Magnetic composites of conducting polyaniline/nano-sized magnetite and their magnetorheology

Magnetorheological (MR) fluids, composed of colloidal particles dispersed in a carrier liquid, possess controllable theological properties by an external magnetic field, showing dramatic changes of yield stress and shear viscosity caused by transformation between solid-like to liquid-like state. As a new MR material, we synthesized conducting polyaniline (PANI)/nano-sized Fe3O4 composites which could be adopted as a dispersed phase of MR fluids. Composites containing nano-sized Fe3O4 were synthesized via a chemical reaction method. Microstructure of the PANI/Fe3O4 composites was characterized by SEM and XRD. Magnetic property of the composites was characterized by VSM. Furthermore, MR fluid based on PANI/Fe3O4 composites was investigated using a rotational rheometer equipped with a magnetic field generator, exhibiting a typical MR performance of which shear stress of the fluids increased abruptly under magnetic fields. (C) 2008 Elsevier B.V. All rights reserved.