Rheological properties and sedimentation stability of magnetorheological fluid based on multi-walled carbon nanotubes/cobalt ferrite nanocomposites

Abstract

In this investigation, nanocomposites of cobalt ferrite (CoFe2O4) nanoparticles grown on multi-walled carbon nanotubes (MWCNTs) were developed by a ultrasonic-assisted co-precipitation technique. The as-prepared MWCNTs/CoFe2O4 nanocomposites were characterized in detail using transmission electron microscope (TEM), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, thermogravimetric analysis (TGA), superconducting quantum interference device (SQUID) magnetometer and nitrogen adsorption and desorption isotherms. The obtained MWCNTs/CoFe2O4 was adopted as the advanced dispersed phase for the fabrication of a uniform magnetorheological (MR) fluid, and its rheological properties and sedimentation stability were comprehensively examined. It had been revealed that the designed MR suspension exhibited typical MR features with increasing viscosity, shear stress, yield stress, storage modulus and loss modulus depending on the applied magnetic fields. It was worthy to note that the sedimentation stability of MR fluid was improved significantly, which was primarily attributed to the special three-dimensional network structure of MWCNTs/CoFe2O4 and the reduced density mismatch between the dispersed phase and carrier fluid.