Noncovalent self-assembly of carbon nanotube wrapped carbonyl iron particles and their magnetorheology

Carbonyl iron (CI) particles with their superior magnetic and physical properties, widely adopted as magnetorheological (MR) fluids, have been modified via diverse strategies to get well dispersed suspension in medium oil. Recently, coating technology has become prevalent due to improved favorable morphology and effective decrease in their particle density, resulting in an abated sedimentation problem. Therefore, considering self-assembling property of carbon nanotube (CNT), a dense nest of CNT onto the surface of CI particles was constructed in this study using 4-aminobenzoic acid as a grafting agent. MR characteristics of the CI/CNT particles which were examined via a rotational rheometer in a parallel plate geometry equipped with a magnetic field supplier were found to be similar with that of pristine CI suspension, while the sedimentation ratio is expected to be improved. (c) 2008 American Institute of Physics.