved. In particular, sedimentation stability is one of the major problems caused by the large size and high density of the magnetic particles used. Herein, dual coated carbonyl iron (CI) particle with silica and carbon nanotubes (CNT) shell was fabricated and applied as for the MRF. The silica shell was synthesized firstly, and then CNT was loaded to the surface of silica coated composite by self-assembly. The obtained dual coated CI particle not only exhibited soft-magnetic properties, but also greatly reduced density compared with CI. The dual-coated CI based MRF was prepared and its rheological properties and damping performances were investigated. Changes in the rheological properties of MRF induced by MF stimulation were tested by a rotational rheometer equipped with a MF applicator for steady-state shear and dynamic oscillation at various MF strengths. Moreover, the sedimentation testing provides information about the dispersion MR response. The CI@SiO2/CNT‐based MRF with a transient, reversible, and controllable MR response is considered a promising MRF for intelligent control applications.