Towards high sedimentation stability:: magnetorheological fluids based on CNT/Fe3O4 nanocomposites

CNT (carbon nanotube)/Fe3O4 nanocomposites were prepared. The diameter of the CNT/Fe3O4 composites prepared was about 60 nm, while the diameter of the CNTs was about 20 nm according to the results of transmission electron microscopy (TEM) measurements. The average apparent density. of the CNT/Fe3O4 nanoparticles was about 1.8 g cm(-3), which is only a quarter of that normally used for magnetic particles. The sedimentation and magnetorheological properties of magnetorheological (MR) fluids based on CNT/Fe3O4 nanocomposites were studied. The MR fluids based on CNT/Fe3O4 nanocomposites exhibit high sedimentation stability and obvious magnetorheological behaviours such as an apparent viscosity depending on the applied field. These predominant properties are mainly due to the special structure of the soft magnetic layer covering the outside of the hollow CNTs and the large length-diameter ratio of the nanocomposites.